E-Flows Scenario Report Hydrology
EPSMO-BIOKAVANGO
Okavango River Basin
Environmental Flow Assessment
Scenario Report : Hydrology
Report No: 06/2009
H. Beuster, et al.
July 2009
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E-Flows Scenario Report Hydrology
DOCUMENT DETAILS
PROJECT
Environment protection and sustainable management of
the Okavango River Basin: Preliminary Environmental
Flows Assessment
TITLE:
Scenario Report: Hydrology
VOLUME:
Volume 1 of 1
DATE: July
2009
LEAD AUTHORS:
H. Beuster.
REPORT NO.:
06/2009
PROJECT NO:
UNTS/RAF/010/GEF
FORMAT:
MSWord and PDF.
CONTRIBUTING AUTHORS:
K Dikgola, A N Hatutale, M Katjimune, N Kurugundla,
D Mazvimavi, P E Mendes, G L Miguel, A C Mostert,
M Quintino, P N Shidute, F Tibe, P Wolski.
THE TEAM
Project Managers
Colin Christian
Hilary Masundire
Chaminda Rajapakse
Barbara Curtis
Dominic Mazvimavi
Nkobi Moleele
Celeste Espach
Joseph Mbaiwa
Geofrey Khwarae
Aune-Lea Hatutale
Gagoitseope Mmopelwa
Mathews Katjimune
Belda Mosepele
Angola
assisted by Penehafo
Keta Mosepele
Manuel Quintino (Team
Shidute
Piotr Wolski
Leader)
Andre Mostert
Carlos Andrade
Shishani Nakanwe
EFA Process
Helder André de Andrade
Cynthia Ortmann
Management
e Sousa
Mark Paxton
Jackie King
Amândio Gomes
Kevin Roberts
Cate Brown
Filomena Livramento
Ben van de Waal
Hans Beuster
Paulo Emilio Mendes
Dorothy Wamunyima
Jon Barnes
Gabriel Luis Miguel
assisted by
Alison Joubert
Miguel Morais
Ndinomwaameni Nashipili
Mark Rountree
Mario João Pereira
Rute Saraiva
Botswana
Okavango Basin
Carmen Santos
Casper Bonyongo (Team
Steering Committee
Leader)
Tracy Molefi-Mbui
Namibia
Pete Hancock
Laura Namene
Shirley Bethune (Team
Lapologang Magole
Leader)
Wellington Masamba
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List of reports in report series
Report 01/2009:
Project Initiation Report
Report 02/2009:
Process Report
Report 03/2009:
Guidelines for data collection, analysis and scenario creation
Report 04/2009:
Delineation Report
Report 05/2009:
Hydrology Report: Data and models
Report 06/2009:
Scenario Report: Hydrology
Report 07/2009:
Scenario Report: Ecological and social predictions
Report 08/2009:
Final Report
Other deliverables:
DSS Software
Process Management Team PowerPoint Presentations
Copyright reserved
No part of this document may be reproduced in any manner
without full acknowledgement of the authors
This report should be cited as:
EPSMO-BIOKAVANGO Eflows Team. 2009. SCENARIO REPORT: HYDROLOGY. Report
06-2009. EPSMO/BIOKAVANGO Okavango Basin Environmental Flows Assessment
Project, OKACOM, Maun, Botswana.
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Acknowledgements
Many thanks for logistical support to:
· Corinne Spadaro of FAO
· Ros Townsend, Karl Reinecke and Rembu Magoba of Southern Waters.
Mathews Katjimune
This report is dedicated to Mathews Katjimune, who passed away in October 2009. He
contributed immensely to the project and we will miss his energy, enthusiasm, knowledge
and outgoing personality.
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E-Flows Scenario Report Hydrology
Executive Summary
E.1. Introduction
The EFA is a joint project of EPSMO and the Biokavango Project. The EFA
methodology is based on the evaluation of a reference flow regime ("natural" or "present
day") and a range of future flow regimes resulting from water resource developments to
make predictions of change for a number of ecological indicators; these usually cover
channel geomorphology, water quality, riverine vegetation, fish and aquatic macro-
invertebrates. For the EFA, modified future flow regimes are produced with hydrological
(and hydraulic) models of the river basin and the delta.
This report (Volume 6) is the second of two reports produced by the EFA hydrological
working group. It provides an overview of the hydrological characteristics of the basin
and describes the outcomes of the hydrological modeling of present and possible future
flow regimes. The report should be read in conjunction with the Hydrology: Data and
Models Report (Volume 5), which describes the models, hydrological data and
development information that form the basis for the simulation of flow regimes at different
points along the Okavango River system, including the Delta.
The hydrological analyses were undertaken to provide summary statistics that are used
as inputs to the response curves that are used to predict the biophysical and social
outcomes for the flow regime of interest. The response curves, and the predicted
ecological and socio-economic implications of the water use scenarios are described in
Report 07/2009: Scenario Report: Ecological and social predictions (Volume 1 of 2)
E.2. The
Study
Area
The Okavango River Basin consists of the areas drained by the Cubango, Cutato, Cuchi,
Cuelei, Cuebe, and Cuito rivers in Angola, the Okavango River in Namibia and Botswana
(in Namibia, the river is called the Kavango), and the Okavango Delta. This basin
includes the Omatako River catchment in Namibia which is topographically linked to the
Okavango River, but due to the low mean annual rainfall (less than 400 mm/year in the
headwaters), the river is ephemeral. Due to the sandy nature of the terrain, no surface
runoff reaches the Okavango River. Outflows from the Okavango Delta are drained
through the Thamalakane and then Boteti Rivers, the latter eventually joining the
Makgadikgadi Pans. The Nata River, which drains the western part of Zimbabwe, also
joins the Makgadikgadi Pans. The Selinda spillway is located in a local depression and
provides an occasional link to the Zambezi River. In times of high flow the Okavango
overtops a local high point in the Selinda and spills toward the Cuando/Chobe/Linyanti
system (2009 Satellite images provided the first recorded evidence of overflow from the
Kavango Panhandle reaching the Kwando/Linyanti/Chobe/Zambezi system through the
Selinda Channel). On the basis of topography, the Okavango River Basin thus includes
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E-Flows Scenario Report Hydrology
the Makgadikgadi Pans and Nata River Basin and has an occasional link to the Zambezi
Basin. This study, however, focuses on the parts of the basin in Angola and Namibia,
and the Panhandle/Delta/Boteti River complex in Botswana. The Makgadikgadi Pans
and Nata River are not included.
Figure E-1 : The Okavango River Basin
E.3.
Delineation of the Okavango Basin into Integrated Units of Analysis
Within the Okavango River Basin, representative areas that are reasonably
homogeneous in character were delineated and used to represent much wider areas.
(EPSMO/Biokavango Report Number 4; Delineation Report). One or more
representative sites were chosen in each area as the focus for data-collection activities.
The results from each representative site could then be extrapolated over the respective
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E-Flows Scenario Report Hydrology
wider areas. The existing and new hydrological models were selected and configured to
provide scenario flow sequences at these sites.
The sites chosen by the national teams are given in Table E-1.
Table E-1
Location of the eight EFA sites
EFA Site No
Country
River
Location
1 Angola
Cuebe
Capico
2 Angola
Cubango
Mucundi
3 Angola
Cuito Cuito
Cuanavale
4 Namibia
Okavango
Kapako
5 Namibia
Okavango
Popa
Falls
6
Botswana
Okavango
Panhandle at Shakawe
7
Botswana
Khwai
Xakanaka in Delta
8 Botswana
Boteti Chanoga
E.4.
Hydrological Modeling of the Basin
A hydrological working group consisting of hydrologists from the three co-basin states
was established to develop and populate the hydrological and hydraulic models for the
river basin and the delta and to develop flow scenarios. The work was undertaken
during the course of five week-long hands-on workshops in Maun, Gaborone and
Windhoek.
In order to provide the hydrological information required for the EFA, a suite of existing
and new models were used. The models were selected and configured to provide
current day (baseline) and scenario flow sequences at the eight EFA sites. Details of the
models and data that were used to configure these are provided in EPSMO/Biokavango
Report Number 5; Hydrology: Data and Models.
The models which were selected for use in the EFA are:
· Catchment hydrology: Estimates of naturalised (undeveloped) long-term runoff
were obtained from an existing Pitman-based rainfall-runoff model developed as
part of the EU funded WERRD and TwinBAS projects (Hughes et. al. 2006). The
model was configured to provide runoff sequences at the outlets of 24 distinct
sub-catchments upstream of the Delta.
· Systems Model: As part of this project, the monthly time-step WEAP systems
model was selected and used to configure a reference (Present Day), Low,
Medium and High Development scenarios. Inputs to the model include the
undeveloped runoff sequences for 24 sub-catchments produced by the Pitman
model, irrigation scheme and urban abstractions, in channel dams for irrigation
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E-Flows Scenario Report Hydrology
water supply, inter-basin transfers, run-of-river and storage based hydropower
schemes.
· HOORC Delta Model: A semi-conceptual model which was previously developed
by the Harry Oppenheimer Okavango Research Centre (HOORC) (Wolski et. al.
2006) was used to model inundation frequencies and extents at the Delta EFA
sites. The model operates on a monthly time step and includes a dynamic
ecotope model that simulates the responses of vegetation assemblages to
changes in hydrological conditions. Scenario inflows to the model are provided by
the WEAP simulations of basin runoff.
· DWA Delta Model: A MIKE-SHE / MIKE 11 hydrodynamic model which was
previously configured by Botswana DWA and DHI for the Okavango Delta
Management (ODMP) project (IHM Report, 2005) was used to model flow
velocities and depths at the Delta EF sites. Scenario flow sequences simulated
with WEAP for Mohembo were used as inflow sequences for the Delta model,
after disaggregating the monthly flow sequences to a daily time step.
· Thamalakane/Boteti Model: Delta outflows simulated by the HOORC model are
routed along the Thamalakane/Boteti system with a linear reservoir spreadsheet
model (Mazvimavi, 2008) to derive scenario flow sequences at the Boteti EF site.
The model was incorporated into the HOORC Delta Model and improved to
provide estimates of wetted river length and state changes of the system.
· Disaggregation and Hydro-Statistics: A custom utility was developed to
disaggregate the simulated monthly WEAP flow sequences to daily flow
sequences, to delineate flow seasons (dry, wet and transition) for each year of
the 43 year long sequences, and to calculate ecologically relevant flow statistics
("flow indicators").
E.5.
The Present Water Resources Situation
Figure E-2 shows the accumulation of mean annual runoff along the main tributaries of
the Okavango upstream of the Delta. The runoff estimates are based on Pitman
modeling undertaken for the WERRD and TwinBas studies, and incorporated into the
WEAP model developed for the Okavango EFA Study. The estimates are for the period
spanning October 1959 to September 2002. Runoff of about 10 200 million m3/a is
generated in the upper catchments of the basin (upstream of the confluences of the
Cubango and Cuartir Rivers in the west, and the Cuito and Longa Rivers in the east).
Downstream of these points, the catchments of the lower Cubango/Kavango and Cuito
River contribute very little additional runoff. Large losses and some abstractions reduce
the cumulative present day runoff to about 9 600 million m3/a at the upper end of the
Delta at Mohembo.
Current water abstractions in the upper basin (upstream of Mohembo) amount to about
60 million m3/a (or about 47 million m3/a if the demands from the nearly completed
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E-Flows Scenario Report Hydrology
Missombo irrigation scheme on the Cuebe River is excluded). In very dry years (1:20
year drought conditions), the flows in the river are significantly restricted as shown by the
flows in Figure E-3. Only about 3 000 million m3/a might be derived from the Cubango
and 3 100 million m3/a from the Cuito, yielding only 6 100 million m3/a at Mohembo.
Runoff generated in the Cubango River catchments is somewhat more than the
contribution of the Cuito River catchments (5 600 and 4 600 million m3/a, respectively).
Simulated average monthly hydrographs for the two rivers just upstream of their
confluence are shown in Figure E-4. The figure illustrates the striking difference in the
seasonality of the two rivers, and also shows that discharges in the Cuito River during
the low flow months of September and October are on average about twice those of the
Cubango/Kavango.
The impact of upstream developments on inflows to the Delta can be assessed in terms
of changes to the extent, duration and frequency of flooding in the Delta. For the
Okavango EFA Study, these changes have been related to changes in vegetation
assemblages (EPSMO/Biokavango Report Number 5; Hydrology: Data and Models).
Figure E-5 shows a timeline of vegetation changes in the Eastern Delta under present
levels of water use in the upstream basin. It can be seen that the proportion of grassland
and savanna on the periphery of the Delta expands in dry periods such as the one that
occurred in the mid-1990s.
Flows in the Thamalakane / Boteti River system receives outflows from the Delta and is
highly susceptible to changes in the flooding regime of the Delta. In addition, the length
of river that is wetted by inflows in any given year depends on the volume of inflows and
state of the groundwater aquifers in previous years. The HOORC model was used to
simulate state changes (changes from a wet river, isolated pools or dry riverbed) along a
200 km reach of the Boteti River under different Delta flooding regimes. The sensitivity
of the wetted length to inflows (note the dry period in the 1990s) can clearly be seen from
Figure E-6.
.
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Cuanavale
ai
Khw
Ca
C
Gomoti
c
u
u
irir
C
c
L
i
u
h
o
c
n
i
g
h
a
T
qoga
i
h
N
L
a
ua
o
X
s
g
u
si
d
n
u
g
e
m
a
C
Cw
u
e
ta
be
T
to
haoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure E-2:
Mean Annual Runoff (106 m3/a) - Present Day
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E-Flows Scenario Report Hydrology
Cuanavale
Khwai
Ca
C
Gomoti
c
u
u
iri
c
r
C
L
i
u
h
o
c
i
ng
h
a
i
T
qoga
h
N
L
a
ua
o
X
s
g
u
si
d
n
u
g
e
m
a
C
Cw
u
e
ta
be
T
t
h
o
aoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure E-3 : Runoff in the driest year in 20 (106 m3/a)
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Figure E-4 : Simulated hydrographs of the Cuito River (blue) and Cubango/Kavango River (red)
Figure E-5 : Vegetation Response to Flooding - Xakanaxa, Present Day
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100%
90%
h
80%
eac
70%
r
k
m
60%
Dry
200
50%
Pool
of
40%
Wet
30%
e
r
c
entage
P
20%
10%
0%
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Figure E-6 : Percentage of the 200-km study reach of the Boteti River that will be inundated
(wet); isolated pools (pool) and dry under the present-day simulated conditions
given climatic conditions that prevailed from 1973-2002.
E.6.
Scenario Selection for the EF Study
While the decision support tools that will be put in place could in future be used to make
preliminary assessments of the socio-economic and ecological consequences of specific
projects, the aim of the current study is not to do project level assessments, but to provide a
planning framework which encompasses most of the water resource development
aspirations of the three co-basin states. This would ensure that OKACOM has information at
hand to assess the consequences of development pathways spanning a range that is as
wide as possible. For this reason preference was given to the selection of a set of scenarios
that cover a broad continuum of development and that are positioned at regular intervals
across this continuum, rather than an approach that is based on an issue-driven, ad hoc
selection of scenarios.
The present, relatively undeveloped state of the basin provides a known reference point from
which extrapolations can be made to assess future development states. This "Present Day"
state represents one of the four scenarios that were assessed as part of the study. (A
climate change scenario will be assessed as an extension to the current project.) The four
development scenarios were constructed along the following lines:
· The Present Day scenario includes all existing water resource developments, notably:
o About 2 700 ha of irrigation in Namibia
o The urban water demands of Menongue and Cuito Cuanavale (Angola),
Rundu (Namibia), and Maun (Botswana)
· A low water use scenario which is based on the continuation of historical growth in
water demands in the three countries. Growth rates in Angola reflect the recent
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E-Flows Scenario Report Hydrology
acceleration associated with resettlement in de-mined areas. Increased water
consumption is mainly due to growth in urban and rural domestic, livestock and
irrigation water demands. The largest water demands are represented by:
o About 3 100 ha of irrigation in Namibia
o About 18 000 ha of irrigation along the Cuebe River in Angola
o One storage based and three run-of-river hydropower stations in Angola
· A medium growth, or "business-as-usual" scenario which includes
o About 8 400 ha of irrigation in Namibia
o Development of a first phase of the Eastern National Carrier (17 Mm3/a) for
water supply from the Kavango to Grootfontein and Windhoek,
o About 198 000 ha of irrigation at various locations in Angola
o One storage based and four run-of-river hydropower stations in Angola
· A high growth scenario which includes:
o About 15 000 ha of irrigation in Namibia.
o About 338 000 ha of irrigation at various locations in Angola
o Completion of all planned hydropower stations in Angola, i.e. one storage
based and nine run-of-river hydropower stations in Angola ,
o Completion of a second phase of the Eastern National Carrier (total capacity
100 Mm3/a),
o Development of a storage based water supply scheme for urban and industrial
water supply from a dam in the Boteti River to Maun.
o At these levels of demand, it was necessary to introduce a hypothetical dam
in the upper basin (Cuchi River) with a capacity of about 500 million m3 to
provide for shortfalls in irrigation water supply and inter-basin transfers.
Irrigation water demands make up the largest component of future water use. In Angola, the
high growth scenario provides for 338 000 ha in the upper catchments of the Cubango River
and in the lower reaches of the Cuito River, but excludes some 170 000 ha of previously
identified irrigation development upstream of the confluence of the Kavango and Cuito
Rivers. The Angolan team decided not to include this area due to a perception that the low
flows in the Kavango would not be sufficient to meet the associated demand. In Namibia, the
High scenario provides for about 15 000 ha of irrigation development upstream and
downstream of the confluence of the Kavango and Cuito Rivers. This area includes the so-
called "Green Scheme" and respects the decision by the Namibian Departments of
Agriculture Water Affairs (Policy Document No. 7/2/10/3) to limit the abstraction rate out of
the Okavango River upstream of the confluence with the Cuito to 5.5 m3/s, and downstream
to 27 m3/s. The water resource developments that were included in the scenarios are
described in more detail in EPSMO/Biokavango Report Number 5; Hydrology: Data and
Models.
The outcomes of scenarios depend on what is included as a water-resource development.
Changing the location, size or any other aspects of a possible development will change the
expected future flow regime and thus the expected ecological and social implications.
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E.7.
Hydrological Consequences of the Water Use Scenarios
General comments
The hydrological consequences of the water use scenarios can be summarised as follows:
· Current day inflows to the Delta of about 9 600 million m3/a decrease by about 370,
880 and 2 900 million m3/a relative to the present day mean annual runoff for the
Low, Medium and High development scenarios, respectively.
· Most of the water resource developments associated with the Low and Medium
scenarios are located in the Cuchi and Cuebe catchments, and the effects of these
can be seen in the middle and lower reaches of the Cubango / Kavango River. As an
example, dry season low flows at Kapako (and Rundu) would be reduced to about
50% of present day values.
· The combined water abstractions in the upper basin for the High scenario equate to
about 3 600 million m3/a. Of this, by far the largest component is made up of
irrigation water demands (3 300 million m3/a in Angola and 223 million m3/a in
Namibia), followed by the relatively smaller demands of the ENWC transfer (100
million m3/a), and the combined urban demands of Menongue, Cuito Cuanavale and
Rundu (22 million m3/a).
· In the High development scenario, large tracts of irrigation developments are located
along the lower reaches of the Cuito River. This has the effect of considerably
reducing the Cuito River's strong base flow contribution to the lower Okavango River.
The combined effect of all upstream developments substantially reduces the
permanent swamp area in the Delta, and virtually dries up the Boteti River.
· The hydrological impacts of the developments in the Cubango/Kavango sub-basin
(upstream of the confluence with the Cuito) is mitigated to some extent by the
presence of two large storage dams a hydropower storage near Mucundi on the
Cubango River (Low scenario), and another in the Cuchi catchment (High scenario).
While the main purpose of the Mucundi Dam is to provide generating head for
hydropower, hydropower releases in the dry season is available for downstream
abstractions such as the Eastern National Carrier.
· It is important to note that, were the storage dams not present, the postulated future
demands under the High scenario would not be met in its entirety. A test was done
by removing the storage dams, and re-simulating the High scenario. It can be seen
that, for example, the ENWC monthly water abstractions cannot be met for a much
longer percentage of time, were the dams not in place.
Site 1 - Capico
All of the developments envisaged for Capico were inserted into the Low Scenario, and so
the following consequences apply to all three scenarios. The developments are: run-of-river
abstractions that feed 28 000 ha of irrigation, increased urban supply for up to 100 000 more
people and a small run-of-river HEP diversion at Liapeca. These result in the mean annual
runoff in the Cuebe dropping to about half, because of water being diverted into croplands.
Diversions take place year round, but the biggest volumes are diverted during the dry
season. Figure 5-6 shows that in all future scenarios low flows are virtually depleted for
about 25% of the simulation period. The impact is greater in the dry season, which starts 3
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E-Flows Scenario Report Hydrology
months earlier, is more than 4 months longer and has flows close to zero. The wet season is
3 months shorter and the volume of flood water is about half of present.
Site 2 Mucundi
All of the developments for Capico still apply, and in addition further major developments in
hydropower generation and croplands are included. Run-of-river HEP schemes with
diversion structures are added with each scenario, but one storage based scheme with a
substantial dam wall. Irrigated cropland gradually increases to a maximum of 175 000 ha, all
areas using run-of-river abstraction, except for a large dam on the Cuchi River, which is
introduced in the High Scenario. The impacts on flow are not as severe as at Capico
because of the contribution of undeveloped tributaries. Mean annual runoff declines
gradually to about 80% of present, and the dry season starts about a month earlier and lasts
up to 2 months longer. Because of the continual abstractions, dry-season flows fall to less
than half of present flows in the Low and Medium Scenarios, but they increase again in the
High Scenario due to dam releases. Wet-season flows start later and with lesser floods,
because of filling of the dams on the Cubango and Cuchi, and are up to a month shorter.
Site 3 Cuito Cuanavale
Most developments included for the Cuito River are downstream of the Cuito-Cuanavale site
and so do not affect it. The scenarios include 50 000 more people in urban areas and a
small run-of-river HEP diversion on the Cuito River upstream of Cuito Cuanavale. These do
not have a noticeable impact on the flow regime although the HEP infrastructure might have
a, presently unknown, impact on sediment movement along the river. If only flow changes
are considered, the developments included for this site would have a minimal impact on the
river ecosystem.
Site 4 Kapako
All developments included for Capico and Mucundi are upstream of this site and so are
included, and in addition a further 48 000 ha of run-of-river irrigation in the Kapako area is
added gradually through the scenarios. There are no significant tributaries between Mucundi
and Kapako and so flow changes upstream are transmitted downstream without amelioration
of other inflows. Figure 5-8 shows the elevation of low flows (tail-end of the duration curve)
under the High scenario due to dry season releases from the two postulated storage dams in
the Cubango sub-basin. The annual volume of water flowing down the river progressively
declines to 80% of present and the dry-season flow falls by about half and the dry season
extends up to 1.5 months longer. The wet season is shorter by about the same length of
time with up to a 30% drop in volume but little change in flood onset time and size of flood
peak.
Sites 5 and 6 : Popa Rapids and Panhandle
All developments upstream in Capico, Mucundi, Cuito Cuanavale and Kapako are included,
plus a gradual increase of run-of-river irrigation along the lower Okavango and a large
increase along the lower Cuito River in the Medium and High scenarios to more than 178
000 ha above present (mostly in Angola), up to 130 m3/s more diversion in Namibia for urban
supply, and three additional run-of-river HEP structures, one with a dam wall height of 7.5 m.
These translate as a decline to 69% of mean annual runoff and a dry season that starts up to
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2 months earlier and is 3 months longer than present. Under the High Scenario, dry-season
flows drop to 18% of present. The flood season onset and peak are only slightly affected but
it is up to 2 months shorter and declines to about two-thirds of its present volume.
The Delta (Site 7 Xakanaka)
Due to the declining upstream inflows into the Delta, there is a decrease in all major types of
permanent swamp to as low as 22% of present under the High scenario, and an increase in
seasonal swamps into these areas. Dry flood-plain savanna also expands to more than four
times its present area, representing a significant drying-out of the Delta.
Delta Outflows (Site 8 Boteti)
The Thamalakane / Boteti River system receives outflows from the Delta and is highly
susceptible to changes in the flooding regime of the Delta. In addition, the length of river that
is wetted by inflows in any given year depends on the volume of inflows and state of the
groundwater aquifers in previous years. Flows in the system normally exhibit dry and wet
cycles of many years in length. Through the scenarios the number of years it contains water
would progressively decline until in the High Scenario it would be completely dry for most of
the time, holding water only in the wettest years.
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Table of Contents
1.
INTRODUCTION .............................................................................................. 24
1.1.
Background ....................................................................................................... 24
1.2.
Objectives of the EF assessment ..................................................................... 24
1.3.
The Study Area ................................................................................................. 25
1.3.1
Topography and Drainage ................................................................................ 25
Extent of the Basin .......................................................................................................... 25
The Okavango River Basin upstream of the Delta .......................................................... 27
The Okavango Delta ....................................................................................................... 28
1.4.
Layout of the report ........................................................................................... 29
2.
Hydrological Modeling of the Basin .................................................................. 30
2.1.
Hydrological Working Group ............................................................................. 30
2.2.
Hydrological Models ......................................................................................... 30
2.3.
Ecologically relevant flow indicators ................................................................. 31
3.
Current Water Resources Situation .................................................................. 35
3.1.
Climate .............................................................................................................. 35
3.2.
Water Resources of the Okavango River Upstream of the Delta ..................... 37
3.2.1
Distribution of Surface Water ............................................................................ 37
3.2.2
Occurrence of Droughts .................................................................................... 37
3.2.3
Flooding ............................................................................................................ 38
3.2.4
Hydrological Functions of the Cubango and Cuito Rivers ................................ 46
3.3.
The Delta .......................................................................................................... 47
3.4.
The Boteti River ................................................................................................ 48
3.5.
Variability of Okavango Stream Flows .............................................................. 49
3.5.1
Seasonal Variability .......................................................................................... 49
3.5.2
Inter Annual Variability ...................................................................................... 49
3.6.
Groundwater ..................................................................................................... 51
3.6.1
Geology and aquifer stratigraphy ...................................................................... 51
3.6.2
Recharge and Discharge .................................................................................. 52
3.6.3
Groundwater quality .......................................................................................... 52
4.
Formulation of the Water Use Scenarios .......................................................... 53
4.1.
Introduction ....................................................................................................... 53
4.2.
Previous Studies ............................................................................................... 53
4.3.
Scenario Selection for the EF Study ................................................................. 54
4.3.1
Approach .......................................................................................................... 54
4.3.2
Selected Scenarios ........................................................................................... 55
4.3.3
General comments on the in- or exclusion of scenario water demands ........... 56
5.
Hydrological Consequences of the Water Use Scenarios ................................ 62
5.1.
Introduction ....................................................................................................... 62
5.2.
Presentation and Discussion of Results ........................................................... 63
5.3.
The Upstream Basin ......................................................................................... 63
5.3.1
General comments ........................................................................................... 63
5.3.2
Site 1 - Capico .................................................................................................. 68
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5.3.3
Site 2 Mucundi ............................................................................................... 69
5.3.4
Site 3 Cuito Cuanavale .................................................................................. 71
5.3.5
Site 4 Kapako ................................................................................................ 71
5.3.6
Sites 5 and 6 : Popa Rapids and Panhandle .................................................... 73
5.4.
The Delta .......................................................................................................... 73
5.4.1
General comments ........................................................................................... 73
5.4.2
Site 7: Xakanaka ............................................................................................... 75
5.5.
Delta Outflows .................................................................................................. 76
5.6.
Process followed after the generation of hydrological summary data .............. 78
6.
Summary and Conclusions ............................................................................... 79
6.1.
The Upper Basin ............................................................................................... 79
6.1.1
General ............................................................................................................. 79
6.1.2
Site 1 - Capico .................................................................................................. 79
6.1.3
Site 2 Mucundi ............................................................................................... 79
6.1.4
Site 3 Cuito Cuanavale .................................................................................. 80
6.1.5
Site 4 Kapako ................................................................................................ 80
6.1.6
Sites 5 and 6 : Popa Rapids and Panhandle .................................................... 80
6.2.
The Delta (Site 7 Xakanaka) .......................................................................... 80
6.3.
Delta Outflows (Site 8 Boteti) ......................................................................... 80
7.
References ....................................................................................................... 82
APPENDIX A : ECOLOGICALLY RELEVANT FLOW STATISTICS
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List of Figures
Figure 1-1 The Okavango River Basin .................................................................................. 26
Figure 1-2 The Okavango River Delta, showing drainage into the Thamalakane / Boteti
System ................................................................................................................. 27
Figure 1-3 Map showing site locations .................................................................................. 29
Figure 2-1 : Hydrological Modeling Components ................................................................... 30
Figure 2-2 : Season Delineation ............................................................................................. 33
Figure 2-3 : Example of Flow Categories - Delta Inflows (Left: Present Day, Right: High
Development) ...................................................................................................... 34
Figure 3-1 : Mean Annual Rainfall (Perennial rivers shown in white and dry tributaries
shown in brown) (Source: Mendelsohn and el Obeid,) ........................................ 35
Figure 3-2 : Rainfall and gross open water evaporation at Menongue ................................... 36
Figure 3-3 : Rainfall and gross open water evaporation at Rundu ......................................... 36
Figure 3-4 : Rainfall and gross open water evaporation at Maun ........................................... 37
Figure 3-5: Mean Annual Runoff (106 m3/a) - Present Day .................................................... 39
Figure 3-6 : Runoff in the driest year in 20 (106 m3/a) ............................................................ 40
Figure 3-7 : 70% Exceedance Monthly Runoff (106 m3)- Present Day .................................... 41
Figure 3-8 : Flood Frequency Distribution of Annual Maximum Daily Flows - Rundu
(1945-2005) ......................................................................................................... 42
Figure 3-9 : Flood Frequency Distribution of Annual Maximum Daily Flows - Mukwe
(1949-2003) ......................................................................................................... 42
Figure 3-10 : A school and homes situated in the flood plain in Caprivi region ...................... 44
Figure 3-11 : Construction in the north that partly contributed to flood damages ................... 44
Figure 3-12 : Culverts constructed in the northern central regions were too small to
accommodate flood and storm water ................................................................... 44
Figure 3-13 : Simulated hydrographs of the Cuito River (blue) and Cubango/Kavango
River (red) ............................................................................................................ 47
Figure 3-14 : Vegetation Response to Flooding - Xakanaxa, Present Day ............................ 48
Figure 3-15 : Percentage of the 200-km study reach of the Boteti River that will be
inundated (wet); isolated pools (pool) and dry under the present-day
simulated conditions given climatic conditions that prevailed from 1973-2002.... 49
Figure 3-16 : Average Annual Runoff at Mukwe .................................................................... 50
Figure 3-17 : Observed monthly flows at at Maun, Samedupi and Rakops ........................... 50
Figure 4-1 : Approximate positions of water-resource developments included in the
wateruse scenarios in the upper portion of the catchment .................................. 60
Figure 4-2 Approximate positions of water-resource developments included in the water-
use scenarios in the lower portion of the catchment. ........................................... 61
Figure 5-1 Simulated monthly inflows to the Delta all scenarios (1959-2001). .................. 62
Figure 5-2 : Percentage of time (months) that the ENWC abstraction is met ........................ 64
Figure 5-3 : Mean Annual Runoff (106 m3/a) - Low Water Use (Blue) compared to Present
Day (Orange) ....................................................................................................... 65
Figure 5-4 : Mean Annual Runoff (106 m3/a) - Medium Water Use (Blue) compared to
Present Day (Orange) .......................................................................................... 66
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Figure 5-5 : Mean Annual Runoff (106 m3/a) - High Water Use (Blue) compared to
Present Day (Orange) .......................................................................................... 67
Figure 5-6 : Monthly Flow Duration Curves for the Cuebe River at Capico (Site 1) ............... 68
Figure 5-7 : Monthly Flow Duration Curves for the Cubango River at Mucundi (Site 2) ........ 69
Figure 5-8 : Monthly Flow Duration Curves for the Kavango River at Kapako (Site 4) .......... 72
Figure 5-9 : Monthly Flow Duration Curves for the Okavango River at Popa Rapids (Site
5) .......................................................................................................................... 73
Figure 5-10 : Time series of vegetation/habitat assemblages for the Low Scenario .............. 75
Figure 5-11 : Time series of vegetation/habitat assemblages for the Medium Scenario ........ 76
Figure 5-12 : Time series of vegetation/habitat assemblages for the High Scenario ............. 76
Figure 5-13 : Percentage of the Boteti River study reach that will be inundated (wet);
isolated pools (pool) and dry under the Present day Scenario ............................ 77
Figure 5-14 : Percentage of the Boteti River study reach that will be inundated (wet);
isolated pools (pool) and dry under the Low Scenario ......................................... 77
Figure 5-15 : Percentage of the Boteti River study reach that will be inundated (wet);
isolated pools (pool) and dry under the Medium Scenario .................................. 78
Figure 5-16 : Percentage of the Boteti River study reach that will be inundated (wet);
isolated pools (pool) and dry under the High Scenario ........................................ 78
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List of Tables
Table 1-1 Location of the eight EFA sites ............................................................................ 28
Table 3-1 : Flood peak recurrence intervals ........................................................................... 38
Table 3-2 : Impact of the 2009 flood disaster ......................................................................... 45
Table 4-1 : Estimated wildlife water consumption (adult animals) .......................................... 56
Table 4.2 Water-resource developments included in each scenario ................................... 58
Table 5.1 Median values for the ecologically-relevant summary statistics for each
scenario for Site 1: Capico. .................................................................................. 68
Table 5.2 Median values for the ecologically-relevant summary statistics for each
scenario for Site 2: Mucundi. ............................................................................... 69
Table 5.3 Median values for the ecologically-relevant summary statistics for each
scenario for Site 3: Cuito Cuanavale. .................................................................. 71
Table 5.4 Median values for the ecologically-relevant summary statistics for each
scenario for Site 4: Kapako. ................................................................................. 72
Table 5.5 Vegetation types used in the model ..................................................................... 75
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Acronyms and abbreviations
DWA
Department of Water Affairs, Botswana
DWAF
Department of Water Affairs and Forestry, Namibia
EFA
Environmental Flow Assessment
ENWC
Eastern National Water Carrier
EPSMO
Environmental Protection and Sustainable Management of the Okavango
River Basin
ha hectare
HEP
Hydro-Electric Power (Station)
HOORC
Harry Oppenheimer Okavango Research Centre
IUA
Integrated Units of Analysis
MAR
Mean Annual Runoff
OBSC
Okavango Basin Steering Committee
OKACOM
Okavango River Basin Water Commission
PD Present
Day
SAP
Strategic Action Programme
TDA
Transboundary Diagnostic Analysis
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1.
INTRODUCTION
1.1.
Background
An Environmental Protection and Sustainable Management of the Okavango River
Basin (EPSMO) Project is being implemented under the auspices of the Food and
Agriculture Organization of the United Nations (UN-FAO). One of the activities is
to complete a transboundary diagnostic assessment (TDA) for the purpose of
developing a Strategic Action Plan for the basin. The TDA is an analysis of current
and future possible causes of transboundary issues between the three countries of
the basin: Angola, Namibia and Botswana. The Okavango Basin Steering
Committee (OBSC) of the Okavango River Basin Water Commission (OKACOM)
noted during a March 2008 meeting in Windhoek, Namibia, that future transboundary
issues within the Okavango River basin are likely to occur due to developments that
would modify flow regimes. The OBSC also noted that there was inadequate
information about the physico-chemical, ecological and socioeconomic effects of
such possible developments. OBSC recommended at this meeting that an
Environmental Flow Assessment (EFA) be carried out to predict possible
development-driven changes in the flow regime of the Okavango River system, the
related ecosystem changes, and the consequent impacts on people using the river's
resources.
The EFA is a joint project of EPSMO and the Biokavango Project. The EFA
methodology is based on the evaluation of a reference flow regime ("natural" or
"present day") and a range of future flow regimes resulting from water resource
developments to make predictions of change for a number of ecological indicators;
these usually cover channel geomorphology, water quality, riverine vegetation, fish
and aquatic macro-invertebrates. For the EFA, modified future flow regimes are
produced with hydrological (and hydraulic) models of the river basin and the delta.
This report (Volume 6) is the second of two reports produced by the EFA
hydrological working group. It provides an overview of the hydrological
characteristics of the basin and describes the outcomes of the hydrological
modelling of present and possible future flow regimes.
The report should be read in conjunction with the Hydrology: Data and Models
Report (Volume 5), which describes the models, hydrological data and
development information that form the basis for the simulation of flow regimes
at different points along the Okavango River system, including the Delta.
1.2.
Objectives of the EF assessment
There were two main objectives.
· Complete a basin-wide EFA of the Okavango River system as a major part of
the wider Technical Diagnostic Analysis. This would be done through
several subsidiary objectives:
o Collate all existing hydrological data on the river system and set up a
basin hydrological model that could simulate flows under various
possible future development scenarios
o Reach agreement with the three riparian governments on the
scenarios to be explored
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o Bring together specialists in a range of relevant disciplines from
across the basin to share knowledge and data, and reach consensus
on the:
relationships between flow and a series of biophysical
indicators of the river system
relationships of the condition of the ecosystem and social
indicators
o Develop a DSS that would capture these relationships and produce
predictions of ecological and social change for each scenario that
would complement the macroeconomic predictions emanating from a
separate exercise
o Incorporate the EFA findings in the TDA document.
· Promote basin-wide communication and collaboration, and build capacity in
collaborative basin-wide Integrated Water Resource Management in all
disciplines in all three countries. This was done by appointing a full
biophysical and socio-economic team from each of the three countries, with
planning, coordination and training done by a Process Management Team.
1.3.
The Study Area
1.3.1
Topography and Drainage
Extent of the Basin
The Okavango River Basin consists of the areas drained by the Cubango, Cutato,
Cuchi, Cuelei, Cuebe, and Cuito rivers in Angola, the Okavango River in Namibia
and Botswana (in Namibia, the river is called the Kavango), and the Okavango Delta.
This basin includes the Omatako River catchment in Namibia which is
topographically linked to the Okavango River, but due to the low mean annual rainfall
(less than 400 mm/year in the headwaters), the river is ephemeral. Due to the sandy
nature of the terrain, no surface runoff reaches the Okavango River. Outflows from
the Okavango Delta are drained through the Thamalakane and then Boteti Rivers,
the latter eventually joining the Makgadikgadi Pans. The Nata River, which drains
the western part of Zimbabwe, also joins the Makgadikgadi Pans. The Selinda
spillway is located in a local depression and provides an occasional link to the
Zambezi River. In times of high flow the Okavango overtops a local high point in the
Selinda and spills toward the Cuando/Chobe/Linyanti system (2009 Satellite images
provided the first recorded evidence of overflow from the Kavango Panhandle
reaching the Kwando/Linyanti/Chobe/Zambezi system through the Selinda Channel).
On the basis of topography, the Okavango River Basin thus includes the
Makgadikgadi Pans and Nata River Basin and has an occasional link to the Zambezi
Basin. This study, however, focuses on the parts of the basin in Angola and
Namibia, and the Panhandle/Delta/Boteti River complex in Botswana. The
Makgadikgadi Pans and Nata River are not included.
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Kavango
Okavango Delta
Figure 1-1
The Okavango River Basin
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Figure 1-2
The Okavango River Delta, showing drainage into the Thamalakane /
Boteti System
The Okavango River Basin upstream of the Delta
The upstream basin is drained by the two main tributaries of the Okavango, namely
the Cubango River in the west, and the Cuito River in the east. The western
headwaters of the Cubango River are characterised by a series of north-south
flowing tributaries with a high drainage density draining the western highlands at an
altitude of around 1800m. From here, the Cubango River flows south through a
gently undulating landscape for about 600 km before it turns toward the east, forming
the border between Angola and Namibia. The confluence of the Cuito and Okavango
Rivers is located about 300km after the Cubango River first reaches the Namibian
border.
The Cuito River rises further to the east than the Cubango River but mean annual
precipitation is of the same order as for the upper Cubango River catchhment. Unlike
the Cubango River, the Cuito River meanders through some very wide flood plains in
Kalahari Sand deposits in southern Angola. While river flows in the Cubango and its
tributaries are characterised by a strong seasonal variation and low dry season base
flows, the Cuito and its tributaries show much less seasonal variation with dampened
wet season peak flows and elevated dry season base flows, mainly due to
considerable groundwater recharge and discharge in this part of the basin.
Just after the village of Mukwe, the river turns more southwards, crosses the
Namibian Caprivi Strip and enters Botswana. Seventy kilometres further downstream
the mainstream starts to divide and the Okavango Delta is formed.
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In terms of catchment area, the Omatako River in Namibia is the biggest tributary to
the Okavango River, but there is no record of this ephemeral river system ever
having flowed as far as the confluence.
The Okavango Delta
The Okavango Delta can be classified in terms of flow regime and habitat; permanent
swamps, seasonal swamps, occasionally flooded areas, and drylands (McCarthy et
al. 1988; Murray-Hudson et al. 2006). The upper part of the delta, commonly referred
to as the Panhandle, consists of a 10-15 km wide and 150 km long valley within
which the main channel meanders through. The Okavango River in the Panhandle
splits into the western distributary, the Thaoge River, Boro River and Maunachira
River. Boro sends out Xudum system in the middle reaches on its west and outflows
to Lake Ngame through Kunyere River while Maunachira splits to form Mboroga and
Santantadibe Rivers (Figure 1-2). Flow of the Okavango River is therefore partitioned
within the delta. Over-spilling of flow from channels onto adjacent floodplains is a
common feature within the delta during the high flow period, and in some cases the
spilled water joins the same or different channel (Wolski and Murrary-Hudson 2006).
Of the three main distributaries, the Thaoge River in the west terminates in a series
of lagoons and extensive floodplains near its upper end. The Boro upstream flows
through lagoons and floodplains and is a single more or less confined channel in the
downstream discharging into Thamalakane River and outflows to the Boteti River.
Channel banks are very porous as most of them are made of papyrus. The
substratum of channels is very permeable resulting in substantial exchange of water
between channels, floodplains, and groundwater.
Within the Okavango River Basin, representative areas that are reasonably
homogeneous in character were delineated and used to represent much wider areas.
One or more representative sites were chosen in each area as the focus for data-
collection activities. The results from each representative site could then be
extrapolated over the respective wider areas. The existing and new hydrological
models were selected and configured to provide scenario flow sequences at these
sites. The basis for selection of the sites is decribed in EPSMO/Biokavango Report
Number 4; Delineation Report.
The sites chosen by the national teams are listed in Table 1-1 and shown on Figure
1-3.
Table 1-1
Location of the eight EFA sites
EFA Site No
Country
River
Location
1 Angola
Cuebe
Capico
2 Angola
Cubango
Mucundi
3 Angola
Cutio Cuito
Cuanavale
4 Namibia
Okavango
Kapako
5 Namibia
Okavango
Popa
Falls
Panhandle at
6 Botswana
Okavango
Shakawe
7
Botswana
Khwai
Xakanaka in Delta
8 Botswana
Boteti Chanoga
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Figure 1-3
Map showing site locations
1.4.
Layout of the report
Chapter 1: Introduction
Chapter 2:
Hydrological Modeling of the Basin
Chapter 3:
Current Water Resource Situation
Chapter 4:
Formulation of the water use scenarios
Chapter 5:
Hydrological Consequences of the Water Use Scenarios
Chapter 6:
Conclusions
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2.
Hydrological Modeling of the Basin
2.1.
Hydrological Working Group
A hydrological working group consisting of hydrologists from the three co-basin
states was established to develop and populate the hydrological and hydraulic
models for the river basin and the delta and to develop flow scenarios. The work was
undertaken during the course of five week-long hands-on workshops in Maun,
Gaborone and Windhoek.
2.2.
Hydrological Models
A series of hydrological and hydraulic models have in the past been developed to
reproduce flow conditions observed in the Okavango Basin and Delta. In order to
provide the hydrological information required for the EFA, a suite of existing and new
models were used. The models were selected and configured to provide current day
(baseline) and scenario flow sequences at the eight EFA sites. Details of the models
and data that were used to configure these are provided in EPSMO/Biokavango
Report Number 5; Hydrology: Data and Models. A short summary is provided here
for ease of reference.
The modelling sequence and linkages between the models are shown in Figure 2-1
below.
Figure 2-1 : Hydrological Modeling Components
The models which were selected for use in the EFA are:
· Catchment hydrology: Estimates of naturalised (undeveloped) long-term
runoff were obtained from an existing Pitman-based rainfall-runoff model
developed as part of the EU funded WERRD project (Hughes et. al. 2006).
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The model was configured to provide runoff sequences at the outlets of 24
distinct sub-catchments upstream of the Delta.
· Systems Model: As part of this project, the monthly time-step WEAP
systems model was selected and used to configure a reference (Present
Day), Low, Medium and High Development scenarios. Inputs to the model
include the undeveloped runoff sequences for 24 sub-catchments produced
by the Pitman model, irrigation scheme and urban abstractions, in channel
dams for irrigation water supply, inter-basin transfers, run-of-river and storage
based hydropower schemes.
· HOORC Delta Model: A semi-conceptual model which was previously
developed by the Harry Oppenheimer Okavango Research Centre (HOORC)
(Wolski et. al. 2006) was used to model inundation frequencies and extents at
the Delta EFA sites. The model operates on a monthly time step and
includes a dynamic ecotope model that simulates the responses of vegetation
assemblages to changes in hydrological conditions. Scenario inflows to the
model are provided by the WEAP simulations of basin runoff.
· DWA Delta Model: A MIKE-SHE / MIKE 11 hydrodynamic model which was
previously configured by Botswana DWA and DHI for the Okavango Delta
Management project (ODMP, 2008) was used to model flow velocities and
depths at the Delta EF sites. Scenario flow sequences simulated with WEAP
for Mohembo were used as inflow sequences for the Delta model, after
disaggregating the monthly flow sequences to a daily time step.
· Thamalakane/Boteti Model: Delta outflows simulated by the HOORC model
are routed along the Thamalakane/Boteti system with a linear reservoir
spreadsheet model (Mazvimavi, 2008) to derive scenario flow sequences at
the Boteti EF site. The model was incorporated into the HOORC Delta Model
and improved to provide estimates of wetted river length and state changes of
the system.
· Disaggregation and Hydro-Statistics: A custom utility was developed to
disaggregate the simulated monthly WEAP flow sequences to daily flow
sequences, to delineate flow seasons (dry, wet and transition) for each year
of the 43 year long sequences, and to calculate ecologically relevant flow
statistics ("flow indicators").
2.3.
Ecologically relevant flow indicators
The ecosystem response curves have been formulated to respond to variations in
daily flow regimes. The catchment hydrology that was previously developed (and
thus the WEAP systems model that was developed for this study) operates on a
monthly time step. Disaggregation of simulated monthly volumes was done by
distributing these monthly volumes according to the relative magnitude of daily flows
measured at a nearby station during the corresponding month in the measured flow
record. In periods for which no measured flows are available, a proxy month in the
measured flow record was selected by finding a month with a measured volume that
has a similar exceedance probability as the simulated volume. The disaggregated
daily flow sequences were then used to delineate the dry season, a transition season
leading into the wet season, a wet season, and a second transition season leading
into the next year's dry season.
A set of threshold-based rules were developed to identify the starting dates of the
seasons. The rules were applied to the disaggregated daily flow sequences to
calculate flow indicators for each year in the record, and for the entire flow sequence.
An example of season delineation, and the rules that these are based on, are shown
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in Error! Reference source not found.. An example of the calculated flow
indicators is shown in Figure 2-3
Error! Reference source not found.. A detailed description of the ecological
relevance and selection of the flow indicators is given in EPSMO/Biokavango Report
Number 2; Process Report.
Details on the division of the flow regime and the generation of ecologically-relevant
summary statistics are provided in Report 03/2009: Guidelines for data collection,
analysis and scenario creation.
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Figure 2-2 : Season Delineation
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Figure 2-3 : Example of Flow Categories - Delta Inflows (Left: Present Day, Right: High Development)
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3.
Current Water Resources Situation
3.1.
Climate
Rainfall in the Okavango River Basin occurs in the period from October to May, while the
rest of the year is dry. The northern parts of the basin receive the highest rainfall in the
December to January period, while the southern parts such as Maun have peak rainfall
during January and February. Mean annual rainfall varies from about 1300 mm/a in the
Huambo and Cuito areas in the headwaters of the basin, to 560 mm/a at Rundu,
550 mm/a at Mohembo, and 450 mm/a at Maun (Figure 3-1).
Figure 3-1 : Mean Annual Rainfall (Perennial rivers shown in white and dry tributaries
shown in brown) (Source: Mendelsohn and el Obeid,)
Rainfall has a high inter-annual variability, with the coefficient of variation being 20% on
the well-watered headwaters and 50% in the dry southern parts. There is a tendency for
years to group, with above average rainfall for a while followed by generally years with
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E-Flows Scenario Report Hydrology
below average rainfall. Due to the high inter-annual variability, years with extremely low
rainfall occur frequently, particularly on the southern parts of the basin.
Average daily maximum temperatures range between 30-35°C from August to March in
the Namibian and Botswana parts of the basin. Average minimum daily temperatures are
in the 7-10°C range during the cool season, June to July. The average daily
temperatures are greater than 20°C throughout the basin. Evaporation increases from
the north to south in line with increasing temperatures. The mean annual open water
evaporation increases from about 1350 mm/a for Menongue, to about 1950 mm/a for
Rundu and 1650 mm/a for Maun. Highest evaporation rates occur in September and
October (Figure 3-2 to Figure 3-4). The average monthly evaporation rate is greater
than monthly rainfall for all months in the middle to southern parts of the basin, indicating
a semi-arid climate.
Menongue
250
200
150
Evaporation
100
Rainfall
50
0
Figure 3-2 : Rainfall and gross open water evaporation at Menongue
Rundu
250
200
150
Evaporation
100
Rainfall
50
0
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Figure 3-3 : Rainfall and gross open water evaporation at Rundu
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Maun
250
200
150
Evaporation
100
Rainfall
50
0
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Figure 3-4 : Rainfall and gross open water evaporation at Maun
3.2.
Water Resources of the Okavango River Upstream of the Delta
3.2.1
Distribution of Surface Water
Figure 3-5 shows the accumulation of mean annual runoff along the main tributaries of
the Okavango upstream of the Delta. The runoff estimates are based on Pitman
modeling undertaken for the WERRD and TwinBas studies, and incorporated into the
WEAP model developed for the Okavango EFA Study. The estimates are for the period
spanning October 1959 to September 2002. Runoff of about 10 200 million m3/a is
generated in the upper catchments of the basin (upstream of the confluences of the
Cubango and Cuartir Rivers in the west, and the Cuito and Longa Rivers in the east).
Downstream of these points, the catchments of the lower Cubango/Kavango and Cuito
River contribute very little additional runoff. Large losses and some abstractions reduce
the cumulative present day runoff to about 9 600 million m3/a at the upper end of the
Delta at Mohembo.
Current water abstractions in the upper basin (upstream of Mohembo) amount to about
60 million m3/a (or about 47 million m3/a if the demands from the nearly completed
Missombo irrigation scheme on the Cuebe River is excluded). Besides the Missombo
scheme, significant Angolan demands include the urban water abstractions of Menongue
(about 9 million m3/a) and Cuito Cuanavale (about 2 million m3/a). Namibian demands
include the urban and industrial demands of Rundu (about 2.8 million m3/a), and
irrigation water demands of about 33 million m3/a. Water demands in Botswana include
rural demands of about 4 million m3/a around the fringes of the Delta and combined
urban and rural demands of Maun and surrounding areas of about 21 million m3/a.
3.2.2
Occurrence of Droughts
In very dry years (1:20 year drought conditions), the flows in the river are significantly
restricted as shown by the flows in Figure 3-6. Only about 3 000 million m3/a might be
derived from the Cubango and 3 100 million m3/a from the Cuito, yielding only
6 100 million m3/a at Mohembo. (The flows shown in Figure 3-6 closely resemble
conditions experienced in 1998).
37
E-Flows Scenario Report Hydrology
Figure 3-7 shows the accumulation of present day monthly runoff volumes that are
equaled or exceeded for 70% of the months in the 42 year simulation period. The
volumes give an indication of run-of-river yields that are available at various points in the
system. It can be seen that the Cuito River plays a major role in sustaining the low flows
entering the Okavango Delta.
3.2.3
Flooding
Flood Occurrence
To provide an indication of the occurrence and magnitude of floods in the study area,
estimates of flood peak recurrence intervals were made by fitting a number of probability
distributions to annual maxima of daily flows at Rundu and Mukwe (Figure 3-8 and
Figure 3-9). For both stations, the General Extreme Value (GEV) distribution provided
the best fit. Estimates of flood peaks and associated return periods are shown in Table
3-1 below.
Table 3-1 : Flood peak recurrence intervals
Station
Rundu
Mukwe
Selected
Gen. Extreme Value
Gen. Extreme Value
Distribution
Parameters
k=-
k=-
0.13439 s=183.8 m=443.99
0.16686 s=197.86 m=570.75
Return Period
Flood Peak (m3/s)
Flood Peak (m3/s)
(years)
1:2 510
641
1:5 694
833
1:10 801
942
1:20 894
1034
1:50 1002
1138
1:100 1075
1206
38
E-Flows Scenario Report Hydrology
Cuanavale
ai
Khw
Ca
C
Gomoti
c
u
u
irir
C
c
L
i
u
h
o
c
n
i
g
h
a
T
qoga
i
h
N
L
a
ua
o
X
s
g
u
si
d
n
u
g
e
m
a
C
Cw
u
e
ta
be
T
to
haoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure 3-5:
Mean Annual Runoff (106 m3/a) - Present Day
39
E-Flows Scenario Report Hydrology
Cuanavale
Khwai
Ca
C
Gomoti
c
u
u
iri
c
r
C
L
i
u
h
o
c
i
ng
h
a
i
T
qoga
h
N
L
a
ua
o
X
s
g
u
si
d
n
u
g
e
m
a
C
Cw
u
e
ta
be
T
t
h
o
aoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure 3-6 : Runoff in the driest year in 20 (106 m3/a)
40
E-Flows Scenario Report Hydrology
Cuanavale
Khwai
Ca
C
Gomoti
c
ui
u
rir
C
c
L
i
u
h
o
c
n
i
g
h
a
i
T
qoga
h
N
L
a
ua
o
X
s
g
u
si
d
n
u
g
e
m
a
C
Cw
u
e
ta
be
T
t
h
o
aoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure 3-7 :
70% Exceedance Monthly Runoff (106 m3)- Present Day
41
E-Flows Scenario Report Hydrology
Probability Density Function
0.28
0.24
0.2
0.16
x
)
f(
0.12
0.08
0.04
0
-0.04
200
400
600
800
1000
x
Histogram
Gen. Extreme Value
Gen. Pareto
Gumbel Max
Lognormal
Figure 3-8 : Flood Frequency Distribution of Annual Maximum Daily Flows - Rundu (1945-
2005)
Probability Density Function
0.32
0.28
0.24
0.2
0.16
x)
f(
0.12
0.08
0.04
0
-0.04
200
400
600
800
1000
x
Histogram
Gumbel Max
Lognormal
Gen. Extreme Value
Gen. Pareto
Figure 3-9 : Flood Frequency Distribution of Annual Maximum Daily Flows - Mukwe (1949-
2003)
The Rundu and Mukwe flow measuring stations are located upstream and downstream
of the confluence of the Kavango and Cuito Rivers, respectively. From Table 3-1 it can
42
E-Flows Scenario Report Hydrology
be seen that flood peak contributions from the Cuito River cause a relatively small
increase to flood peaks downstream of the confluence. This is due to the difference in
flood response (lag) times of the two sub-basins, with the Cubango/Kavango floods
rising much faster, and peaking at higher levels, than the Cuito.
The 2009 Flood
The Cuvelai and Okavango regions experienced one of the worst flood disasters during
the year 2009. In Namibia, the 2009 flood affected six regions in northern and north
eastern regions (Caprivi, Kavango, Ohangwena, Oshana, Oshikoto and Omusati region)
from early February 2009. Although the flood waters have completely drained off in the
four northern central regions, many areas along the Zambezi, Chobe, Kwando rivers and
Lake Liambezi basin in Caprivi region were still inundated in May 2009.
The causes of the flood was a combination of the above-normal rainfall received in
affected regions and the high inflows in the Cuvelai basin, Kwando and Kavango rivers
with flood waters from southern Angola. The Caprivi region floods were due to the high
inflows of the Zambezi River from heavy rain falls in Zambia.
The flood in the Cuvelai was higher than the flood that occurred in 2008, which then was
already said to be the highest in living memory. The floods in the Kavango and Zambezi
rivers were the highest on record since 1969, and the flood in the Kwando River was the
highest on record (starting in the sixties). Satellite images provided the first recorded
evidence of overflow from the Kavango Panhandle reaching the
Kwando/Linyanti/Chobe/Zambezi system through the Selinda Channel.
Due to the extensive nature and potential long term impact of the floods, on 17 March
2009 the President of the Republic of Namibia H.E. President Hifikepunye Pohamba
declared a national emergency for the flood affected areas appealing for external
assistance.
Although historically flooding in Cuvelai basin, Kavango, Zambezi and Chobe rivers have
been occurring, the 2009 flood has so far been the largest in terms of the geographical
area affected. The extensive nature of the impact of the 2009 floods was attributed to
increased population settlement in the Cuvelai basin and in the flood plains in Caprivi
and Kavango regions, road and rail construction and emerging informal settlements in
peri-urban areas that interfered with the natural river flows. Flooding in some urban
areas in Ondangwa, Outapi, Helao Nafidi and Katima Mulilo was mainly due to
inadequate storm water drainage. The other major risk factor were the construction of
public and private infrastructure such as railway line, roads, homes and schools in the
flood plain without disaster risk reduction considerations (Figure 3-10). There certainly is
a need to find a lasting solution to people who are continuously affected by floods due to
their location in the flood prone areas.
43
E-Flows Scenario Report Hydrology
Figure 3-10 : A school and homes situated in the flood plain in Caprivi region
Road construction and small culverts contributed to flooding as these impeded the flow
of storm water (Figure 3-11 and Figure 3-12 below).
Figure 3-11 : Construction in the north that partly contributed to flood damages
Figure 3-12 : Culverts constructed in the northern central regions were too small to
accommodate flood and storm water
44
E-Flows Scenario Report Hydrology
Impact of the 2009 Flood Disaster
The 2009 flood disaster caused an estimated N$1.7 billion (1% of Gross Domestic
Product) worth of damages and losses to the public and the private sectors. The private
sector experienced N$800.4m worth of damages and N$600.3m losses and thus
experienced the higher burden of the flood impact. The PDNA, Nam-VAC and other local
assessments revealed that, the productive sector mainly agriculture, commerce (trade
and markets) were among the worst affected sectors with an estimated 70-80% loss of
crop production in the 2009/10 consumption year (NamVac 2009). The flood disaster
affected people that were recovering from another devastating flood disaster of 2008
thus further compromising the resilience of the affected communities. Furthermore the
cumulative effect of 2008 and 2009 floods preceded by a devastating drought of 2007
severely have reduced the resilience of a significant number of severely poor and poor
households. Table 3-2 below shows the impact of the 2009 flood disaster by region.
The six affected regions are resident to nearly sixty percent (60%) of Namibia's
population and thus have the highest population densities. Due to the high population
concentrations in the flood high risk regions, the 2009 flood disaster affected 56.1% of
the total population flood affected regions making up 32% of the county's population see
Table 1 below. Flood disaster in the four central northern regions where 41% of the
population resides has brought in a new dimension to NDMS in Namibia. NDMS was
used to dealing with no more than 20,000 people requiring emergency humanitarian
support caused by floods in any year mostly confined to Caprivi region. In the past two
years it has had to deal with first ten times and then thirty times more i.e. 215,257 in
2008 and 677,5421 in 2009 (Directorate Emergency Management: Report on National
Response to 2008 Flood Disaster and FEMCO report 2009).
Table 3-2 : Impact of the 2009 flood disaster
Region
Caprivi
Kavang
Ohangwen
Omusati Oshan
Oshikoto
Total
o
a
a
Total population (2009)2
87,058
257,347 261,323
243,657 176,58
181,304
1,207,27
6
5
Number of people affected
26,263
9,000
133,703
228,842 161,91
117,818
677,542
(30.2%)
(3.5%)
(51.2%)
(93.9%)
6
(65%)
(56.1%)3
(91.7%
)
No displaced
26,263
9,000
12,056
401
8,549
276
56,545
Number in relocation
19,738 4,718
1,296 564 2,478
138 28,932
camps
Number deaths
3
0
22
32
48
0
105
No of schools affected
29
7
63
107
83
39
328
No of school children
6,571 2,366
24,355 39,163
15,301
6,014
93,770
affected
Health facilities affected
4
2
10
10
5
1
32
Health facilities closed
1
0
0
0
4
1
5
No of SMEs affected
0
28
387
250
350
53
1,068
1 Figure worked out based on the population of the affected constituencies and based on the 2001
population projections.
2 Population projection 2009. Source: Namibia Population Projection. 2001.
3 People affected as a percentage of total population in the affected regions
45
E-Flows Scenario Report Hydrology
No of farmers with crop
2,790 968 5,671 4,392
3,437
7,496
24,754
fields affected
Hectares of crop fields
2,854
362.41 10,117
15,652 6,900 17,323 53,208
damaged
Number of livestock
3,000
0 0
0 0 0 3,000
affected
Number of livestock lost
18
0
2,161
693
2,093
5,038
10,003
Number of wild life
300
0
0
0
0
0
300
Number of roads damaged
2
2
5
12
8
4
33
Source: FEMCO, Kavango and Caprivi Regional Councils' flood report 2009.
3.2.4
Hydrological Functions of the Cubango and Cuito Rivers
The northern parts of the Cubango sub-basin are underlain by Pre-Cambrian granites,
some Karoo Group sandstone and mudstone. The hard rock has low hydraulic
conductivity and is overlain with a relatively thin mantle of Kalahari sand which is
interrupted by outcrops of granite along the banks of the Cubango, Cutato, Cuchi, Cuelei
and Cuebe Rivers. The sub-basin has a high surface water drainage density, with
numerous small tributaries draining the area from north to south. Together, these factors
indicate limited groundwater storage, which explains the low dry season base flows and
strong seasonal variation of discharge observed in the Cubango River. This is illustrated
by the fact that, on average, the driest six months of the year contribute only about 23%
of the total annual runoff of the Cubango River.
Water demands for irrigation and urban use peak during the dry season. Unless wet
season flows are stored in dams, yields of water abstraction schemes are limited by the
availability of dry-season flows. In the Cubango/Kavango sub-basin, this places a
relatively low ceiling on water availability for consumptive use. This was illustrated in the
simulation of the scenarios, where it was shown that, even under low water development
conditions, planned developments along the Cuebe River would virtually dry-up the
currently perennial river. In recognition of this fact, the Namibian Department of
Agriculture and the Department of Water Affairs has taken a decision to limit the
Namibian abstraction rate out of the Okavango River upstream of the confluence with the
Cuito to 5.5 m3/s, and downstream to 27 m3/s (Liebenberg, 2009).
The Cuito sub-basin is underlain by thick deposits of Kalahari sands and is characterised
by low drainage density, high baseflows, and a relatively small seasonal variability,
indicating considerable groundwater recharge and discharge. In sharp contrast with the
Cubango, 40% of the total annual runoff occur during the six driest months of the year.
Runoff generated in the Cubango River catchments is somewhat more than the
contribution of the Cuito River catchments (5 600 and 4 600 million m3/a, respectively).
Simulated average monthly hydrographs for the two rivers just upstream of their
confluence are shown in Figure 3-13. The figure illustrates the striking difference in the
seasonality of the two rivers, and also shows that discharges in the Cuito River during
the low flow months of September and October are on average about twice those of the
Cubango/Kavango.
46
E-Flows Scenario Report Hydrology
Figure 3-13 : Simulated hydrographs of the Cuito River (blue) and Cubango/Kavango River
(red)
3.3.
The Delta
The impact of upstream developments on inflows to the Delta can be assessed in terms
of changes to the extent, duration and frequency of flooding in the Delta. For the
Okavango EFA Study, these changes have been related to changes in vegetation
assemblages (EPSMO/Biokavango Report Number 5; Hydrology: Data and Models).
Figure 3-14 shows a timeline of vegetation changes in the Eastern Delta under present
levels of water use in the upstream basin. It can be seen that the proportion of grassland
and savanna on the periphery of the Delta expands in dry periods such as the one that
occurred in the mid-1990s.
47
E-Flows Scenario Report Hydrology
Figure 3-14 : Vegetation Response to Flooding - Xakanaxa, Present Day
3.4.
The Boteti River
Flows in the Thamalakane / Boteti River system receives outflows from the Delta and is
highly susceptible to changes in the flooding regime of the Delta. In addition, the length
of river that is wetted by inflows in any given year depends on the volume of inflows and
state of the groundwater aquifers in previous years. The HOORC model was used to
simulate state changes (changes from a wet river, isolated pools or dry riverbed) along a
200 km reach of the Boteti River under different Delta flooding regimes. The sensitivity
of the wetted length to inflows (note the dry period in the 1990s) can cllearly be seen from
Figure 3-15.
100%
90%
h
80%
r
eac
70%
r
eac
k
m
km
60%
Dry
200
Pool
of
50%
of
40%
Wet
c
entage
30%
e
r
c
entage
er
P
20%
10%
0%
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
48
E-Flows Scenario Report Hydrology
Figure 3-15 : Percentage of the 200-km study reach of the Boteti River that will be
inundated (wet); isolated pools (pool) and dry under the present-day
simulated conditions given climatic conditions that prevailed from 1973-
2002.
3.5.
Variability of Okavango Stream Flows
River flows in the Okavango River Basin exhibit strong seasonal and inter annual
variability.
3.5.1
Seasonal Variability
In the upper parts of the basin the seasonal variability corresponds closely to the
occurrence of rainfall, but in the semi-arid Delta the high flow season occurs several
months after the rainy season. Seasonal river flow patterns in different parts of the
basin vary widely. River flows in the Cubango and its tributaries are characterised by a
strong seasonal variation and low dry season base flows, while the Cuito and its
tributaries show much less seasonal variation with dampened wet season peak flows
and elevated dry season base flows, mainly due to considerable groundwater recharge
and discharge in this part of the basin.
Seasonal flooding in the Okavango Delta is the result of a complex interaction of local,
regional and basin-wide influences (McCarthy et al. 2000). At the upstream end of the
Delta, the flood peak occurs in April, and moves slowly across the Delta, taking 34
months to travel to Maun. Seasonal variation in the western parts of the Delta is strong
compared to the eastern parts where water levels show little seasonal variation.
Delta outflows arrive in Maun during May and June. The magnitude of flooding in the
Delta, antecedent groundwater levels and other factors determine the distance that water
travels along the Thamalakane and Boteti Rivers.
3.5.2
Inter Annual Variability
In the Okavango River Basin, measured stream flows exhibit a long-term cyclic
behaviour pattern of the order of 65 years, with a maximum in the 1960s, and a minimum
in the late 1990s. The cause for this is still unknown but it was found to be statistically
significant by Mazvimavi and Wolski (2006).
Figure 3-16 shows the average annual runoff measured at Mukwe, upstream of the
Delta. The 1930s and 1940s had generally below average runoff, while above average
runoff occurred during the 1950s to 1980s. This was followed by an abnormally dry
period in the 1990s. The system is currently in a wetter period.
49
E-Flows Scenario Report Hydrology
18,000
16,000
14,000
[Mm3]
12,000
10,000
Runoff
8,000
6,000
Annual
4,000
2,000
Average
0
1949
1951
1953
1955
1957
1959
1961
1963
1965
1967
1969
1971
1973
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
Hydrological Year (Oct Sept)
Figure 3-16 : Average Annual Runoff at Mukwe
River flow measurements made on Thamalakane River at Maun, and Boteti River at
Samedupi and Rakops show that the 1972-80 period was characterised by very high
flows (Figure 3-17). The highest flow occurred in July 1979. Very low flows occurred
from 1990 to 2008, and the whole section of the Boteti River from Chanoga to its distal
end including Rakops was dry during this period (Mazvimavi 2008).
Figure 3-17 : Observed monthly flows at at Maun, Samedupi and Rakops
50
E-Flows Scenario Report Hydrology
3.6.
Groundwater
3.6.1
Geology and aquifer stratigraphy
The Angolan Headwaters
The western headwaters of the basin are underlain by Pre-Cambrian granites and some
Karoo Group sandstone and mudstone. The granites underwent various orogenic and
magmatic processes which formed gneisses, migmatites and other metamorphic rocks.
The hard rock has low hydraulic conductivity and is overlain with a relatively thin mantle
of Kalahari sand. The Kalahari sand layer is interrupted by outcrops of granite along the
banks of the Cubango, Cutato, Cuchi, Cuelei and Cuebe Rivers. Together, these factors
contribute to the low base flows and strong seasonal variation of discharge observed in
the Cubango River and its tributaries (Hughes et al. 2006).
The eastern headwaters are located on a much thicker layer of Kalahari sands, and
consequently have a larger base flow component and less seasonal variation of
discharge.
The Lower Basin
Toward the south, in the vicinity of the Namibia/Angola border, the basin is underlain by
basal rocks of the Damara Sequence, followed by the Karoo Sequence sediments
overlain and intruded by volcanic rocks and covered by the Cretaceous Kalahari Group
sediments (NGDC. 1991). The soils in this part of the basin are made up of light coloured
sands, limestone, silicified sandstones and orchreous sands of the Kalahari Sequence
that are low in organic matter content. The sandy soils are enriched with silt deposited
by the Okavango River in terraces and floodplains (Hydrology Division, 1994).
Two aquifer types are common in this area, (a) Primary Kalahari aquifers i.e. sand and
sand stones that hold water in intergranular pore space and (b) Secondary aquifers i.e.
fractured aquifers that hold water in the fractures and weathered strata. Some boreholes
in the area penetrate the primary aquifer of the Kalahari which extends from the surface
to approximately 350 m deep (NGDC. 1991).
According to the Hydrogeological Map of Angola (scale 1:250.000), the yield of
boreholes situated nearby the Cuito River, in the downstream section of the basin, is less
than 1 litre per second (3.6 m3/h). Namibian drilling reports for Rural Water Supply show
that the groundwater yields in the Kavango region are relatively good with 90% of
boreholes drilled having a possibility of yielding more than 1m3/h in the Kalahari aquifers,
and less in areas were fractures are intersected. Boreholes yields along the Okavango
River in Namibia range between 0 - 8m3 /h, with areas that yield more than 10m3/h where
boreholes are drilled deeper than 100m into the Kalahari aquifers, (NGDC. 1991).
In areas were the water is intersected in fractures, the water level is normally higher than
those in the Kalahari aquifers (Christelis & Struckmeier, 2001).
In areas were the Kalahari aquifers have a shallow groundwater gradient, the Kavango
River recharges the aquifers but in most sections the river gains groundwater.
(NGDC.1991).
The Okavango Delta
The Okavango Delta lies within a north-easterly trending half graben, related to the east
African Rift System (Hotchins et al 1976). The major boundary structures are the
Thamalakane and Kunyere faults with a down throw to the north-west and are still active.
51
E-Flows Scenario Report Hydrology
The Gumare Fault has a parallel strike to the major faults. The oldest rocks in the region
are of the metavolcanic Kgwebe Formation and metasedimentary Ghanzi Group of upper
Proterozoic age. Karoo Supergroup rocks unconformably overlie lower proterozoic
basement rock outcrops south west of the delta at Lake Ngami (on the graben side of the
Kunyere Fault). The Kalahari Group sediments occur as Aeolian sands in the grabens of
the Panhandle of the Delta.
Three major aquifers formations occur in the Delta region. These are the Basement
rocks, Karoo and Kalahari Group sediments. Where Karoo and Basement rocks are
present at shallow depth, also form locally important aquifers. The Kalahari group
sediments comprise the most important known aquifers.
3.6.2
Recharge and Discharge
There is no consistent description of groundwater recharge over the entire basin. In the
lower basin in the vicinity of the Angola/Namibia border, shallow aquifers of less than
20m are recharged directly either by rainfall and emphemeral runoff while deeper
aquifers are recharged from the Kalahari basin margins or the underlying fractured
aquifers. Studies on water level elevation and hydrochemical evidence suggests
significant recharge from the Otavi Group dolomites in the Tsumeb Grootfontein area.
The eastern boundary of the Cuvelai - Etosha Basin seems to be discharging into the
Kavango Basin (Christelis & Struckmeier, 2001). Discharges from the aquifer are by
means of abstractions, inter-basin flow, and discharge of groundwater to the river where
the river is incised into the aquifer.
Recharge in the Okavango Delta has been estimated to be of the order of 7 to
10mm/annum (ODMP 2008).
3.6.3
Groundwater quality
Groundwater quality in the Kavango area is variable with "stripes" of saline water in
Kalahari aquifer where calcrete is present, and other areas with high fluoride
concentrations. Groundwater in the Kalahari aquifer along the banks of the river often
show poor quality due to its iron and manganese content, which occasionally exceeds
the safe limits for drinking water. During flood events, the river recharges the aquifer and
improves the groundwater quality.
Total dissolved solids (TDS) concentrations in groundwater along the Kavango River are
of the order of 1000 mg/l. In isolated areas values of more than 3000 mg/l have been
recorded and the lowest value of 36 mg/l has been recorded at Shakashi.
The shallow aquifers surrounding the Okavango Delta are generally saline, but
interspersed with freshwater lenses along the ephemeral streams that are recharged by
the wetlands of the Okavango Delta (Campbell et al. 2006; McCarthy et al. 1998). The
freshwater lenses around the streams are important for water supply.
Groundwater quality in the Delta itself is characterised by salt accumulation zones in the
islands with TDS values of up to 20 000 mg/l, surrounded and underlain by a fresh
aquifer with TDS of around 180 mg/l, and a deeper saline aquifer with TDS of around
2 600 mg/l.
52
E-Flows Scenario Report Hydrology
4.
Formulation of the Water Use Scenarios
4.1.
Introduction
The objective of the Okavango EFA is to provide information on the ecological, socio-
economic and macro-economic consequences of realizing the water resource
development aspirations of the three co-basin states. To ensure that OKACOM has
information at hand to assess the consequences of development pathways spanning a
range that is as wide as possible, preference was given to the selection of a set of
scenarios that cover a broad continuum of development and that are positioned at
regular intervals across this continuum.
The water use scenarios are simply ways of exploring possible management options.
None of the scenarios, as laid out in this study will necessarily happen but they can
inform negotiations on cooperative basin development.
Several previous studies have been undertaken to assess the impacts of future water
resource developments in the Okavango basin and in the delta. The assessments have
in most cases focused on the effect that future water resource developments may have
on water resource availability in the upstream basin, and on the hydrological functioning
of the delta. The Okavango EF Study is building on this work by using changes in river
flows and water resource availability to predict the ecological and socio-economic
consequences of the development scenarios. The study is also unique in the sense that
assessments of river health in the upstream basin enjoy equal priority with assessments
of impacts on the delta.
4.2.
Previous Studies
Scenario based planning exercises have been undertaken for the Water and Ecosystem
Resources in Regional Development (WERRD) and TwinBas projects, the Sharing
Water (USAID, 2004) project, and the Okavango Delta Management Plan (ODMP)
(Government of Botswana, 2005).
A hydrological model of the upstream basin (Pitman-based Spatsim) was developed for
the WERRD project, and refined as part of the TwinBas project. Scenario assessments
that were undertaken for the recent Sharing Water and ODMP projects were based on
this hydrology.
A prototype planning model was developed for the Sharing Water project and used to (a)
assess the extent to which postulated demands in the upstream basin can be met, and
(b) to simulate the impact of future developments on the extent of flooding in the delta.
The modeling work was undertaken with a systems model of the basin (WEAP) which
included a coarse, regression-based predictor of delta inundation. The scenarios that
were assessed are:
· A
baseline (no change, present day) scenario
· Scenario 1 - Growth in Existing Demand. A steady increase of growth in
domestic and agricultural water demands. No major scheme developments.
· Scenario 2 - Growth in Existing Demand, Angola Irrigation, Okavango Link
to Central Namibia. As for Scenario 1, but with the introduction of accelerated
irrigation demand in Angola, and the implementation of the Central Namibian
Water Supply Scheme.
· Management Strategy 1 Angolan Surface Storage. As for Scenario 2, but
with the introduction of a large dam downstream of the confluence of the
53
E-Flows Scenario Report Hydrology
Cubango and Cutato Rivers. The purpose of the dam is to provide water supply
for Scenario 2 demands that cannot be met, and also to provide flood control.
A hydrological model of the basin (Pitman-based Spatsim) and a hydrodynamic delta
model (MIKE 11 / MIKE SHE) were used to assess a range of development scenarios for
the Okavango Delta Management Plan. The impacts of the development scenarios were
assessed in terms of changes to the hydrological functioning of the delta, primarily
changes in frequency, extent and depth of inundation. The scenarios that were
assessed are:
· Upstream water resources developments: dams and irrigation schemes in
Angola and Namibia. Construction of three run-of-river and seven storage based
hydropower schemes. Large (54 500 ha) expansion of irrigated areas in Angola,
and relatively small (7 500 ha) expansion of irrigation in Namibia.
· Deforestation in Angola and Namibia. Simulated as the clearing of a 2km
riparian buffer.
· Surface and ground water abstractions from the delta. Increased abstraction
from the delta, from about 17 Mm3/year to 25 Mm3/year for domestic, livestock,
game, small scale irrigation and construction water use.
· Clearing major blocked channels in the delta.
· Regional
climate changes. Reduction in delta inflows of about 38%, reduction in
precipitation over the delta of about 9%, and a temperature increase of about 2.2
°C.
· Combinations of the above scenarios
There are two significant differences in the approaches that were adopted to construct
scenarios for the Sharing Water and ODMP projects:
· The ODMP scenarios were based on static development states in the basin (i.e.
water demands were projected to a planning horizon of 2025 and kept constant
over the simulation period) , whereas the Sharing Water scenarios were based on
growing water demands and timed implementation of new water infrastructure
over a 13 year simulation period.
· The Sharing Water scenarios span a development continuum from the baseline,
no development scenario, to a high development scenario (Management Strategy
1). For the ODMP, an issue-based list of development scenarios were identified
and assessed individually before combining groups of scenarios to determine the
most adversarial combination.
4.3.
Scenario Selection for the EF Study
4.3.1
Approach
For the EF Study, scenarios that are based on static development states were preferred.
It is possible to model dynamic basin development with growing demands and timed
implantation of water resources developments, but for scenario based planning, this
introduces unnecessary complexities regarding the coincidence of water resource
developments with hydrologic events.
While the decision support tools that will be put in place could in future be used to make
preliminary assessments of the socio-economic and ecological consequences of specific
projects, the aim of the current study is not to do project level assessments, but to
provide a planning framework which encompasses most of the water resource
development aspirations of the three co-basin states. This would ensure that OKACOM
54
E-Flows Scenario Report Hydrology
has information at hand to assess the consequences of development pathways spanning
a range that is as wide as possible. For this reason preference was given to the
selection of a set of scenarios that cover a broad continuum of development and that are
positioned at regular intervals across this continuum, rather than an approach that is
based on an issue-driven, ad hoc selection of scenarios.
A two step approach to the selection and construction of scenarios was followed:
· Step 1: An agreed number of possible future development states, ranging from a
baseline, no (or present) development to a high development state were
described.
· Step 2: The broad descriptions were fleshed out with a selection of water
resource developments that were comprised of a mixture of actual, planned
developments, and hypothetical developments that could conceivably be
implemented at some point in the future.
4.3.2
Selected Scenarios
The present, relatively undeveloped state of the basin provides a known reference point
from which extrapolations can be made to assess future development states. This
"Present Day" state represents one of the four scenarios that will be assessed as part of
the study. (A climate change scenario will be assessed as an extension to the current
project.) The four development scenarios were constructed along the following lines:
· The Present Day scenario includes all existing water resource developments,
notably:
o About 2 700 ha of irrigation in Namibia
o The urban water demands of Menongue and Cuito Cuanavale (Angola),
Rundu (Namibia), and Maun (Botswana)
· A low water use scenario which is based on the continuation of historical growth
in water demands in the three countries. Growth rates in Angola reflect the
recent acceleration associated with resettlement in de-mined areas. Increased
water consumption is mainly due to growth in urban and rural domestic, livestock
and irrigation water demands. The largest water demands are represented by:
o About 3 100 ha of irrigation in Namibia
o About 18 000 ha of irrigation along the Cuebe River in Angola
o One storage based and three run-of-river hydropower stations in Angola
· A medium growth, or "business-as-usual" scenario which includes
o About 8 400 ha of irrigation in Namibia
o Development of a first phase of the Eastern National Carrier (17 Mm3/a)
for water supply from the Kavango to Grootfontein and Windhoek,
o About 198 000 ha of irrigation at various locations in Angola
o One storage based and four run-of-river hydropower stations in Angola
· A high growth scenario which includes:
o About 15 000 ha of irrigation in Namibia
o About 338 000 ha of irrigation at various locations in Angola
o Completion of all planned hydropower stations in Angola, i.e. one storage
based and nine run-of-river hydropower stations in Angola ,
o Completion of a second phase of the Eastern National Carrier (total
capacity 100 Mm3/a),
o Development of a storage based water supply scheme for urban and
industrial water supply from a dam in the Boteti River to Maun.
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E-Flows Scenario Report Hydrology
o At these levels of demand, it was necessary to introduce a hypothetical
dam in the upper basin (Cuchi River) with a capacity of about 500 million
m3 to provide for shortfalls in irrigation water supply and inter-basin
transfers.
Irrigation water demands make up the largest component of future water use. In Angola,
the high growth scenario provides for 338 000 ha in the upper catchments of the
Cubango River and in the lower reaches of the Cuito River, but excludes some 170 000
ha of previously identified irrigation development upstream of the confluence of the
Kavango and Cuito Rivers. The Angolan team decided not to include this area due to a
perception that the low flows in the Kavango would not be sufficient to meet the
associated demand. In Namibia, the High scenario provides for about 15 000 ha of
irrigation development upstream and downstream of the confluence of the Kavango and
Cuito Rivers. This area includes the so-called "Green Scheme" and respects the
decision by the Namibian Departments of Agriculture Water Affairs (Policy Document No.
7/2/10/3) to limit the abstraction rate out of the Okavango River upstream of the
confluence with the Cuito to 5.5 m3/s, and downstream to 27 m3/s. It is based, not only
on the low flow in the river, but also on assumptions that a portion of the minimum flow
should be reserved for environment, that there would be no regulation by dams
upstream, that a demand peak factor 3 would be applicable for the month with the lowest
flow and that the other countries would adopt the same approach. This limitation is far
more than the limitation by the availability of dry-season flows.4 The water resource
developments that were included in the scenarios are described in more detail in
EPSMO/Biokavango Report Number 5; Hydrology: Data and Models.
4.3.3
General comments on the in- or exclusion of scenario water demands
Water demands from wildlife
Wildlife also exert a water demand, and there are standard unit water requirements for
different species of game (Table 4-1). However, the hydrological models used by the
TDA are based on the assumption that water use by game (and natural vegetation) is an
integral part of the hydrological cycle and is accounted for prior to arriving at a reference,
or "naturalised" condition. Thus, the naturalised runoff has already been "reduced" by
water use by game and natural vegetation. It should therefore not be added back into
the water balance as a "demand", as this would be double-counting. The exception to
this rule is if game concentrations are expected to increase beyond long-term historical
levels, but this is considered unlikely.
Table 4-1 : Estimated wildlife water consumption (adult animals)
Water Consumption
Species
Water Dependence
(Litres/day)
Blue Wildebeest
WD
9
Buffalo WD
31
Burchell's Zebra
WD
12
Common Duiker
WI
1
Eland WI
23
Elephant
WD
225
Gemsbok WI
9
Giraffe WI
40
Impala WD
2.5
4 Clarification provided by G Van Langehove, 2009.
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E-Flows Scenario Report Hydrology
Kudu WD
9
Red Hartebeest
WD
5.5
Reedbuck WD
3
Roan WD
10
Sable WD
9
Springbok WI
1.5
Steenbok WI
0
Tsessebe WD
5
Warthog WI
3.5
Waterbuck WD
9
Wild water-dependent (WD; obligate drinkers) and water-independent (WI) species and estimated
consumption per adult animal per day (du P Bothma et al. 2002; du Toit 2002). A: aquatic species, SA: semi-
aquatic species.
Deforestation
The water related benefits of forestation have been the subject of much debate recently.
Research undertaken in India, Costa Rica, South Africa and Tanzania as part of the
Forestry Research Programme of the UK Department for International Development
(Hayward, 2005) have lead the authors of the study to conclude that forests reduce
overall water availability in catchments. The studies indicate that there are areas where
forests do increase localised rainfall through moisture harvesting from clouds, but that
these areas tend to be isolated and small, and that the increased transpiration from the
trees themselves tends to cancel out the benefits of increased precipitation.
Counter views are expressed by researchers who, while conceding that "newly
established tropical plantations evaporate more water directly to the atmosphere in
comparison to nonforest vegetation", hold that deep aquifers, mature trees and climate
feedback combine to reduce the negative water budget impacts (Chappel, Bonnel,
2006), and that if other, non-water related benefits are taken into account when
assessing the public benefits of forests, the overall public benefit would be positive.
The impacts of deforestation on water availability in the Okavango River Basin was
initially assessed as part of the TwinBas project, and subsequently used to assess the
impacts on the flooding regime of the Delta as part of the Okavango Delta Management
Plan (ODMP, 2008). The approach was based on the view that forests reduce water
availability in catchments, and conversely, that deforestation would lead to a reduction in
evapotranspiration by catchment vegetation, less storage of rain water in the vegetation
and the root zone, resulting in more rapid and increased runoff to the rivers. It was
assumed that increased population pressure along the river banks would lead to
deforestation of a 2km wide band along the main river courses. Analysis of the
hydrological impacts of the deforestation scenario indicated that average inflow to the
delta would increase by around 7%, with an associated increase in average ground
water levels (+0.03m) in the Delta. These increases were partially offset by increased
evapotranspiration from the greater flooded area. Outflows from the delta were
minimally affected.
Other hydrological impacts that were not assessed as part of these studies, but that can
be attributed to deforestation include an increased occurrence of minor flood events
(stormflows rather than peak flows), soil erosion, downstream sedimentation and
associated water quality problems. Prolonged, severe soil degradation could also affect
infiltration and groundwater recharge, thereby increasing surface runoff and lowering
base flows in the rivers.
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E-Flows Scenario Report Hydrology
Water Resource Developments
The outcomes of scenarios depend on what is included as a water-resource
development. Changing the location, size or any other aspects of a possible
development will change the expected future flow regime and thus the expected
ecological and social implications.
The water resource developments that formed part of each water-use scenario are
summarised in Table 4.2 and displayed in Error! Reference source not found. and
Figure 4-2.
Table 4.2
Water-resource developments included in each scenario
Medium High
Site Present
Low
Low schemes plus:
Medium schemes plus:
Menongue: 246 000
Menogue: 257 000 people Menogue: 30 000 people Menogue: 70 000 people
people
Irrigation: Missombo 1000 ha, weir diversion
Site 1
Capico
Irrigation: Menongue Agriculture 10 000 ha, pump sump on river bank
Irrigation: Ebritex 17 000 ha, pump sump on river bank
HEP: Liapeca, run-of-river, low weir, turbines d/s
ALL CAPICO DEVELOPMENTS PLUS:
HEP: Cuvango Existing / not functioning. Rehabilitation in 2009. 40m high
reservoir, 1250 Mm3, Qmax = 3.5 m3/s
HEP: Cuchi (Kaquima (Malobas)). Run-of-river. H = 14m, Qmax = 3 m3/s
HEP: Maculungungu (on Cubango u/s Caiundo). Run-of-river. H = 22m, Qmax =
24 m3/s
Site 2
Mucundi
HEP: Cutato. Run-of-river.
H = 30m, Qmax = 6 m3/s
HEP: Rapides do Cuelei.
Run-of-river. H = 22m,
Qmax = 8 m3/s
Irrigation: Cuchi, 15 000
Irrigation: Cuchi, 150 000 ha, pump intake
ha, pump intake
Irrigation : Cuvango, 10 000 ha, pump sump on river
bank
Cuito Cuanavale: 110 435 Cuito Cuanavale: 115 000 Cuito Cuanavale: 128 600 Cuito Cuanavale: 160 000
people
people
people
people
Site 3
Cuito
Cuanavale
HEP: Cuito Cuanavale (13 km u/s confluence).
Diversion, Run-of-river. H = 7m, Qmax = 90 m3/s
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E-Flows Scenario Report Hydrology
Medium High
Site Present
Low
Low schemes plus:
Medium schemes plus:
ALL CAPICO & MUCUNDI DEVELOPMENTS PLUS:
Irrigation: Kahenge 300
Irrigation: Kahenge 700
ha, pump intake on river ha, pump intake on river Irrigation: Kahenge 900 ha, pump intake on river bank
Site 4
bank
bank
Kapako
Irrigation: Rundu Future 1100 ha, pump intake on river
bank
Irrigation: Cuangar Calai
45 000 ha, pump intake on
river bank
ALL CAPICO, MUCUNDI, KAPAKO AND CUITO CUANAVALE DEVELOPMENTS PLUS:
Irrigation: Longa 10 000 ha, pump intake on river bank
Irrigation: Calais Dirico 35
000 ha, pump intake on
river bank
Irrigation: Calais Dirico B
60 000 ha, pump intake on
river bank
Irrigation: Mukwe 560 ha, pump intake on river bank
Irrigation: Rundu-Mashare
521 ha, pump intake on
Irrigation: Rundu-Mashare 551 ha, pump intake on river bank
river bank
Irrigation: Ndiyona 870 ha, Irrigation: Ndiyona 1270 ha, pump intake on river bank
pump intake on river bank
Site 5&6
Rundu Urban, Tower on
Rundu Urban, Tower on
Rundu Urban, Tower on
Rundu Urban, Tower on
Popa and
right bank, 2.8 Mm3/a
right bank, 3.0 Mm3/a
right bank, 3.4 Mm3/a
right bank, 4.3 Mm3/a
Panhandle
(Shakawe)
Irrigation: Mukwe Future Irrigation: Mukwe Future
4000 ha, pump intake on 10 600 ha, pump intake on
river bank
river bank
Eastern National Water
Eastern National Water
Carrier (ENWC) for water Carrier (ENWC) for water
supply from Kavango to
supply from Kavango to
Namibia, Tower on right
Namibia, Tower on right
bank, 17 Mm3/a
bank, 100 Mm3/a
HEP: Popa Falls. Run-of-
river, Weir at Site 2. H =
7.5 m, Qmax = 280 m3/s,
22.5 Mm3 capacity.
HEP: Cuito M'Pupa.
Run-of-river. H = 5m,
Qmax = 100 m3/s
HEP: Cuito Chamavera
(d/s M'Pupa). Run-of-river.
H = 6m, Qmax = 100 m3/s
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E-Flows Scenario Report Hydrology
Medium High
Site Present
Low
Low schemes plus:
Medium schemes plus:
Site 7
Khwai
ALL CAPICO, MUCUNDI, KAPAKO, CUITO CUANAVALE AND POPA/PANHANDLE DEVELOPMENTS
(Xakanaka)
ALL CAPICO, MUCUNDI, KAPAKO, CUITO CUANAVALE, POPA/PANHANDLE DEVELOPMENTS, PLUS:
Site 8
Boteti
Dam at Samedupi (37
Mm3)
Figure 4-1 : Approximate positions of water-resource developments included in the
wateruse scenarios in the upper portion of the catchment
60
E-Flows Scenario Report Hydrology
Figure 4-2
Approximate positions of water-resource developments included in the
water-use scenarios in the lower portion of the catchment.
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E-Flows Scenario Report Hydrology
5.
Hydrological Consequences of the Water Use
Scenarios
5.1.
Introduction
The hydrological modeling of the three scenarios yielded times series of monthly flows
for a 43-year hydrological period (1959 - 2001) for the river sites (Sites 1-6) and a 20-
year hydrological period (1983 - 2002) for the Delta (Site 7) and Boteti (Site 8). For each
scenario, the level of water use outlined in Table 4.2 was imposed on the full
hydrological period.
It is important to emphasise that the modeling period (1959/60 2001/02), show a
declining trend in mean annual runoff (Figure 5-1). This trend was primarily driven by
climatic conditions, as was borne out by a reversal of the trend in 2004-2009.
Thus, for the river sites (Sites 1, 2, 3, 4, 5 and 6), the present-day situation is defined as
a 43-year hydrological period (1959 - 2001) with 2008 levels of water use applied
throughout.
Figure 5-1
Simulated monthly inflows to the Delta all scenarios (1959-2001).
For the delta (Site 7) and the Boteti River (Site 8), the present-day situation is defined as
a 20-year hydrological period (1983 - 2002) with 2008 levels of water use applied
throughout. Figure 5-1 shows simulated inflows to the Delta for the 1959-2003 period
and illustrates the fact that all of the upstream developments envisaged in a particular
scenario would be in place for the entire time.
To facilitate comparison between the scenarios, each scenario comprises the same
hydrological period as the present-day scenario, with its water use levels applied
throughout.
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E-Flows Scenario Report Hydrology
5.2.
Presentation and Discussion of Results
The hydrological consequences of the three future water use scenarios are discussed in
the remainder of this chapter. Impacts are described in separate sections dealing with
the upstream basin, the Delta, and the Boteti. In each section a site-by-site discussion of
the changes that were observed in the flow regime is given:
· For the river and floodplain sites in the upper basin, the impacts of the water use
scenarios are described in terms of changes to the monthly flow duration curves,
and the ecologically relevant flow indicators that were derived from the
disaggregated daily time series (refer to Section 2.3). Listings of the flow
indicators that were calculated for each site and each scenario are provided in
Appendix A.
· For the Delta sites, the impacts of the water use scenarios are described in terms
of changes to the vegetation assemblages that were modeled with the HOORC
Delta Model. The Botswana DWA MIKE SHE-MIKE 11 Integrated Hydrologic
Model (IHM) was used to develop discharge-depth and discharge-velocity
relationships at the Delta sites. The relationships were used by the ecological
specialists to translate simulated flows (median wet season flood peaks and dry
season minimum flows) to depths and discharges in order to populate some of
the eco-system response curves. The relationships are provided in
EPSMO/Biokavango Report Number 5; Hydrology: Data and Models.
· For the Boteti site, hydrological impacts are described in terms of state changes
observed over the period of simulation (i.e. whether the river is inundated,
contains disconnected pools, or is dry).
5.3.
The Upstream Basin
5.3.1
General comments
Figure 5-3 to Figure 5-5 show changes in mean annual runoff (MAR) associated with the
Low, Medium and High development scenarios relative to the reference (present day)
scenario. It can be seen that:
· Inflows to the Delta decrease by about 370, 880 and 2 900 million m3/a relative to
the present day MAR for the Low, Medium and High development scenarios,
respectively.
· Most of the water resource developments associated with the Low and Medium
scenarios are located in the Cuchi and Cuebe catchments, and the effects of
these can be seen in the middle and lower reaches of the Cubango / Kavango
River. As an example, dry season low flows at Kapako (and Rundu) would be
reduced to about 50% of present day values.
· The combined water abstractions in the upper basin for the High scenario equate
to about 3 600 million m3/a. Of this, by far the largest component is made up of
irrigation water demands (3 300 million m3/a in Angola and 223 million m3/a in
Namibia), followed by the relatively smaller demands of the ENWC transfer (100
million m3/a), and the combined urban demands of Menongue, Cuito Cuanavale
and Rundu (22 million m3/a).
· In the High development scenario, large tracts of irrigation developments are
located along the lower reaches of the Cuito River. This has the effect of
considerably reducing the Cuito River's strong base flow contribution to the lower
Okavango River, and as will be seen later, the combined effect of all upstream
developments substantially reduces the permanent swamp area in the Delta, and
virtually dries up the Boteti River.
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E-Flows Scenario Report Hydrology
· The hydrological impacts of the developments in the Cubango/Kavango sub-
basin (upstream of the confluence with the Cuito) is mitigated to some extent by
the presence of two large storage dams a hydropower storage near Mucundi on
the Cubango River (Low scenario), and another in the Cuchi catchment (High
scenario). While the main purpose of the Mucundi Dam is to provide generating
head for hydropower, hydropower releases in the dry season is available for
downstream abstractions such as the Eastern National Carrier.
· It is important to note that, were the storage dams not present, the postulated
future demands under the High scenario would not be met in its entirety. A test
was done by removing the storage dams, and re-simulating the High scenario. It
can be seen that, for example, the ENWC monthly water abstractions cannot be
met for a much longer percentage of time, were the dams not in place.
Figure 5-2 : Percentage of time (months) that the ENWC abstraction is met
64
E-Flows Scenario Report Hydrology
Cuartir
264
Cuebe
438
Cuchi/Cuelei
2 046
Cutato
790
79
4 71
7 5
1
4 977
4 939
1 879
2 669
Upper Cubango
Upper Cubango 2
Middle
Middle Cubango 2
Kavango
Cubango
9 260
Longa
562
Cuanavale
645
Lower Okavango
3 160
4 005
4 328
Upper Cuito
Middle Cuito
Lower Cuito
Cuanavale
ai
Khw
Ca
C
Gomoti
c
u
u
irir
C
c
L
i
u
h
o
c
n
i
g
h
a
T
qoga
i
h
N
L
a
ua
o
X
s
g
u
si
d
n
u
g
e
m
a
C
Cw
u
e
ta
be
T
to
haoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure 5-3 :
Mean Annual Runoff (106 m3/a) - Low Water Use (Blue) compared to Present Day (Orange)
65
E-Flows Scenario Report Hydrology
Cuanavale
ai
Khw
Ca
C
Gomoti
c
u
u
irir
C
c
L
i
u
h
o
c
n
i
g
h
a
T
qoga
i
h
N
L
a
ua
o
X
ss
g
u
i
d
n
u
g
e
m
a
C
Cw
u
e
ta
be
T
to
haoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure 5-4 :
Mean Annual Runoff (106 m3/a) - Medium Water Use (Blue) compared to Present Day (Orange)
66
E-Flows Scenario Report Hydrology
Cuanavale
Khwai
Ca
C
Gomoti
c
u
u
irir
C
c
L
i
u
h
o
c
n
i
g
h
a
i
T
qoga
h
N
L
a
ua
o
X
s
g
u
s
d
in
u
g
e
m
a
C
Cw
u
e
ta
be
T
t
h
o
aoge
C
Cuito
u
C
e
u
io
elei
Cuatir
Cubango
Figure 5-5 :
Mean Annual Runoff (106 m3/a) - High Water Use (Blue) compared to Present Day (Orange)
67
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5.3.2
Site 1 - Capico
All of the developments envisaged for Capico were inserted into the Low Scenario, and so
the following consequences apply to all three scenarios. The developments are: run-of-river
abstractions that feed 28 000 ha of irrigation, increased urban supply for up to 100 000 more
people and a small run-of-river HEP diversion at Liapeca. These result in the mean annual
runoff in the Cuebe dropping to about half, because of water being diverted into croplands.
Diversions take place year round, but the biggest volumes are diverted during the dry
season. Figure 5-6 shows that in all future scenarios low flows are virtually depleted for
about 25% of the simulation period. The impact is greater in the dry season, which starts 3
months earlier, is more than 4 months longer and has flows close to zero. The wet season is
3 months shorter and the volume of flood water is about half of present.
Figure 5-6 : Monthly Flow Duration Curves for the Cuebe River at Capico (Site 1)
Table 5.1
Median values for the ecologically-relevant summary statistics for each
scenario for Site 1: Capico.
Flow category
PD
Low
Medium
High
Comment
All Scenarios similar and
Mean Annual Runoff (Mm3/a) 22
14
14
13
lower than PD
All Scs similar and 11 wks
Dry season onset
Aug
May
May
May
earlier than PD
All Scs similar and approx 18
Dry season duration (days)
86
212
212
213
wks longer than PD (ie ends
later and starts earlier)
Dry season minimum flow
All Scs similar. Drastic drop
12 0.4 0.3
0.3
(m3s-1)
from PD
All Scs similar and delayed
Flood season onset
Dec
Jan
Jan
Jan
by about 7 weeks compared
to PD
All Scs similar and slightly
Flood season peak (m3s-1)
38 35 35
35 smaller than PD
Flood season volume (Mm3)
456
231
231
230
All Scs similar and half of PD
All Scs similar and approx 14
Flood season duration (days) 197
97
97
97
wks shorter than PD
PD = simulated present day flow regime. L = low scenario; M = medium scenario; and H = high scenario
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5.3.3
Site 2 Mucundi
All of the developments for Capico still apply, and in addition further major developments in
hydropower generation and croplands are included. Run-of-river HEP schemes with
diversion structures are added with each scenario, but one storage based scheme with a
substantial dam wall. Irrigated cropland gradually increases to a maximum of 175 000 ha, all
areas using run-of-river abstraction, except for a large dam on the Cuchi River, which is
introduced in the High Scenario. The impacts on flow are not as severe as at Capico
because of the contribution of undeveloped tributaries. MAR declines gradually to about
80% of present, and the dry season starts about a month earlier and lasts up to 2 months
longer. Because of the continual abstractions, dry-season flows fall to less than half of
present flows in the Low and Medium Scenarios, but they increase again in the High
Scenario due to dam releases (Figure 5-7). Wet-season flows start later and with lesser
floods, because of filling of the dams on the Cubango and Cuchi, and are up to a month
shorter.
Figure 5-7 : Monthly Flow Duration Curves for the Cubango River at Mucundi (Site 2)
Table 5.2
Median values for the ecologically-relevant summary statistics for each
scenario for Site 2: Mucundi.
Flow category
PD
Low
Medium
High
Comment
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E-Flows Scenario Report Hydrology
Gradual decline to 93%,
Mean Annual Runoff (Mm3/a) 166
155
140
128 85%, 77% of PD
All Scs similar. Onset 2-3
Dry season onset
July
July
July
July
weeks earlier than PD.
Progressive lengthening of
Dry season duration (days)
96
124
143
152
dry season by 4, 7 and 8
weeks
Min Q drops to 50% (L),
Dry season minimum flow
38% (M) of PD and then
32 16 12
24
(m3s-1)
under H increases to 75% -
dam releases in dry season
Progressively delayed by 2-
Flood season onset
Jan
Jan
Jan
Jan
3 weeks
Peak not affected until (H),
Flood season peak (m3s-1)
429 430 429
401 when drops to 93% of PD
Progressive loss of volume:
Flood season volume (Mm3) 3713 3558 3178
2531 96%, 86%, 68 of PD
Progressive shortening of
Flood season duration (days) 148
135
123
111
flood season by 2, 3, 5
weeks
PD = simulated present day flow regime. L = low scenario; M = medium scenario; and H = high scenario.
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E-Flows Scenario Report Hydrology
5.3.4
Site 3 Cuito Cuanavale
Most developments included for the Cuito River are downstream of the Cuito-Cuanavale site
and so do not affect it. The scenarios include 50 000 more people in urban areas and a
small run-of-river HEP diversion on the Cuito River upstream of Cuito Cuanavale. These do
not have a noticeable impact on the flow regime although the HEP infrastructure might have
a, presently unknown, impact on sediment movement along the river. If only flow changes
are considered, the developments included for this site would have a minimal impact on the
river ecosystem.
Table 5.3
Median values for the ecologically-relevant summary statistics for each
scenario for Site 3: Cuito Cuanavale.
Flow category
PD
Low
Medium
High
Comment
Mean Annual Runoff (Mm3/a) 119
119
119
119
Dry season onset
July
July
July
July
Much longer duration than
Dry season duration (days)
182
182
182
182
other Angolan sites
Dry season minimum flow
Much higher flow than other
80 80 80
80
(m3s-1)
Angolan sites
Flood season onset
Jan
Jan
Jan
Jan
Quite a small peak compared
Flood season peak (m3s-1)
163 163 163
163 to Mucundi
Flood season volume (Mm3)
1968
1968
1968
1968
About half of Mucundi
Within range of other
Flood season duration (days) 162
162
162
162
Angolan sites
PD = simulated present day flow regime.
5.3.5
Site 4 Kapako
All developments included for Capico and Mucundi are upstream of this site and so are
included, and in addition a further 48 000 ha of run-of-river irrigation in the Kapako area is
added gradually through the scenarios. There are no significant tributaries between Mucundi
and Kapako and so flow changes upstream are transmitted downstream without amelioration
of other inflows. Figure 5-8 shows the elevation of low flows (tail-end of the duration curve)
under the High scenario due to dry season releases from the two postulated storage dams in
the Cubango sub-basin. The annual volume of water flowing down the river progressively
declines to 80% of present and the dry-season flow falls by about half and the dry season
extends up to 1.5 months longer. The wet season is shorter by about the same length of
time with up to a 30% drop in volume but little change in flood onset time and size of flood
peak.
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E-Flows Scenario Report Hydrology
Figure 5-8 : Monthly Flow Duration Curves for the Kavango River at Kapako (Site 4)
Table 5.4
Median values for the ecologically-relevant summary statistics for each
scenario for Site 4: Kapako.
Flow category
PD
Low
Medium
High
Comment
Progressive decline to 93%,
Mean Annual Runoff (Mm3/a) 164
152
140
129 85%, 79% of PD
Dry season onset
July
July
July
July
Approx same throughout
Progressively longer: 2, 5, 6
Dry season duration (days)
135
150
168
176
weeks more than PD
Dry season minimum flow
Decline through L and M to
35 20 15
19 43% then increase for H to
(m3s-1)
54%
Slight delay by about 2 wks in
Flood season onset
Jan
Jan
Jan
Feb
H
Medium about same as PD; L
Flood season peak (m3s-1)
452 446 453
433 slightly lower at 99% and H at
96% of PD
Progressive decline to 96%,
Flood season volume (Mm3) 3694 3535 3209
2580 87%, 70% of PD
Progressively shorter flood
Flood season duration (days) 154
147
130
117
season: 1, 4, 6 weeks shorter
than PD
PD = simulated present day flow regime. L = low scenario; M = medium scenario; and H = high scenario.
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E-Flows Scenario Report Hydrology
5.3.6
Sites 5 and 6 : Popa Rapids and Panhandle
All developments upstream in Capico, Mucundi, Cuito Cuanavale and Kapako are included,
plus a gradual increase of run-of-river irrigation along the lower Okavango and a large
increase along the lower Cuito River in the Medium and High scenarios to more than 178 000
ha above present (mostly in Angola), up to 130 m3/s more diversion in Namibia for urban
supply, and three additional run-of-river HEP structures, one with a dam wall height of 7.5 m.
These translate as a decline to 69% of mean annual runoff and a dry season that starts up to
2 months earlier and is 3 months longer than present. Under the High Scenario, dry-season
flows drop to 18% of present. The flood season onset and peak are only slightly affected but
it is up to 2 months shorter and declines to about two-thirds of its present volume.
Figure 5-9 : Monthly Flow Duration Curves for the Okavango River at Popa Rapids (Site 5)
5.4.
The Delta
5.4.1
General comments
Hydrological flow sequences are not particularly useful in the analysis of the Okavango Delta.
The extent and frequency of flooding drive the distribution of vegetation types and habitats.
Thus, while the overall proportion of inundated area may be similar in years with similar flow
characteristics, the location of the inundated areas varies over time. For his reason, a semi-
conceptual hydraulic model (Wolski et al. 2006), which was calibrated using observed flow
and inundation data for the period of 1968-2002, was used to generate inundation patterns
over the south-western portion of the Okavango delta, as represented by Site 7: Xakanaka.
The output of the model is a series of vegetation types/habitat based on duration and
frequency of inundation (
73
E-Flows Scenario Report Hydrology
Table 5.5). The Delta and Boteti models were run over the same period (1973 to 2002),
however the vegetation responses in the Delta model are dependent on conditions in
antecedent years and therefore requires a "warm-up" period. The Delta vegetation
responses are therefore only reported from 1983.
74
E-Flows Scenario Report Hydrology
Table 5.5
Vegetation types used in the model
Abbreviation Description
CH-ps
Channels in permanent swamp
L-ps
Lagoons in permanent swamp
BS-ps
Backswamp in permanent swamp
SP-sf
Seasonal pools in seasonally flooded zone
Sed-sf
Seasonal sedgeland in seasonally flooded zone
Gr-sf
Seasonal grassland in seasonally flooded zone
S-sf
Savanna- dried floodplain in seasonally flooded areas
5.4.2
Site 7: Xakanaka
Due to the declining upstream inflows into the Delta, there is a decrease in all major types of
permanent swamp to as low as 22% of present under the High scenario, and an increase in
seasonal swamps into these areas. Dry flood-plain savanna also expands to more than four
times its present area, representing a significant drying-out of the Delta.
Figure 5-10 : Time series of vegetation/habitat assemblages for the Low Scenario
75
E-Flows Scenario Report Hydrology
Figure 5-11 : Time series of vegetation/habitat assemblages for the Medium Scenario
Figure 5-12 : Time series of vegetation/habitat assemblages for the High Scenario
5.5.
Delta Outflows
The percentage of the 200-km study reach of the Boteti River that will be inundated (wet);
isolated pools (pool) and dry under the Present day, Low, Medium and High scenarios is
provided in Figure 5-13 to Figure 5-16, respectively.
76
E-Flows Scenario Report Hydrology
Details of the model used to provide these data are provided in EPSMO/BioKavango Report
05/2009: Hydrology Report: Data and models.
The Thamalakane / Boteti River system receives outflows from the Delta and is highly
susceptible to changes in the flooding regime of the Delta. In addition, the length of river that
is wetted by inflows in any given year depends on the volume of inflows and state of the
groundwater aquifers in previous years. Flows in the system normally exhibit dry and wet
cycles of many years in length. Through the scenarios the number of years it contains water
would progressively decline until in the High Scenario it would be completely dry for most of
the time, holding water only in the wettest years.
100%
90%
h
80%
eac
70%
r
k
m
60%
Dry
200
50%
Pool
of
40%
Wet
30%
e
r
c
entage
P
20%
10%
0%
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Figure 5-13 : Percentage of the Boteti River study reach that will be inundated (wet); isolated
pools (pool) and dry under the Present day Scenario
100%
90%
h
80%
eac
70%
r
k
m
60%
Dry
200
50%
Pool
of
40%
Wet
30%
e
r
c
entage
P
20%
10%
0%
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Figure 5-14 : Percentage of the Boteti River study reach that will be inundated (wet); isolated
pools (pool) and dry under the Low Scenario
77
E-Flows Scenario Report Hydrology
100%
90%
h
80%
eac
70%
r
k
m
60%
Dry
200
50%
Pool
of
40%
Wet
c
entage
30%
er
P
20%
10%
0%
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Figure 5-15 : Percentage of the Boteti River study reach that will be inundated (wet); isolated
pools (pool) and dry under the Medium Scenario
100%
90%
h
80%
eac
70%
r
k
m
60%
Dry
200
50%
Pool
of
40%
Wet
30%
e
r
c
entage
P
20%
10%
0%
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Figure 5-16 : Percentage of the Boteti River study reach that will be inundated (wet); isolated
pools (pool) and dry under the High Scenario
5.6.
Process followed after the generation of hydrological summary data
The hydrological summary statistics are used as inputs to the response curves that are used
to predict the biophysical and social outcomes for the flow regime of interest. The response
curves, and the predicted ecological and socio-economic implications of the water use
scenarios are described in Report 07/2009: Scenario Report: Ecological and social
predictions (Volume 1 of 2)
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E-Flows Scenario Report Hydrology
6.
Summary and Conclusions
6.1.
The Upper Basin
6.1.1
General
The hydrological consequences of the water use scenarios can be summarised as follows:
· Current day inflows to the Delta of about 9 600 million m3/a decrease by about 370,
880 and 2 900 million m3/a relative to the present day mean annual runoff for the Low,
Medium and High development scenarios, respectively.
· Most of the water resource developments associated with the Low and Medium
scenarios are located in the Cuchi and Cuebe catchments, and the effects of these
can be seen in the middle and lower reaches of the Cubango / Kavango River. As an
example, dry season low flows at Kapako (and Rundu) would be reduced to about
50% of present day values.
· The combined water abstractions in the upper basin for the High scenario equate to
about 3 600 million m3/a. Of this, by far the largest component is made up of
irrigation water demands (3 300 million m3/a in Angola and 223 million m3/a in
Namibia), followed by the relatively smaller demands of the ENWC transfer (100
million m3/a), and the combined urban demands of Menongue, Cuito Cuanavale and
Rundu (22 million m3/a).
· In the High development scenario, large tracts of irrigation developments are located
along the lower reaches of the Cuito River. This has the effect of considerably
reducing the Cuito River's strong base flow contribution to the lower Okavango River.
The combined effect of all upstream developments substantially reduces the
permanent swamp area in the Delta, and virtually dries up the Boteti River.
· The hydrological impacts of the developments in the Cubango/Kavango sub-basin
(upstream of the confluence with the Cuito) is mitigated to some extent by the
presence of two large storage dams a hydropower storage near Mucundi on the
Cubango River (Low scenario), and another in the Cuchi catchment (High scenario).
While the main purpose of the Mucundi Dam is to provide generating head for
hydropower, hydropower releases in the dry season is available for downstream
abstractions such as the Eastern National Carrier.
· It is important to note that, were the storage dams not present, the postulated future
demands under the High scenario would not be met in its entirety. A test was done
by removing the storage dams, and re-simulating the High scenario. It can be seen
that, for example, the ENWC monthly water abstractions cannot be met for a much
longer percentage of time, were the dams not in place.
6.1.2
Site 1 - Capico
All of the developments envisaged for Capico were inserted into the Low Scenario, and so
the following consequences apply to all three scenarios. The developments are: run-of-river
abstractions that feed 28 000 ha of irrigation, increased urban supply for up to 100 000 more
people and a small run-of-river HEP diversion at Liapeca. These result in the mean annual
runoff in the Cuebe dropping to about half, because of water being diverted into croplands.
Diversions take place year round, but the biggest volumes are diverted during the dry
season. Figure 5-6 shows that in all future scenarios low flows are virtually depleted for
about 25% of the simulation period. The impact is greater in the dry season, which starts 3
months earlier, is more than 4 months longer and has flows close to zero. The wet season is
3 months shorter and the volume of flood water is about half of present.
6.1.3
Site 2 Mucundi
All of the developments for Capico still apply, and in addition further major developments in
hydropower generation and croplands are included. Run-of-river HEP schemes with
diversion structures are added with each scenario, but one storage based scheme with a
79
E-Flows Scenario Report Hydrology
substantial dam wall. Irrigated cropland gradually increases to a maximum of 175 000 ha, all
areas using run-of-river abstraction, except for a large dam on the Cuchi River, which is
introduced in the High Scenario. The impacts on flow are not as severe as at Capico
because of the contribution of undeveloped tributaries. Mean annual runoff declines
gradually to about 80% of present, and the dry season starts about a month earlier and lasts
up to 2 months longer. Because of the continual abstractions, dry-season flows fall to less
than half of present flows in the Low and Medium Scenarios, but they increase again in the
High Scenario due to dam releases. Wet-season flows start later and with lesser floods,
because of filling of the dams on the Cubango and Cuchi, and are up to a month shorter.
6.1.4
Site 3 Cuito Cuanavale
Most developments included for the Cuito River are downstream of the Cuito-Cuanavale site
and so do not affect it. The scenarios include 50 000 more people in urban areas and a
small run-of-river HEP diversion on the Cuito River upstream of Cuito Cuanavale. These do
not have a noticeable impact on the flow regime although the HEP infrastructure might have
a, presently unknown, impact on sediment movement along the river. If only flow changes
are considered, the developments included for this site would have a minimal impact on the
river ecosystem.
6.1.5
Site 4 Kapako
All developments included for Capico and Mucundi are upstream of this site and so are
included, and in addition a further 48 000 ha of run-of-river irrigation in the Kapako area is
added gradually through the scenarios. There are no significant tributaries between Mucundi
and Kapako and so flow changes upstream are transmitted downstream without amelioration
of other inflows. Figure 5-8 shows the elevation of low flows (tail-end of the duration curve)
under the High scenario due to dry season releases from the two postulated storage dams in
the Cubango sub-basin. The annual volume of water flowing down the river progressively
declines to 80% of present and the dry-season flow falls by about half and the dry season
extends up to 1.5 months longer. The wet season is shorter by about the same length of
time with up to a 30% drop in volume but little change in flood onset time and size of flood
peak.
6.1.6
Sites 5 and 6 : Popa Rapids and Panhandle
All developments upstream in Capico, Mucundi, Cuito Cuanavale and Kapako are included,
plus a gradual increase of run-of-river irrigation along the lower Okavango and a large
increase along the lower Cuito River in the Medium and High scenarios to more than 178 000
ha above present (mostly in Angola), up to 130 m3/s more diversion in Namibia for urban
supply, and three additional run-of-river HEP structures, one with a dam wall height of 7.5 m.
These translate as a decline to 69% of mean annual runoff and a dry season that starts up to
2 months earlier and is 3 months longer than present. Under the High Scenario, dry-season
flows drop to 18% of present. The flood season onset and peak are only slightly affected but
it is up to 2 months shorter and declines to about two-thirds of its present volume.
6.2.
The Delta (Site 7 Xakanaka)
Due to the declining upstream inflows into the Delta, there is a decrease in all major types of
permanent swamp to as low as 22% of present under the High scenario, and an increase in
seasonal swamps into these areas. Dry flood-plain savanna also expands to more than four
times its present area, representing a significant drying-out of the Delta.
6.3.
Delta Outflows (Site 8 Boteti)
The Thamalakane / Boteti River system receives outflows from the Delta and is highly
susceptible to changes in the flooding regime of the Delta. In addition, the length of river that
80
E-Flows Scenario Report Hydrology
is wetted by inflows in any given year depends on the volume of inflows and state of the
groundwater aquifers in previous years. Flows in the system normally exhibit dry and wet
cycles of many years in length. Through the scenarios the number of years it contains water
would progressively decline until in the High Scenario it would be completely dry for most of
the time, holding water only in the wettest years.
81
E-Flows Scenario Report Hydrology
7.
References
Adamson, P. 2006. Hydrological background and the generation of exploratory flow regimes
for the development of the impact analysis tools. Integrated Basin Flow Management.
Internal Report of the Mekong River Commission, Laos PDR. 45 pp.
Church J. T., Crerar S. E (1988). Evaporation Map for Namibia. Hydrology Division,
Department of Water Affairs, Ministry of Agriculture, Water and Rural Development.
Windhoek. File No. 11/1/8/1/H1.
Hotchins, D.G. et al 1976. A summary geology, siemicity, geomorphology and hydro geology
of the Okavango Delta. Department of Geological Survey, MMEWR. Gaborone. Botswana
Hughes DA, Andersson L, Wilk J, Savenije HHG (2006) Regional calibration of the Pitman
model for the Okavango River. J Hydrol 331:304
King, J.M., Brown, C.A. and Sabet, H. 2003. A scenario-based holistic approach to
environmental flow assessments for regulated rivers. Rivers Research and Applications 19
(5-6). Pg 619-640.
Liebenberg, P. 2009. Technical report on irrigation development in the Namibia Section of
the Okavango River Basin. Unpublished report produced for the Okavango Basin TDA.
Mazvimavi D, Wolski P (2006) Long-term variations of annual flows of the Okavango and
Zambezi rivers. Phys Chem Earth 31:944951
Mazvimavi, D. and Motsholapheko, R.M. 2008. Water Resource Use and Challenges for
River Basin Management along the Ephemeral Boteti River, Botswana. In Manzungu, E.
(Ed), Towards a new water creed. Water management, governance and livelihoods in
southern Africa. InWent Capacity Building International, Germany.
McCarthy TS, Bloem A, Larkin PA (1998a) Observations on the hydrology and geohydrology
of the Okavango Delta. S Afr JGeol 101(2):101117
McCarthy TS, Cooper GRJ, Tyson PD, Ellery WN (2000) Seasonal flooding in the Okavango
Delta, Botswana: recent history and future prospects. S Afr J Sci 96:2533
Murray-Hudson M, Wolski P, Ringrose S (2006) Scenarios of the impact of local and
upstream changes in climate and water use on hydro-ecology in the Okavango Delta,
Botswana. J Hydrol 331:7384
ODMP 2008. Okavango Delta Management Plan January 2008. Department of
Environmental Affairs, Gaborone, Botswana
Pinheiro, I., Gabaake G. and Heyns P. (2003). "Cooperation in the Okavango River basin:
The OKACOM perspective." In Anthony Turton, Peter Ashton, & Eugene Cloete (Eds.),
Transboundary rivers, sovereignty and development: Hydropolitical drivers in the Okavango
River basin (pages 105-118). Pretoria, South Africa: African Water Issues Research Unit &
Green Cross International.
Wolski P, Murray-Hudson M (2006) Flooding dynamics in a large low-gradient alluvial fan,
the Okavango Delta, Botswana, from analysis and interpretation of a 30-year hydrometric
record. Hydrol Earth Syst Sci 10:127137
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E-Flows Scenario Report Hydrology
APPENDIX A : ECOLOGICALLY RELEVANT FLOW STATISTICS
83
E-Flows Scenario Report Hydrology
APPENDIX A1 : Site 1 : Capico
--------------------------------------------------
Capico Present Day
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/15 01:46:56 PM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.20
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 0.07
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 40.47
Mean Flood Volume (Mm3): 437.10
Dry/T1 threshold (m3/s): 15.40
T1/Wet threshold (m3/s): 22.26
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 22.3
Mean flood peak (m3/s) 40.47
Mean flood vol (Mm3): 437.10
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 11.7
*Dry season duration (Dd) [days]: 86.0
*Max 5d flood season Q (Fq) [m3/s]: 38.5
*Flood volume (Fv) [Mm3]: 455.84
*Wet season duration (Fd) [days]: 197.0
*T2 recession slope (T2s) [m3/s/d]: -0.122
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 33.0
*Wet season onset (Fo) [cal week]: 45.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 1.5
Dry season duration (Dd) [days]: 40.5
Max 5d flood season Q (Fq) [m3/s]: 10.7
Flood volume (Fv) [Mm3]: 210.04
Wet season duration (Fd) [days]: 69.5
T2 recession slope (T2s) [m3/s/d]: 0.045
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 5.5
Wet season onset (Fo) [cal week]: 21.9
FP inund onset (FPDo) [cal week]: N/A
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E-Flows Scenario Report Hydrology
--------------------------------------------------
Capico Low Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/15 01:50:37 PM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.20
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 0.07
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 40.47
Mean Flood Volume (Mm3): 437.10
Dry/T1 threshold (m3/s): 15.40
T1/Wet threshold (m3/s): 22.26
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 13.9
Mean flood peak (m3/s) 38.08
Mean flood vol (Mm3): 253.56
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 0.4
*Dry season duration (Dd) [days]: 212.0
*Max 5d flood season Q (Fq) [m3/s]: 36.0
*Flood volume (Fv) [Mm3]: 230.74
*Wet season duration (Fd) [days]: 97.0
*T2 recession slope (T2s) [m3/s/d]: -0.249
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 22.0
*Wet season onset (Fo) [cal week]: 5.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 0.2
Dry season duration (Dd) [days]: 46.9
Max 5d flood season Q (Fq) [m3/s]: 9.9
Flood volume (Fv) [Mm3]: 150.90
Wet season duration (Fd) [days]: 49.6
T2 recession slope (T2s) [m3/s/d]: 0.172
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 5.2
Wet season onset (Fo) [cal week]: 18.1
FP inund onset (FPDo) [cal week]: N/A
85
E-Flows Scenario Report Hydrology
--------------------------------------------------
Capico Medium Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/15 01:53:25 PM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.20
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 0.07
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 40.47
Mean Flood Volume (Mm3): 437.10
Dry/T1 threshold (m3/s): 15.40
T1/Wet threshold (m3/s): 22.26
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 13.9
Mean flood peak (m3/s) 38.07
Mean flood vol (Mm3): 253.02
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 0.3
*Dry season duration (Dd) [days]: 212.0
*Max 5d flood season Q (Fq) [m3/s]: 36.0
*Flood volume (Fv) [Mm3]: 230.62
*Wet season duration (Fd) [days]: 97.0
*T2 recession slope (T2s) [m3/s/d]: -0.249
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 22.0
*Wet season onset (Fo) [cal week]: 5.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 0.2
Dry season duration (Dd) [days]: 46.9
Max 5d flood season Q (Fq) [m3/s]: 9.9
Flood volume (Fv) [Mm3]: 151.30
Wet season duration (Fd) [days]: 49.8
T2 recession slope (T2s) [m3/s/d]: 0.172
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 5.2
Wet season onset (Fo) [cal week]: 18.1
FP inund onset (FPDo) [cal week]: N/A
86
E-Flows Scenario Report Hydrology
--------------------------------------------------
Capico High Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/15 01:55:41 PM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.20
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 0.07
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 40.47
Mean Flood Volume (Mm3): 437.10
Dry/T1 threshold (m3/s): 15.40
T1/Wet threshold (m3/s): 22.26
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 13.9
Mean flood peak (m3/s) 38.03
Mean flood vol (Mm3): 251.98
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 0.3
*Dry season duration (Dd) [days]: 212.0
*Max 5d flood season Q (Fq) [m3/s]: 36.0
*Flood volume (Fv) [Mm3]: 230.35
*Wet season duration (Fd) [days]: 97.0
*T2 recession slope (T2s) [m3/s/d]: -0.243
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 22.0
*Wet season onset (Fo) [cal week]: 5.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 0.2
Dry season duration (Dd) [days]: 47.2
Max 5d flood season Q (Fq) [m3/s]: 9.9
Flood volume (Fv) [Mm3]: 150.11
Wet season duration (Fd) [days]: 49.3
T2 recession slope (T2s) [m3/s/d]: 0.174
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 5.2
Wet season onset (Fo) [cal week]: 18.1
FP inund onset (FPDo) [cal week]: N/A
87
E-Flows Scenario Report Hydrology
APPENDIX A2 : Site 2 : Mucundi
--------------------------------------------------
Mucundi Present Day
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/07 11:35:38 AM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 5.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 472.41
Mean Flood Volume (Mm3): 3863.85
Dry/T1 threshold (m3/s): 61.61
T1/Wet threshold (m3/s): 170.47
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 170.5
Mean flood peak (m3/s) 472.41
Mean flood vol (Mm3): 3863.85
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 31.8
*Dry season duration (Dd) [days]: 96.0
*Max 5d flood season Q (Fq) [m3/s]: 429.2
*Flood volume (Fv) [Mm3]: 3712.45
*Wet season duration (Fd) [days]: 148.0
*T2 recession slope (T2s) [m3/s/d]: -1.658
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 31.0
*Wet season onset (Fo) [cal week]: 26.5
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 8.1
Dry season duration (Dd) [days]: 43.0
Max 5d flood season Q (Fq) [m3/s]: 178.6
Flood volume (Fv) [Mm3]: 1856.11
Wet season duration (Fd) [days]: 49.4
T2 recession slope (T2s) [m3/s/d]: 0.261
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 5.1
Wet season onset (Fo) [cal week]: 23.7
FP inund onset (FPDo) [cal week]: N/A
88
E-Flows Scenario Report Hydrology
--------------------------------------------------
Mucundi Low Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/07 11:37:55 AM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 5.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 472.41
Mean Flood Volume (Mm3): 3863.85
Dry/T1 threshold (m3/s): 61.61
T1/Wet threshold (m3/s): 170.47
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 157.7
Mean flood peak (m3/s) 471.18
Mean flood vol (Mm3): 3607.24
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 15.5
*Dry season duration (Dd) [days]: 124.0
*Max 5d flood season Q (Fq) [m3/s]: 432.4
*Flood volume (Fv) [Mm3]: 3557.81
*Wet season duration (Fd) [days]: 135.0
*T2 recession slope (T2s) [m3/s/d]: -1.971
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 28.0
*Wet season onset (Fo) [cal week]: 5.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 6.4
Dry season duration (Dd) [days]: 42.9
Max 5d flood season Q (Fq) [m3/s]: 181.5
Flood volume (Fv) [Mm3]: 1751.55
Wet season duration (Fd) [days]: 44.8
T2 recession slope (T2s) [m3/s/d]: 0.273
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 5.0
Wet season onset (Fo) [cal week]: 23.5
FP inund onset (FPDo) [cal week]: N/A
89
E-Flows Scenario Report Hydrology
--------------------------------------------------
Mucundi Medium Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/07 11:39:10 AM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 5.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 472.41
Mean Flood Volume (Mm3): 3863.85
Dry/T1 threshold (m3/s): 61.61
T1/Wet threshold (m3/s): 170.47
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 144.3
Mean flood peak (m3/s) 475.34
Mean flood vol (Mm3): 3287.12
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 11.6
*Dry season duration (Dd) [days]: 143.0
*Max 5d flood season Q (Fq) [m3/s]: 434.2
*Flood volume (Fv) [Mm3]: 3177.74
*Wet season duration (Fd) [days]: 123.0
*T2 recession slope (T2s) [m3/s/d]: -2.169
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 27.0
*Wet season onset (Fo) [cal week]: 4.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 4.7
Dry season duration (Dd) [days]: 32.4
Max 5d flood season Q (Fq) [m3/s]: 178.7
Flood volume (Fv) [Mm3]: 1669.38
Wet season duration (Fd) [days]: 43.4
T2 recession slope (T2s) [m3/s/d]: 0.389
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 3.6
Wet season onset (Fo) [cal week]: 19.9
FP inund onset (FPDo) [cal week]: N/A
90
E-Flows Scenario Report Hydrology
--------------------------------------------------
Mucundi High Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/07 11:40:21 AM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 5.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 472.41
Mean Flood Volume (Mm3): 3863.85
Dry/T1 threshold (m3/s): 61.61
T1/Wet threshold (m3/s): 170.47
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 131.9
Mean flood peak (m3/s) 457.80
Mean flood vol (Mm3): 2658.64
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 23.7
*Dry season duration (Dd) [days]: 152.0
*Max 5d flood season Q (Fq) [m3/s]: 425.8
*Flood volume (Fv) [Mm3]: 2531.32
*Wet season duration (Fd) [days]: 111.0
*T2 recession slope (T2s) [m3/s/d]: -2.074
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 27.0
*Wet season onset (Fo) [cal week]: 4.5
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 7.1
Dry season duration (Dd) [days]: 43.1
Max 5d flood season Q (Fq) [m3/s]: 185.3
Flood volume (Fv) [Mm3]: 1701.93
Wet season duration (Fd) [days]: 50.8
T2 recession slope (T2s) [m3/s/d]: 0.265
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 3.7
Wet season onset (Fo) [cal week]: 15.8
FP inund onset (FPDo) [cal week]: N/A
91
E-Flows Scenario Report Hydrology
APPENDIX A3 : Site 3 : Cuito Cuanavale
(Note: The Low, Medium and High scenarios do not include significant development upstream
of Cuito Cuanavale, hence only a Present Day summary is provided here).
92
E-Flows Scenario Report Hydrology
--------------------------------------------------
Cuito Cuanavale Present Day
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/05/07 11:42:00 AM
Software: v1.02
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 2.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 186.63
Mean Flood Volume (Mm3): 1990.20
Dry/T1 threshold (m3/s): 108.44
T1/Wet threshold (m3/s): 120.57
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 120.6
Mean flood peak (m3/s) 186.63
Mean flood vol (Mm3): 1990.20
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 80.1
*Dry season duration (Dd) [days]: 182.0
*Max 5d flood season Q (Fq) [m3/s]: 163.5
*Flood volume (Fv) [Mm3]: 1967.56
*Wet season duration (Fd) [days]: 162.0
*T2 recession slope (T2s) [m3/s/d]: -0.700
*FP area of inundation (FPA) [km2]: 1.07
*FP inundation dur (FPDi) [days]: 144.0
*Dry season onset (Do) [cal week]: 25.0
*Wet season onset (Fo) [cal week]: 8.0
*FP inund onset (FPDo) [cal week]: 5.0
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 13.0
Dry season duration (Dd) [days]: 92.7
Max 5d flood season Q (Fq) [m3/s]: 66.0
Flood volume (Fv) [Mm3]: 1331.89
Wet season duration (Fd) [days]: 87.2
T2 recession slope (T2s) [m3/s/d]: 1.037
FP area of inundation (FPA) [km2]: 0.26
FP inundation dur (FPDi) [days]: 74.2
Dry season onset (Do) [cal week]: 9.9
Wet season onset (Fo) [cal week]: 22.1
FP inund onset (FPDo) [cal week]: 21.5
93
E-Flows Scenario Report Hydrology
APPENDIX A4 : Site 4 : Kapako
--------------------------------------------------
Kapako Present Day
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 03:54:35 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 6.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 518.90
Mean Flood Volume (Mm3): 3800.52
Dry/T1 threshold (m3/s): 89.05
T1/Wet threshold (m3/s): 168.29
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 168.3
Mean flood peak (m3/s) 518.90
Mean flood vol (Mm3): 3800.52
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 35.0
*Dry season duration (Dd) [days]: 135.0
*Max 5d flood season Q (Fq) [m3/s]: 460.6
*Flood volume (Fv) [Mm3]: 3693.53
*Wet season duration (Fd) [days]: 154.0
*T2 recession slope (T2s) [m3/s/d]: -1.804
*FP area of inundation (FPA) [km2]: 37.30
*FP inundation dur (FPDi) [days]: 158.5
*Dry season onset (Do) [cal week]: 30.0
*Wet season onset (Fo) [cal week]: 4.0
*FP inund onset (FPDo) [cal week]: 4.0
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 8.6
Dry season duration (Dd) [days]: 46.7
Max 5d flood season Q (Fq) [m3/s]: 199.0
Flood volume (Fv) [Mm3]: 1830.29
Wet season duration (Fd) [days]: 49.1
T2 recession slope (T2s) [m3/s/d]: 0.372
FP area of inundation (FPA) [km2]: 3.64
FP inundation dur (FPDi) [days]: 42.3
Dry season onset (Do) [cal week]: 4.7
Wet season onset (Fo) [cal week]: 18.6
FP inund onset (FPDo) [cal week]: 23.0
94
E-Flows Scenario Report Hydrology
--------------------------------------------------
Kapako Low Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 03:57:36 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 6.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 518.90
Mean Flood Volume (Mm3): 3800.52
Dry/T1 threshold (m3/s): 89.05
T1/Wet threshold (m3/s): 168.29
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 156.8
Mean flood peak (m3/s) 514.11
Mean flood vol (Mm3): 3588.66
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 20.2
*Dry season duration (Dd) [days]: 150.0
*Max 5d flood season Q (Fq) [m3/s]: 455.9
*Flood volume (Fv) [Mm3]: 3535.06
*Wet season duration (Fd) [days]: 147.0
*T2 recession slope (T2s) [m3/s/d]: -2.207
*FP area of inundation (FPA) [km2]: 37.25
*FP inundation dur (FPDi) [days]: 149.5
*Dry season onset (Do) [cal week]: 28.0
*Wet season onset (Fo) [cal week]: 4.0
*FP inund onset (FPDo) [cal week]: 4.0
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 7.3
Dry season duration (Dd) [days]: 45.2
Max 5d flood season Q (Fq) [m3/s]: 198.4
Flood volume (Fv) [Mm3]: 1749.68
Wet season duration (Fd) [days]: 45.5
T2 recession slope (T2s) [m3/s/d]: 0.454
FP area of inundation (FPA) [km2]: 3.72
FP inundation dur (FPDi) [days]: 40.2
Dry season onset (Do) [cal week]: 4.9
Wet season onset (Fo) [cal week]: 15.4
FP inund onset (FPDo) [cal week]: 22.0
95
E-Flows Scenario Report Hydrology
--------------------------------------------------
Kapako Medium Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 04:00:50 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 6.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 518.90
Mean Flood Volume (Mm3): 3800.52
Dry/T1 threshold (m3/s): 89.05
T1/Wet threshold (m3/s): 168.29
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 144.8
Mean flood peak (m3/s) 504.79
Mean flood vol (Mm3): 3270.22
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 15.4
*Dry season duration (Dd) [days]: 168.0
*Max 5d flood season Q (Fq) [m3/s]: 455.5
*Flood volume (Fv) [Mm3]: 3209.08
*Wet season duration (Fd) [days]: 130.0
*T2 recession slope (T2s) [m3/s/d]: -2.370
*FP area of inundation (FPA) [km2]: 37.20
*FP inundation dur (FPDi) [days]: 134.5
*Dry season onset (Do) [cal week]: 27.0
*Wet season onset (Fo) [cal week]: 3.5
*FP inund onset (FPDo) [cal week]: 4.0
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 5.5
Dry season duration (Dd) [days]: 41.4
Max 5d flood season Q (Fq) [m3/s]: 198.0
Flood volume (Fv) [Mm3]: 1660.50
Wet season duration (Fd) [days]: 42.8
T2 recession slope (T2s) [m3/s/d]: 0.515
FP area of inundation (FPA) [km2]: 3.86
FP inundation dur (FPDi) [days]: 38.6
Dry season onset (Do) [cal week]: 4.6
Wet season onset (Fo) [cal week]: 11.8
FP inund onset (FPDo) [cal week]: 15.4
96
E-Flows Scenario Report Hydrology
--------------------------------------------------
Kapako High Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 04:05:14 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 6.00
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.00
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 518.90
Mean Flood Volume (Mm3): 3800.52
Dry/T1 threshold (m3/s): 89.05
T1/Wet threshold (m3/s): 168.29
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 135.0
Mean flood peak (m3/s) 491.90
Mean flood vol (Mm3): 2704.10
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 19.1
*Dry season duration (Dd) [days]: 176.0
*Max 5d flood season Q (Fq) [m3/s]: 441.6
*Flood volume (Fv) [Mm3]: 2580.08
*Wet season duration (Fd) [days]: 117.0
*T2 recession slope (T2s) [m3/s/d]: -2.143
*FP area of inundation (FPA) [km2]: 36.04
*FP inundation dur (FPDi) [days]: 120.5
*Dry season onset (Do) [cal week]: 27.0
*Wet season onset (Fo) [cal week]: 5.0
*FP inund onset (FPDo) [cal week]: 4.0
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 8.7
Dry season duration (Dd) [days]: 47.1
Max 5d flood season Q (Fq) [m3/s]: 200.7
Flood volume (Fv) [Mm3]: 1727.04
Wet season duration (Fd) [days]: 52.1
T2 recession slope (T2s) [m3/s/d]: 0.594
FP area of inundation (FPA) [km2]: 4.22
FP inundation dur (FPDi) [days]: 50.5
Dry season onset (Do) [cal week]: 5.1
Wet season onset (Fo) [cal week]: 12.0
FP inund onset (FPDo) [cal week]: 12.0
97
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APPENDIX A5 : Sites 5 an 6 : Popa Falls and Panhandle
--------------------------------------------------
Popa Present Day
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 04:23:14 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.20
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 697.89
Mean Flood Volume (Mm3): 5737.14
Dry/T1 threshold (m3/s): 167.79
T1/Wet threshold (m3/s): 289.09
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 289.1
Mean flood peak (m3/s) 697.89
Mean flood vol (Mm3): 5737.14
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 113.9
*Dry season duration (Dd) [days]: 115.0
*Max 5d flood season Q (Fq) [m3/s]: 624.8
*Flood volume (Fv) [Mm3]: 5269.15
*Wet season duration (Fd) [days]: 150.0
*T2 recession slope (T2s) [m3/s/d]: -1.877
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 33.0
*Wet season onset (Fo) [cal week]: 3.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 18.5
Dry season duration (Dd) [days]: 42.1
Max 5d flood season Q (Fq) [m3/s]: 255.9
Flood volume (Fv) [Mm3]: 2750.45
Wet season duration (Fd) [days]: 47.5
T2 recession slope (T2s) [m3/s/d]: 0.260
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 3.9
Wet season onset (Fo) [cal week]: 13.7
FP inund onset (FPDo) [cal week]: N/A
98
E-Flows Scenario Report Hydrology
--------------------------------------------------
Popa Low Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 04:30:57 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.20
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 697.89
Mean Flood Volume (Mm3): 5737.14
Dry/T1 threshold (m3/s): 167.79
T1/Wet threshold (m3/s): 289.09
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 278.2
Mean flood peak (m3/s) 693.61
Mean flood vol (Mm3): 5498.58
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 101.3
*Dry season duration (Dd) [days]: 130.0
*Max 5d flood season Q (Fq) [m3/s]: 622.8
*Flood volume (Fv) [Mm3]: 4980.77
*Wet season duration (Fd) [days]: 143.0
*T2 recession slope (T2s) [m3/s/d]: -2.112
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 31.0
*Wet season onset (Fo) [cal week]: 3.5
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 17.1
Dry season duration (Dd) [days]: 41.2
Max 5d flood season Q (Fq) [m3/s]: 256.0
Flood volume (Fv) [Mm3]: 2679.00
Wet season duration (Fd) [days]: 45.7
T2 recession slope (T2s) [m3/s/d]: 0.313
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 4.3
Wet season onset (Fo) [cal week]: 13.6
FP inund onset (FPDo) [cal week]: N/A
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E-Flows Scenario Report Hydrology
--------------------------------------------------
Popa Medium Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 04:33:53 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.20
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 697.89
Mean Flood Volume (Mm3): 5737.14
Dry/T1 threshold (m3/s): 167.79
T1/Wet threshold (m3/s): 289.09
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 263.0
Mean flood peak (m3/s) 681.27
Mean flood vol (Mm3): 5012.48
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 92.5
*Dry season duration (Dd) [days]: 145.0
*Max 5d flood season Q (Fq) [m3/s]: 613.3
*Flood volume (Fv) [Mm3]: 4450.10
*Wet season duration (Fd) [days]: 129.0
*T2 recession slope (T2s) [m3/s/d]: -2.149
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 30.0
*Wet season onset (Fo) [cal week]: 4.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 15.3
Dry season duration (Dd) [days]: 42.7
Max 5d flood season Q (Fq) [m3/s]: 256.0
Flood volume (Fv) [Mm3]: 2618.76
Wet season duration (Fd) [days]: 45.8
T2 recession slope (T2s) [m3/s/d]: 0.536
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 4.6
Wet season onset (Fo) [cal week]: 11.7
FP inund onset (FPDo) [cal week]: N/A
100
E-Flows Scenario Report Hydrology
--------------------------------------------------
Popa High Development
SUMMARY HYDROLOGICAL DATA
--------------------------------------------------
DateTime: 2009/06/04 04:36:31 PM
Software: v1.03
--------------------------------------------------
PARAMETERS:
Hydro year start month: 10
Dry Season:
Ephemeral: Mean Ann Q factor: 0.40
Perennial: Min Dry Q factor: 2.10
Wet season crossings:
Mean Ann Q factor: 1.00
T2:
Recession rate < (m3/s/d): 1.20
Rate calculated over (days): 15
Reference thresholds:
Mean Flood Peak (m3/s): 697.89
Mean Flood Volume (Mm3): 5737.14
Dry/T1 threshold (m3/s): 167.79
T1/Wet threshold (m3/s): 289.09
--------------------------------------------------
SUMMARY STATISTICS:
--------------------------------------------------
Do: Dry Season Onset (cal week)
MAR (m3/s): 203.4
Mean flood peak (m3/s) 648.66
Mean flood vol (Mm3): 3809.54
Median(*) / Mode(+) values:
*Min 5d dry season Q (Dq) [m3/s]: 21.1
*Dry season duration (Dd) [days]: 193.0
*Max 5d flood season Q (Fq) [m3/s]: 578.0
*Flood volume (Fv) [Mm3]: 3294.28
*Wet season duration (Fd) [days]: 103.0
*T2 recession slope (T2s) [m3/s/d]: -3.171
*FP area of inundation (FPA) [km2]: N/A
*FP inundation dur (FPDi) [days]: N/A
*Dry season onset (Do) [cal week]: 26.0
*Wet season onset (Fo) [cal week]: 5.0
*FP inund onset (FPDo) [cal week]: N/A
Standard deviations:
Min 5d dry season Q (Dq) [m3/s]: 11.9
Dry season duration (Dd) [days]: 42.9
Max 5d flood season Q (Fq) [m3/s]: 263.0
Flood volume (Fv) [Mm3]: 2486.67
Wet season duration (Fd) [days]: 46.5
T2 recession slope (T2s) [m3/s/d]: 1.058
FP area of inundation (FPA) [km2]: N/A
FP inundation dur (FPDi) [days]: N/A
Dry season onset (Do) [cal week]: 5.0
Wet season onset (Fo) [cal week]: 12.4
FP inund onset (FPDo) [cal week]: N/A
101
E-Flows Scenario Report Hydrology
The Okavango River Basin Transboundary Diagnostic Analysis Technical Reports
In 1994, the three riparian countries of the Okavango
Diagnostic Analysis to establish a base of available
River Basin Angola, Botswana and Namibia
scientific evidence to guide future decision making.
agreed to plan for collaborative management of the
The study, created from inputs from multi-disciplinary
natural resources of the Okavango, forming the
teams in each country, with specialists in hydrology,
Permanent Okavango River Basin Water Commission
hydraulics, channel form, water quality, vegetation,
(OKACOM). In 2003, with funding from the Global
aquatic invertebrates, fish, birds, river-dependent
Environment Facility, OKACOM launched the
terrestrial wildlife, resource economics and socio-
Environmental Protection and Sustainable
cultural issues, was coordinated and managed by a
Management of the Okavango River Basin (EPSMO)
group of specialists from the southern African region
Project to coordinate development and to anticipate
in 2008 and 2009.
and address threats to the river and the associated
communities and environment. Implemented by the
The following specialist technical reports were
United Nations Development Program and executed
produced as part of this process and form substantive
by the United Nations Food and Agriculture
background content for the Okavango River Basin
Organization, the project produced the Transboundary
Transboundary Diagnostic Analysis
Final Study
Reports integrating findings from all country and background reports, and covering the entire
Reports
basin.
Aylward, B.
Economic Valuation of Basin Resources: Final Report to
EPSMO Project of the UN Food & Agriculture Organization as
an Input to the Okavango River Basin Transboundary
Diagnostic Analysis
Barnes, J. et al.
Okavango River Basin Transboundary Diagnostic Analysis:
Socio-Economic Assessment Final Report
King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment Project
C.A.
Initiation Report (Report No: 01/2009)
King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment EFA
C.A.
Process Report (Report No: 02/2009)
King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Guidelines for Data Collection, Analysis and Scenario Creation
(Report No: 03/2009)
Bethune, S. Mazvimavi,
Okavango River Basin Environmental Flow Assessment
D. and Quintino, M.
Delineation Report (Report No: 04/2009)
Beuster, H.
Okavango River Basin Environmental Flow Assessment
Hydrology Report: Data And Models(Report No: 05/2009)
Beuster,
H. Okavango River Basin Environmental Flow Assessment
Scenario Report : Hydrology (Report No: 06/2009)
Jones, M.J.
The Groundwater Hydrology of The Okavango Basin (FAO
Internal Report, April 2010)
King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Scenario Report: Ecological and Social Predictions (Volume 1
of 4)(Report No. 07/2009)
King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Scenario Report: Ecological and Social Predictions (Volume 2
of 4: Indicator results) (Report No. 07/2009)
King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Scenario Report: Ecological and Social Predictions: Climate
Change Scenarios (Volume 3 of 4) (Report No. 07/2009)
King, J., Brown, C.A.,
Okavango River Basin Environmental Flow Assessment
Joubert, A.R. and
Scenario Report: Biophysical Predictions (Volume 4 of 4:
Barnes, J.
Climate Change Indicator Results) (Report No: 07/2009)
King, J., Brown, C.A.
Okavango River Basin Environmental Flow Assessment Project
and Barnes, J.
Final Report (Report No: 08/2009)
Malzbender, D.
Environmental Protection And Sustainable Management Of The
Okavango River Basin (EPSMO): Governance Review
Vanderpost, C. and
Database and GIS design for an expanded Okavango Basin
Dhliwayo, M.
Information System (OBIS)
Veríssimo, Luis
GIS Database for the Environment Protection and Sustainable
Management of the Okavango River Basin Project
102
E-Flows Scenario Report Hydrology
Wolski,
P.
Assessment of hydrological effects of climate change in the
Okavango Basin
Country Reports
Angola
Andrade e Sousa,
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Biophysical Series
Helder André de
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina: Sedimentologia &
Geomorfologia
Gomes, Amândio
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina: Vegetação
Gomes,
Amândio
Análise Técnica, Biofísica e Socio-Económica do Lado
Angolano da Bacia Hidrográfica do Rio Cubango: Relatório
Final:Vegetação da Parte Angolana da Bacia Hidrográfica Do
Rio Cubango
Livramento, Filomena
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina:Macroinvertebrados
Miguel, Gabriel Luís
Análise Técnica, Biofísica E Sócio-Económica do Lado
Angolano da Bacia Hidrográfica do Rio Cubango:
Subsídio Para o Conhecimento Hidrogeológico
Relatório de Hidrogeologia
Morais, Miguel
Análise Diagnóstica Transfronteiriça da Bacia do Análise Rio
Cubango (Okavango): Módulo da Avaliação do Caudal
Ambiental: Relatório do Especialista País: Angola Disciplina:
Ictiofauna
Morais,
Miguel
Análise Técnica, Biófisica e Sócio-Económica do Lado
Angolano da Bacia Hidrográfica do Rio Cubango: Relatório
Final: Peixes e Pesca Fluvial da Bacia do Okavango em Angola
Pereira, Maria João
Qualidade da Água, no Lado Angolano da Bacia Hidrográfica
do Rio Cubango
Santos,
Carmen
Ivelize
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Van-Dúnem S. N.
Okavango: Módulo do Caudal Ambiental: Relatório de
Especialidade: Angola: Vida Selvagem
Santos, Carmen Ivelize
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Van-Dúnem S.N.
Okavango:Módulo Avaliação do Caudal Ambiental: Relatório de
Especialidade: Angola: Aves
Botswana Bonyongo, M.C.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Botswana: Discipline: Wildlife
Hancock, P.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module : Specialist Report: Country:
Botswana: Discipline: Birds
Mosepele,
K. Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Botswana: Discipline: Fish
Mosepele, B. and
Okavango River Basin Technical Diagnostic Analysis:
Dallas, Helen
Environmental Flow Module: Specialist Report: Country:
Botswana: Discipline: Aquatic Macro Invertebrates
Namibia
Collin Christian &
Okavango River Basin: Transboundary Diagnostic Analysis
Associates CC
Project: Environmental Flow Assessment Module:
Geomorphology
Curtis, B.A.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report Country:
Namibia Discipline: Vegetation
Bethune, S.
Environmental Protection and Sustainable Management of the
Okavango River Basin (EPSMO): Transboundary Diagnostic
Analysis: Basin Ecosystems Report
Nakanwe, S.N.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Namibia: Discipline: Aquatic Macro Invertebrates
Paxton,
M. Okavango River Basin Transboundary Diagnostic Analysis:
Environmental Flow Module: Specialist
Report:Country:Namibia: Discipline: Birds (Avifauna)
Roberts, K.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Namibia: Discipline: Wildlife
Waal,
B.V. Okavango River Basin Technical Diagnostic Analysis:
103
E-Flows Scenario Report Hydrology
Environmental Flow Module: Specialist Report: Country:
Namibia:Discipline: Fish Life
Country Reports
Angola
Gomes, Joaquim
Análise Técnica dos Aspectos Relacionados com o Potencial
Socioeconomic
Duarte
de Irrigação no Lado Angolano da Bacia Hidrográfica do Rio
Series
Cubango: Relatório Final
Mendelsohn,
.J.
Land use in Kavango: Past, Present and Future
Pereira, Maria João
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina: Qualidade da Água
Saraiva, Rute et al.
Diagnóstico Transfronteiriço Bacia do Okavango: Análise
Socioeconómica Angola
Botswana Chimbari, M. and
Okavango River Basin Trans-Boundary Diagnostic Assessment
Magole, Lapologang
(TDA): Botswana Component: Partial Report: Key Public Health
Issues in the Okavango Basin, Botswana
Magole,
Lapologang
Transboundary Diagnostic Analysis of the Botswana Portion of
the Okavango River Basin: Land Use Planning
Magole, Lapologang
Transboundary Diagnostic Analysis (TDA) of the Botswana p
Portion of the Okavango River Basin: Stakeholder Involvement
in the ODMP and its Relevance to the TDA Process
Masamba,
W.R.
Transboundary Diagnostic Analysis of the Botswana Portion of
the Okavango River Basin: Output 4: Water Supply and
Sanitation
Masamba,W.R.
Transboundary Diagnostic Analysis of the Botswana Portion of
the Okavango River Basin: Irrigation Development
Mbaiwa.J.E. Transboundary Diagnostic Analysis of the Okavango River
Basin: the Status of Tourism Development in the Okavango
Delta: Botswana
Mbaiwa.J.E. &
Assessing the Impact of Climate Change on Tourism Activities
Mmopelwa, G.
and their Economic Benefits in the Okavango Delta
Mmopelwa,
G.
Okavango River Basin Trans-boundary Diagnostic Assessment:
Botswana Component: Output 5: Socio-Economic Profile
Ngwenya, B.N.
Final Report: A Socio-Economic Profile of River Resources and
HIV and AIDS in the Okavango Basin: Botswana
Vanderpost,
C.
Assessment of Existing Social Services and Projected Growth
in the Context of the Transboundary Diagnostic Analysis of the
Botswana Portion of the Okavango River Basin
Namibia
Barnes, J and
Okavango River Basin Technical Diagnostic Analysis:
Wamunyima, D
Environmental Flow Module: Specialist Report:
Country: Namibia: Discipline: Socio-economics
Collin Christian &
Technical Report on Hydro-electric Power Development in the
Associates CC
Namibian Section of the Okavango River Basin
Liebenberg, J.P.
Technical Report on Irrigation Development in the Namibia
Section of the Okavango River Basin
Ortmann, Cynthia L.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module : Specialist Report Country:
Namibia: discipline: Water Quality
Nashipili,
Okavango River Basin Technical Diagnostic Analysis: Specialist
Ndinomwaameni
Report: Country: Namibia: Discipline: Water Supply and
Sanitation
Paxton,
C.
Transboundary Diagnostic Analysis: Specialist Report:
Discipline: Water Quality Requirements For Human Health in
the Okavango River Basin: Country: Namibia
.
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