E-Flows Hydrology Report: Data and models
EPSMO-BIOKAVANGO
Okavango River Basin
Environmental Flow Assessment
Hydrology Report:
Data and Models
Report No: 05/2009
H. Beuster, et al.
April 2010
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E-Flows Hydrology Report: Data and models
DOCUMENT DETAILS
PROJECT
Environment protection and sustainable management of
the Okavango River Basin: Preliminary Environmental
Flows Assessment
TITLE:
Hydrology Report: Data and models
DATE: June
2009
LEAD AUTHORS:
H. Beuster
REPORT NO.:
05/2009
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 G Quintino, P N Shidute, F Tibe, P Wolski
.THE TEAM
Project Managers
Celeste Espach
Keta Mosepele
Chaminda Rajapakse
Aune-Lea Hatutale
Piotr Wolski
Nkobi Moleele
Mathews Katjimune
Geofrey Khwarae
assisted by Penehafo
EFA Process
Shidute
Management
Angola
Andre Mostert
Jackie King
Manual Quintino (Team
Shishani Nakanwe
Cate Brown
Leader and OBSC
Cynthia Ortmann
Hans Beuster
member)
Mark Paxton
Jon Barnes
Carlos Andrade
Kevin Roberts
Alison Joubert
Helder André de Andrade
Ben van de Waal
Mark Rountree
e Sousa
Dorothy Wamunyima
Amândio Gomes
assisted by
Okavango Basin Steering
Filomena Livramento
Ndinomwaameni Nashipili
Committee
Paulo Emilio Mendes
Tracy Molefi-Mbui
Gabriel Luis Miguel
Botswana
Laura Namene
Miguel Morais
Casper Bonyongo (Team
Mario João Pereira
Leader)
Rute Saraiva
Pete Hancock
Carmen Santos
Lapologang Magole
Wellington Masamba
Namibia
Hilary Masundire
Shirley Bethune (Team
Dominic Mazvimavi
Leader)
Joseph Mbaiwa
Colin Christian
Gagoitseope Mmopelwa
Barbara Curtis
Belda Mosepele
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E-Flows Hydrology Report: Data and models
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 (3 Volumes)
Report 08/2009:
Final Project Report
Other deliverables:
DSS Software
Process Management Team PowerPoint Presentations
Citation
No part of this document may be reproduced in any manner
without full acknowledgement of its source
This report should be cited as:
EPSMO-BIOKAVANGO Eflows Team. 2009. HYDROLOGY REPORT: DATA AND
MODELS. Report 05-2009. EPSMO/BIOKAVANGO Okavango Basin Environmental Flows
Assessment Project, OKACOM, Maun, Botswana.
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E-Flows Hydrology Report: Data and models
Acknowledgements
The Angolan hydrology team members acknowledge the following institutions and individuals
for their valuable support data collection of the Angolan portion of the Okavango River Basin:
· Gabinete do Vice Ministro do Planeamento, Dr. Pedro Luis da Fonseca (Office of the
Vice Minister for Planning, Dr. Pedro Luis da Fonseca);
· Direcção Nacional de Águas (National Directorate of Water);
· Direcção Nacional de Hidráulica Agrícola e Engenharia Rural (National Directorate of
Agrarian Hydraulics and Rural Engineering);
· Mr. Francisco Manuel Mateus, Provincial Director of Agriculture and Rural
Development in Kuando Kubango;
· National Coordination Unit (EPSMO);
· Project Management Unit (EPSMO)
The Botswana hydrology team members wish to acknowledge everyone who has
contributed in helping towards the completion and success of this study.
· It would have been difficult to in progress of this study had it not been work done
during the ODMP exercise.
· The team would like to thank everyone who took part in the development of the
Okavango Integrated Hydrological Model (DWA MIKE SHE model) as it helped a lot
in simulating flows in this exercise.
· The Botswana National Water Master Plan Review of 2006 was a valuable source of
information as it helped to establish the present water situation and possible future
water demands in the Botswana portion of the basin.
The Namibian hydrology team members would like to express their appreciation to the
following institutions and persons for supplying the data used in the report.
· The Ministry of Agriculture, Water and Forestry, Department of Water Affairs and
Forestry, Directorate of Resource Management, Division Hydrology, Namibia
· The Ministry of Agriculture, Water and Forestry, Department of Water Affairs and
Forestry, Directorate of Rural Water Supply
· The Ministry of Agriculture, Water and Forestry, Department of Water Affairs and
Forestry, Directorate of Agricultural Research and Training, Division of Analytical
Services
· The Ministry of Agriculture, Water and Forestry, Division of Agricultural Engineering
· The Ministry of Agriculture, Water and Forestry, Directorate of Veterinary Services
· The Ministry of Works and Transport, Namibia Meteorological Services
· Namibia OKACOM Basin Steering Committee member, Laura Namene
· Mr. Basil Dax from Nampower
· Informal discussions with Mr. Piet Heyns on Central Area water demands from the
Okavango River
· Namibia Water Corporation Ltd
· Collin Christiaan and Hans Beuster for the photographs
Finally, the hydrology team acknowledges the valuable contributions on flooding and
hydrological data exchange provided by Mr Guido van Langehove of the Namibian
Department of Water Affairs and Forestry.
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E-Flows Hydrology Report: Data and models
Executive Summary
Introduction
Flow scenarios form the basis of the environmental flow assessments that are being
undertaken for the Okavango River Basin. A hydrological working group consisting
of hydrologists from the three co-basin states of the Okavango River basin was
established to develop and populate the hydrological and hydraulic models for the
river basin and the delta and to develop flow scenarios.
This report (Volume 5) is the first of two reports produced by the Ecological Flow
Assessment (EFA) hydrological working group. The report provides an overview of
the current water resource situation and 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 report
should be read in conjunction with the Hydrological Scenario Modelling Report
(Volume 6), which describes the outcomes of the hydrological modelling of present
and possible future flow regimes.
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 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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E-Flows Hydrology Report: Data and models
Availability of Hydrological Data and Information
Hydrological modelling of the Okavango River basin is complicated by the limited
availability of measured stream flow and rainfall records. Long stream flow records
(starting in the 1930s) are available along the lower reaches of the Kavango and
Okavango at Rundu, Mukwe and Mohembo, but stream flow records in Angola are
only of the order of 10 years long, covering the early 1960s to mid 1970s. Measured
rainfall records in Angola are only available until 1972. These sequences were
extended with satellite rainfall by Wilk et al. (2006) to September 2003, which means
that a calibrated rainfall-runoff model could be used to generate stream flow
sequences for the period spanning hydrological years 1958-2002.
Hydrological and Hydraulic Models of the Basin
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. The modelling
sequence and linkages between the models are shown in Figure E-1 below.
Figure E-1 : Hydrological Modelling 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).
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
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E-Flows Hydrology Report: Data and models
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 (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 categories").
A summary of sub-basin rainfall and naturalised (undeveloped) runoff is shown in
Error! Reference source not found.E-1. The estimates are based on a re-
arrangement of rainfall-runoff simulations for the 24 sub-catchments in the Pitman
model configured by Hughes et. al. (2006).
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E-Flows Hydrology Report: Data and models
Table E-1 : Sub-basin Runoff
River / zone
Mean Annual
Mean Annual
Percentage
Area
Rainfall
Runoff
contribution
km2 mm million
m3/year
Cubango
14 400
1 028
1 846.3
17%
Cutato
4 200
1 220
800.1
7%
Cuchi
8 900
1 117
821.2
8%
Cacuchi
4 800
1 207
759.5
7%
Cuelei
7 500
1 114
697.4
6%
Cuebe 11
200
969
678.8
6%
Cuatir 11
600
787
134.3
1%
Cueio 3
700
787
57.0
1%
Cuiriri 12
900
986
565.8
5%
Cuito
24 300
1 051
3 338.7
31%
Cuanavale
7 750
1 073
595.6
5%
Lower Okavango
45 000
608
620.0
6%
Total (upstream of
Delta)
156 250
837
10 914
100%
Considering the limited availability of measured rainfall and stream flow records, the
existing Pitman-based rainfall-runoff model of the basin (Hughes et. al., 2006)
performs reasonably well, with good simulation of low flows and errors in peak flows
of about 20% (the model more often than not under-estimates peak flows). For
traditional water resource assessments the errors in peak flow simulation are not
considered to be serious, as it does not significantly affect estimates of run-of-river or
storage based yields. In the EFA study it was found that this does pose problems, in
that ecologists attach much greater importance to the magnitude of flood peaks and
found it difficult to relate simulated peak flows to their knowledge of observed floods
and associated ecosystem responses.
A recommendation of this study is that the rainfall-runoff model be re-calibrated with
a view to improve peak flow simulation. As part of the same exercise, the model
should be extended to cover the hydrological years from 2003 to as recently as
possible, as this period includes the recent above-normal flood events of 2009 and
2010. The re-calibration should make use of the stream flow records that are
becoming available from rehabilitated flow measuring stations in Angola.
The assembled suite of existing and new models provided adequate information on
river flow regimes and inundation patterns at the EFA sites, with some scope for
improvement. Major shortcomings include:
· The inability to provide modelled (scenario) information on water quality
changes in the system, mainly due to a lack of historical water quality
measurements for model calibration
· The absence of a sediment transport model (or models) in the basin upstream
of the Delta
· Basic one-dimensional, steady state hydrodynamic models were configured
for the floodplain sites in the basin (Cuito Cuanavale and Kapako), but these
could be improved substantially by using higher resolution topographical
information and the configuration of two-dimensional models.
Water Resource Development Information
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E-Flows Hydrology Report: Data and models
The hydrological working group engaged in an intensive exercise to collect
information about existing and possible future water resource developments in the
Okavango River basin. The information was assembled by means of literature
reviews and extensive consultations with water resource planners and managers in
the three co-basin states, and formed the basis for formulation of the water resource
development scenarios that were evaluated in the EFA.
The water resources of the basin are relatively un-developed at present. Current
water use consists mainly of:
· The urban water demands of Menongue and Cuito Cuanavale (Angola),
Rundu (Namibia), and Maun (Botswana)
· About 2 700 ha of irrigation in the Namibian portion of the basin
· Rural domestic and subsistence agricultural water demands and water
demands of the tourism sector (Namibia and Botswana), all of which are
small compared to the irrigation and urban demands
The end of the civil conflict in Angola has provided impetus to plans to develop the
dormant agricultural economy in the Angolan portion of the basin and to revive plans
for the construction of a number of hydropower schemes. Agricultural development
and the rehabilitation of the transport network will see associated growth in the urban
water demands of Menongue and Cuito Cuanavale. In Namibia, plans to improve
food security could result in substantial growth in irrigation water requirements,
although not at the same scale as foreseen for Angola. In Botswana, growth in urban
and agricultural water demand could be tempered by the need to conserve natural
resources and protect income derived from tourism in the Delta region. Against this
backdrop, the following water resource developments that could be associated with a
high water demand scenario were identified by the working group:
· About 15 000 ha of irrigation in Namibia
· About 338 000 ha of irrigation at various locations in Angola
· Completion of all planned hydropower stations in Angola, i.e. one storage
based and nine run-of-river hydropower stations,
· Extension of Grootfontein-Okavango link of the Eastern National Carrier in
Namibia (total capacity 100 Mm3/a)
· The possible construction of a hydropower station at Popa Falls in Namibia.
· Substantial growth in the urban water demands of Menongue, Cuito
Cuanavale, Rundu, and (to a lesser extent), Maun.
· Construction of a reservoir in the Boteti to supplement Maun's future water
demands.
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E-Flows Hydrology Report: Data and models
Table of Contents
EXECUTIVE SUMMARY
1INTRODUCTION ......................................................................................................... 15
1.1 Background ...................................................................................................... 15
1.2 Scope and purpose of hydrological working group .......................................... 15
1.3 Layout of this report ......................................................................................... 16
2STUDY AREA ............................................................................................................. 17
2.1 Description of the Okavango Basin .................................................................. 17
2.2 Delineation of the Okavango Basin into Integrated Units of Analysis .............. 19
3Hydrological and Hydraulic Models ............................................................................. 21
3.1 Overview .......................................................................................................... 21
3.2 Basin Hydrology ............................................................................................... 23
3.2.1
Estimates of naturalised (undeveloped) catchment runoff ..................... 23
3.2.2
Generation of Scenario Flow Sequences .............................................. 25
3.3 Delta Hydrology ................................................................................................ 27
3.3.1
Botswana Department of Water Affairs and Forestry MIKE SHE Model 27
3.3.2
HOORC Conceptual Model of the Delta ................................................ 29
3.3.3
Boteti Hydrology ..................................................................................... 30
3.3.4
Disaggregation and Hydro-Statistics ...................................................... 31
4Field Data Collection ................................................................................................... 34
4.1 Angola .............................................................................................................. 34
4.1.1
Introduction ............................................................................................ 34
4.1.2
Site 1: Cuebe River at Capico ................................................................ 34
4.1.3
Site 2: Cubango River at Mucundi ........................................................ 35
4.1.4
Site 3: Cuito River at Cuito Cuanavale .................................................. 36
4.2 Namibia ............................................................................................................ 37
4.2.1
Site 4: Okavango River at Kapako ......................................................... 37
4.2.2
Site 5: Okavango River at Popa Falls .................................................... 39
4.3 Botswana ......................................................................................................... 44
4.3.1
Site 6: Okavango River in the Panhandle at Shakawe .......................... 44
4.3.2
Site 7: Eastern Okavango Delta around Xakanaka .............................. 46
4.3.3
Site 8: Boteti River at Chanoga .............................................................. 46
5Hydrological Data and Information .............................................................................. 48
5.1 Measured flow records ..................................................................................... 48
5.1.1
Angola .................................................................................................... 48
5.1.2
Namibia .................................................................................................. 48
5.1.3
Botswana ............................................................................................... 48
5.2 Rainfall ............................................................................................................. 49
5.2.1
Angola .................................................................................................... 49
5.2.2
Namibia .................................................................................................. 49
5.2.3
Botswana ............................................................................................... 50
5.3 Evaporation ...................................................................................................... 50
5.3.1
Angola .................................................................................................... 50
5.3.2
Namibia .................................................................................................. 51
5.3.3
Botswana ............................................................................................... 51
5.4 Geohydrological data and information ............................................................. 51
5.4.1
Angola .................................................................................................... 51
5.4.2
Namibia .................................................................................................. 52
5.4.3
Botswana ............................................................................................... 58
6Water Resource Development Information ................................................................. 59
6.1 Population ........................................................................................................ 59
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E-Flows Hydrology Report: Data and models
6.1.1
Angola .................................................................................................... 59
6.1.2
Namibia .................................................................................................. 60
6.1.3
Botswana ............................................................................................... 61
6.2 Irrigation and Urban Water Demands .............................................................. 61
6.2.1
Angola Irrigation Water Demands ....................................................... 61
6.2.2
Angola Urban Water Demands ........................................................... 62
6.2.3
Namibia Irrigation Water Demands ..................................................... 62
6.2.4
Namibia Urban Water Demands ......................................................... 63
6.2.5
Botswana Irrigation and Urban Water Demands ................................ 64
6.3 Rural water demands ....................................................................................... 65
6.3.1
Angola .................................................................................................... 65
6.3.2
Namibia .................................................................................................. 66
6.3.3
Botswana ............................................................................................... 67
6.4 Hydropower ...................................................................................................... 67
6.4.1
Angola .................................................................................................... 67
6.4.2
Namibia .................................................................................................. 67
6.4.3
Botswana ............................................................................................... 68
7Water Resources Management Information ............................................................... 68
7.1 Data and Information Management .................................................................. 68
7.1.1
Angola .................................................................................................... 68
7.1.2
Namibia .................................................................................................. 68
7.1.3
Botswana ............................................................................................... 69
7.2 Data Sharing and Exchange ............................................................................ 70
7.2.1
Introduction ............................................................................................ 70
7.2.2
The existing situation ............................................................................. 71
7.2.3
Disaster Management ............................................................................ 71
8Conclusions and Recommendations ........................................................................... 72
8.1 General ............................................................................................................ 72
8.1.1
Hydrological and Hydraulic Models ........................................................ 72
8.1.2
Water Resource Development ............................................................... 73
8.2 Angola .............................................................................................................. 74
8.3 Namibia ............................................................................................................ 74
8.4 Botswana ......................................................................................................... 75
9REFERENCES ............................................................................................................ 76
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E-Flows Hydrology Report: Data and models
LIST OF TABLES
Table 2-1 : Location of the eight EFA sites ................................................................... 20
Table 5-1 : Location of Angolan flow measurement stations ........................................ 48
Table 5-2 : Location of Namibian flow measurement stations ...................................... 48
Table 5-3 : Location of Botswana flow measurement stations ...................................... 49
Table 5-4 : Location of Angolan rainfall stations ........................................................... 49
Table 5-5 : Location of Namibian rainfall stations ......................................................... 50
Table 5-6 : Location of Botswana rainfall stations ......................................................... 50
Table 5-7 : Location of Angolan evaporation measuring stations ................................. 50
Table 5-8 : Monthly gross evaporation for the Okavango River in Namibia .................. 51
Table 6-1 : Angola population projections(1) .................................................................. 59
Table 6-2 : Population of Kavango Region 2001 .......................................................... 60
Table 6-3 : Estimated urban population of Kavango Region ......................................... 60
Table 6-4 : Estimated rural population of Kavango Region ........................................... 60
Table 6-5 : Estimated and projected population growth and Water Demands for
the Ngamiland Region as per the National Water Master
Review of 2006 ........................................................................ 61
Table 6-6 - Angolan population projections ................................................................... 62
Table 6-7 : Combined schemes per Constituency for present and future irrigation ...... 63
Table 6-8 : Water Demand Projections for schemes at Rundu ..................................... 64
Table 6-9 : Surface Water Abstractions (ODMP Analysis of Water Resources
Scenarios 2006) ....................................................................... 64
Table 6-10 : Groundwater Abstractions (ODMP Analysis of Water Resources
Scenarios 2006) ....................................................................... 65
Table 6-11 : Angola Livestock Projections .................................................................... 66
Table 6-12 : Rural water demand projections for Kavango Region .............................. 66
Table 6-13 : Livestock census for the Kavango Region ................................................ 66
Table 6-14 : Projected livestock units (' 000) by livestock category per 5 year
Duration range in Maun Region Table 6-22 to 6-31 page
119/120 NWMPR Volume 8, March 2006 ................................ 67
Table 6-15 : Possible hydropower scheme at Popa Falls ............................................. 67
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E-Flows Hydrology Report: Data and models
LIST OF FIGURES
Figure 2-1 The Okavango River Basin ......................................................................... 18
Figure 2-2 The Okavango River Delta, showing drainage into the Thamalakane /
Boteti System ........................................................................... 19
Figure 2-3 Map showing site locations ......................................................................... 20
Figure 3-1 : Hydrological Modelling Components ......................................................... 22
Figure 3-2 : Comparison of observed (blue) and simulated (brown) monthly
duration curves at Rundu ......................................................... 24
Figure 3-3 : Comparison of observed (blue) and simulated (brown) monthly time
series at Rundu ........................................................................ 24
Figure 3-4 : Comparison of WEAP Simulation with Observed Flows at Mukwe ........... 26
Figure 3-5 : Inundation at the Kapako Site (1000 m3/s) ................................................ 27
Figure 3-6 : Discharge - Depth Relationship - Shakawe ............................................... 28
Figure 3-7 : Discharge - Velocity Relationship Shakawe ........................................... 28
Figure 3-8 : Discharge - Depth Relationship Xakanaka ............................................. 29
Figure 3-9 : Discharge - Velocity Relationship Xakanaka .......................................... 29
Figure 3-10 : Season Delineation .................................................................................. 32
Figure 3-11 : Example of Flow Categories - Delta Inflows (Left: Present Day,
Right: High Development) ........................................................ 33
Figure 4-1 : Capico hydrometric station, on the Cuebe River, flooded in mid-
March 2009 .............................................................................. 35
Figure 4-2 : Barrier-Islands on the Cubango River at Mucundi (March, 2009) ............. 36
Figure 4-3 : Cuito River at Cuito Cuanavale (March, 2009) ........................................ 37
Figure 4-4 : Water depth readings of Kapako during the dry season ............................ 38
Figure 4-5 : Water depth readings of Kapako during the wet season ........................... 39
Figure 4-6 : Aerial view of the Popa Falls site ............................................................... 40
Figure 4-7 : Left bank of the Popa Falls site ................................................................. 41
Figure 4-8 : Aerial view and cross section presentation of Popa Falls left channel
(dry season) ............................................................................. 42
Figure 4-9 : Aerial view and cross section presentation of Popa Falls right channel
(dry season) ............................................................................. 42
Figure 4-10 : Aerial view and cross section presentation of Popa Falls left channel
(wet season) ............................................................................ 43
Figure 4-11 : Aerial view and cross section presentation of Popa Falls left channel
(wet season) ............................................................................ 44
Figure 4-12 : Okavango Delta System .......................................................................... 45
Figure 4-13 : Gauging Site at Mohembo ....................................................................... 45
Figure 4-14 : The Panhandle ........................................................................................ 46
Figure 4-15 : Eastern Delta Xakanaxa Lagoon .......................................................... 46
Figure 4-16 : The Boteti River - Chanoga ..................................................................... 47
Figure 5-1 : The Namibian portion of the basin, including the two EFA sites: Popa
and Kapako .............................................................................. 53
Figure 5-2 : Rest water level for WW35408 over the past 12 years .............................. 54
Figure 5-3 : Rest water level for WW 35409 for the past 12 years ............................... 54
Figure 5-4 : Rest water level for WW 9140 from 1989-2009 ......................................... 55
Figure 5-5 : pH, Conductivity for WW 35408 and WW 35409 and Fe for WW
35408 measured over four years ............................................. 57
Figure 6-1 : Existing irrigation developments along the Okavango River ..................... 63
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E-Flows Hydrology Report: Data and models
Acronyms and abbreviations
DTM
Digital Terrain Model
(MAWRD), MAWF
(Ministry of Agriculture Water and Rural Development),
Ministry of Agriculture, Water and Forestry (Namibia)
DWAF
Department of Water Affairs and Forestry in Namibia
ENWC
Eastern National Water Carrier
NamWater
Namibia Water Corporation Ltd
SADC
Southern African Development Community
DNA
National Directorate of Water (Angola)
INAMET
National Institute of Meteorology and Geophysics (Angola)
DPA
Provincial Directorate of Water (Angola)
HYDATA Hydrological
Database
UNDP
United Nations Development Programme
EPSMO
Project on the Environmental Protection and Sustainable Management of the
Okavango River Basin
ORB
Okavango River Basin
SNPC
National Service of Civil Protection (Angola)
FAO
United Nations Organization for Food and Agriculture
INOT
National Institute of Territorial Cadastre (Angola)
NWMPR
National Water Master Plan Review
ODMP
Okavango Delta Management Plan
DMS
Department of Meteorological Services (Botswana)
DSM
Department of Surveys and Mapping (Botswana)
DGS
Department of Geological Surveys (Botswana)
WUC
Water Utilities Cooperation (Botswana)
NIGIS National
Integrated Geosciences Information Systems (Botswana)
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E-Flows Hydrology Report: Data and models
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 5) is the first of two reports produced by the EFA
hydrological working group and 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 report should be read in conjunction with the Hydrological Scenario
Modeling Report (Volume 6), which 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.
1.2
Scope and purpose of 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. The workshop activities are detailed in Appendix A. The
members of the group are:
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E-Flows Hydrology Report: Data and models
Country Person
Organisation
Angola
Mr Manuel Quintino
FAO / GEF EPSMO
Dr Gabriel Miguel
University of Agostinho Neto
Mr Paulo Emilio Mendes
DNA Angola
Botswana
Ms Kobamelo Dikgola
DWA Botswana
Mr France Tibe
DWA Botswana
Dr Chandrasekar Kurugundla
DWA Botswana
Dr Dominic Mazvimavi
HOORC
Dr Piotr Wolski
HOORC
Mr Geofry Khwarae
BIOKAVANGO
Namibia Mr
Andre
Mostert
NamWater
Ms Aune Hatutale
NamWater
Mr Matthews Katjimune
DWA Namibia
Ms Penehafo Shidute
DWA Namibia
(Coordinator)
Mr Hans Beuster
EPSMO Process Management
Team
Mr Guido van Langehove of the Namibian Department of Water Affairs and Forestry
provided valuable contributions on flooding and hydrological data exchange in the
basin.
1.3
Layout of this report
Chapter 2 provides an overview of the Okavango River basin and its sub-basins, and
lists the representative sites which served as the focus of data collection and for
which information on hydrological flow regimes were generated.
Chapter 3 describes the existing and new hydrological and hydraulic models that
were selected or developed to provide provide current day (baseline) and scenario
flow sequences at the eight EFA sites.
Chapter 4 outlines the field data collection activities of the hydrological working
group.
Chapter 5 documents the availability and sources of hydrological data and
information that were obtained for the EFA study.
Chapter 6 provides a summary of the water resource development information that
formed the basis for the water use scenarios that were assessed in the study.
Data and information sharing arrangements within, and between the riparian
countries of the Okavango River basin is described in Chapter 7.
Chapter 8 provides conclusions about the availability and quality of hydrological data
in the basin, the modelling process and recommendations on how these could be
improved.
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E-Flows Hydrology Report: Data and models
2 STUDY
AREA
2.1
Description of the Okavango Basin
A brief description of the extent of the Okavango River Basin and its sub-basins is
provided in the remainder of this section. The hydrological characteristics of the
basin is described in more detail in EPSMO/Biokavango Report Number 6; Scenario
Report: Hydrology.
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
(Error! Reference source not found.). 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. Toward the west and south, outflows from the Okavango Delta are
drained through Kunyere to Lake Ngami, and through the Boteti River which
eventually joins 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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Figure 2-1 The Okavango River Basin
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E-Flows Hydrology Report: Data and models
Figure 2-2 The Okavango River Delta, showing drainage into the Thamalakane / Boteti
System
2.2
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.
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 Error! Reference source not
found. and shown on Figure 2-3.
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E-Flows Hydrology Report: Data and models
Table 2-1 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
Figure 2-3 Map showing site locations
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3
Hydrological and Hydraulic Models
3.1 Overview
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 (
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E-Flows Hydrology Report: Data and models
Table 2-1). The modelling sequence and linkages between the models are shown in
Figure 3-1.
Figure 3-1 : Hydrological Modelling Components
The models which were selected for use in the EFA are listed below. More detailed
descriptions of the basin and Delta modelling components are provided in Sections
3.2 and 3.3.
· Catchment hydrology: Estimates of naturalised (undeveloped) long-term
runoff were obtained from an existing Pitman-based rainfall-runoff model
(Pitman 1976) developed as part of the EU funded WERRD project (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 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 EF 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
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E-Flows Hydrology Report: Data and models
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 categories").
3.2 Basin
Hydrology
3.2.1
Estimates of naturalised (undeveloped) catchment runoff
The hydrology of the data-poor Okavango River Basin was for the first time modelled
at a spatial resolution that would allow for assessments of development impacts at
various locations in the basin and on inflows to the Delta by Anderson et. al. (2003).
The original model was based on the monthly time step Pitman Model (Pitman, 1973)
and consisted of 23 sub-catchments upstream of the Delta. Since then, a modified
Pitman model for the Cuito River, which accounts for groundwater recharge and
discharge and drainage density was developed (Hughes 2004). The model for the
entire basin upstream of the Delta was updated in 2006 (Hughes et. al. 2006) and
comprised of 24 distinct sub-basins. Calibration of the model was complicated by the
limited availability of measured stream flow and rainfall records. Long stream flow
records (starting in the 1930s) are available along the lower reaches of the Kavango
and Okavango at Rundu, Mukwe and Mohembo, but stream flow records in Angola
are only of the order of 10 years long, covering the early 1960s to mid 1970s.
Measured rainfall records in Angola are only available until 1972. These sequences
were extended with satellite rainfall by Wilk et al. (2006) to September 2003, which
means that the calibrated model could be used to generate stream flow sequences
for the period spanning hydrological years 1958-2002. Earlier versions of the model
over-predicted low flows and under-predicted wet season peak flows at Rundu and
Mukwe. The latest version which was completed in 2006 shows much better
predictions of low flows. The under-prediction of peak flows (of up to 20%) is still
present, as can be seen from comparisons of observed and simulated flows at
Rundu (Figure 3-2 and Figure 3-3).
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E-Flows Hydrology Report: Data and models
Figure 3-2 : Comparison of observed (blue) and simulated (brown) monthly duration
curves at Rundu
Figure 3-3 : Comparison of observed (blue) and simulated (brown) monthly time series
at Rundu
Presently, the Pitman catchment model is the only distributed hydrological model of
the basin. While it has improved the understanding of the upstream hydrology, the
breakdown of the Angolan gauging stations from the 1970's onwards have put
limitations to the validation of the model and the hydrology is still associated with
uncertainties. For traditional water resource assessments the errors in peak flow
simulation are not considered to be serious, as it does not significantly affect
estimates of run-of-river or storage based yields. Of more concern is the fact that the
simulation period excludes the recent large flood events of 2009 and 2010, preceded
by a devastating drought in 2007. The floods in the Kavango River (and the
Zambezi) were the highest on record since 19691. (A discussion of flooding and
drought issues is provided in EPSMO/Biokavango Report Number 6; Scenario
Hydrology Report.) In the EFA study it was found that the under-estimation of flood
peaks does pose problems, in that the ecologists attach much greater importance to
1 G Van Langehove, pers. comm.
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E-Flows Hydrology Report: Data and models
the magnitude of flood peaks and found it difficult to relate simulated peak flows to
their knowledge of observed floods and associated ecosystem responses.
A recommendation of this study is that the rainfall-runoff model be re-calibrated with
a view to improve peak flow simulation. As part of the same exercise, the model
should be extended to cover the hydrological years from 2003 to as recently as
possible. The re-calibration should make use of the stream flow records that are
becoming available from rehabilitated flow measuring stations in Angola. .
3.2.2
Generation of Scenario Flow Sequences
To simulate the effects of future water resource developments on flow sequences at
the EF sites, a hydrological systems model was required. The modified Pitman
model developed by Hughes et. al. is included in the SPATSIM hydrological
modelling system (http://www.ru.ac.za/static/institutes/iwr/software/spatsim.php).
The system was used to model the effects of scenario water resource developments
on flow regimes in the Okavango as part of the WERRD project. For the EFA Study,
the hydrological working group opted to make use of the WEAP modelling system, as
it incorporates a simple but powerful scenario creation tool, is capable of simulating
run-of-river and storage based hydropower schemes and is especially well suited for
the training of hydrologists in systems analysis and scenario planning techniques.
The naturalised (undeveloped) runoff sequences of the 24 sub-catchments upstream
of the Delta were exported from SPATSIM and used as inflow time series in the
WEAP model. Present day (reference) and future water resource developments
(irrigation scheme and urban abstractions, in channel dams for irrigation water
supply, inter-basin transfers, run-of-river and storage based hydropower schemes)
were then configured in the WEAP model for use in the scenario simulations. Flows
simulated at Mukwe for the reference scenario were compared with the measured
flow record at the Mukwe station to verify that the WEAP model reproduces the
original SPATSIM simulation faithfully, and to confirm that the simulation of measured
flows is reasonable. The comparison is shown in Figure 3-4.
In order to reflect the current water abstraction practices in the basin, the WEAP
model was configured with equal priorities of water supply assigned to all water
abstractions. This implies that water supplies to upstream water users are not
constrained by downstream demands (such as environmental and cross-border flow
requirements). The same approach was followed for the configuration of future water
use scenarios, as the intention of the scenario modelling was to illustrate the full
impact of increasing upstream water use on downstream water users.
The WEAP model was configured with static development states, i.e. water demands
and infrastructure associated with a particular water use scenario were
superimposed on the full simulation period. 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
hydrological events.
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E-Flows Hydrology Report: Data and models
Figure 3-4 : Comparison of WEAP Simulation with Observed Flows at Mukwe
EFA Sites 3 (Cuito Cuanavale) and 4 (Kapako) are situated in river reaches with
extensive floodplains. To get an indication of the degree to which the floodplains are
inundated under different flow conditions, peak flow - inundated area relationships
were developed for the two sites. A first attempt was made by delineating inundated
areas from satellite images and correlating these with measured flows at nearby
stations. The USGS Glovis Landsat / Modis archive was searched to find images
that show a range of inundations for the Kapako and Cuito Cuanavale sites that
could be correlated to available streamflow records at Rundu and Cuito Cuanavale,
respectively. For Cuito Cuanavale, no images dated before closure of the station
were available. For Kapako, there were not enough images showing recognizably
different levels of inundation. It was then decided to configure one-dimensional,
steady-state hydraulic models for each of the two sites with the US Army Corps of
Engineer's freely available HEC-RAS and HEC-GeoRAS modelling systems
(http://www.hec.usace.army.mil/software/hec-ras/hec-georas.html). Cross-sections
were extracted from the 90m NASA SRTM digital elevation model and improved with
main channel cross-sections surveyed during field visits (Section 4). An example of
the modelled inundated area associated with a steady flow of 1000 m3/s at the
Kapako site is shown in Figure 3-5.
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E-Flows Hydrology Report: Data and models
Figure 3-5 : Inundation at the Kapako Site (1000 m3/s)
3.3 Delta
Hydrology
3.3.1
Botswana Department of Water Affairs and Forestry MIKE SHE
Model
In March 2004 the development of an Integrated Hydrologic Model (IHM) for the
Okavango Delta was initiated under the Okavango Delta Management (ODMP)
project, and it was completed in March 2005. The model was transferred to the
Department of Water Affairs for use and analysis of scenarios to support the ODMP
(IHM Report, 2005). The model was used in this study to estimate the sharing and
partitioning of flows amongst the three major river systems of the Delta.
The model was developed using the DHI Water and Environment, MIKE SHE-MIKE
11, 2005 modelling system and was run up to 2004. The model integrates the
following four components:
· Soil-vegetation-atmosphere transfer module, describing, in space and time, the
loss of water from open water, swamp and terrestrial vegetation to the
atmosphere
· MIKE 11 surface water module describing water levels and flows through the
main river channels of the delta
· The distributed overland flow module (MIKE SHE) to simulate the two
dimensional flow pattern through the swamps and flood plains, with a full
automatic coupling with MIKE 11
· MIKE SHE ground water module, based on a three dimensional representation of
saturated and unsaturated zones
The calibration of the model against measured flows in the Thamalakane River is not
as good as the calibration of the HOORC model at the same point. As simulated
outflows into the Thamalakane / Boteti system were required for assessment of
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E-Flows Hydrology Report: Data and models
impacts at Site 8 (Chanoga), and the fact that the HOORC model is capable of
simulating the effect of inundation frequencies and extents on vegetation
assemblages, lead to a decision to use the HOORC model for simulation of
inundation frequencies and extents and for outflows into the Thamalakane / Boteti
system. However, the HOORC model does not simulate flow dynamics in the Delta
distributaries whereas the MIKE-SHE model does. As the performance of the MIKE-
SHE model in the upper parts of the Delta is acceptable, it could be used to develop
flow-depth-velocity relationships at Site 6 (Panhandle at Shakawe) and Site 7 (Delta
at Xakanaka) for use in the EF assessments. The relationships are shown in Figures
3-6 to 3-9.
Figure 3-6 : Discharge - Depth Relationship - Shakawe
Figure 3-7 : Discharge - Velocity Relationship Shakawe
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E-Flows Hydrology Report: Data and models
Figure 3-8 : Discharge - Depth Relationship Xakanaka
Figure 3-9 : Discharge - Velocity Relationship Xakanaka
3.3.2
HOORC Conceptual Model of the Delta
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 EF sites.
It is composed of two sub-models. The reservoir sub-model simulates flow of water
through the Delta as flow through an array of nine quasi-non-linear reservoirs, each
representing a large subdivision of the modelled system. It incorporates a rather
complex representation of surface water-groundwater interactions, where floodplains
and dryland/island groundwater are simulated separately. The reservoir sub-model
maintains closure of surface water and groundwater balances in the system by
accounting for all hydrological inputs (inflow, rainfall) and outputs (evaporation and
surface water outflows) and internal fluxes (infiltration and groundwater flow). It uses
local rainfall and temperatures, and flow at Mohembo as input, and provides water
storage, inundated area and outflows through main terminal rivers as output. It runs
on a monthly basis, and has been calibrated using observed data for the period of
1968-2002, with calibration targeting agreement between simulated and observed
inundated areas in the nine Delta units and outflows through terminal rivers. Second
sub-model is a GIS-based model of inundation distribution. In this sub-model the
lumped inundated area obtained on a monthly basis from the hydrological sub-model
is represented as a map of inundation of 1*1 km resolution. The GIS sub-model is
based on the assumption that floods of similar sizes are similarly distributed. In this
sub-model, each 1*1 km pixel is characterized by a function describing the probability
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E-Flows Hydrology Report: Data and models
that it is inundated while inundation area is of a given size. The function was derived
based on analysis of inundation maps obtained from NOAA AVHRR images. Monthly
inundation maps obtained from this model are further analysed to obtain pixel-scale
indices such as inundation duration for each of modeled years and long term
frequency of inundation etc.
The dynamic ecotope model was developed in order to classify hydrological
conditions obtained from the hydrological/GIS models for the Okavango Delta in
terms of hydro-ecological functionality. The model is based on assumption that
vegetation assemblages observed at any given site change in response to varying
hydrological conditions, which is meant to capture the inherent hydrological and
ecological variability in the Okavango Delta. In the original version of the model,
hydrological conditions are represented by duration of inundation, while vegetation is
captured using four functional classes: aquatics, sedges, grasses and savanna (or
permanent swamp vegetation, primary floodplains, secondary floodplains and dry
floodplains). The model has a nature of a rule-based expert system, and in its version
used in this study, rules were based on experience of authors rather than on rigorous
scientific analysis, as the available datasets do no as yet support the latter. The area
of additional classes used in the EFA, i.e. channels, lagoons and floodplain pools,
was determined as a percentage of the main hydro-ecological classes, based on the
analysis of satellite images.
3.3.3 Boteti
Hydrology
Flows along the Thamalakane-Boteti River are derived from outflows from the delta,
and any rain falling onto the water surface within the channel. There are no
tributaries contributing any significant flows along the Thamalakane-Boteti River. The
dominant hydrological processes along this river are storage and transmission of
outflows from the delta, groundwater recharge, evapo-transpiration, and channel
precipitation. A linear reservoir model was selected for modelling flow of water along
this river on a monthly time interval. The river was divided into the following sections
for modelling purposes:
· from Maun Bridge on Thamalakane River to Samedupi on the Boteti River,
· from Samedupi to Rakops on the Boteti River.
The storage in, and outflow of water from each of these reservoirs was estimated by
means of a monthly reservoir balance. The starting and ending points of these
reservoirs were selected in order to coincide with the locations of flow gauging
stations with data used for model calibration. The contribution of rain falling directly
onto the channel was estimated using rainfall measured at Maun and the surface
area of each reservoir estimated from the surface area storage volume relationship
derived from a survey (Kraatz, 1976). Evaporation from the reservoirs was estimated
from mean monthly evaporation rates measured at Maun. Outflow from each
reservoir was a function of the storage volume above a minimum threshold volume.
Recharge to groundwater was modelled as a loss which is a function of the volume of
water stored in each reservoir.
For the purpose of determination of wetted length of the Boteti river a model has
been developed based on the reservoir model of the Okavango Delta. The model
strives to account to represent the strong hysteresis in volume-flow relationship
observed at hydrometric stations along the Boteti. This hysteresis is conceptually
related to the influence of surface water-groundwater interactions on flows in the
Boteti, similar to that observed in the floodplains of the Okavango Delta (Ramberg et
al. 2006). The model represents the Boteti River between Maun and Mopipi as a
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E-Flows Hydrology Report: Data and models
single quasi-linear reservoir characterized by a certain volume-area relationship. To
capture the interactions between surface water and groundwater, a series of 5
independent groundwater reservoirs each representing groundwater at a reach of the
river are used. Each of these is composed of a reservoir representing groundwater
storage directly under the river channel, and another one, linked to the first,
representing groundwater storage within the riparian/riverine woodland zone. The
groundwater reservoirs are recharged from the surface water reservoir, and the
recharge occurs only to these reservoirs which represent currently inundated reach
of the river. The model works under assumption that the surface water-groundwater
flows are one-directional, i.e. there is only infiltration from surface water to channel
groundwater reservoir, and that there is only flow from channel groundwater to
riverine groundwater. The latter is ultimately removed by riverine woodland
evapotranspiration. The model has been calibrated based on the wetted lengths
observed between 2000 and 2009, which were derived from field visits and satellite
images.
3.3.4
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 categories"). 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 exceedence 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 rules were developed to identify the starting dates of the seasons. Rules
that were developed for a similar study on the Mekong River were used as a
departure point and modified to suit the highly variable ("peaky") flow regimes that
are associated with the Okavango tributaries. The rules were applied to the
disaggregated daily flow sequences to calculate flow categories 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 in Figure 3-10. The figure shows a
simulated daily flow sequence (red) which was derived by disaggregating a simulated
monthly sequence with the daily distribution of a measured flow record. The second
line (blue) shows a 5 day moving average of the red line. The moving average
sequence was used to calculate flow indicators (5-day minimum dry season flow, 5-
day wet season peak flow, etc.). An example of the calculated flow categories is
shown in Figure 3-11. A detailed description of the ecological relevance and
selection of the flow categories is given in EPSMO/Biokavango Report Number 2;
Process Report.
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E-Flows Hydrology Report: Data and models
Figure 3-10 : Season Delineation
32
E-Flows Hydrology Report: Data and models
Figure 3-11 : Example of Flow Categories - Delta Inflows (Left: Present Day, Right: High Development)
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4
Field Data Collection
4.1 Angola
4.1.1 Introduction
The main purpose of the team was to collect relevant data on the Angola portion of
the Okavango River Basin (ORB) for the WEAP model. Due to civil war faced by
Angola for about 30 years most of accurate data were produced until the end of
1980's. In terms of hydrologic information, due to the obsolescence of data and lack
of new data, the team had to resort to the existing historic data. The main data on
irrigation potential were collected from the field, through the provincial Director of
Agriculture in Kuando Kubango and through the visits made by the National Project
Coordinator of EPSMO, to the Okavango River Basin. The National Directorate of
Agrarian Hydraulics and Rural Engineering, under the central Ministry of Agriculture
provided data on irrigation schemes. It also worth to mention that some relevant
data on the Angolan portion of the ORB was provided by the Office of the Vice
Minister for Planning.
DNA, Direcção Nacional de Águas, provided relevant historic data on Hydrology.
Within DNA, the hydrological data were collected from Database (HYDATA) and from
existing Yearbooks within DNA.
The data collected from DNA comprised:
· Average daily flows for several old hydrometric stations;
· Monthly flows for several old hydrometric stations;
· Annual flows for several old hydrometric stations;
· Rating curves (for the EFA sites).
The rainfall data were collected from old records of INAMET, the National Institute
for Meteorology and Geophysics and from the book "Caracterização Sumária das
Condições Ambientais de Angola", dated of 1973.
Here is important to mention that INAMET data have too many gaps and the last
data were recorded in 2004.
The dispersion of data among various institutions was one of the main constraints.
4.1.2
Site 1: Cuebe River at Capico
Capico site is located in the southern part of Menongue municipality. It falls within the
IUA no. 3. Capico is 110 kilometers south of Menongue, the capital city of Kuando
Kubango province, driving to the Nambian border. Its geographic coordinates are:
latitude - 15°33 South; longitude - 17°34 East. The altitude of the zone varies from
1160 to 1250 meters. Most of the people living in Capico belong to the ethnic group
Ngangela. There is a small group of resident, which belong to the ethnic group
Cocwe (original from Moxico province), who during the civil war displaced from its
place of origin and fixed residence in Capico. The existing closed nearby settlements
to site are: Massosse and Bitângua on the North and Caïndo on the South.
Cuébe River, one of the tributaries of Cubango (Okavango ) River, is the only source
of water in the area.
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From the lithological point of view the detritic formation, also known as Kalahari
formation dominates in the area.
The existing hydrometric station was rehabilitated in December 2005. Nearby the
hydrometric station, specifically in zones where the erosion is considerable, were
identified ferruginous concrections, typical of lateritic soils.
Observations carried out during the dry season (May September), indicate that the
bottom of Cuebe River is 2,0 meters deep in relation to the surface level of its banks.
The natural channel of the river is "U"-shaped. This kind of shape is not observable
during the rain season during the peak of the floods, which normally occurs in March
of each year.
The main livelihoods of local people are rainfed agriculture (during the rain season
from October to April), fishery using the Cuébe River, wild fruits picking and hunting.
Handcrafting is also practiced by local people.
Figure 4-1 : Capico hydrometric station, on the Cuebe River, flooded in mid-March 2009
4.1.3
Site 2: Cubango River at Mucundi
Mucundi site is located in the southern part of Menongue municipality, just
downstream the settlement of Caïndo. It falls under the IUA no. 2. Mucundi is 192
kilometers south of Menongue, the capital city of Kuando Kubango province, driving
to the Namibian border. Its geographic coordinates are: latitude - 16°13 South;
longitude - 17°41 East. The altitude of the zone varies from 1120 to 1250 meters.
People living in Mucundi belong to the ethnic group Ngangela. The existing closed
nearby settlements to site are: Chimbueta on the North and Kendelela on the South.
The Cubango (Okavango) River, after receiving contributions from Cutato, Cuchi,
Cuélei and Cuébe Rivers, is the main source of water in the zone.
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The area is dominated by the Kalahari formation, although old granitic formation
(Pre-Cambrian), also do exist.
Figure 4-2 : Barrier-Islands on the Cubango River at Mucundi (March, 2009)
In some places it can be observed rapids of small magnitude, originated by the
presence of granite in the bottom of the river. On the left bank of the river, the
morphology provokes the appearance of a considerable floodplain..
The hydrometric station at Mucundi will be rehabilitated during the second semester
of 2009. Approximately 500 meters upstream the hydrometric station, small islands
configure the natural channel of the river. In some cases these islands play a role of
natural barriers on the sedimentary dynamics of the environment.
The main livelihoods of local people are rainfed agriculture (during the rain season
from October to April), fishery using the Cubango (Okavango) River and livestock
production. Beekeeping is also practised in the area, but at a small extent.
4.1.4
Site 3: Cuito River at Cuito Cuanavale
Cuito Cuanavale site is located in the eastern side of Kuando Kubango. It falls within
the IUA no. 6. The site is located in the municipality of same name. Cuito Cuanavale
is 189 kilometers from Menongue, the capital city of Kuando Kubango province,
moving easternwards in the direction to Mavinga municipality. Its geographic
coordinates are: latitude - 15°10 South; longitude - 19°12 East. People living in
Cuito Cuanavale belong to the ethnic group Ngangela. The existing closed nearby
settlements to the site are: Sacalumbo on the North-West, Chissamba on the North-
East, Bocota on the South, Caripa on the South-West and Samungure on the East.
The site is located 3 kilometers downstream the junction between rivers Cuito and
Cuanavale. The altitude of the zone varies from 1180 to 1250 meters.
The Kalahari sands are the dominant geological formation in the area. There is a
geological fault which occurs on the direction NW-SE, which coincides with the main
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natural channel, the Cuito River. There is also in the area a considerable floodplain
crossed by the Cuito River.
Figure 4-3 : Cuito River at Cuito Cuanavale (March, 2009)
The main livelihoods of local are rainfed agriculture (during the rain season from
October to April), fishery using the Cuito and Cuanavale Rivers, wild fruit picking and
hunting.
4.2 Namibia
4.2.1
Site 4: Okavango River at Kapako
Kapako (GPS: 17° 51' 50.81" S; 19° 34' 47.74" E) is located 20 km west of Rundu
where weekly water levels are recorded. The Kapako area is characterised as a well
defined river channel with extensive flood plains surrounding the site. To the north of
the river is a pool of water that is presently disconnected from the main river.
No water level monitoring equipment is available at the Kapako site. The processed
flow record at Rundu was used to disaggregate simulated monthly volumes at
Kapako.
Kapako Dry season visit:
The Kapako site was identified from maps as a potential site for this study and was
subsequently visited during the period 18 - 24 October 2008. Water was only
confined to the river channel and a cross section was run for the wetted area of
which the results are presented in Error! Reference source not found.. The water
level recorded at Rundu on the same day was 3.54 m, equating to a flow rate of
about 30 m3/s.
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Figure 4-4 : Water depth readings of Kapako during the dry season
Kapako Wet season visit:
The Kapako site was visited during the period 7 - 12 February 2009. The water level
recorded at Rundu during this time was 5.26 m, equating to a flow rate of
approximately 235 m3/s. A cross section was run for the same wetted area as during
October 2008 and an attempt was made to obtain some depth readings of the flood
plain. This proved to be difficult as the area was inundated and due to vegetation was
not accessible by boat. Some water depths in the flood plain were logged along the
edges of the right river bank and the left flood bank. The collected data is presented
in Figure 4-5.
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Figure 4-5 : Water depth readings of Kapako during the wet season
For future monitoring it would be required that a correlation between flows in the
Kapako flood plain and at Rundu be established. Ideally, a gauge plate along with a
water level recording station with a pressure probe should be installed on the flood
plain.
4.2.2
Site 5: Okavango River at Popa Falls
Popa Falls (GPS: 18° 06' 58.24" S; 21° 34' 56.06" E) is located 5 km downstream of
the Bagani Bridge. The Department of Water Affairs and Forestry of Namibia used to
operate a cable way river gauging site just downstream of the Bagani Bridge,
however this site has been abandoned. As there is no hydrological data for the Popa
site, runoff data from the nearby Mukwe station were used for to estimate flows at
Popa Falls.
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The area is characterised with a well defined river channel with stable embankments
with the main feature being the falls. Refer to Figure 4-6 and
Figure 4-7 for photos of the site. As no water level monitoring equipment was
available at the Popa Falls site, it was opted to install a gauge plate at the irrigation
pump station..
Figure 4-6 : Aerial view of the Popa Falls site
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Figure 4-7 : Left bank of the Popa Falls site
Popa Falls Dry season visit:
The Popa Falls site was visited during the period 18-24 October 2008. Water was
confined to the main river channel and a cross section was run for the wetted area.
Results are presented in Error! Reference source not found. and Error! Reference
source not found.. Approximately 23 km upstream of the Popa Fall site the
Department of Water Affairs and Forestry of Namibia records water levels at Mukwe
(GPS; 18° 02' 09.19" S; 21° 25' 39.37" E). The water level recorded at Mukwe during
this time was 2.49 m which equates to a flow rate of approximately 120 m³/s. The
results are presented in Figure 4-8 and Figure 4-9.
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Figure 4-8 : Aerial view and cross section presentation of Popa Falls left channel (dry
season)
Figure 4-9 : Aerial view and cross section presentation of Popa Falls right channel (dry
season)
Popa Falls Wet season visit:
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The Popa Falls site was visited during the period 7-12 February 2009. During this
visit a gauge plate was installed at the irrigation abstraction point. The water level
recorded during this time at Mukwe was 3.25 m which equates to a flow rate of
approximately 395 m³/s. A cross section in the right channel was run for the same
wetted area as during October 2008 and a second cross section was run at the
position of the gauge plate next to the left channel. The results are presented in
Figure 4-10 and Figure 4-11.
Figure 4-10 : Aerial view and cross section presentation of Popa Falls left channel (wet
season)
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Figure 4-11 : Aerial view and cross section presentation of Popa Falls left channel (wet
season)
4.3 Botswana
4.3.1
Site 6: Okavango River in the Panhandle at Shakawe
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 4-12). 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.
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Figure 4-12 : Okavango Delta System
The panhandle of the Okavango River basin in Botswana forms the upper part of the
Okavango Delta and its inflow hydro station is at Mohembo (Figure 4-13). The
Mohembo station comprises of a hydrometric station where gauging of water levels
and discharges are done. The flow rate at Mohembo varies from 120m3/s in the dry
season to 815m3/s in the peak flood season. The River banks are characterised by
savannas and deciduous trees relying on continuous of flow of the river throughout
the year..
Figure 4-13 : Gauging Site at Mohembo
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The site has a few animals such as Hippos and crocodiles (Figure 4-14) in the river
and livestock that graze and feed along the banks. Away from the river banks, the
vegetation is completely dry during the dry season. The people who reside along the
Panhandle harvest the reeds and practise molapo farming in the floodplain areas.
Figure 4-14 : The Panhandle
4.3.2
Site 7: Eastern Okavango Delta around Xakanaka
This site is situated along the Eastern Okavango Delta around Xakanaka on the
Maunachira River. It is characterised by very long dry grassland with dry season
flows of about 3m3/s flows of about 8m3/s in the flood season. The site can be
divided into three flood regimes namely permanantly inundated, partially inundated
and completely dry. Wildlife that are completely dependant on the water for drinking
include elephant, giraffe and kudu (Figure 4-15). The hydrometric station at
Xakanaka measures discharges and water levels.
Figure 4-15 : Eastern Delta Xakanaxa Lagoon
4.3.3
Site 8: Boteti River at Chanoga
This site is located in the downstream of the delta, along the Boteti River. The area
has little or very dry grass during the dry season. Various forms of farming are
practiced along the river, including stock farming (mainly cattle see Figure 4-16)
and subsistence irrigation of vegetables. The river is also used for fishing and as a
supply of drinking water. The hydrometric station at Chanoga is only used for water
level measurements.
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Figure 4-16 : The Boteti River - Chanoga
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5
Hydrological Data and Information
5.1 Measured
flow
records
5.1.1 Angola
In Angola, EFA sites were positioned close to river flow measurement stations so that
rating curves and discharge records were available for use in the assessments. The
stations that were selected are shown in Table 5-1.
Table 5-1 : Location of Angolan flow measurement stations
Station name Number
Latitude
Longitude
From
To
Status
Rating
(ID)
(DMS)
(DMS)
curve
available?
Cuito
637507 15°10' 19°12'
Feb. 1980 Not
Yes
Cuanavale
1962
operational
Capico 637501
15°33'
17°34'
Feb.
1980 Operational Yes
1962
(*)
Mucundi 637512
16°13'
17°41' May
1980 Not
Yes
1957
operational
(*) Operational since June 2006, when OKACOM handed over the station to the
Provincial Government of Kuando Kubango
5.1.2 Namibia
There are three river flow stations, Rundu, Mukwe and Andara, along the Okavango
River that are operated by the Department of Water Affairs and Forestry; Hydrology
Division. Table 5-2 summarizes the details of the stations.
Table 5-2 : Location of Namibian flow measurement stations
Rating
Station
Number
Latitude
Longitude
From To
Status
curve
name
(ID)
(DMS)
(DMS)
available
Rundu
2511M01 17° 54' 30.81" 19° 45' 46.46"
Oct. 1945 20-10-2008 Open Yes
Mukwe
2521M04 18° 02' 09.19" 21° 25' 39.37"
Oct. 1949 24-06-2008 Open Yes
Andara
No
5.1.3 Botswana
The following Botswana flow measuring stations can be associated with the three
sites that were selected for analysis in this study.
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Table 5-3 : Location of Botswana flow measurement stations
Number
Latitude
Longitude
Station Name
From Status
(ID)
(DMS)
(DMS)
Mohembo
7112
18° 9' 50.5434"
21° 28' 16.8018"
Oct. 1974 Open
(Okavango)
Xakanaxa (Khwai) 7525
19° 6' 18.8634"
23° 14' 35.3394"
Oct. 1971 Open
Maun Bridge
7812
20° 0' 6.5514"
23° 15' 11.955"
Oct. 1970 Open
(Thamalakane)
Samedupi
8112
20° 3' 50.652"
23° 18' 46.947"
Oct. 1970 Open
(Boteti)
5.2 Rainfall
5.2.1 Angola
Table 5-4 : Location of Angolan rainfall stations
Station name
Number
Latitude
Longitude
From
To
Status
(ID)
(DMS)
(DMS)
Chianga
N/A 12°44'
15°50' 1951
1970
Not
operational
(Huambo)
Chitembo (Bié)
N/A
13°31'
16°46'
1941
1970
Not operational
Cangamba
N/A N/A N/A
N/A
N/A
Not
operational
(Moxico)
Cuvango (ex-
N/A 14°28'
16°18' 1951
1970
Not
operational
Artur de Paiva)
Menongue N/A 14°40'
17°12' 1951
1970
Open
Cuito Cuanavale N/A
N/A
N/A N/A
N/A
Not
operational
Cuangar N/A
17°35'
18°39'
1955
1967
Not
Operational
5.2.2 Namibia
In the Kavango Region, the Namibia Meteorological Services (NMS) which is
responsible for the collection of the country's rainfall data operates rain-gauges and
these are summarised in Table 5-5.
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Table 5-5 : Location of Namibian rainfall stations
Number
Latitude
Longitude
Station name
From To Status
(ID)
(DM)
(DM)
Njangana 11592117
18°01'
20°38'
01-1951
12-1963
Closed
Andara 11607833
18°04'
21°28'
06-1914
09-1995
Open
Bagani 1161065
Mpungu
12057660 17°46'
18°26'
12-1962
12-1980
Closed
Nkuren Kuru
12061871 17°37'
18°37'
01-1924
05-2007
Open
Tondoro 12064961
17°46'
18°47'
10-1931
08-2004
Open
Rupara 12071418
17°51'
19°05'
06-1958
05-1997
Closed
Bunja 12076214
17°51'
19°21'
01-1953
04-2004
Open
Rundu 12084758
17°55'
19°46'
01-1940
10-2007
Open
Sambiu 12090545
17°54'
20°02'
09-1935
02-1981
Closed
Mashare 12092649
17°54'
20°09'
01-1969
12-2003
Open
Rundu is only full-time NMS station with a standing international arrangement that is
operated by NMS Staff. The other stations are volunteer-based. Bagani is the only
automatic station but was only installed in 2009. Temperature, relative humidity,
atmospheric pressure and wind are the other parameters measured by weather
stations at Namibia Meteorological Services.
5.2.3 Botswana
Table 5-6 : Location of Botswana rainfall stations
Station Name
Number (ID) Latitude
Longitude
From
To
Status
Maun
130-MAUN
19° 33' 0"S
26°5'0"S
1-Oct-21
Present
Open
Shakawe
223-SHAK
18° 22' 0"S
21° 50'0"S
1-Feb-32
Present
Open
Nokaneng
169-NOKA
19° 39' 0"S
22° 11' 0"S
1-Jan-55
Present
Open
Sehithwa
211-SEHI
20° 20' 0"S
20° 24' 0"S
1-Sep-58
Present
Open
Gumare
043-GUMA
22° 29' 0"S
28° 42' 0"S
1-May-59
Present
Open
5.3 Evaporation
5.3.1 Angola
Monthly evaporation figures that were used in reservoir simulations and irrigation
demand calculations in the WEAP model was based on class A evaporation pan
records. The source of information was the book "Caracterização Sumária das
Condições Ambientais de Angola, Nova Lisboa, 1972".
Angolan evaporation records are available for the stations listed in Table 5-7.
Table 5-7 : Location of Angolan evaporation measuring stations
Station name
Number
Latitude
Longitude
From
To
Status
(ID)
(DMS)
(DMS)
Chianga
N/A 12°44'
15°50' 1951
1970 Not
operational
(Huambo)
Chitembo (Bié)
N/A
13°31'
16°46'
1941
1970
Not operational
Cangamba N/A N/A N/A
N/A N/A Not
operational
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E-Flows Hydrology Report: Data and models
(Moxico)
Cuvango (ex-
14°28'
16°18'
1951
1967
Not
operational
Artur de Paiva)
Menongue
14°40'
17°12' 1953
1967 Operational
(*)
Cuito Cuanavale N/A
N/A
N/A N/A
N/A
Not
operational
Cuangar N/A
17°35'
18°39'
1955
1967
Not
operational
(*) INAMET has one climatologic station installed in the premises of Menongue airport.
Although the figures provided by "Caracterização Sumária das Condições Ambientais de Angola" were
recorded only up to 1967, there are data recorded up to 1980s, on a non regular basis.
5.3.2 Namibia
The Namibian Map of Annual Evaporation and Precipitation was used in estimating
the gross evaporation for the Okavango River in Namibia. Two evaporation stations
that were operated by the Department of Water Affairs and Forestry, Hydrology
Division were closed in the 1980's and due to their short records, the data is not
provided.
From the evaporation map, an annual gross A-pan evaporation of 2 600 mm was
estimated for the Namibian portion of the basin. A pan-to-lake conversion factor of
0.8 was used from January to June, and a factor of 0.7 was used from July to
December. The monthly gross evaporation is shown in Table 5.3.
Table 5-8 : Monthly gross evaporation for the Okavango River in Namibia
Gross monthly evaporation (mm)
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
218 173 151 162 154 173 158 150 129 127 157 184
5.3.3 Botswana
The DWA does not have any evaporation stations in the Okavango Delta proper. The
Meteorological Services under the Ministry of Environment Wildlife and Tourism
operates a pan evaporation station in Maun and another station at Shakawe about
7km from Mohembo.
5.4
Geohydrological data and information
5.4.1 Angola
Data on groundwater in the Angolan portion of the Okavango River Basin is very
poor. The only source of information used by the team was the Hydrological Map of
Angola at scale 1:250.000. The map was produced in 1989 by Mac Donald &
Partners Limited (UK) and HIPROJECTO, Consultores de Hidráulica e Salubridade
S.A under the framework of a SADC project called "Hydrologic Assessment of Sub-
Saharan Countries".
The maximum altitude in the Angolan portion of the ORB is approximately 1 780
metres, nearby the surrounding area of Huambo, whereas in the downstream reach,
nearby the border with Namibia, the altitude is approximately 1 100 metres. Although
the hydraulic gradient for the altitudes mentioned before is about 14%, most of the
slope in the basin is gentle (monotonous). This means that the erosive process in
the basin occurs more frequently in the upper areas rather than in the downstream
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E-Flows Hydrology Report: Data and models
areas, where the deposition of sediments of sediments occurs in more considerable
manner.
From the geological point of view, the old rocks in the basin are represented by Pre-
Cambrian granites. The granites underwent various orogenic processes and
simultaneously by the occurrence of various magmatic processes, which originated
rocks, such as gneisses, migmatites, etc. The tectonics of the basin are
characterized by two directions of geological faults. In the upper basin the geological
are predominantly NE-SW, allowing the contact between old granitic formation and
the most recent ones (fine sands, silt and clayey schist). In the middle and lower part
of the basin, the geological faults are predominantly NW-SE, coinciding with the main
natural drain of the area, which is the Cuito River.
The Kalahari sands are found on old granitic rocks and on old igneous complexes. In
certain points of the basin, the Kalahari sands have a thickness of more than 10
metres. In the middle section of the basin, the outcrops of granite are met along the
bank of Cubango, Cutato, Cuchi, Cuelei and Cuebe Rivers. These granitic outcrops
occur due to erosion in the bottom of the rivers before mentioned.
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.
5.4.2 Namibia
a) Introduction
The Namibian- Okavango sub- basins are a huge flat areas located in the north
eastern Namibia covering part of the Omatako- Omuramba subbasin. The only
visible surface features are the permanent longitudinal, eastward oriented dunes.
This area represents a huge aquifer system with sediments of the Kalahari formation,
with most part of the area covered by a thick layer of calcrete covering the underlying
bedrock. Groundwater in this part of the country is mainly used for domestic
purposes and stock watering. (NGDC. 1991)
Several studies have been carried out in the Basin, these include the Groundwater
Investigation in the Kavango and Bushmanland, were various geophysical methods
have been employed to locate suitable aquifers in the study area. Methods included
the Seismology that was carried out in 1968, the Aeromagnetics survey between
1918 and 1920, Resisitivity and the Ground Magnetic survey, in addition to the
GROWAS data base and various Rural Water Supply drilling reports at different
settlements in the Basin, Groundwater in Namibia: An explanation to the
Hydrogeological Map (G Christelis and W Struckmeier, 2001) that were used in
compiling this report.
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E-Flows Hydrology Report: Data and models
Figure 5-1 : The Namibian portion of the basin, including the two EFA sites: Popa and
Kapako
b) Geology and aquifer stratigraphy
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 Kavango 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 the study area, (I) Primary Kalahari aquifers i.e.
sand and sand stones that hold water in intergranular pore space and (II) Secondary
aquifers i.e. fractured aquifers that holds water in the fractures and weathered strata.
Some boreholes in the area penetrate the primary aquifer of the Kalahari i.e. the
sand and sandstone Kalahari, which extends from the surface to approximately 350
m deep (NGDC. 1991).
c) Water levels and groundwater flow
The water table rises and falls according to the season of the year and the amount of
rain that occurs. The typical pattern is that heavy rainfall proportionally increases the
groundwater level whilst drought or dry conditions reduce the groundwater level. The
groundwater level is the rest water level in the borehole measured with a dip meter
the main component used in the monitoring of groundwater as part of standard water
resource management in Namibia. Long term monitoring of groundwater levels can
determine the status of the aquifer, to indicate whether groundwater levels have
dropped significantly and abstraction should be reduced or if the aquifer is coping
53
E-Flows Hydrology Report: Data and models
well and the aquifer could be utilized more efficiently. In areas were the water is
intersected in fractures, the water level is normally higher than those in the Kalahari
aquifers (Christelis & Struckmeier, 2001).
Groundwater Gradient: determines the flow direction of a groundwater source. The
river feeds the aquifers during floods and in areas were the Kalahari aquifers have a
shallow groundwater gradient, the Okavango River feeds the aquifers but in most
sections of the Okavango River the river gains groundwater. (NGDC.1991).
Figure 5-2 : Rest water level for WW35408 over the past 12 years
Figure 5-3 : Rest water level for WW 35409 for the past 12 years
54
E-Flows Hydrology Report: Data and models
Figure 5-4 : Rest water level for WW 9140 from 1989-2009
Figure 5-2 and Figure 5-3 show rest water levels for boreholes located at Mupini near
the Kakapo EFA site which are 200m apart from each other. Rest water level data
records are available from 1996-2008. Both WW35408 and WW35409 rest water
level are recorded below 12m for most months of the year, with few exceptions of
19.74 m in November 2008, 19.41m in February 1998 and a lowest value of 23, 02m
recorded in 2000 for WW 35409. For WW 9140 the average rest water level is above
12m, with the lowest level of 19.94m recorded in June 1996. In comparison the rest
water level at WW 9140 is generally a few meters lower than at the two boreholes at
Mupini, this could be a result of a deeper aquifer or higher pumping rate or elongated
pumping hours.
d) Recharge and Discharge
Groundwater recharge is yet to be understood in the basin, however the Okavango
Basin generally receives good rainfall of 400-500mm between the months October
and March. Shallow aquifers of less than 20m are recharged directly either by rainfall
and ephemeral 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.
e) Hydraulic properties
The hydraulic properties of the Kalahari aquifer vary because of its differing amounts
of gravel, sand, clay and other rock types. Coarse- grained sediment like sand and
gravel have a higher porosity than small-grained sediments like clay and silt, and the
pore spaces are better connected and this determines the permeability of the aquifer.
Some geological formations allow water to travel through them at a faster or slower
rate than others, depending on the porosity and thickness of the medium
55
E-Flows Hydrology Report: Data and models
(Transmissivity) (DWAF-SA, 2006). The better the transmissivity the more water will
reach the borehole in a specific time.
Aquifer characteristics can be estimated from data found in borehole reports, such as
geologic logs, static water level records, pump test data etc. For instance the pump
test is analyzed and interpreted to determine the aquifer potential. Evidence obtained
from drilling reports for Rural Water Supply shows that the groundwater yields in the
region is relatively good with 90% of boreholes drilled having a possibility of yielding
more than 1m3/h in the Kalahari, or less in areas were fractures are intersected in
other parts of the Basin. Boreholes yields along the Okavango river ranges between
0 - 8m3 /h and with areas that yield up to more than 10m3 /h that are drilled deeper
than 100m into the Kalahari aquifers, (NGDC. 1991). A report for rural water supply
compiled by Bitner, 2004 showed a varied range of water yield between 3, 7and
8m3/h at Makandu, Ngcangcana and Shamahiho respectively (Bitner Water Consult
CC, 2006).
A study done on the Andara Water scheme estimated Transimissivity values in the
order of 0-15m3/day/m and a Storativity value of about 0.005 in the sandstone
aquifers (Hydrology Division, 1994). Data from WW 9140 at Bagani (popa falls) has a
yield of 2.5m3/h while WW 35409 and 35408 all have a yield estimate of 6m3/h
(GROWAS database).
f) Water
quality
Groundwater quality is a chemical indicator, which looks at the chemical and
bacteriological properties of the groundwater. The groundwater samples in Namibia
classified according to the "Guideline for the evaluation of drinking water for human
consumption" with reference to the chemical, physical and bacteriological quality of
Namibia (The Water ACT, 1956). This groundwater quality classification is used for
rural water distribution throughout the country to determine whether water from a
certain groundwater source is fit for human consumption or other uses for instance
irrigation.
The water quality in the area varies as stripes of saline water and high fluoride
concentrations are found in the area. Details of water quality data, lithological logs of
boreholes and pumping test results reveal the existence of saline and fresh water
groundwater stripes. However there is no consistent system regarding the spatial
distribution of fresh and saline and the distribution of the depths and potential yields
of the different layers is yet to be known. The type of formation that makes up an
aquifer and the travel time determines the type of water an aquifer has, for example
pre-Kalahari with calcrete is characterized by saline water and depending on the
groundwater gradient the saline water might be discharging into the river.
Groundwater in the Kalahari aquifer along the banks of the river often shows poor
quality due to its iron and manganese content, which occasionally exceeds the limits
for drinking water. During flood when the river recharges the aquifer, it improves the
groundwater quality in those areas. According to NGDC, 1991 good groundwater
quality predominates along the river with TDS (Total Dissolved Solids) in some area
reaching 1000mg/l and values of more than 3000mg/l have also been recorded and
the lowest value recorded of 36mg/l (TDS) at Shakashi. A typical example is the TDS
value of 6686mg/l recorded at Mayana borehole in Kavango. Cases of elevated
values of iron have also been reported, a typical example is a borehole at Makandu
with an iron (Fe) value of 1.62mg/l, however these boreholes are considered critical
and can still be utilized for human consumption as they do not exceed the limit for
human consumption of 2 mg/l of Fe (NGDC, 1991) .
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E-Flows Hydrology Report: Data and models
WW 35408 and 35409 at Mupini are all within 200m from the river. The PH values in
these boreholes ranges between 7.7 - 8.2 and the conductivity measured is between
193-330mS/m. A record of 4mg/l of Fe was measured at WW 35408 in 1999 and in
WW 35409 the Fe level was never measured above 1mg/l. Thus water from these
two boreholes is classified as group C (low risk water) according to the Guideline for
the evaluation of drinking water for human consumption in Namibia (GROWAS,
2004).
Two other boreholes at Kakapo (WW 43046 and WW 43045) were classified as
group B (good water quality). The groundwater at Bagani (WW 9140) is classified as
group D (High health risk-unfit for human consumption) due to high TDS of 3183mg/l
and 4mg/l of Fe recorded in 2000 (GROWAS, 2004).
Figure 5-5 : pH, Conductivity for WW 35408 and WW 35409 and Fe for WW 35408
measured over four years
g) Groundwater Surface water links
The management of water resources in Namibia has focused either on surface water
hydrology or groundwater as two separate entities. With the increasing knowledge
and development of land and water resources, it is clear that nearly all surface-water
features (rivers, lakes etc.) interact with groundwater. The interaction between these
57
E-Flows Hydrology Report: Data and models
two bodies take different forms, mostly, surface water bodies gain water and solutes
from groundwater systems and in other situations surface water act as a source of
groundwater recharge altering the water quality depending on the source (Jones,
1997).
Consequently the withdrawal of water from the Okavango River can deplete
groundwater or alternatively excessive groundwater abstraction can deplete water in
river. Throughout this process water constantly moves between the two bodies,
sharing contaminants and all solutes. Thus effective IWRM (Integrated Water
Resource Management) requires a clear understanding of the linkages between
groundwater and surface water as it applies to any given natural resource.
h) Conclusions
· The low number of boreholes at the Kapako and Popa rapids sites are
actually not sufficient to get representative values for the groundwater
information of these areas and thus monitoring boreholes need to be drilled.
· The water level data for the river was required to compare with the
groundwater level, however the database containing these data was not
functional and data could not be made available.
· More detailed investigations are yet to be done to determine values of
storativity, transimissivity and hydraulic conductivity of the aquifers in
Kavango and most of Namibia.
5.4.3 Botswana
a) Soils and Geomorphology
The Okavango delta predominantly has the histosols and arenosols soil types, while
islands and ridges have calcium arenosols (ODMP 2008)._The drylands are mostly
characterized by white sandy soils with very low inherent fertility and water holding
capcity and they are commonly called as Kalahari sandsOther soil types include the
gleysols in the lower fringes of the Delta, the luvisols in the lower end and the soil
types of the phaeozens found in the surrounds of Nokaneng and Tsau South East.
b) Geology
The Okavango Delta lies within a north-easterly trending half graben, related to the
east African Rift System (Hutchins 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. The Gumare Fault has a parallel strike to the major faults. The oldest rocks in
the district consist of metavolcanic Kgwebe Formation and metasedimentary Ghanzi
Group of upper Proterozoic age. Karoo Supergroup rocks unconformably overlie
lower proterozoic basement rock outcrop south west of the delta at Lake Ngami on
the graben side of the Kunyere Fault. The Kalahari Group sediments occue as
Aeolian sands in the grabens of the Panhandle of the Delta.
c) Hydrogeology
Three major aquifers formations exist in the Okavango Delta region. These are the
Basement rocks, Karoo and Kalahari Group sediments. Karoo and Basement rocks,
where they occur shallow depth, also form locally important aquifers. The Kalahari
group sediments comprise the most important known aquifers. Recharge in the
Okavango Delta has been estimated in the order of 7 to 10mm/annum (ODMP 2008).
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E-Flows Hydrology Report: Data and models
6
Water Resource Development Information
To provide information for the construction of three development scenarios for the
EFA ((EPSMO/Biokavango Report Number 6; Hydrological Scenario Modelling
Report), the three country teams collected information on possible and planned water
resource developments from national water resource development plans, feasibility
studies and regional and sub-regional water resource development plans. The
information are summarised in the remainder of Section 6.
6.1 Population
6.1.1 Angola
The last census of population in Angola took place in the 1970s. Most of the current
figures on population are obtained through statistical manipulations. For the purpose
of the modelling exercise data were collected from the Rapid Assessment Water
Resources and Water Uses in Angola, carried out in 2005. Using data from 2005
and using the appropriate formula, projections were made for the various time
horizons.
Another valid source of data on population was the information provided by a joint
survey made FAO and IDA, the Agrarian Development Institute of the Ministry of
Agriculture.
Table 6-1 : Angola population projections(1)
Municipality
Sub-Basin
2006 2008 2010 2015 2020 2025 Remarks
(Province)
Catchiungo
Cubango /
142 688 148 453 155 057 172 881 192 754 214 911 Rural
(Huambo)
Okavango
Chitembo
Cuito
117 729 122 486 127 935 142 641 159 038 177 319 Rural
(Bié)
Cangamba
Cuito
11 482
11 946
12 477
13 912
15 512
17 295
Rural
(Moxico)
Cuvango
Cubango/Okavang 77 677 80 816 84 411 94 114 104 933 116 995 Rural
(Huíla)
o
Cuito-Cuanavale
Cuito
105 731 110 435 115 348 128 607 143 390 159 873 Rural
(Kuando Kubango)
Menongue
Cubango/Okavang 235 515 245 992 256 935 286 469 319 398 356 112 Urban
(Kuando Kubango) o
Cuchi
Cubango/Okavang 43 316 45 066 47 071 52 482 58 515 65 242 Rural
(Kuando Kubango) o
Cuangar
Cubango/Okavang 42 428 44 316 46 287 51 608 57 541 64 156 Rural
(Kuando Kubango) o
Calai
Cubango/Okavang 77 250 80 687 84 276 93 964 104 765 116 808 Rural
(Kuando Kubango) o
Dirico
Cuito / Cubango
8 627
8 976
9 375
10 453
11 655
12 995
Rural
(1) Sources of Information: 1) GEPE Kuando Kubango 2) FAO / IDA
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E-Flows Hydrology Report: Data and models
6.1.2 Namibia
a) Population Census of 2001 of Kavango Region
The Population and Housing Census was last taken in 2001 and the Kavango Region
had a total population of 202 694. The distribution for each constituency is shown in
Table 6-2 (National Planning Commission, 2001).
Table 6-2 : Population of Kavango Region 2001
Constituency Population
Kahenge 30
903
Kapako 26
263
Mashare 16
007
Mpunge 18
660
Mukwe 27
250
Ndyona 19
565
Rundu Rural East
18 250
Rundu Rural West
26 623
Rundu Urban
19 173
Total
202 694
b) Projected urban population
In 2007, in the analysis of future water demands for the Kavango Region, the
Namibia Water Corporation had used a total population for Rundu urban of 41 342 in
2001 which included two settlements, Sauyemwa and Kaisosi, located on the
outskirts of the town (NamWater, 2007). A growth rate of 2.5% per annum was used
to project the population. Because of lack of population data for the two settlements,
the population of 41 342 and the 2.5% growth rate was adopted to project the urban
population until 2025 as shown in Table 6-3.
Table 6-3 : Estimated urban population of Kavango Region
Estimated population
2008 2010 2015 2025
Rundu Urban 49 000
52 000
58 000
75 000
c) Projected rural population
For the rural population in the Kavango Region, the population projections to 2017
are presented in Table 6-4 (Lund Consulting Engineers, 2003). A growth rate of
1.5% as used in the report was adopted to project the rural population to 2025.
Table 6-4 : Estimated rural population of Kavango Region
Estimated population
2008
2010 2015 2025
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E-Flows Hydrology Report: Data and models
Kavango Rural
201 743
207 968
224 041
260 009
6.1.3 Botswana
The Okavango Delta region is comprised of mostly settlements with population that
does not cause any significant impact on the Okavango Delta resource. The few
areas with significant population are Maun, Shakawe/Gumare, Ikoga, Beetsha,
Seronga and Sepopa. Estimates and projections of water demands were done during
the National Water Master Plan review of 2006. The estimated and projected
population growth and Water Demands for the Ngamiland Region as per the National
Water Master Review of 2006 is shown below.
Table 6-5 : Estimated and projected population growth and Water Demands for the
Ngamiland Region as per the National Water Master Review of 2006
Year
2005 2010 2015 2020 2025 2030 2035
Population
Growth
133 000 139 360
141 948 143 943
144 765
145 204
145 418
Water Demand
(m3/year)
3 654.4
4 064.66 4 384
4 727.66
5 099.69
5 524.37 6 008.8
The major gap with regard to water demands and populations is that the village
populations in the delta are not reflected. The projections are made based on the
region as a whole.
6.2
Irrigation and Urban Water Demands
6.2.1
Angola Irrigation Water Demands
Data on irrigation were collected from FAO statistics, from the Directorate of Irrigation
and Rural Engineering of the Ministry of Agriculture and from the Provincial Director
of Agriculture in Kuando Kubango. Additional data on irrigation were collected from
field visits by the National Project Coordinator of EPSMO, to the Okavango River
Basin.
In the low development water use scenario 3 irrigation schemes were identified
downstream of Menongue, namely Missombo, Menongue Agriculture Scheme and
EBRITEX, totalling an area of 28 000 hectares. These schemes are intended to
abstract water from the Cuebe River, upstream of Capico.
In the medium development water use scenario 6 irrigation schemes totalling
198 000 hectares were identified, namely Missombo, Menongue Agriculture Scheme
and EBRITEX, with an area of 28.000 hectares and with water abstraction from the
Cuebe River, and Cuvango, on the Cubango River, Cuchi on the Cuchi River and
Longa on the Longa River, with a combined area of 170 000 hectares.
The high development water use scenario involves all the irrigation schemes of the
medium water use development scenario, plus irrigation schemes in Cuangar/Calai
on the Cubango River, Calai/Dirico on the Cuito River. In this scenario, the total area
to be irrigated is 338 000 hectares.
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E-Flows Hydrology Report: Data and models
It is worth mentioning that due to water limitation in the ORB, a total of 170 000
hectares that are considered to be arable were not taken into consideration when the
high development scenario was constructed. These areas are distributed as follows:
· 90 000 hectares in Cuito Cuanavale,
· 45 000 hectares in Cuangar/ Calai, and
· 35 000 hectares in Calai/Dirico.
6.2.2
Angola Urban Water Demands
Two demand centres were considered for the urban water projections, namely
Menongue and Cuito Cuanavale. Water demands of centres such as Tchicala
Tcholoanga and Ctchiungo (Huambo province), Cuvango (Huila province), Chitembo
(Bié province), Cangamba (Moxico province) and Cuchi, Cuangar, Calai and Dirico
(Kuando Kubango province) were not included in the hydrological model of the basin,
as they are small compared to the urban and irrigation water demands.
According to the projections the city of Menongue will have the following population:
· 356 000 inhabitants in the high water use scenario (2025);
· 286 000 inhabitants in the medium water use scenario (2015) and
· 257 000 inhabitants in the low water use scenario (2010).
The city of Cuito Cuanavale will have the following population:
· 160 000 inhabitants in the high water use scenario;
· 128 600 inhabitants in the medium water use scenario and
· 115 000 inhabitants in the low water use scenario.
For the purposes of calculation of the volume of water consumed by the population, a
per capita useage of 100 litres/person/day was used for the urban areas.
Population projections are shown in the table 6.3.1.1, below:
Table 6-6 - Angolan population projections
Municipality 2008
2010
2015
2020
2025
Catchiungo
148 453
155 057
172 881
192 754
214 911
Chitembo
122 486
127 935
142 641
159 038
177 319
Cagamba
11 946
12 477
13 912
15 512
17 295
Cuvango
80 816
84 411
94 114
104 933
166 995
Cuito Cuanavale
110 435
115 348
128 607
143 390
159 873
Menongue
245 992
256 935
286 469
319 398
356 112
Cuchi
45 066
47 071
52 482
58 515
65 242
Cuangar
44 316
46 287
51 608
57 541
64 156
Calai
80 687
82 276
93 964
104 765
116 808
Dirico
8 976
9 375
10 453
11 655
12 995
At the beginning of the exercise an annual population growth rate of 2.2% was
considered. After presentation of the preliminary results to OKACOM-Angola, this
figure was changed to 2.7%.
6.2.3
Namibia Irrigation Water Demands
The Division of Agricultural Engineering in the Ministry of Agriculture, Water and
Forestry provided the existing and future irrigation development information along the
Okavango River. Refer to Figure 6-1 for a schematic map of the present irrigation
schemes.
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E-Flows Hydrology Report: Data and models
Figure 6-1 : Existing irrigation developments along the Okavango River
The individual irrigation schemes were grouped together for each constituency, and
the total present and future hectares anticipated for agriculture presented in Table
6-7. The future irrigation areas are based on a development scenario that was
developed by the Green Scheme Agency which allowed for the equal and fair
distribution of water allocation between the different Tribal Areas. Water allocations
were arrived at after providing for environmental flow requirements in the Kavango
River. The scenario is described in detail in an irrigation report produced for the TDA
(Liebenberg, 2009)
Table 6-7 : Combined schemes per Constituency for present and future irrigation
Constituency
Total irrigable land (hectares)
2008 2010 2015 2025
Kahenge 300 700 900 900
Rundu - Mashare 521
551
551
551
Ndiyona
870
1 270
1 270
1 270
Mukwe 560
560 560 560
Rundu (future)1
-
-
1 674
1 674
Mukwe (future)
-
-
4 000
10 600
1574 hectares were inadvertently excluded, and water use result calculations indicate that the amount is
negligible
6.2.4
Namibia Urban Water Demands
a) Rundu
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E-Flows Hydrology Report: Data and models
The Namibia Water Corporation supplies bulk water to the town of Rundu, in the
Kavango Region. A summary of the projected water demands for Rundu is
presented in Table 6-8. Demand projections to 2015 (NamWater, 2007), and a
growth rate of 2.5% was used to project the demand to 2025.
Table 6-8 : Water Demand Projections for schemes at Rundu
Year N'karapamwe
Reservoir
Industrial Tower
Total
(m³/a)
(m³/a)
(Mm³/a)
2008
1 836 815
1 004 266
2.841
2010
1 929 804
1 055 107
2.985
2015
2 183 396
1 193 757
3.377
2025
2 794 931
1 528 110
4.323
b) Central Area of Namibia
The Eastern National Water Carrier (ENWC) is envisaged to be linked with the
Okavango River using the Grootfontein-Omatako Canal to supply water to the
Central Area. A volume of 17 Mm3/a (Water Transfer Consultants, 1997) for the
Medium Development scenario was used as the demand required from the
Okavango River for 2015, while for the High Development scenario (2025), a water
demand of 100 Mm3/a (Heyns, personal comment, 2009) was used. The preliminary
design of the scheme is based on a premise that the dams in the system will provide
balancing storage to meet peak demands. This was done to minimise the cost of the
pipeline from the abstraction point. The pipeline was therefore sized to deliver flows
at a constant rate equal to the mean annual demand.
6.2.5
Botswana Irrigation and Urban Water Demands
Permits for abstractions of specified quantities are issued by the Department of
Water Affairs. 342 permits of surface water abstractions were used during the ODMP
exercise to assess their impacts in the delta. Abstractions are taken from the surface
waters of the delta for purposes including domestic water supply, livestock, game,
small scale irrigation and construction. The abstractions were summarised as shown
in Table 6-9 below. The 2025 projected abstraction was based on increasing
population and an additional water demand of 21.5 Mm3/year, or 0.20% of the
average annual inflow.to the Delta
Table 6-9 : Surface Water Abstractions (ODMP Analysis of Water Resources Scenarios
2006)
River Abstractions
(m3/day)
2005 2025
Okavango 6,285
9,107
Thaoge 1,475
2,140
Boro 1,483
2,710
Maunachira 275
399
Khwai 148
215
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E-Flows Hydrology Report: Data and models
Thamalakane 26,571
38,553
Nhabe 5,100
7,400
Boteti 5,203
7,549
Total 46,540
68,073
Groundwater abstractions were also included during the ODMP exercise. Ground
water is abstracted from boreholes around the Delta, mainly to supply Maun and
settlements along the western margin. The groundwater abstraction amounts are
shown in table below and the total amounts to 6Mm3 per annum, 0.08% of the
average inflow. The projection for 2025, is around 14Mm3 or 0.17% of the inflow.
Table 6-10 : Groundwater Abstractions (ODMP Analysis of Water Resources Scenarios
2006)
LOCATION Abstractions
(m3/day)
2005 2025
Seronga 210 287
Ngarange 137
185
Etsha 6
387
522
Etsha 13
136
184
Nokaneng 212
286
Gumare 515 696
Sehitwa 230 310
Tsao 191
257
Toteng 234 316
Shorobe 230 310
Tsutsubega 1,643
4,026
Shashe 4,654
-
Gomoti 7,666
10,066
Kunyere -
12,079
Matsibe -
8,053
TOTAL 16,445
37,577
6.3 Rural
water
demands
6.3.1 Angola
Due to the scale at which the basin model was configured, water demands of rural
settlements not considered, as they are very small compared to the irrigation and
urban demands. For the purposes of calculation of the volume of water consumed
by the rural population, a per capita consumption of 50 litres/person/day can be used.
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E-Flows Hydrology Report: Data and models
There is a small number of livestock in the Angolan portion of the Okavango River
Basin. Due to the insignificant amount of water consumption associated with
livestock, the basin model does not include this demand.
Livestock projections are shown in Table 6-11, below:
Table 6-11 : Angola Livestock Projections
Type of
Year 2008
Year 2015
Year 2020
Year 2025
Remarks
Animal
Cattle 101342 124638 144490 167503 Annual
gouwth
of 3%
Sheep 27372 36020 43824 53319 Annual
growth
of 4%
Goats 27372 36020 43824 53319 Ditto
Pigs 27372 36020 43824 53319 Ditto
6.3.2 Namibia
Water consumption for the rural areas in the Kavango Region was obtained from the
Ministry of Agriculture, Water and Rural Development (Lund Consulting Engineers,
2003). In the report, a growth rate of 1.5% was used to project the water demands
from 2010 until 2017. The same growth rate was used to project the water demands
until 2025, and collectively, the rural water demands including livestock water
requirements are shown in Table 6-12.
Table 6-12 : Rural water demand projections for Kavango Region
Growth rate Rural water Demand (Mm3/a)2
Total Demand
Year (%)
(Mm3/a)
Human Schools Clinics Livestock
2008 1.63 1.841
0.385
0.014 3.478
5.718
2010 1.50 1.898
0.397
0.015 3.585
5.895
2015 1.50 2.044
0.428
0.016 3.862
6.350
2025 1.50 2.373
0.497
0.018 4.482
7.370
2The rural water demands are met mainly by groundwater and were not used as input data into the
WEAP model.
The last livestock census was taken in 2006. For the Kavango Region, the livestock
results since 2001 are summarized in
Table 6-13 as provided by the Directorate of Veterinary Services in the Ministry of
Agriculture, Water and Forestry.
Table 6-13 : Livestock census for the Kavango Region
Census
Cattle Sheep Goats Horses Donkeys Pigs
Poultry Dogs Total
Year
2000
127 043
446
61 736
542
1 341
3 007
63 269
15 121 272 505
2001
122 301
1 165
50 812
456
1 665
2 899
59 340
8 209
246 847
2002
122 633
410
50 893
502
1 685
2 580
87 227
7 329
273 259
2003
120 454
470
45 997
460
1 568
3 344
56 145
8 243
236 681
2004
120 496
88
46 411
598
1 600
2 536
62 372
6 284
240 385
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E-Flows Hydrology Report: Data and models
2005
120 894
1 388
49 519
301
1 699
*N/A
48 169
10 255 232 225
2006
125 927
1 472
44 135
524
1 555
1 778
55 116
7 122
237 629
*Data not available
6.3.3 Botswana
Rural domestic water demands in the Delta region are included in the water demand
estimates shown in Table 6-9 and Table 6-10. For the NWMPR- 2006, in order to
estimate the livestock water demands, the projected livestock population by region
was converted to livestock units. One livestock unit requires 45 litres of water per
day; this translates into 16.4 m3 per head per annum. To obtain water demands, the
rate was applied to livestock units.
Table 6-14 : Projected livestock units (' 000) by livestock category per 5 year Duration
range in Maun Region Table 6-22 to 6-31 page 119/120 NWMPR Volume 8,
March 2006
Category
2005-2010 2011-2015 2016-2020 2021-2025 2026-2030 2031-2036
Cattle 625 526 543 561 588 745
Goats 243 208 221 209 229 289
Sheep 21 17 17 15 16 18
Donkeys
70 54 53 44 41 46
TOTAL
LSU
959 805 834 829 874 1098
WATER
REQUIRE-
MENTS
(m3)
15916 13222 13698 13616 14355 18035
6.4 Hydropower
6.4.1 Angola
Data on hydropower potential were obtained from old studies carried out by
Technicians from Portugal and from the former Republic of Yugoslavia. Mr. Paulo
Emílio Mendes, the Head of the Water Resources Division of DNA, provided some
additional data. The hydropower scenarios include the development of 10 run-of-the
river schemes (Cuvango, Cutato, Malobas/Cuchi, Cuelei, Lyapeca, Mucundi,
Maculungungu, Cuito, Mpupa and Xamavera), and the construction of one storage-
based regulation dam at Mucundi.
6.4.2 Namibia
Pre-feasibility studies have been carried out for the development of hydropower
scheme at Popa Falls near Divindu in the Kavango Region. At the time it was
decided not proceed with feasibility level assessment of the scheme due to the need
for extensive environmental impact studies. A possible run-of-river hydropower
scheme was modelled for the medium and high development scenarios with the
characteristics shown in Table 6-15. This information was provided by Nampower.
Table 6-15 : Possible hydropower scheme at Popa Falls
Parameter Estimated
amount
Maximum turbine flow
280 (m3/s)
Fixed head
9.75 (m)
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E-Flows Hydrology Report: Data and models
Generating efficiency
94.5 (%)
Plant factor
100 (%)
6.4.3 Botswana
To date, no hydropower schemes have been planned in the Botswana portion of the
basin.
7
Water Resources Management Information
7.1
Data and Information Management
7.1.1 Angola
In Angola, DNA is the government body for hydrological data collection and
management. DNA works in a close collaboration with Provincial Directorates of
Water (DPA). Data collected in the field are sent to DNA for processing and
dissemination. The data collected is stored in the national database, the HYDATA.
Currently the hydrological data management is poor. In the past the national
hydrometric network consisted of about 189 stations. Most of the stations were
derelict during the civil war, leaving the country with a paucity of hydrological data to
support water resources management.
The database, HYDATA, was populated with data collected until the end of 1980s.
Currently the HYDATA is not functioning, despite many attempts to repair it.
Therefore, most of the data used for the Environmental Flows Assessment are
historic.
Due to lack of incentives the Water Sector is understaffed. There are government
plans targeting at the rehabilitation of the hydrological network, enabling the sound
management of water resources. Multilateral, like the World Bank, have also plans to
help the development of the national Water Sector, including the rehabilitation of
hydrometric stations.
7.1.2 Namibia
The Directorate of Resource Management in the Department of Water Affairs and
Forestry is responsible for water resource management nation wide. Data collection
and management of surface water is by the Hydrology Division; groundwater by
Geohydrology Division and water quality by Water Environment.
The Namibia Water Corporation collects hydrological data and then forwards it to the
Department of Water Affairs and Forestry who are the custodians of the country's
data. The collection of data is done by Hydrology and Geohydrology sections under
the Planning and Water Resources Division, and by the Water Quality Services
Division.
Namibia Meteorological Services in the Ministry of Works and Transport is
responsible for the collection of the national rainfall data.
Currently, there are two databases in use to store hydrological and geo-hydrological
data. The HYDSYS database is used by the Hydrology Division, DWAF. While the
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E-Flows Hydrology Report: Data and models
Geohydrology Division, DWAF uses the Ground Water Information System
(GROWAS) database. NamWater does not have databases and use Excel in the
Division, but database options are being investigated.
Data collection is done by observers near the site, like farmers who read daily rain
gauges, and staff at regional offices that send the forms through the mail. Also, staff
members from head office go and collect data from the stations. While some
telemetry data is being received directly in the office via the telephone lines.
One major constraint is financing to purchase equipment and vehicles. Lack of
manpower and trained staff, training, lack of instruments, the need to replace the old
with newer and accurate instruments compounds the problems in the collection and
management of hydrological data.
The Department of Water Affairs and Forestry as a government institution provides
data to the public upon request and also keeps the nation informed. The Water
Resources Management Act of 2004 states that Namibia must abide by the Southern
African Development Community Protocol on Shared Water Courses which stipulates
that "Member States within a shared watercourse system shall exchange information
and data regarding the hydrological, hydrological, water quality, meteorological and
ecological condition of such watercourse system."
The Namibia Water Corporation Act of 1997 stipulates that upon request from the
Department of Water Affairs and Forestry, NamWater is to provide rainfall, river flow,
groundwater levels, water abstraction from water resources and water quality data.
Also NamWater is to make provision for the dissemination of data to the public.
The Department of Water Affairs and Forestry through the Okavango River Basin
Management Committee provides hydrological information to the co-basin countries.
The Hydrology Division, DWAF is a participant in the SADC Hydrological Cycle
Observation System project (SADC-HYCOS).
During the rainy season, Hydrology, NamWater provides weather information (from
NMS) and daily water levels of dams via email and press releases to keep the public
informed. The NamWater website, www.namwater.com.na does archive a weekly
bulletin of dam levels in the country.
7.1.3 Botswana
The Hydrology and Water Resources Division is responsible for the collection of
hydrological data on a daily basis at Mohembo and at monthly intervals in the other
hydrometric stations in the delta. The data collected by the Maun and Gumare Water
Affairs Stations are passed on to the Head Office in Gaborone where the data is
processed for use in various projects relating to the Delta. Currently, emphasis is
placed on entering the hydrometric data to improve availabity to the stakeholders.
The Harry Oppenheimer Okavango Research Centre (HOORC) in Maun also collects
hydrological data for their research purposes at selected sites in the rivers of the
Delta. The HOORC has established a hydro monitoring station on the Boro River to
conduct research on water quality and flow measurements.
HOORC developed the Okavango Delta Information System during the Okavango
Delta Management Plan Project. The available data categories include boundaries,
climate, culture, ecology, hydrology, environmental hazards, flora, fauna, land use,
geology and other features. Information about the Okavango Delta and other
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E-Flows Hydrology Report: Data and models
planning processes including hydro models, consultancy reports, documents, journal
articles, websites of the institutions, photographs and other databases including the
Peter Smith collections are also available in HOORC.
Data sharing agreements among the stakeholders were drawn up by HOORC with
the assistance of the Chief Technical Advisor. However, there are several constraints
in sharing the data collected by the Hydrology Division. The primary concern for the
stakeholders is that the data cannot be obtained by interested parties as the
Department of Water Affairs has a policy of charging for data procurement. In
addition, there is still confusion in sharing of data between institutions such as Water
Affairs and HOORC and the other Government Departments. The other reason is
that the databases used by the various institutions are incompatible.
The major institutions responsible for hydrological data collection in Botswana are the
Department of Water Affairs (DWA), Department of Meteorological Services (DMS),
Department of Surveys and Mapping (DSM), Department of Geological Surveys
(DGS) and the Water Utilities Cooperation (WUC). The table below shows a list of
data collected in each department;
Department
Data Collected
Flow, Water Levels, Cross sections,
DWA
Water Quality Data, Groundwater levels,
Pumping data, Rainfall
Rainfall, Temperature
DMS
DEM's, Maps
DSM
Soil Data, Boreholes information
DGS
Dams information
WUC
The DWA's Hydrology and Water Resources Division is responsible for Hydrological
services. The division used HYDATA for data archiving. It is anticipated that the
division will soon shift to HYDSTRA database under the SADC HYCOS project. DWA
and DGS share a common database called NIGIS National Integrated Geosciences
Information Systems, mainly for borehole information storage.
7.2
Data Sharing and Exchange
7.2.1 Introduction
It is often the case in international shared river basin, that the hydrological institutions
of the countries have differing views and priorities regarding hydrological information
exchange. Downstream countries tend to place a high priority on effective data
exchange, either to ensure timely reaction to water disasters, or to monitor water use
in catchments upstream of their country and cross-border inflows. The views in this
section have been collated from the hydrological institutions in the three riparian
countries of the Okavango Basin.
In an international shared river basin, exchange of hydrological (river flow and
quality) information should serve particular purposes, most importantly:
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E-Flows Hydrology Report: Data and models
· Exchange of water levels in near real-time, in order to pass on information on
events (`disasters') that may have negative impacts, in particular flood
conditions (or drought situations or pollution accidents).
· Regular sharing of processed water levels and/or flows, in order to inform
about hydrological conditions, and to possibly identify and correct
discrepancies between data sets at an early stage.
· Passing on of data in case of ad-hoc requests for particular projects.
In none of the above cases, passed on information should be used for setting up
parallel databases. The data should be used for the specific purpose for which it was
asked and/or passed on. If the same data is needed for another purpose again at a
later stage, the newest data should be asked and passed on, or at least the validity of
the previous data sets should be confirmed.
Good courtesy in all cases is also to fully acknowledge the source of information in
any documents, reports and publications and to send copies thereof to the source
organization.
7.2.2
The existing situation
Within the framework of OKACOM, the three member countries are negotiating a
Protocol on Hydrological Data Sharing. At present there are no formal mechanisms
in place, but Namibia and Botswana have been exchanging river flow information
from as early as in 1982. Despite political issues then, combined flow gaugings were
carried out in the common border area to resolve apparent differences between the
Mohembo and Mukwe stations in Botswana and Namibia respectively.
Until recently, there has been virtually no formal exchange of hydrological and water
disaster information between Angola and Namibia. The situation has improved
somewhat during the course of 2009, when information on flood levels in Angola
were communicated to Namibia via email and cell phone.
There are attempts by the Government of Angola (Goa), through the SNPC, Serviço
Nacional de Protecção Civil (the National Service of Civil Protection) to establish a
sound Early Warning System nationwide. The SNPC is working in a close
collaboration with UNDP, with the United Nations Organization for Food and
Agriculture (FAO), through EPSMO, with DNA, with INAMET and with INOT, Instituto
de Ordenamento do Território (the Institute for Territorial Cadastre)
7.2.3 Disaster
Management
While the implementation of the draft protocol on hydrological data sharing will go
some way to alleviate the situation, it does not specifically address water disaster
management requirements. It is a recommendation of this study that a set of
comprehensive disaster preparedness, implementation and management plans,
protocols and decision support systems be developed for the basin to mitigate the
possible effects of floods, droughts and major pollution accidents.
Typical components of such a disaster management system include:
· A Disaster Information Management system consisting of:
o A GIS / Database system to collect, process, manage and control data
and critical information to predict upcoming floods, droughts and
surface water pollution disasters.
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E-Flows Hydrology Report: Data and models
o Hydrodynamic and hydrological models to predict the extent and
severity of flooding, droughts and pollution plume dispersion.
· Emergency Response Plans to define emergency response activities with
regard to floods, droughts and pollution. The protocols should consider
critical issues related to emergency response to floods, drought and major
pollution accidents, including:
o Early notification and internal communication
o Early public communication on national and local levels
o Early response (evacuation, recovery and rescue plans) including
transport and logistics
o Tasks of different organizations in implementing early response
measures, lines of command
o Trans-boundary communication and mutual assistance aspect
o Other relevant aspects
· Disaster preparedness plans to enhance flood, drought and pollution disaster
preparedness, including:
o An information management system as mentioned previously
o Government response information, including flow of information and
lines of command and decision structures; and
o A Public information system.
· A Mitigation Preparation Plan. Once the emergency responses to the
disaster have been delivered, the responsible governments have to deal with
rehabilitation, restoration and possibly repatriation. A general framework and
guidance for preparation and implementation of rehabilitation, restoration and
repatriation activities should be provided. The plans should emphasize
logistic, organizational, legal, financial and international aspects and
recommendation for organizing rehabilitation and reconstruction works.
8
Conclusions and Recommendations
8.1 General
8.1.1
Hydrological and Hydraulic Models
Considering the limited availability of measured rainfall and stream flow records, the
existing Pitman-based rainfall-runoff model of the basin (Hughes et. al., 2006)
performs reasonably well, with good simulation of low flows and errors in peak flows
of about 20% (the model more often than not under-estimates peak flows). For
traditional water resource assessments the errors in peak flow simulation are not
considered to be serious, as it does not significantly affect estimates of run-of-river or
storage based yields. In the EFA study it was found that this does pose problems, in
that the ecologists attach much greater importance to the magnitude of flood peaks
and found it difficult to relate simulated peak flows to their knowledge of observed
floods and associated ecosystem responses.
A recommendation of this study is that the rainfall-runoff model be re-calibrated with
a view to improve peak flow simulation. As part of the same exercise, the model
should be extended to cover the hydrological years from 2003 to as recently as
possible to include the severe drought of 2007 and the major flood events of 2009
and 2010. The re-calibration should make use of the stream flow records that are
becoming available from rehabilitated flow measuring stations in Angola.
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E-Flows Hydrology Report: Data and models
The assembled suite of existing and new models provided adequate information on
river flow regimes and inundation patterns at the EFA sites, with some scope for
improvement. Major shortcomings include:
· The inability to provide modelled (scenario) information on water quality
changes in the system, mainly due to a lack of historical water quality
measurements for model calibration
· The absence of a sediment transport model (or models) in the basin upstream
of the Delta
· Basic one-dimensional, steady state hydrodynamic models were configured
for the floodplain sites in the basin (Cuito Cuanavale and Kapako), but these
could be improved substantially by using higher resolution topographical
information and the configuration of two-dimensional models.
The hydrological working group engaged in an intensive exercise to collect
information about existing and possible future water resource developments in the
Okavango River basin. The information was assembled by means of literature
reviews and extensive consultations with water resource planners and managers in
the three co-basin states, and formed the basis for formulation of the water resource
development scenarios that were evaluated in the EFA.
The water resources of the basin are relatively un-developed at present. Current
water use consists mainly of:
· The urban water demands of Menongue and Cuito Cuanavale (Angola),
Rundu (Namibia), and Maun (Botswana)
· About 2 700 ha of irrigation in the Namibian portion of the basin
· Rural domestic and subsistence agricultural water demands and water
demands of the tourism sector (Namibia and Botswana), all of which are
small compared to the irrigation and urban demands
8.1.2
Water Resource Development
The end of the civil conflict in Angola has provided impetus to plans to develop the
dormant agricultural economy in the Angolan portion of the basin and to revive plans
for the construction of a number of hydropower schemes. Agricultural development
and the rehabilitation of the transport network will see associated growth in the urban
water demands of Menongue and Cuito Cuanavale. In Namibia, plans to improve
food security could result in substantial growth in irrigation water requirements,
although not at the same scale as foreseen for Angola. In Botswana, growth in urban
and agricultural water demand could be tempered by the need to conserve natural
resources and protect income derived from tourism in the Delta region. Against this
backdrop, the following water resource developments that could be associated with a
high water demand scenario were identified by the working group:
· About 15 000 ha of irrigation in Namibia
· About 338 000 ha of irrigation at various locations in Angola
· Completion of all planned hydropower stations in Angola, i.e. one storage
based and nine run-of-river hydropower stations,
· Extension of Grootfontein-Okavango link of the Eastern National Water
Carrier in Namibia (total capacity 100 Mm3/a)
· The possible construction of a hydropower station at Popa Falls in Namibia.
· Substantial growth in the urban water demands of Menongue, Cuito
Cuanavale, Rundu, and (to a lesser extent), Maun.
Construction of a reservoir in the Boteti to supplement Maun's future water demands.
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E-Flows Hydrology Report: Data and models
8.2 Angola
Recording of hydrological information in Angola stopped in the 1980s, when the civil
war increased in intensity. Therefore most of the data and information used by the
team are historic. The age of the existing data and information will have an effect on
the accuracy of the study results.
The first pre-condition for better water resource planning and management is the
rehabilitation of the hydrometric network nationwide. Based on the new data and
information to be collected, the Water Authorities need to re-think the management of
the Water Sector.
Actions on flood response and the calibration of stations should be prioritised.
The inventory and monitoring of groundwater should also be seen as a priority area
for research.
8.3 Namibia
Both the monitoring sites Kapako and Popa Falls sites do not have hydrological
monitoring equipment and reference was made to stations upstream and
downstream of the investigated sites. Funding will be required to develop and
monitor hydrological stations at Kapako and Popa Falls. Present recording of water
levels and flow gaugings, as been conducted by the MAWF should continue to be
carried out to enable to record comprehensive information of the sensitive sites
identified.
The recommendations are broken up into two phases as further data collection and
monitoring will depend on future project and funding. It is recommended that for the
present situation:
· Satellite images be obtained for Kapako during the dry and wet seasons to
monitor the extent of the floodplain inundation.
· Field observations be done and correlated with Rundu water levels to
determine when the flood starts inundating the floodplain and when the flood
subsides to such an extent that the floodplains are exposed at Kapako.
· Weekly water level readings to be taken at the pump station at Popa Falls.
· Flow gaugings be carried out downstream of Popa Falls to establish a rating
curve for Popa Falls.
For phase 2 it recommended that:
· Hydrological water level recording stations be constructed at a representative
site for Kapako and Popa Falls, and that funding be sourced for this.
The responsibilities for these actions will have to be agreed internally between
Namwater and DWAF Namibia.
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E-Flows Hydrology Report: Data and models
8.4 Botswana
There is a disconnection between government departments in terms of data sharing.
There is also duplication of responsibilities. The departments are not informed of the
needs of sister departments. The Meteorological Services should for example be
aware of the Department of Water Affair's rainfall and climate information
requirements.
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E-Flows Hydrology Report: Data and models
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The Okavango River Basin Transboundary Diagnostic Analysis
Technical Reports
In 1994, the three riparian countries of the
a base of available scientific evidence to guide
Okavango River Basin Angola, Botswana and
future decision making. The study, created
Namibia agreed to plan for collaborative
from inputs from multi-disciplinary teams in
management of the natural resources of the
each country, with specialists in hydrology,
Okavango, forming the Permanent Okavango
hydraulics, channel form, water quality,
River Basin Water Commission (OKACOM). In
vegetation, aquatic invertebrates, fish, birds,
2003, with funding from the Global
river-dependent terrestrial wildlife, resource
Environment Facility, OKACOM launched the
economics and socio-cultural issues, was
Environmental Protection and Sustainable
coordinated and managed by a group of
Management of the Okavango River Basin
specialists from the southern African region in
(EPSMO) Project to coordinate development
2008 and 2009.
and to anticipate and address threats to the
river and the associated communities and
The following specialist technical reports were
environment. Implemented by the United
produced as part of this process and form
Nations Development Program and executed
substantive background content for the
by the United Nations Food and Agriculture
Okavango River Basin Transboundary
Organization, the project produced the
Diagnostic Analysis.
Transboundary Diagnostic Analysis to establish
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,
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Scenario Report : Hydrology (Report No: 06/2009)
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The Groundwater Hydrology of The Okavango Basin (FAO
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Okavango River Basin Environmental Flow Assessment
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Scenario Report: Ecological and Social Predictions (Volume 1
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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.
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Malzbender, D.
Environmental Protection And Sustainable Management Of The
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E-Flows Hydrology Report: Data and models
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Angola
Andrade e Sousa,
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Biophysical Series
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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
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Amândio
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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:
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
79
E-Flows Hydrology Report: Data and models
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
80
E-Flows Hydrology Report: Data and models
80