TDA Namibia Vegetation


Okavango River Basin Technical
Diagnostic Analysis:
Environmental Flow Module
Specialist Report
Country: Namibia
Discipline: Vegetation
B.A. Curtis
June 2009
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TDA Namibia Vegetation






Okavango River Basin Technical
Diagnostic Analysis:
Environmental Flow Module



Specialist Report

Country: Namibia

Discipline: Vegetation

Author: B. A. Curtis

Date: June 2009
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TDA Namibia Vegetation
EXECUTIVE SUMMARY

As part of a Transboundary Diagnostic Assessment (TDA) of the Okavango River, this
preliminary Environmental Flow Assessment (EFA) was undertaken from January until
June 2009. The goals were to summarise all relevant information on the Okavango River
system and to collect new data within very limited time constraints. This information was
then used to provide scenarios of possible development pathways into the future for
consideration by decision makers, enabling them to discuss and negotiate on sustainable
development of the Okavango River Basin. Within each scenario the major positive and
negative ecological, resource-economic and social impacts of the relevant developments
have been included. This was undertaken by a team of specialists from the three Basin
countries, namely Angola, Namibia and Botswana.

The specific objectives of the EFA were to ascertain the relationships between the flow
regime and the ecological nature and functioning of the river ecosystem, as well as the
relationships between the river ecosystem and the people's livelihoods. This was then
used to predict possible development-driven changes to the flow regime and thus to the
river ecosystem.

Eight sampling sites were selected along the length of the river; three each in Angola and
Botswana and two in Namibia. These sites were chosen as typical representatives of
different reaches of the river. At each site, discipline-specific "indicators" were selected.
An indicator is a discipline-specific attribute of the river system that responds to a change
in the river flow. Indicators were selected collaboratively by the discipline specialists from
the three countries. At each site, no more than ten indicators were assessed.

This report gives details on the vegetation indicators at the two sampling sites along the
Namibian section of the river. The indicators selected were based largely on the findings
of a reconnaissance fieldtrip to the two Namibian sites in January 2009, when the water
was too high to do extensive sampling. Information about the ecology and occurrence of
the dominant plants in each indicator was obtained from the literature which the author
had at hand, this being mainly field guides. There was insufficient time for extensive
literature searches. Very little information was available on the effects of flooding or lack
of flooding on the plants concerned, so the predictions are based largely on the intuition
and experience of the author, in collaboration with colleagues from the other two
countries. Ten indicators were identified for the two sites in Namibia, of which nine were
present at site 4 (Kapako) and five were present at site 5 (Popa).


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TDA Namibia Vegetation
Contents
EXECUTIVE SUMMARY ................................................................................................ 3
LIST OF TABLES ........................................................................................................... 6
ABBREVIATIONS ........................................................................................................... 8
ACKNOWLEDGEMENTS ............................................................................................... 9
1INTRODUCTION ........................................................................................................ 10
1.1 Background ...................................................................................................... 10
1.2 Okavango River Basin EFA Objectives and Workplan .................................... 10
1.2.1 Project objectives ....................................................................................... 10
1.3 Layout of this report ......................................................................................... 11
2STUDY AREA ............................................................................................................. 12
2.1 Description of the Okavango Basin ................................................................. 12
2.2 Delineation of the Okavango Basin into Integrated Units of Analysis .............. 13
2.3 Overview of sites ............................................................................................. 14
2.3.1 Site 4: Okavango River at Kapako ............................................................. 15
2.3.2 Site 5: Okavango River at Popa Falls ........................................................ 17
2.4 Discipline-specific description of Namibian sites ............................................. 19
2.4.1 Site 4: Kapako ............................................................................................. 19
2.4.2 Site 5: Popa Falls ........................................................................................ 21
3.IDENTIFICATION OF INDICATORS AND FLOW CATEGORIES ............................ 23
1.1 Indicators ......................................................................................................... 23
3.1.1 Introduction ................................................................................................ 23
3.1.2 Indicator list for Vegetation ......................................................................... 23
3.1.3 Description and location of indicators ........................................................ 24
3.2 Flow categories ­ river sites ............................................................................ 28
3.3 Inundation categories ­ delta sites .................................................................. 32
4LITERATURE REVIEW .............................................................................................. 33
4.1 Introduction ......................................................................................................... 33
4.2 Indicator No 1: Channel macrophytes (submerged) ........................................ 33
4.3 Indicator No 2: Lower wet bank ­ papyrus and hippo grass ........................... 34
4.4 Indicator No 3: Upper wet bank 1 - reeds ........................................................ 35
4.5 Indicator No 4: Upper wet bank 2 ­ trees and shrubs...................................... 35
4.6 Indicator No 5: River dry bank ......................................................................... 36
4.7 Indicator No 6: River floodplain residual pools ................................................ 36
4.8 Indicator 7: River lower floodplain .................................................................... 37
4.9 Indicator No 8: River middle floodplain ............................................................ 37
4.10 Indicator No 9: River upper floodplain (islands) ............................................... 38
4.11 Indicator No 10: Floodplain dry bank ............................................................... 39
4.12 Summary ......................................................................................................... 39
5DATA COLLECTION AND ANALYSIS ....................................................................... 40
5.1 Methods for data collection and analysis ......................................................... 40
5.2 Results ............................................................................................................. 40
5.3 A summary of present understanding of the predicted responses of all
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TDA Namibia Vegetation
vegetation indicators to potential changes in the flow regime ......................... 40
5.3.1 Indicator 1 ­ (Submerged) Channel Macrophytes ..................................... 41
5.3.2 Indicator 2 - Lower wet bank (papyrus and hippo grass) ......................... 41
5.3.3 Indicator 3 ­ Upper wet bank 1 (reeds) ...................................................... 43
5.3.4 Indicator 4 ­ Upper wet bank 2 (trees and shrubs) ................................... 44
5.3.5 Indicator 5 ­ River Dry Bank ..................................................................... 45
5.3.6 5.3.6 Indicator 6 - River floodplain residual pools ..................................... 46
5.3.7 Indicator 7 - River lower floodplain ............................................................ 47
5.3.8 Indicator 8 - Rivermiddle floodplain (grasses) ........................................... 48
5.3.9 Indicator 9 ­ River upper floodplain (islands) ............................................ 49
5.3.10 Indicator 6 ­ Floodplain Dry Bank .............................................................. 50
5.4 Conclusion ......................................................................................................... 51
6. Flow-response relationships for use in the Okavango EF_DSS ............................ 52
7.REFERENCES .......................................................................................................... 53
APPENDIX A: PICTORIAL DESCRIPTIONS OF NAMIBIAN VEGETATION
INDICATORS ...................................................................................................... 54
APPENDIX B: RAW DATA FROM FIELDTRIP ............................................................ 63



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TDA Namibia Vegetation
LIST OF TABLES
Table 2. 1: Location of the eight EFA sites ................................................................... 14

Table 3. 1: List of indicators for river vegetation and those chosen to represent each
site in Namibia ......................................................................... 24
Table 3. 2: Questions to be addressed at the Knowledge Capture Workshop, per
indicator per site. In all cases, `natural' embraces the full range
of natural variability .................................................................. 32
Table 3. 3: Inundation categories for the Okavango Delta as recognised by the
HOORC inundation model ....................................................... 32

Table 4. 1: . Floodplain and river bank grasses as listed by Correira & Bredenkamp
(1987) ...................................................................................... 33
Table 4. 2: Plant species recorded by Bethune (1991) in permanently flowing water. . 34

Table 5. 1: Predicted response to possible changes in the flow regime of (Submerged)
Channel Macrophytes in the Okavango River ecosystem ....... 41
Table 5. 2: Predicted response to possible changes in the flow regime of Lower wet
bank in the Okavango River ecosystem .................................. 42
Table 5. 3: Predicted response to possible changes in the flow regime of Upper wet
bank 1 in the Okavango River ecosystem ............................... 43
Table 5. 4: Predicted response to possible changes in the flow regime of Upper wet
bank 2 in the Okavango River ecosystem ............................... 44
Table 5. 5: Predicted response to possible changes in the flow regime of River Dry
Bank in the Okavango River ecosystem .................................. 45
Table 5. 6: Predicted response to possible changes in the flow regime of River
floodplain residual pools in the Okavango River ecosystem ... 46
Table 5. 7: Predicted response to possible changes in the flow regime of River lower
floodplain in the Okavango River ecosystem........................... 47
Table 5. 8: Predicted response to possible changes in the flow regime of River middle
floodplain in the Okavango River ecosystem........................... 48
Table 5. 9: Predicted response to possible changes in the flow regime of River upper
floodplain in the Okavango River ecosystem........................... 49
Table 5. 10: Predicted response to possible changes in the flow regime of Floodplain
Dry Bank in the Okavango River ecosystem ........................... 50
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TDA Namibia Vegetation
LIST OF FIGURES

Figure 2. 1: Upper Okavango River Basin from the sources to the northern end of the
Delta ........................................................................................ 12
Figure 2. 2: The Okavango River Basin, showing drainage into the Okavango Delta
and the Makgadikgadi Pans .................................................... 13
Figure 2. 3: 15
Figure 2. 4: Satellite images of the wet (below) and dry (top) season for Popa rapids
(site 5). Transect and main sampling sites for all disciplines
other than vegetation are shown. Maps prepared by Celeste
Espach. .................................................................................... 18
Figure 2. 5: Kapako floodplains showing the location of the nine vegetation indicators 20
Figure 2. 6: Popa Falls showing the location of the five vegetation indicators ............. 22
Figure 3. 1: Three representative years for Site 1: Cuebe River @ Capico, illustrating
the approximate division of the flow regime into four flow
seasons ................................................................................... 29
Figure 3. 2: Three representative years for Site 2: Cubango River @ Mucindi,
illustrating the approximate division of the flow regime into four
flow seasons ............................................................................ 30
Figure 3. 3: Three representative years for Site 3 Cuito River @ Cuito Cuanavale,
illustrating the approximate division of the flow regime into four
flow seasons ............................................................................ 30
Figure 3. 4: Three representative years for Site 4: Okavango River @ Kapoka
(hydrological data from Rundu), illustrating the approximate
division of the flow regime into four flow seasons .................... 31
Figure 3. 5: Three representative years for Site 5: Okavango River @ Popa
(hydrological data from Mukwe), illustrating the approximate
division of the flow regime into four flow seasons .................... 31

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TDA Namibia Vegetation
ABBREVIATIONS

ABBREVIATION
MEANING
EF Environmental
Flow
EFA
Environmental Flow Assessment
DSS
Decision Support System
IUA
Integrated Units of Analysis
NBRI
National Botanical Research Institute (of Namibia)



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TDA Namibia Vegetation
ACKNOWLEDGEMENTS

Thanks to Frances Crawford and Shirley Bethune for assistance with plant collections
and deciding on indicators; to Amândio Gomes (Angola vegetation specialist) and
Casper Bonyongo (Botswana vegetation specialist) for discussions on responses of
indicators to changes in flow; to Coleen Mannheimer of the NBRI for help with plant
identification; to Esmerialda Klaassen of the NBRI for plant species lists; to Ben van der
Waal for boat transport during the January fieldtrip; to Shirley Bethune, Namibian team
leader, for co-ordination of the project in Namibia, comments on the manuscript and input
during the scenario workshop; to Celeste Epach for production of the maps. Special
thanks to Prof. William (Fred) Ellery of Rhodes University for commenting on the
manuscript.

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TDA Namibia Vegetation
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.

This preliminary EFA is a joint project of EPSMO and the Biokavango Project. One
component of the preliminary EFA is a series of country-specific specialist studies, of which
this is the Vegetation Report for Namibia.

1.2
Okavango River Basin EFA Objectives and Workplan
1.2.1 Project
objectives
The goals of the preliminary EFA are:
·
to summarise all relevant information on the Okavango River system and its
users, and collect new data as appropriate within the constraints of the EFA
·
to use these to provide scenarios of possible development pathways into the
future for consideration by decision makers, enabling them to discuss and
negotiate on sustainable development of the Okavango River Basin;
·
to include in each scenario the major positive and negative ecological, resource-
economic and social impacts of the relevant developments;
·
to complete this suite of activities as a pilot EFA, due to time constraints, as input
to the TDA and to a future comprehensive EFA.


The specific objectives at a preliminary level are:
·
to ascertain at different points along the Okavango River system, including the
Delta, the existing relationships between the flow regime and the ecological
nature and functioning of the river ecosystem;
·
to ascertain the existing relationships between the river ecosystem and peoples'
livelihoods;


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TDA Namibia Vegetation
·
to predict possible development-driven changes to the flow regime and thus to the
river ecosystem;
·
to predict the impacts of such river ecosystem changes on people's livelihoods.
·
to use the EFA outputs to enhance biodiversity management of the Delta.
·
to develop skills for conducting EFAs in Angola, Botswana, and Namibia.

1.3
Layout of this report
Chapter 1 gives a brief introduction to the background of the project and lists project
objectives. Chapter 2 describes the broad study area of the Okavango River Basin and gives
more detail on the two specific sites chosen for this preliminary EFA within the Namibian
section of the river - Kapako and Popa rapids. In Chapter 3, the nine vegetation indicators
are described for the two Namibian sites. Flow categories are also indicated. A short
literature review pertinent to vegetation work in the Okavango River is given in Chapter 4,
with indicators described in more detail. The field survey work undertaken for the vegetation
investigation within Namibia in January 2009 (wet season), including data collection, analysis
and results, is outlined in Chapter 5. Chapter 6 is a first attempt to link vegetation to flow and
to provide information on the flow-response relationships for use in the Okavango EF-DSS.
References are found in Chapter 7. Appendix A shows photographs of the Namibian
vegetation indicators, while Appendix B contains some of the raw field data.


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TDA Namibia Vegetation
2 STUDY
AREA
2.1 Description of the Okavango Basin
The Okavango River Basin consists of the areas drained by the Cubango, Cutato, Cuchi,
Cuelei, Cuebe, and Cuito rivers in Angola, the Okavango River in Namibia and Botswana,
and the Okavango Delta (Figure 2.1). This basin topographically includes the area that was
drained by the now fossil Omatako River in Namibia. 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. On the basis of topography, the Okavango River Basin thus
includes the Makgadikgadi Pans and Nata River Basin (Figure 2.2). 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.

Upper Okavango River Basin
N
W
E
S
Cu
t
Cu
a
#
t
o
c
h
i
#
C
C
u
u
#
it
a
o
nava
#
le
Cu
#
C
Menongue
ba
u
n
c
g
h
#
Major settlement
o
i
# Cuito Cuanavale
River
C
#
ue
Fossil river
be
C
Panhandle
ANGOLA
uir
Permanent swamps
iri
#
Seasonal swamps
Cubango
Cuito
NAMIBIA
Okavango
#
Rundu
#
#
#
0
300 Kilometers
#

Figure 2. 1: Upper Okavango River Basin from the sources to the northern end of the Delta


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TDA Namibia Vegetation
Okavango River Basin
N
W
E
S
C
u
ta
Cu
#
to
c
h
i#
C
C
ui
ua
#
t
o
nav
#
ale
C
# Menongue
ub
C
a
u
n
c
g
h
o
i
# Cuito Cuanavale
# Cuebe
C
ANGOLA
uiri
#
ri
Cubango
Cuito
NAMIBIA
Okavango
#
Rundu
#
# #
#
##
#
#
#
Maun
#
Makgadikgadi Pans
# Ghanzi
#
Major settlement
River
Fossil river
Panhandle
0
600 Kilometers
Permanent swamps
Seasonal swamps

Figure 2. 2: The Okavango River Basin, showing drainage into the Okavango Delta and the
Makgadikgadi Pans

2.2 Delineation of the Okavango Basin into Integrated Units of Analysis
Within the Okavango River Basin, no study could address every kilometre stretch of the river,
or every person living within the area, particularly a pilot study such as this one. Instead,
representative areas that are reasonably homogeneous in character may be delineated and
used to representative much wider areas, and then one or more representative sites chosen
in each as the focus for data-collection activities. The results from each representative site
can then be extrapolated over the respective wider areas.

Using this approach, the Basin was delineated into Integrated Units of Analysis
(EPSMO/Biokavango Report Number 2; Delineation Report) by:
dividing the river into relatively homogeneous longitudinal zones in terms of:
hydrology;
geomorphology;
water
chemistry;
fish;


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TDA Namibia Vegetation
aquatic
macro-invertebrates;
vegetation;
other
wildlife
harmonising the results from each discipline into one set of biophysical river zones;
dividing the basin into relatively homogeneous areas in terms of social systems;
harmonising the biophysical river zones and the social areas into one set of Integrated Units
of Analysis (IUAs).

The 19 recognised IUAs were then considered by each national team as candidates for the
location of the allocated number of study sites:
Angola:
three sites
Namibia:
two
sites
Botswana: three sites.

The sites chosen by the national teams are given in Table 2.1.
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
6 Botswana
Okavango
Panhandle
at
Shakawe
7 Botswana
Khwai Xakanaka
in
Delta
8 Botswana
Boteti Chanoga
Table 2. 1: Location of the eight EFA sites

2.3 Overview
of
sites
In the Namibian section of the Okavango River, the majority of the human population lives
along the river and the main road, with several hot spots such as Rundu, Divundu and
Nkurenkuru which have a high population density. The river can be divided into four clear
units of analysis; the longest section that extends from where the river enters Namibia at
Katwitwi to the Cuito confluence that is typified by the meandering mainstream and large
seasonally-flooded floodplains on either side to the river (Kapako site 4, was chosen as a
typical floodplain and mainstream site within this section); the section immediately
downstream of the Cuito confluence that has permanently swamped areas and large islands
(not included in the preliminary survey but essential to include in a later more detailed EFA
study); the southward flowing rocky, braided section from Mukwe to just below the Popa
rapids where the river is largely confined to the mainstream and flows around several sand
and rock based islands (Popa rapids Site 5, was chosen as a typical rocky river site within
this section) and the protected section of the river downstream of Popa to the border with
Botswana at Mohembo that lies within the newly declared Bwabwata National Park which has
two of its core conservation areas on either side of the river, the Buffalo core area on the east
bank and the Muhango core area on the west bank.



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TDA Namibia Vegetation
2.3.1 Site 4: Okavango River at Kapako






























Satellite images of the Kapako floodplain (site 4) in the dry season (top) and wet
Figure 2. 3: season (below). The main sampling sites used by all disciplines except
vegetation are indicated. Maps by Celeste Espach.

The riverine landscape includes the main Okavango River channel or mainstream, the
annually flooded floodplains with several braided side channels and deeper pools or
backwaters, as well as the higher fluvial terrace with alluvial deposits that are very seldom
flooded. There is a steep, well vegetated bank at the edge of the floodplain close to the main
road that rises to several metres above the floodplain (this was vegetation indicator 6,
Floodplain dry bank)



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TDA Namibia Vegetation
Kapako area has a population of approximately 2,500 people within 10 km of Kapako village.
The greatest density of people (over 100 per km2) live alongside the river in the area just west
of the Kapako study site whilst at the site itself the density varies from no people on the
floodplain, 6 ­ 25 / km2 at the Ebenezer mission, to a density of 25 ­ 50 /km2 closer to the
road and 51 ­ 100 /km2 on the other side of the main road, rapidly decreasing again with
distance inland. (See Map 3 in Poplations Demographics Report prepared by Celeste
Espach). We can assume that some of these people make some use of the floodplain site at
Kapako and elsewhere along this stretch of river.

During the focus group discussion held at Kapako village, the basin residents mentioned that
the flooding starts when the rising river and channel waters push out over flat surrounding
ground and the biggest floodplains form in years when river levels are highest. They said that
the most important feature of the flooded areas is that they are rich in nutrients. The
floodplains also offer the young fish refuge from larger, predatory species and thus offer the
greatest survival of young fish. They had noted that an overall increase in fish population
occurs in years when water levels are high and flooding lasts longest. Local people have
recognised that water quality and fish resources are decreasing in the Okavango River. Fish
and fishing remain significant features in the lives of people at Kapako, who fish for food or to
earn incomes by selling their catches. In addition, some earn money by providing trips for
tourists. They estimate fish stocks in the floodplains to be four times higher than in the main
channel. About 47% of households at Kapako catch fish, and each person consumes an
average of 10-20 kilograms of fish per year. September to December is the peak fishing
period at Kapako when the river is at its lowest and fish are concentrated in the mainstream.

At Kapako, as elsewhere along the Namibian section of the river, the ever increasing human
population and clearing for crops and livestock has put increasing pressure on the natural
resources along the main channel. The vegetation along the river bank is overgrazed and in
some areas depleted, thus at Kapako the residents graze their livestock across the river on
the Angolan floodplain. Cattle were routinely seen being swam across the river at this site
during fieldwork. Associated with this population growth, has been an increase in livestock,
fire frequency as well as the area of land cleared for crops and fuel. These associated land
use changes are an undeniable factor of increasing settlement and development at a Kapako
and indeed all along the Okavango.

The road westwards from Rundu has been upgraded and is currently being tarred. It runs
parallel to the Okavango River all the way to the border post with Angola at Katwitwi. This
has opened up the region allowing people to exploit the land alongside the road. As
expected, highest densities are alongside the road parallel to the river. As the population
continues to increase, exploitation of the land that new roads have opened up should
disperse the pressure on the Okavango River floodplains and its resources to land further
inland from the river, although the river will always remain the main source of water even for
livestock watering.

The extent of clearing and thus of bare ground and erosion has also increased; yet the
people perceive the overall water quality not to have declined substantially. The only
exceptions mentioned were an increase in phosphate concentrations, a decrease in water
clarity and a related increase in suspended sediments. There are more short term, seasonal
variations in water quality particularly in the floodplain pools, than any long term water quality
change. So far there does not seem to have been an excessive exploitation of the water
resources in the main channel, although the basin further inland has some serious water


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TDA Namibia Vegetation
shortages at times and a lack of deep boreholes. The Kalahari sands that overlay the area
are deep.

2.3.2
Site 5: Okavango River at Popa Falls
At the Popa rapids, the entire width of the river cascades down several meters before
resuming its normal slow and leisurely flow. The quartzite rocks were formed from sediments
deposited in rift valleys about 900 million years ago (Mendelsohn & el Obeid, 2004).

Papyrus (Cyperus papyrus) dominates the deepest water margins alongside the main
channels. Water can seep through the walls of papyrus to the reed beds behind the papyrus
and in places into backwaters and side channels. The sandy sediments are confined to the
channels. These are flanked by reed beds of Phragmites australis, bulrushes, Typha and the
grass Miscanthus junceus in the shallower waters. The residents do not experience floods as
there are no floodplains in this area. They depend in the main channel for most of their water
and wetland resources. Most houses at Popa village are thatched with grass and reeds, while
reeds are used extensively to make sleeping mats, walls, palisades, courtyards and fences.

Farming activity is an important source of income; households are engaged in both crop and
livestock farming. Planting is staggered through the raining reason and is initiated only after a
good rainfall event. This increases the chance of crop survival during the hot dry periods.
Livestock farming is dominated by cattle and goats, not kept within fields but are moved for
grazing and between water sources, mainly the Okavango River.

Tourism is a major source of income to the Popa resident; most of them are employed within
the lodges around the Popa area. They value tourism as their major source of income.




















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TDA Namibia Vegetation

Figure 2. 4: Satellite images of the wet (below) and dry (top) season for Popa rapids
(site 5). Transect and main sampling sites for all disciplines other than
vegetation are shown. Maps prepared by Celeste Espach.




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TDA Namibia Vegetation
2.4
Discipline-specific description of Namibian sites
2.4.1 Site 4: Kapako
At Kapako the river curves to the north. On either side of the mainstream, but more so on the
southern (Namibian) side, there are extensive floodplains in the form of concentric scroll bars
formed as the river channel has changed with time. This means that as the flood comes
down, the deeper channel areas fill first, with the water gradually spreading over the whole
area. Although the satellite images show clear concentric bands on the floodplain, the
differences in vegetation are not as clear cut. There are patches of one species interspersed
with individuals of another, and then scattered individuals of the first species among other
vegetation again. The highest points of the bars, forming the upper floodplain "islands" that
are flooded for the shortest periods of time, are dominated by the shrubby river rhus (Searsia
quartiniana), with the Chobe candle-pod acacia (Acacia hebeclada ssp. chobiensis) and a
few shrubby umbrella thorns (Acacia tortilis). A few islands have striking specimens of the
paperbark acacia (Acacia sieberiana). Various grass species are found. Slightly lower, on the
edges of these "islands" and flooded for longer, are the pygmy fig (Ficus pygmaea) and the
spindly shrub Tacazzea apiculata, along with young reeds and grasses Setaria sphacelata
var. sericea and Panicum coloratum var. coloratum. In the lower-lying sections of the
floodplain are extensive stands of grasses Setaria sphacelata var. sericea and Panicum
coloratum var. coloratum, and deeper still are beds of hippo grass (Vossia cuspidata). There
are also some permanent floodplain pools that seem to retain water, even in the dry season.

Along the outer edge of the floodplain (on the Namibian side ­ we did not look at the Angolan
side) is the river bank, which has a moderate to steep slope out of the floodplain (This has
been called Floodplain Dry Bank). The upper wet bank, closest to the water and periodically
flooded at very high water, is dominated by the river rhus (Searsia quartiniana), with buffalo
thorn (Ziziphus mucronata). Both of these species are often standing in water. Along the
banks and playing an important role in stabilising the bank is the large-leaved albizia (Albizia
versicolor) and an occasional strangler fig (Ficus burkei). Dominant shrubs in the under-story
include the rough-leaved raisonberry (Grewia flavescens) and G. olukondae. The outer, dry
bank is dominated by lead wood (Combretum imberbe) and umbrella thorn (Acacia tortilis),
with patches of camel thorn (Acacia erioloba) and occasional buffalo thorn. Dominant shrubs
include the magic guarri (Euclea divinorum), bloubos (Diospyros lycioides), Grewia
flavescens, G. schinzii and G. olukondae.






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Figure 2. 5: Kapako floodplains showing the location of the nine vegetation indicators



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TDA Namibia Vegetation
2.4.2 Site 5: Popa Falls
The main river splits and flows around a number of islands. Each main channel is lined by
submerged vegetation; then a zone of papyrus (Cyperus papyrus) with numerous water
daisies (Aspilia mossambicensis) and occasional pygmy figs (Ficus pygmea) and bog ferns
(Thelypteris interrupta); then reeds which span the interface between permanently flooded
river and the dry bank. The river bank has a dense riparian woodland. The upper wet bank is
dominated by the river rhus, with the water pear (Syzygium guineense ssp. barotsense), the
safsaf willow (Salix mucronata ssp. mucronata), the waterberry (Syzygium cordatum), the
lance-leaved waxberry (Morella serrata), the wild date palm (Phoenix reclinata) and buffalo
thorn. The species stabilising the banks include the African mangosteen (Garcinia
livingstonei), the large-leaved albizia (Albizia versicolor) and the jackal berry (Diospyros
mespiliformis). The large tree component of the dry bank vegetation is dominated by the
jackal berry and African mangosteen, with sausage tree (Kigelia africana). Dominant shrubs
include (Friesodielsia obovata), Antidesma venosum, Diospyros lycioides, Grewia flavescens,
knobbly combretum (Combretum mossambicense), Markhamia obtusifolia, potato bush
(Phyllanthus reticulates). The forest well beyond the water line is dominated by Acacia
nigrescens and Terminalia sericea with Philenoptera violacea and Peltophorum africanum.

The larger islands have a vegetation structure similar to that of the banks of the main
channel, but with narrower zones, and sometimes with the vegetation of the zones becoming
intermixed. Thus there can be papyrus and reeds growing together, and in places the
papyrus/reed zone was part of the upper wet bank zone. Much of the under-story of the
island was dominated by the softly woody pioneer shrub Acalypha ornata. Due to the dense
riparian woodland there is very little grass cover, but grass Setaria sphacelata var. sericea
was found on the gently sloping edges of the islands.



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Figure 2. 6: Popa Falls showing the location of the five vegetation indicators


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TDA Namibia Vegetation
3. IDENTIFICATION
OF
INDICATORS AND FLOW
CATEGORIES
1.1 Indicators
3.1.1 Introduction
Biophysical indicators are discipline-specific attributes of the river system that respond to a
change in river flow by changing in their:
· abundance;
· concentration;
or
· extent
(area).

Social indicators are attributes of the social structures linked to the river that respond to
changes in the availability of riverine resources (as described by the biophysical indicators).

The indicators are used to characterise the current situation and changes that could occur
with development-driven flow changes.

Within any one biophysical discipline, key attributes can be grouped if they are expected to
respond in the same way to the flow regime of the river. By example, fish species that all
move on to floodplains at about the same time and for the same kinds of breeding or feeding
reasons could be grouped as Fish Guild X.


3.1.2 Indicator list for Vegetation
In order to cover the major characteristics of the river system and its users many indicators
may be deemed necessary. For any one EF site, however, the number of indicators is limited
to ten (or fewer) in order to make the process manageable. The full list of indicators was
developed collaboratively by the country representatives for the discipline ­ Amândio Gomes,
Barbara Curtis and Casper Bonyongo - and is provided in Table 3.1. Further details of each
indicator, including the representative species of each biological one, are given below, and
are discussed fully in Chapter 4. Photographs are provided in Appendix A.









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TDA Namibia Vegetation
Sites represented ­ no more than ten indicators
Indicator
Indicator name
per site
Number
1 2 3 4 5 6 7 8
1 Channel
macrophytes
x x

2
Lower wet bank (papyrus / hippo grass)



x
x



3
Upper wet bank 1 (reeds)



x
x



4
Upper wet bank 2 (trees & shrubs)



x
x



5 River
dry
bank
- x
6 (River)
floodplain
residual
pools
x -
7
(River) lower floodplain



x
-



8 (River)
middle
floodplain



x
-


9 (River)
upper
floodplain

x -
10 Floodplain
dry
bank
x -
Table 3. 1: List of indicators for river vegetation and those chosen to represent each site in
Namibia

3.1.3 Description and location of indicators
Vegetation Indicator 1
Name:

Channel macrophytes (submerged)
Description:
Totally or almost entirely submerged, rooted or floating
macrophytes in the main river channel(s).

Representative species:
Potamogeton spp. (pondweed), Vallisneria aethiopica (no
common name), Lagarosiphon ilicifolius (oxygen weed)
(Bethune, 1991).


Other characteristic species: Myriophyllum seratum (Bethune, pers. comm.)

Flow-related location:
Inner edge or centre of the channel; moving water. Will always
be inundated, even at low flow. If the river divides and goes
around islands, this indicator is likely to be found in all the
channels.

Known water needs:
This community is totally dependent on permanent inundation
and would die if it dried out, even for short periods. Will be
impacted by sediment load and turbidity, which could reduce
light penetration. Thus linked to water quality and water level.




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TDA Namibia Vegetation
Vegetation Indicator 2
Name:

Lower wet bank

Description:
Community of floating macrophytes with stems forming a dense
mat and leaves and inflorescences carried well above the water.


Representative species:
Vossia cuspidata (hippo grass) (sites 4 and 5); Cyperus papyrus
(papyrus) (site 5) (pers. obs.)

Other characteristic species: Aspilia mossambicensis (river daisy) (site 5), Thelypteris
interrupta (bog fern), Ficus pygmaea (pygmy fig) (site 5; maybe
site 4) (pers. obs.), Miscanthus junceus (swamp savanna
grass/pampas grass) (Barnes, in litt., 2009; Ellery & Ellery,
1997).

Flow-related location:
Edge of main channel, beyond indicator 1, but always
inundated, even at low flow. Moving water.

Known water needs:
Needs permanent inundation. Sine it is floating it can tolerate
any high water levels.

Vegetation Indicator 3
Name:

Upper wet bank 1 (reeds)



Description:
Rooted macrophytes at wetted edge during low flow, submerged
at high flow.

Representative species:
Phragmites australis (pers. obs.)

Other characteristic species: Phragmites mauritianus (NBRI database, 2009)

Flow-related location:
At the location of the wetted edge during dry-season low flow.
Moving water.

Known water needs:
Can withstand dry periods for up to several months. Can
withstand total inundation for long periods as well. Linked to
social.

Vegetation Indicator 4
Name:

Upper wet bank 2 (trees and shrubs)

Description:
Edge of wetted bank of main channel or floodplain at high flow;
can be inundated during high flow.

Representative species:
Searsia (Rhus) quartiniana (river rhus) (sites 4 & 5); Syzygium
guineense ssp. barotsense (water pear) (site 5) (pers. obs.).

Other characteristic species: Ziziphus mucronata (buffalo thorn) (mainly site 4); Salix
mucronata ssp. mucronata (safsaf willow), Syzygium cordatum


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TDA Namibia Vegetation
(waterberry), Morella (Myrica) serrata (lance-leaved waxberry),
Phoenix reclinata (wild date palm) (Site 5) (pers. obs.)

Flow-related location:
Seasonally inundated. Edge of wetted bank at high flow.
Moving water or standing water.

Known water needs:
Tolerant of long periods of inundation; generally on edge of
river, with some roots in the wet and some on dry land; most will
probably not tolerate long period of desiccation. Important for
holding the river bank, therefore linked to geomorphology.
Vegetation Indicator 5
Name:

River dry bank
Description:
Upper river bank of river channel or river islands, influenced by
the high water table associated with the river, but seldom to
never totally inundated. Riparian species that need to be near
but not in water.

Representative species:
Diospyros mespiliformis (jackal berry) (site 5) (pers. obs.).

Other characteristic species: Combretum imberbe (lead wood), Acacia tortilis (umbrella
thorn), (site 4), Grewia flavescens, G. olukondae, G. schinzii,
magic guarri (Euclea divinorum), bloubos (Diospyros lycioides)
(sites 4 & 5); (Friesodielsia obovata), Antidesma venosum,
bloubos, Grewia flavescens, knobbly combretum (Combretum
mossambicense), Markhamia obtusifolia, potato bush
(Phyllanthus reticulata), sausage tree (Kigelia africana); Garcinia
livingstonei (African mangosteen), (site 5) (pers. obs.).

Flow-related location:
Above all but the highest flows; taps water table, which is
recharged and thus influenced by river flows.

Known water needs:
Can withstand short periods of inundation in very wet years but
cannot withstand long periods of inundation. Would only be
influenced by reduced flow if these have an effect on the water
table. Representative species dependent on high water table.
Some of the associated species are terrestrial species that do
not need the high water table. These are also important for
stabilising the river banks, and are therefore linked to
geomorphology.

Vegetation Indicator 6
Name:

River floodplain residual pools


Description:
Pools on floodplain at site 4 that are deep enough to retain
water permanently.

Representative species:
Nymphaea nouchalii var. caerulea, N. lotus (pers. obs.)



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TDA Namibia Vegetation
Other characteristic species: Nymphoides indica ssp. occidentalis; Aeschynomene fluitans;
Utricularia cf. benjaminiana (pers. obs.)

Flow-related location:
Standing water, recharged seasonally by flood waters.
Connected to river during high flow but retain water during
normal low flow.

Known water needs:
Cannot withstand desiccation. Plants will die if they dry out. Can
withstand higher inundation, provided inundation does not occur
too quickly. These plants are rooted, with leaves on the surface
and flowers protruding above the water.

Vegetation Indicator 7
Name:

(River) lower floodplain

Description:
The deeper sections of channels between scroll bars that flood
seasonally, but probably often retain water in the dry season.

Representative species:
Vossia cuspidata (pers. obs.)

Other characteristic species: Persicaria attenuata ssp. africana; Ludwigia sp. (pers. obs.)

Flow-related location:
Inundated at high water for longer periods

Known water needs:
Can withstand some desiccation and long periods of inundation

Vegetation Indicator 8
Name:
(River)
middle
floodplain
Description:
The shallower sections of floodplain channels, on the lower
edges of the floodplain islands, on clay or sand. This area can
be quite extensive in places and supports the floodplain grasses
that are important for grazing and maybe thatching grass.

Representative species:
Grasses Setaria sphacelata var. sericea (specimen BC2009/2)
and Panicum coloratum var. coloratum (specimen BC2009/4)
(field collection, January 2009 ­ see chapter 5)

Other characteristic species: young Phragmites sp; Ficus pygmaea; Tacazzea apiculata;
other grasses e.g. Vetiveria, Eragrostis, Sporobolus (pers. obs.)

Flow-related location:
Seasonally flooded for shorter periods than indicator 7, but
longer than indicator 9.

Known water needs:
Needs periodic flooding, can withstand periods of total
inundation or desiccation. Grazing for cattle in dry season ­
linked to social.

Vegetation Indicator 9


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TDA Namibia Vegetation
Name:

(River) upper floodplain (islands)


Description: The
highest
points
of
the scroll bars on the floodplain, often
forming islands. Only inundated during high flow.

Representative species:
River rhus (Searsia quartiniana); Chobe candle-pod acacia
(Acacia hebeclada ssp. chobiensis).

Other characteristic species: Shrubby umbrella thorns (Acacia tortilis) and Combretum
imberbe. Occasional large Acacia sieberiana (pers. obs.).
Grasses.

Flow-related location:
only inundated at high flow

Known water needs:
Can withstand standing in water from long period, and limited
periods of desiccation. Linked to water level and social.

Vegetation Indicator 10
Name:
Floodplain
Dry
Bank

Description:
Upper bank of river floodplain adjacent to the floodplain,
influenced by the high water table associated with the river, but
seldom to never totally innundated. Tree and shrub species with
a wide tolerance to desiccation and occasional inundation.

Representative species:
Combretum imberbe (lead wood), Acacia tortilis (umbrella
thorn).

Other characteristic species: Albizia versicolor (large-leafed albizia); Grewia flavescens, G.
olukondae, G. schinzii, magic guarri (Euclea divinorum), bloubos
(Diospyros lycioides) (sites 4) (pers. obs.).

Flow-related location:
Above all but the highest flows; taps water table, which is
influenced and recharged by floods.

Known water needs:
Essentially terrestrial species that cannot withstand long periods
of inundation. Would only be influenced by reduced flow if these
have an effect on the water table. Acacia tortilis better able to
withstand drop in water table than Combretum imberbe. These
are also important for stabilising the river banks, and are
therefore linked to geomorphology.

3.2 Flow categories ­ river sites
One of the main assumptions underlying the EF process to be used in the TDA is that it is
possible to identify parts of the flow regime that are ecologically relevant in different ways and
to describe their nature using the historical hydrological record. Thus, one of the first steps in
the EFA process, for any river, is to consult with local river ecologists to identify these


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TDA Namibia Vegetation
ecologically most important flow categories. This process was followed at the Preparation
Workshop in September 2008 and four flow categories were agreed on for the Okavango
Basin river sites:
Dry
season
Transitional
Season
1
Flood
Season
Transitional
Season
2

Tentative seasonal divisions for river Sites 1-5 are shown in Figures 3.1 to 3.5. These
seasonal divisions will be formalised by the project hydrological team in the form of
hydrological rules in the hydrological model. In the interim they provide useful insights into
the flow regime of the river system suggesting, along with the hydrographs, a higher within-
year flow variability of the Cuebe River and a higher year-on-year variability of the Cubango
River.

It is planned to use similar flow seasons for the remaining river sites: 6 and 8.

120
Wet
100
Trans
n 1
Trans 2
Dry
80
Year 2
r
60
Year 1
r
Year 3
r
40
20
0
O
N
D
J
D
F
M
A
M
J
J
M
J
A
S

Figure 3. 1: Three representative years for Site 1: Cuebe River @ Capico, illustrating the
approximate division of the flow regime into four flow seasons



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TDA Namibia Vegetation
1200
Wet
1000
Trans 1
Trans 2
Dry
800
Year
Y
1
600
Year
Y
2
Year
Y
3
400
200
0
O
N
D
J
D
F
M
A
M
J
J
M
J
A
S

Figure 3. 2: Three representative years for Site 2: Cubango River @ Mucindi, illustrating the
approximate division of the flow regime into four flow seasons


250
Wet
Dry
200
Trans 1
Trans 2
150
Year 1
ear
Year 2
ear
100
Year 3
ear
50
0
O
N
D
J
F
M
A
M
J
J
M
J
A
S

Figure 3. 3: Three representative years for Site 3 Cuito River @ Cuito Cuanavale, illustrating the
approximate division of the flow regime into four flow seasons




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TDA Namibia Vegetation
1000
900
Wet
We
800
Dry
Dr
Tra
Tr n
a s
n 1
s
Tra
Tr n
a s
n 2
s
Dry
Dr
700
600
Year 1
500
Year 2
400
Year 3
300
200
100
0
O
N
D
J
F
M
A
M
J
J
M
J
A
S

Figure 3. 4: Three representative years for Site 4: Okavango River @ Kapoka (hydrological data
from Rundu), illustrating the approximate division of the flow regime into four flow
seasons


1800
1600
Wet
1400
Dry
Trans 1
Tr
T ans 2
Dry
1200
1000
Year 3
1000
Year 2
800
Year 1
600
400
200
0
O
N
D
J
F
M
A
M
J
J
M
J
A
S

Figure 3. 5: Three representative years for Site 5: Okavango River @ Popa (hydrological data
from Mukwe), illustrating the approximate division of the flow regime into four flow
seasons

The literature review (Chapter 4) and data collection and analysis exercises (Chapter 5) are
focused on addressing what was initially expected to be nine main questions related to these
flow seasons (Table 3.2). In the end, owing to time constraints, transition 1 with its two
questions was omitted at the workshop, and transition 2 was also omitted from the final
scenarios.





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TDA Namibia Vegetation
Question
Season
Response of indicator if:
number
1
Onset is earlier or later than natural median/average
2
Dry Season
Water levels are higher or lower than natural median/average
3
Extends longer than natural median/average
Duration is longer or shorter than natural median/average - i.e. hydrograph is
4
Transition 1
steeper or shallower
5
Flows are more or less variable than natural median/average l
Onset is earlier or later than natural median/average ­ synchronisation with rain
6
Flood season
may be changed
7
Natural median/average proportion of different types of flood year changed
8
Onset is earlier or later than natural median/average
Transition 2
Duration is longer or shorter than natural median/average ­ i.e. hydrograph is
9
steeper or shallower
Table 3. 2: Questions to be addressed at the Knowledge Capture Workshop, per indicator per
site. In all cases, `natural' embraces the full range of natural variability

3.3 Inundation categories ­ delta sites
Although these categories were not relevant to the Namibian sites, this section has been
included for completeness. The recognised river flow categories are not relevant in the Delta,
where inundation is the major driver of ecosystem form and functioning. The main inundation
categories recognised by the inundation model developed by the Harry Oppenheimer
Okavango Research Centre (HOORC) are used here (Table 3.3).



Inundation
Inundation category name
category number
Delta 1
Channel in permanent swamp
Delta 2
Lagoons in permanent swamp
Delta 3
Backswamp in permanent swamp
Delta 4
Seasonal pools in seasonally flooded zones
Delta 5
Seasonal sedgelands in seasonally flooded zones
Delta 6
Seasonal grasslands
Table 3. 3: Inundation categories for the Okavango Delta as recognised by the HOORC
inundation model



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4 LITERATURE
REVIEW
4.1 Introduction
As far as I am aware, no detailed studies have been undertaken on the vegetation of the
Okavango River in Namibia. Mostly the vegetation is described in very broad terms. Correira
& Bredenkamp (1987) listed the dominant grasses for swamps and river banks together
(Table 4.1). Ellery (1997) identified eight communities on the floodplains and river banks. He
did not go into any detail regarding the nature of the communities, nor the species found in
them. Hines (2001) described broad plant communities on the floodplains east of Rundu.
The National Botanical Research Institute (NBRI 2009) provided a list of species collected
from the Okavango River as recorded on their specimen database, but these were only
assigned to very broad habitats.

Grass species
Occurrence and life cycle
Vetiveria nigritana
Dense, perennial
Trachypogon spicatus
Dense, perennial
Phragmites mauritianus
Dense, perennial
Setaria sphacelata
Dense, perennial
Hypertelia dissolute
Dense, perennial
Andropogon gayanus
Dense, perennial
Schyzachyrium sanguineum
Dense, perennial
Eragrostis pallens
Dense, perennial
Eragrostis rotifer
Dense, perennial
Themeda triandra
Dense, perennial
Table 4. 1: . Floodplain and river bank grasses as listed by Correira & Bredenkamp (1987)
The indicators described in chapter 3 and presented in Table 3.1 are based on observations
made during the field visit in January 2009 (chapter 5). Field guides and checklists were
used to obtain information on the ecology of the species recorded during this field visit. Part
of the discussion of the indicators in this section therefore also refers to observations made in
January since there is nothing in the literature to describe some of these habitats.

Time did not permit an extensive search of the literature or the internet.


4.2
Indicator No 1: Channel macrophytes (submerged)
Main characteristics of Indicator 1

This indicator is in the permanently flowing water of the main river. Bethune (1991) listed
Potamogeton spp. (pondweed), Vallisneria aethiopica (no common name) and Lagarosiphon
ilicifolius (oxygen weed) as the characteristic species for this habitat. All members are either
totally submerged, or the main body of the plant is submerged, with only the reproductive


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TDA Namibia Vegetation
structures extending above the surface of the water. The plants may be rooted or floating.
They are important because of their need for permanent, flowing, clear water. Poor water
quality or low light penetration due to a high silt load are likely to affect it.

Species notes
Potamogeton octandrus
rooted in main riverbed or in shallow margins (1)
Potamogeton schweinfurthii running water and floodplain pools (1)
Vallisneria aethiopica
main channel of perennial rivers (1); backswamps of delta (2)
Lagarosiphon ilicifolius
rivers, backswamps (1); still or slow-flowing water (2)
Table 4. 2: Plant species recorded by Bethune (1991) in permanently flowing water.
Life cycle attributes of Indicator 1

Potamogeton spp flower in summer; flowers emergent or floating (Ellery & Ellery, 1997). In
both Vallisneria aethiopica and Lagarosiphon ilicifolius, female flowers float on the water
surface, attached to the plant while male flowers are released and free floating (Clarke &
Klaassen, 200). Flowers in summer (Ellery & Ellery, 1997).
Links to flow
Entirely dependent on water for whole life cycle. Speed of current may affect these plants, as
they may not be able to withstand currents that are too swift. Slower flow would probably not
affect them as they all occur in slow flowing water as well as the swifter main channel. Would
be expected to expand and contract in response to areas of permanent flooding. Changes in
sediment flux as would be experienced by dam and weir construction could impact this
indicator (Ellery, pers. com.).

4.3
Indicator No 2: Lower wet bank ­ papyrus and hippo grass
Main characteristics of Indicator 2
Vossia cuspidata is a "robust, perennial grass with spongy, floating, creeping stems,
associated with deep, permanent water; common along the edges of primary channels.
Usually dominant and may form floating rafts" (Ellery & Ellery 1997). It is rooted in the
channel bed, but the extremely long, floating stems can trail out into the current. It generally
occurs on the inner (convex) side of the channel where sediment flux is low (Ellery, pers.
com.). Cyperus papyrus is a "very robust perennial sedge with stout creeping stems and
erect stems in permanent swamps, especially fringing the major rivers where nutrient status
of the water is higher than elsewhere. Can form floating rafts. Is very unpalatable and has a
low forage quality, therefore supports few herbivores. Sitatunga feed on young shoots"
(Ellery & Ellery 1997). It is rooted in the peat bank and grows into the channel from the peat
bank on the edges of the channel (Ellery, pers. cm.). This indicator differs from indicator 1 by
being on the edges of the main channel. It forms a covering blanket over the water that
keeps out sunlight and therefore submerged plant life. It provides a refuge for animals such
as fish.
Life cycle attributes of Indicator 2
Vossia cuspidata flowers early spring to autumn; Cyperus papyrus in summer (Ellery & Ellery,
1997). Both are perennial.
Links to flow


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TDA Namibia Vegetation
The plants can rise and fall with the water level since the majority of the plant is floating.
Vossia cuspidata is able to withstand wide ranges in water level due to its very long stems, as
well as a certain amount of desiccation. Cyperus papyrus is less tolerant of wide water level
fluctuations. It cannot withstand as much deep inundation as Vossia can and cannot
withstand desiccation as its roots require permanent, flowing water. Papyrus typically occurs
where there is permanent water with a fairly small seasonal variation (Ellery, pers. com.). It
only occurs at site 5 along the Namibian and Angolan sections of the river due to the deep
water immediately upstream of Popa Rapids, which act as a natural spillway, ensuring a
reduction in the normally high seasonal variations in water level (Ellery, pers. comm.). Hippo
grass will therefore be more adaptable to changes in water level than will papyrus. As long
as the water continues to flow, hippo grass should be alright at any water level, whereas
papyrus may decline with declining water levels or marked changes to the flood regime.

4.4
Indicator No 3: Upper wet bank 1 - reeds
Main characteristics of Indicator 3
Phragmites australis can grown in damp ground, or standing water up to a metre deep or
even as a floating mat (Wikipedia 2009). It can grow tall on the edges of the main channel of
the river as it has the best access to nutrients that are brought down with the river water
(Mendelsohn & El Obeid, 2004). It can withstand long dry periods in ephemeral rivers, but
generally where there is groundwater close to the surface (pers. obs.). It reproduces
vegetatively by means of stolons (underground horizontal stems) and rapidly colonises new
areas, extending into areas that are further away from water and often becoming the
dominant plants. It can occur where sedimentation is active, and will rapidly colonise recently
formed depositional features (Ellery, pers. com.).
Life cycle attributes of Indicator 3
It flowers from late summer to early winter (Ellery & Ellery, 1997).
Links to flow
It is very adaptable to variations in water level, being able to withstand long periods of
desiccation as well as permanent flooding. It does not need flowing water but it does best
where there is at least some soil moisture. With a lowering of the volume and duration of
flooding it is likely to expand into areas occupied by the indicators on either side of it.

4.5
Indicator No 4: Upper wet bank 2 ­ trees and shrubs
Main characteristics of Indicator 4
This indicator possibly corresponds with Ellery's (1997) community number 5 ­ transitional
between floodplain and terrestrial environment, dominated by the grass Cynodon dactylon
(couch grass).
At site 4 (Kapako), where there is a much greater seasonal fluctuation in water levels than at
site 5 (Popa) the representative species of this indicator reflect the variable nature of the
indicator. Searsia (Rhus) quartiniana is a dense shrub or tree with a wide range of ecological
tolerances within the context of perennial rivers (Ellery, pers. com.). It is found along the
banks and floodplains of perennial rivers, on islands in permanent swamps, as well as
occasionally in ephemeral watercourses (Curtis & Mannheimer, 2005, Ellery, pers. com.).
Ziziphus mucronata is found in a variety of different habitats; very often close to water, but it
can also be found far from water. At Popa, the species associated with this indicator are also


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TDA Namibia Vegetation
always associated with permanent water, and reflect the fact that the water levels are much
higher for longer than at site 4.
Life cycle attributes of Indicator 4
Searsia (Rhus) quartiniana flowers from October to June (Curtis & Mannheimer, 2005).
Ziziphus mucronata flowers from October to April, while Phoenix reclinata flowers from
August to December (Coates Palgrave, 2002; Curtis & Mannheimer, 2005). The other
species flower from late winter to early summer (Curtis & Mannheimer, 2005; Ellery & Ellery,
1997).
Links to flow
Searsia (Rhus) quartiniana occurs where there is permanent water (Ellery & Ellery, 1997), but
can withstand some drying out, as long as its roots have access to ground water. The other
species associated with this indicator at site 4 are very tolerant of desiccation. A
prolongation of the flood season may affect the roots of many of these species due to water-
logging of the soil. The associated species at site 5 can withstand longer periods of
inundation, but are not tolerant of desiccation.

4.6
Indicator No 5: River dry bank
Main characteristics of Indicator 5
Large trees and a dense shrub layer are important for stabilising the river bank. They grow
near water but generally not in the water. This corresponds with Ellery's (1997) community
number 6 ­ broadleaved riparian woodland dominated by broadleaved evergreen trees, with
a low cover of the grass Cynodon dactylon (couch grass).

Life cycle attributes of Indicator 5
Garcinia livingstonei and Albizia versicolor flower in spring and early summer, while
Diospyros mespiliformis flowers from August to January (Curtis & Mannheimer, 2005).
Combretum imberbe and Acacia tortilis flower in summer (Ellery & Ellery, 1997). Flowering is
probably more related to daylength, temperature and rainfall than to river flow.
Links to flow
These trees and shrubs do not get water directly from the river, but from groundwater
seepage from the river. Combretum imberbe and Acacia tortilis are not water dependent and
are found in many habitats away from water, although the former is most often associated
with rivers. Albizia versicolor, Garcinia livingstonei and Diospyros mespiliformis are never
found far away from permanent water (Curtis & Mannheimer, 2005). The latter three species
can presumably tolerate standing in water for longer periods than the former two, but none is
adapted to long periods of inundation.

4.7
Indicator No 6: River floodplain residual pools
Main characteristics of Indicator 6
This correlates with Ellery's (1997) aquatic community dominated by Nymphaea nouchali var.
caerulea. The plants of this community are all dependent on standing or slow-flowing,
permanent water, which is linked to and recharged by the main river.
Life cycle attributes of Indicator 6


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TDA Namibia Vegetation
Nymphaea lotus flowers in summer, while N. nouchali flowers throughout the year, but most
commonly in summer (Ellery & Ellery, 1997).
Links to flow
This community would die if the pools dry out. They would be tolerant of increased water
levels or periods of inundation. Nymphaea spp have the ability to adapt rapidly to changing
water levels as the leaf stalks grow continuously and quickly (Ellery & Ellery, 1997).

4.8
Indicator 7: River lower floodplain
Main characteristics of Indicator 7
These are the deeper parts of the channels on the floodplains that receive water from the
river at high flow, and presumably retain water for long periods, based on the water-loving
species that are found in them. They link up with the residual pools. They seem to have a
mixture of species that prefer permanent water (Vossia cuspidata) and species that are found
along the waters edge and can also grow on dry land but close to water (Persicaria, Ludwigia
and some P. australis). These species are tolerant of total inundation for long periods and
desiccation for varying periods. Their leaves float on the surface of the water, while the
flowers are held above the water. This could correspond with Ellery's (1997) lower floodplain
community (see indicator 8 below).
Miscanthus junceus (swamp savanna grass/pampas grass) is an important floodplain
thatching grass in Namibia (Barnes, in litt. 2009), and would probably also occur in this
indicator. According to Ellery & Ellery (1997) it is usually found in permanent water, often in
channel fringes. It is an unpalatable climax species. It grows in coarse, sandy soil, and
plays an important part in purifying water and stabilising river banks (van Oudtshoorn, 2006).

Life cycle attributes of Indicator 7
Vossia cuspidata flowers early spring to autumn. Persicaria spp flower in summer, while
Ludwigia spp. flower most of the year (Ellery & Ellery, 1997). Miscanthus junceus flowers
from November to June (van Oudtshoorn, 2006).
Links to flow
Vossia cuspidata and Miscanthus junceus prefer permanent water, while the two
dicotyledonous plants can probably withstand a short periods of desiccation. None would be
able to withstand long totally dry periods.

4.9
Indicator No 8: River middle floodplain
Main characteristics of Indicator 8.
This possibly corresponds with Ellery's (1997) lower floodplain community dominated by
Brachiaria sp., Echinochloa pyramidalis and Phragmites australis. Brachiaria humidicola
(creeping signal grass) (Klaassen & Craven, 2003) was collected in this habitat during the
January fieldtrip (Appedix B). It is a palatable climax grass that is mostly found in damp
places along floodplain margins in Botswana (Ellery & Ellery, 1997). Echinochloa pyramidalis
(antelope grass) is a palatable climax grass that occurs typically in swamps, standing in water
or floating (Ellery & Ellery, 1997; Klaassen & Craven, 2003).
Setaria sphacelata var. sericea and Panicum coloratum var. coloratum were the two species
found to be the most abundant during the fieldtrip described below (see chapter 5).
According to Ellery & Ellery (1997), the former occurs in a wide range of habitats, but prefers
seasonally wet areas with heavy textured soils. It is a climax grass that is moderately


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palatable but unable to withstand continuous grazing. In Namibia, it occurs mainly along the
perennial rivers in the north-east, but is also found in vleis and marshes, and occasionally in
other habitats (Klaassen & Craven, 2003) and has been described as `dense' (Correira &
Bredenkamp, 1987 - see table 4.9 below) and `common' (NBRI 2009) along the Okavango.
Panicum coloratum var. coloratum is a very palatable climax grass that is extremely valuable
graze for large herbivores (Müller, 2007). It thrives on heavy clay soils as well as damp sandy
soils, and is widespread in Namibia.

In Angola Vetiveria nigritana is one of the dominant grasses in this indicator (King, in litt.
2009). This is also a common grass in the upper panhandle (Ellery & Ellery, 1997). It
normally occurs in seasonally flooded or wet areas on heavy clay, but in the Okavango it is
found on organic-rich sand. It is an unpalatable climax grass (Ellery & Ellery, 1997), which is
used as thatching grass in Namibia (Klaassen & Craven 2003). It was not listed in the NBRI
species list for the river (NBRI 2009).
Life cycle attributes of Indicator 8.
Setaria sphacelata var. sericea and Panicum coloratum var. coloratum are both perennial
grasses. Both flower from summer to autumn (Ellery & Ellery, 1997; van Oudtshoorn, 2006).
Links to flow
Both the dominant species are able to grow in areas away from water, but thrive in seasonally
wet areas. An increase in the length of inundation may be detrimental, but they would
probably survive longer dry periods.

4.10
Indicator No 9: River upper floodplain (islands)
Main characteristics of Indicator 9
This probably corresponds with Ellery's (1997) two upper floodplain communities although
those two may correspond with indicator 8. Ellery lists three species of Eragrostis, only one
of which (E. porosa) has been recorded once along the Okavango (Klaassen & Craven 2003;
Müller, 2007). Eragrostis rotifer was collected in January (Appendix B). This is a widespread
species that is sometimes found in damp places (Müller, 2007).
This indicator is somewhat higher than indicator 8, with trees and shrubs that are absent from
indicator 8. However, the distinction between the two in terms of grass species present is not
clear cut. Some of the woody species that occur here are the same as those found in
indicator 4, namely Searsia quartiniana, which can withstand being submerged for part of the
season. The really water-dependent species
Life cycle attributes of Indicator 9
Searsia (Rhus) quartiniana flowers from October to June; Acacia hebeclada in August and
Acacia sieberiana mainly in Octobe (Curtis & Mannheimer, 2005). Most of the grasses
collected are perennials that flower late summer and autumn (Ellery & Ellery, 1997; van
Oudtshoorn, 2006).
Links to flow
This indicator will be inundated for short periods during high floods, but will also be exposed
during the dry season. It will be better able to tolerant longer dry periods than longer wet
periods.



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4.11
Indicator No 10: Floodplain dry bank
Main characteristics of Indicator 10
This indicator is similar in composition to indicator 5, but has none of the species that are
strongly dependent on a high ground water table, and more terrestrial species that can
survive being far from water but do not mind standing in water for short periods.
Life cycle attributes of Indicator 10
Combretum imberbe and Acacia tortilis flower in summer (Ellery & Ellery, 1997). Flowering is
probably more related to day length, temperature and rainfall than to river flow.
Links to flow
These trees and shrubs do not get water directly from the river, but from groundwater
seepage from the floodplain. Combretum imberbe and Acacia tortilis are not water
dependent and are found in many habitats away from water, although the former is most
often associated with rivers. Albizia versicolor is generally found near water or in areas with a
high water table (Curtis & Mannheimer, 2005). None of these species is adapted to long
periods of inundation.

4.12 Summary
A far more detailed survey needs to be undertaken during each of the four flow seasons in
order to be able to really define the indicators and see which species are associated with
each. The boundaries between indicators are fuzzy, with the same species occurring in a few
indicators in greater or lesser abundances.
The plants along the river are all probably fairly adaptable. Communities are very fluid and
will shift with changes in the flow regime, unless these changes are very drastic.
The major gaps are:
1) the boundaries of the indicators or the component species of the indicators.
2) how these plants will respond to changes in water level and duration of inundation /
exposure
3) the extent of flooding of the river and floodplains under various flow regimes
4) the relationship between ground water and surface flow


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5 DATA
COLLECTION AND ANALYSIS
5.1
Methods for data collection and analysis
Vegetation was samples at sites 4 and 5 from 5 - 9 January 2009. As this was before the
main team sampling took place in February, the sites used for vegetation are not the same as
those used by the other specialists. The water was much higher than it normally is at this time
of the year, and could be regarded as high flood, but not yet maximum flood for the season.
It was not possible to get to the main river at site 4, but the floodplain communities were
sampled in an area close to the south bank (Sampling site 1 in Map of Kapako). It was
assumed that these were representative of the whole floodplain. At site 5 I was able to get
onto one of the islands and look at the eastern side of the island. Due to the impenetrable
nature of the vegetation on the centre of the island, it was not possible to cross the island and
look at the other side, but it is assumed that the vegetation structure would be similar.

Plant specimens were collected of all the dominant grasses, for identification. Notes were
made on the presence of woody species. The dominant species were recorded by observing
how often they were seen and the extent of their occurrence. No quantitative data were
collected.

5.2 Results
The communities described in chapter 3 are mainly based on observations made during this
field trip and will not be repeated here.

Setaria sphacelata var. sericea and Panicum coloratum var. coloratum were the two species
found to be the most abundant on the shallower margins of the floodplain pools (indicator 8
habit). Other species collected are given in Appendix B.

5.3
A summary of present understanding of the predicted responses
of all vegetation indicators to potential changes in the flow regime
The tables that follow summarise the predicted responses for each vegetation indicator to
changes in the flow regime.


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5.3.1 Indicator 1 ­ (Submerged) Channel Macrophytes
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
medium
natural
There will be no significant changes. With an increase in water volume, there could be an increase in
cover. With a slight decrease in volume, there could be an increase in light penetration and
Water levels are higher or lower
nutrients, leading to more growth and thus more cover. With a larger decrease in volume, there will
2
Dry Season
medium
than natural
be less water area for the plants to cover, therefore a decrease in cover. With a stop in flow, only
remnant pools will be left in which the plants can survive, thus there will be an overall decrease in
the area available to them and thus in cover.
An extended dry season means reduced or no flood, therefore less input of nutrients, which could
3
Extends longer than natural
medium
affect the growth of these plants resulting in decreased cover.
Onset is earlier or later than
Seed germination and seedling growth may be affected if the start of the flood season is extended
6
natural ­ synchronisation with
into the winter, or comes too early in the summer before seeds have been produced.
medium
rain may be changed
Even with no flood onto the floodplain, there will still be water in the main channel, which will move
Flood season
further into or out of the channel, depending on the depth, thus no change in cover. In a big flood,
Natural proportion of different
7
the rate of increase of the water could be too rapid for the plants to be able to respond. This will
low
types of flood year changed
result in too little light which will adversely affect them. There will also be a dislodging of the plants
with a faster current. This will result in a decrease in cover.
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
If the flood drops too quickly the plants will collapse as they are supported by the water, thus a
9
natural ­ i.e. hydrograph is
steeper hydrograph will result in reduced plant cover.
medium
steeper or shallower
Table 5. 1: Predicted response to possible changes in the flow regime of (Submerged) Channel Macrophytes in the Okavango River ecosystem


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TDA Namibia Vegetation
5.3.2 Indicator 2 - Lower wet bank (papyrus and hippo grass)
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
medium
natural
Water levels are higher or lower
No effect on Vossia at site 4. Could affect papyrus at site 5 if dry season flows are low.
2
medium
Dry Season
than natural
An extremely long dry period would exacerbate the effects of desiccation and stress the plant
3
Extends longer than natural
further, resulting in a decrease in cover with increase in dry season length. Vossia will be ok,
medium
papyrus will be affected.
Onset is earlier or later than
nil
6
natural ­ synchronisation with
medium
Flood season
rain may be changed
Natural proportion of different
nil
7
medium
types of flood year changed
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 2: Predicted response to possible changes in the flow regime of Lower wet bank in the Okavango River ecosystem




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TDA Namibia Vegetation
5.3.3 Indicator 3 ­ Upper wet bank 1 (reeds)
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
high
natural
Water levels are higher or lower
A stop in flow could result in the reeds being out of water for the dry season, which will stress them a
2
high
Dry Season
than natural
bit and could lead to a slight decrease in cover.
The longer it is dry, the more the plants will be stressed, thus an extension of the dry season could
3
Extends longer than natural
result in a decrease in cover. A decrease in length of dry season could result in an increase in
high
cover.
Duration is longer or shorter than
nil
4
natural - i.e. hydrograph is
high
Transition 1
steeper or shallower
Flows are more or less variable
nil
5
high
than natural
Onset is earlier or later than
nil
6
natural ­ synchronisation with
high
rain may be changed
Flood season
No flood at all will lead to the reduction in extent of this Indicator unless the water table is very close
Natural proportion of different
7
to surface (<0.5m). It doesn't matter how high the flood is, the ground remains as saturated.
high
types of flood year changed
Extended duration of flood could result in a slight increase in cover.
Onset is earlier or later than
nil
8
high
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
high
steeper or shallower
Table 5. 3: Predicted response to possible changes in the flow regime of Upper wet bank 1 in the Okavango River ecosystem


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TDA Namibia Vegetation
5.3.4 Indicator 4 ­ Upper wet bank 2 (trees and shrubs)
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
medium
natural
Water levels are higher or lower
These plants need to have a certain amount of water in the dry season. They cannot withstand a
2
Dry Season
low
than natural
long period of desiccation. No flow in the dry season could lead to a decrease in cover.
If the dry season lasts a year, this will affect the water level and these water-loving trees may be
3
Extends longer than natural
medium
stressed, with a resultant decrease in cover.
Duration is longer or shorter than
nil
4
natural - i.e. hydrograph is
medium
Transition 1
steeper or shallower
Flows are more or less variable
nil
5
low
than natural
Onset is earlier or later than
nil
6
natural ­ synchronisation with
medium
Flood season
rain may be changed
Natural proportion of different
Very little. Too long a flood will cause plants to stand in water for too long, which will have a negative
7
medium
types of flood year changed
impact.
Onset is earlier or later than
nil
8
low
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 4: Predicted response to possible changes in the flow regime of Upper wet bank 2 in the Okavango River ecosystem


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TDA Namibia Vegetation
5.3.5 Indicator 5 ­ River Dry Bank
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
medium
natural
Water levels are higher or lower
Possibly a very slight negative impact if there is no flow in the dry season ­ could affect the water
2
Dry Season
medium
than natural
table.
If dry season carries on for too long, i.e. if there is a reduced flood, this would affect the ground
3
Extends longer than natural
medium
water recharge, which would have a negative impact.
Duration is longer or shorter than
nil
4
natural - i.e. hydrograph is
medium
Transition 1
steeper or shallower
Flows are more or less variable

5
medium
than natural
Onset is earlier or later than
nil
6
natural ­ synchronisation with
medium
rain may be changed
Flood season
An exceptionally high flood could cause the dry bank species to be inundated for period that could
Natural proportion of different
7
be detrimental to them. A long duration flood will cause water-logging of the soil, which will have a
medium
types of flood year changed
negative impact on these trees
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 5: Predicted response to possible changes in the flow regime of River Dry Bank in the Okavango River ecosystem


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TDA Namibia Vegetation
5.3.6 5.3.6 Indicator 6 - River floodplain residual pools
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
little
1
medium
natural
Water levels are higher or lower
nil
2
high
Dry Season
than natural
A long dry season will result in increased evaporation, which will affect the pools, leading to a
3
Extends longer than natural
decrease in cover. A short dry season will be good for the plants in the pools, leading to an increase high
in cover.
Onset is earlier or later than
nil
6
natural ­ synchronisation with
medium
rain may be changed
Flood season
The bigger the flood, the better for the pools, therefore a positive impact. No flood will result in the
Natural proportion of different
7
pools not being replenished and therefore reducing in size or drying up, thus a negative impact. The medium
types of flood year changed
longer the flood season, the better for the pools. The shorter, the more likely the pools are to dry up.
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 6: Predicted response to possible changes in the flow regime of River floodplain residual pools in the Okavango River ecosystem


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5.3.7 Indicator 7 - River lower floodplain
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
medium
natural
Water levels are higher or lower
nil
2
Dry Season
medium
than natural
The longer the dry season, the more these plants will decrease. A short dry season will result in an
3
Extends longer than natural
medium
increase.
Onset is earlier or later than
nil
6
natural ­ synchronisation with
medium
Flood season
rain may be changed
Natural proportion of different
A higher flood will extend the area in which these plants can grow and thus have a positive impact,
7
medium
types of flood year changed
and vice versa. The longer the flood, the better for these plants, and vice versa.
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 7: Predicted response to possible changes in the flow regime of River lower floodplain in the Okavango River ecosystem


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5.3.8 Indicator 8 - Rivermiddle floodplain (grasses)
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
little effect as dominant plants are also terrestrial
1
medium
natural
Water levels are higher or lower
little
2
medium
Dry Season
than natural
When dry season is short, lower floodplain grasses will increase at the expense of these grasses
3
Extends longer than natural
(encroachment). And these grasses will be waterlogged for longer. With longer dry period, these
medium
grasses can move into the lower floodplains.
Onset is earlier or later than
nil
6
natural ­ synchronisation with
low
Flood season
rain may be changed
Natural proportion of different
Middle grasses can move into areas now occupied by lower floodplain grasses at low volume and
7
low
types of flood year changed
vice versa in big flood.
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 8: Predicted response to possible changes in the flow regime of River middle floodplain in the Okavango River ecosystem


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TDA Namibia Vegetation
5.3.9 Indicator 9 ­ River upper floodplain (islands)
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
medium
natural
Water levels are higher or lower
little
2
medium
Dry Season
than natural
If the dry season is too short, the soil may not dry out sufficiently for the roots of these trees and
3
Extends longer than natural
shrubs, thus there will be a slight negative effect. However, if the dry season lasts a year or more,
medium
the ground will become too dry for these species, and there will also be a negative effect.
Onset is earlier or later than
nil
6
natural ­ synchronisation with
low
rain may be changed
Flood season
Too much water will waterlog these species. Too little water can be detrimental. Thus both
Natural proportion of different
extremes would have a negative impact. If the flood doesn't reach the floodplain, this will result in the
7
low
types of flood year changed
plants becoming a bit stressed due to dry roots. At the other extreme, if the flood lasts too long, the
roots could become waterlogged.
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 9: Predicted response to possible changes in the flow regime of River upper floodplain in the Okavango River ecosystem


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5.3.10 Indicator 6 ­ Floodplain Dry Bank
Confidence in
Question
Season
Possible flow change
Predicted response of indicator
prediction (very low,
number
low, medium, high)
Onset is earlier or later than
nil
1
medium
natural
Dry Season
Water levels are higher or lower
nil
2
medium
than natural
3
Extends longer than natural
nil
medium
Onset is earlier or later than
nil
6
natural ­ synchronisation with
medium
rain may be changed
This indicator is dependent on ground water. Big floods would spill further onto the floodplain and
Flood season
there would be more recharge of the ground water, which could result in a positive impact. Small
Natural proportion of different
7
floods that do not get onto the floodplain will not recharge the aquifer, which could result in a
medium
types of flood year changed
negative impact. The longer the water stays on the floodplain, the greater the recharge of the
aquifer.
Onset is earlier or later than
nil
8
medium
natural
Transition 2
Duration is longer or shorter than
nil
9
natural ­ i.e. hydrograph is
medium
steeper or shallower
Table 5. 10: Predicted response to possible changes in the flow regime of Floodplain Dry Bank in the Okavango River ecosystem


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5.4 Conclusion
The combination of extent and duration of inundation, volume and speed of flood, timing
of flooding, changes in sediment erosion and deposition, as well as changes in water
chemistry all act together to affect the response of the indicators to change. Another very
important aspect that should not be overlooked is the cumulative effect of changes over a
period of time. While plants may be able to withstand changes for a year or two,
prolonged unnatural flow regimes will push the plants beyond their tolerance limits. The
whole situation is also compounded by the impact of human and human-induced
activities on the plants.

Much more time needs to be spent in the field in the dry and wet seasons in order to
determine which species are included in each indicator, and to delineate the indicators, as
well as to monitor their response to normal seasonal and non-seasonal changes in flow.

Nevertheless, based on what we currently know of the response of plants to a variable
flow regime, we can make informed predictions as to how these indicators will react to
unnatural changes in flow regime.





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TDA Namibia Vegetation
6. Flow-response relationships for use in the Okavango EF_DSS
Flow response curves were built at the Knowledge Capture Workshop, held in Windhoek
in March 2009. They are all available on CD. From these response curves, predictions
can be made about the response of the various indicators to possible water-related
development scenarios. This is discussed fully in a separate report.




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7. REFERENCES
Bethune, S. 1991. Kavango River Wetlands. Madoqua 17(2): 77-112.
Clarke, N.V. & Klaassen, E.S. 2001. Wetland plants of Namibia, an identification manual.
Occasional Contributions 2, National Botanical Research Institute, Windhoek, Namibia.
185 p.
Coates Palgrave, K. 2002. Trees of Southern Africa. Revised and updated by M. Coates
Palgrave. Struik Publishers, South Africa. 1212 p.

Correira, R.J. de Sousa & Bredenkamp, G.J. 1987. A reconnaissance survey of the
vegetation of the Okavango, South West Africa. SWA Scientific Society Journal 40/41:
29-45.

Curtis, B.A. & Mannheimer, C.A. 2005. Tree Atlas of Namibia. National Botanical
Research Institute, Windhoek, Namibia. 674 p.

Ellery, K. & Ellery, W. 1997. Plants of the Okavango Delta, a field guide. Tsaro Publishers,
Durban, South Africa. 224 p.

Elllery, W.N. 1997. The Okavango River floodplain ecosystem in Namibia. In: Feasibility
study on the Okavango River to Grootfontein link of the Eastern National Water Carrier
4(3) C 1-30. Water Transfer Consultants for Ministry of Agriculture, Water and Rural
Development, Department of Water Affairs, Namibia.

Hines, C.H.J. 2001. The eastern floodplain. In: Rundu floodplain development plan
investigation report. LUX-DEVELOPMENT PROJECT NAM 320 : 01 161

Klaassen, E.S. & Craven, P. 2003. Checklist of grasses in Namibia. Southern African
Botanical Diversity Network Report no.20. SABONET, Pretoria and Windhoek. 130 p.

Mendelsohn, J.M. & el Obeid, S. 2004. Okavango River: the flow of a lifeline. Struik
Publishers, Cape Town, South Africa. 176 p.

Müller, M.A.N. 2007. Grasses of Namibia. Revised and updated by J. van Eck. Ministry of
Agriculture, Water and Forestry, Windhoek, Namibia. 320 p.

Van Oudtdhoorn, F. 2006. Guide to grasses of southern Africa. Briza Publications,
Pretoria, South Africa. 288 p.

Wikipedia 2009 http://en.wikipedia.org/wiki/Phragmites




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APPENDIX A: PICTORIAL DESCRIPTIONS OF NAMIBIAN
VEGETATION INDICATORS
The pictures below show the various indicators at the two Namibian sites, numbered according to table 3.1.
In sections of the river and floodplain not all the indicators are present, and one indicator may be immediately
adjacent to another that does not follow after it numerically. On the floodplains it is very difficult to delineate
the various habitats (indicators) as they merge into each other and plant species do not stick to their
demarcated habitats.







5



2


1



Figure A1: Kapako ­ River, looking north (Angola) where the river is adjacent to the bank, showing three
indicators. Trees in indicator 5a - on left are Acacia sp., on right Combretum imberbe. (photo: Colin Christian,
February 2009)






5



3



2



1

Figure A2: Kapako ­ River, looking north, where the river is adjacent to the bank, showing four river habitats.
Habitat 4 has been removed to make fields. (photo: Colin Christian, February 2009)


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4



2

3





1


4





1


Figure A3: Kapako ­ River looking north, showing tree indicators. In places (e.g. below) indicator 4 is
immediately adjacent to indicator 1. Indicator 4 is represented by Searsia (Rhus) quartiniana here. (photos:
Colin Christian, Feb 2009).



Figure A4: Kapako ­ River looking north, showing how the river has eroded the bank, adjacent to indicator 8
on the floodplains. (photo: Colin Christian, February 2009)






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Figure A5: Kapako floodplain, looking from an open water channel (indicator 7) lined with hippo grass on the
left and right, southwards towards the floodplain dry bank (indicator 5b) with Albizia versicolor on the left,
Combretum imberbe in the centre (with cars and people underneath). On the right are Searsia quartiniana
and Ziziphus mucronata (indicator 4) with reeds just in front (indicator 8) (enlarged below). (photo: Barbara
Curtis, January 2009)















Figure A6: Kapako floodplain
pool (indicator 6) right up against
the upper wet bank 2 (indicator
4) and floodplain dry bank
(indicator 5b) on the southern
edge of the floodplain. Beyond
is hippo grass (indicator 7), with
small floodplain islands (indicator
9) interspersed among the hippo
grass. (photo: Barbara Curtis, January
2009)



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APPENDIX B: RAW DATA FROM FIELDTRIP
Plants collected 5-9 January 2009. G = grass;
Species name
habit indicator
notes
Setaria sphacelata var. sericea
G
8
Abundant at site 4; ca 2 m
high.
Panicum coloratum var. coloratum G
8
Abundant at site 4; ca 2 m high.
Chrysopogon nigritanus
G
8
Common at site 4;
Heteropogon melanocarpus ?
G
9
present at site 4 ­ ID uncertain
Themeda triandra
G
9
present at site 4
Brachiaria humidicola
G
9
present at site 4
Eragrostis rotifer
G
9
present at site 4
Setaria sagittifolia
G
9
present at site 4
Bothriochloa bladhii
G
9
present at site 4
















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The Okavango River Basin Transboundary Diagnostic Analysis Technical Reports

In 1994, the three riparian countries of the
Transboundary Diagnostic Analysis to establish a
Okavango River Basin ­ Angola, Botswana and
base of available scientific evidence to guide
Namibia ­ agreed to plan for collaborative
future decision making. The study, created from
management of the natural resources of the
inputs from multi-disciplinary teams in each
Okavango, forming the Permanent Okavango
country, with specialists in hydrology, hydraulics,
River Basin Water Commission (OKACOM). In
channel form, water quality, vegetation, aquatic
2003, with funding from the Global Environment
invertebrates, fish, birds, river-dependent
Facility, OKACOM launched the Environmental
terrestrial wildlife, resource economics and socio-
Protection and Sustainable Management of the
cultural issues, was coordinated and managed by
Okavango River Basin (EPSMO) Project to
a group of specialists from the southern African
coordinate development and to anticipate and
region in 2008 and 2009.
address threats to the river and the associated

communities and environment. Implemented by
The following specialist technical reports were
the United Nations Development Program and
produced as part of this process and form
executed by the United Nations Food and
substantive background content for the Okavango
Agriculture Organization, the project produced the
River Basin Transboundary Diagnostic Analysis.

Final Study
Reports integrating findings from all country and background reports, and covering the entire
Reports
basin.


Aylward, B.
Economic Valuation of Basin Resources: Final Report to
EPSMO Project of the UN Food & Agriculture Organization as
an Input to the Okavango River Basin Transboundary
Diagnostic Analysis


Barnes, J. et al.
Okavango River Basin Transboundary Diagnostic Analysis:
Socio-Economic Assessment Final Report


King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment Project
C.A.
Initiation Report (Report No: 01/2009)


King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment EFA
C.A.
Process Report (Report No: 02/2009)


King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Guidelines for Data Collection, Analysis and Scenario Creation
(Report No: 03/2009)

Bethune,
S.
Mazvimavi,
Okavango River Basin Environmental Flow Assessment
D. and Quintino, M.
Delineation Report (Report No: 04/2009)


Beuster, H.
Okavango River Basin Environmental Flow Assessment
Hydrology Report: Data And Models(Report No: 05/2009)

Beuster,
H. Okavango River Basin Environmental Flow Assessment
Scenario Report : Hydrology (Report No: 06/2009)


Jones, M.J.
The Groundwater Hydrology of The Okavango Basin (FAO
Internal Report, April 2010)


King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Scenario Report: Ecological and Social Predictions (Volume 1
of 4)(Report No. 07/2009)


King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Scenario Report: Ecological and Social Predictions (Volume 2
of 4: Indicator results) (Report No. 07/2009)


King, J.M. and Brown,
Okavango River Basin Environmental Flow Assessment
C.A.
Scenario Report: Ecological and Social Predictions: Climate
Change Scenarios (Volume 3 of 4) (Report No. 07/2009)


King, J., Brown, C.A.,
Okavango River Basin Environmental Flow Assessment
Joubert, A.R. and
Scenario Report: Biophysical Predictions (Volume 4 of 4:
Barnes, J.
Climate Change Indicator Results) (Report No: 07/2009)


King, J., Brown, C.A.
Okavango River Basin Environmental Flow Assessment Project
and Barnes, J.
Final Report (Report No: 08/2009)


Malzbender, D.
Environmental Protection And Sustainable Management Of The
Okavango River Basin (EPSMO): Governance Review


Vanderpost, C. and
Database and GIS design for an expanded Okavango Basin
Dhliwayo, M.
Information System (OBIS)


Veríssimo, Luis
GIS Database for the Environment Protection and Sustainable
Management of the Okavango River Basin Project

Wolski,
P.
Assessment of hydrological effects of climate change in the
Okavango Basin




Country Reports
Angola
Andrade e Sousa,
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Biophysical Series
Helder André de
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina: Sedimentologia &


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Geomorfologia


Gomes, Amândio
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina: Vegetação

Gomes,
Amândio
Análise Técnica, Biofísica e Socio-Económica do Lado
Angolano da Bacia Hidrográfica do Rio Cubango: Relatório
Final:Vegetação da Parte Angolana da Bacia Hidrográfica Do
Rio Cubango


Livramento, Filomena
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina:Macroinvertebrados


Miguel, Gabriel Luís
Análise Técnica, Biofísica E Sócio-Económica do Lado
Angolano da Bacia Hidrográfica do Rio Cubango:
Subsídio Para o Conhecimento Hidrogeológico
Relatório de Hidrogeologia


Morais, Miguel
Análise Diagnóstica Transfronteiriça da Bacia do Análise Rio
Cubango (Okavango): Módulo da Avaliação do Caudal
Ambiental: Relatório do Especialista País: Angola Disciplina:
Ictiofauna

Morais,
Miguel
Análise Técnica, Biófisica e Sócio-Económica do Lado
Angolano da Bacia Hidrográfica do Rio Cubango: Relatório
Final: Peixes e Pesca Fluvial da Bacia do Okavango em Angola


Pereira, Maria João
Qualidade da Água, no Lado Angolano da Bacia Hidrográfica
do Rio Cubango

Santos,
Carmen
Ivelize
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Van-Dúnem S. N.
Okavango: Módulo do Caudal Ambiental: Relatório de
Especialidade: Angola: Vida Selvagem


Santos, Carmen Ivelize
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Van-Dúnem S.N.
Okavango:Módulo Avaliação do Caudal Ambiental: Relatório de
Especialidade: Angola: Aves

Botswana Bonyongo, M.C.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Botswana: Discipline: Wildlife


Hancock, P.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module : Specialist Report: Country:
Botswana: Discipline: Birds

Mosepele,
K. Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Botswana: Discipline: Fish


Mosepele, B. and
Okavango River Basin Technical Diagnostic Analysis:
Dallas, Helen
Environmental Flow Module: Specialist Report: Country:
Botswana: Discipline: Aquatic Macro Invertebrates

Namibia
Collin Christian &
Okavango River Basin: Transboundary Diagnostic Analysis
Associates CC
Project: Environmental Flow Assessment Module:
Geomorphology


Curtis, B.A.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report Country:
Namibia Discipline: Vegetation


Bethune, S.
Environmental Protection and Sustainable Management of the
Okavango River Basin (EPSMO): Transboundary Diagnostic
Analysis: Basin Ecosystems Report


Nakanwe, S.N.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Namibia: Discipline: Aquatic Macro Invertebrates

Paxton,
M. Okavango River Basin Transboundary Diagnostic Analysis:
Environmental Flow Module: Specialist
Report:Country:Namibia: Discipline: Birds (Avifauna)


Roberts, K.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Namibia: Discipline: Wildlife

Waal,
B.V. Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module: Specialist Report: Country:
Namibia:Discipline: Fish Life
Country Reports
Angola
Gomes, Joaquim
Análise Técnica dos Aspectos Relacionados com o Potencial
Socioeconomic
Duarte
de Irrigação no Lado Angolano da Bacia Hidrográfica do Rio
Series
Cubango: Relatório Final

Mendelsohn,
.J.
Land use in Kavango: Past, Present and Future


Pereira, Maria João
Análise Diagnóstica Transfronteiriça da Bacia do Rio
Okavango: Módulo do Caudal Ambiental: Relatório do
Especialista: País: Angola: Disciplina: Qualidade da Água


Saraiva, Rute et al.
Diagnóstico Transfronteiriço Bacia do Okavango: Análise
Socioeconómica Angola

Botswana Chimbari, M. and
Okavango River Basin Trans-Boundary Diagnostic Assessment
Magole, Lapologang
(TDA): Botswana Component: Partial Report: Key Public Health
Issues in the Okavango Basin, Botswana


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Magole,
Lapologang
Transboundary Diagnostic Analysis of the Botswana Portion of
the Okavango River Basin: Land Use Planning


Magole, Lapologang
Transboundary Diagnostic Analysis (TDA) of the Botswana p
Portion of the Okavango River Basin: Stakeholder Involvement
in the ODMP and its Relevance to the TDA Process

Masamba,
W.R.
Transboundary Diagnostic Analysis of the Botswana Portion of
the Okavango River Basin: Output 4: Water Supply and
Sanitation


Masamba,W.R.
Transboundary Diagnostic Analysis of the Botswana Portion of
the Okavango River Basin: Irrigation Development

Mbaiwa.J.E. Transboundary Diagnostic Analysis of the Okavango River
Basin: the Status of Tourism Development in the Okavango
Delta: Botswana


Mbaiwa.J.E. &
Assessing the Impact of Climate Change on Tourism Activities
Mmopelwa, G.
and their Economic Benefits in the Okavango Delta

Mmopelwa,
G.
Okavango River Basin Trans-boundary Diagnostic Assessment:
Botswana Component: Output 5: Socio-Economic Profile


Ngwenya, B.N.
Final Report: A Socio-Economic Profile of River Resources and
HIV and AIDS in the Okavango Basin: Botswana

Vanderpost,
C.
Assessment of Existing Social Services and Projected Growth
in the Context of the Transboundary Diagnostic Analysis of the
Botswana Portion of the Okavango River Basin

Namibia
Barnes, J and
Okavango River Basin Technical Diagnostic Analysis:
Wamunyima, D
Environmental Flow Module: Specialist Report:
Country: Namibia: Discipline: Socio-economics


Collin Christian &
Technical Report on Hydro-electric Power Development in the
Associates CC
Namibian Section of the Okavango River Basin


Liebenberg, J.P.
Technical Report on Irrigation Development in the Namibia
Section of the Okavango River Basin


Ortmann, Cynthia L.
Okavango River Basin Technical Diagnostic Analysis:
Environmental Flow Module : Specialist Report Country:
Namibia: discipline: Water Quality


Nashipili,
Okavango River Basin Technical Diagnostic Analysis: Specialist
Ndinomwaameni
Report: Country: Namibia: Discipline: Water Supply and
Sanitation

Paxton,
C.
Transboundary Diagnostic Analysis: Specialist Report:
Discipline: Water Quality Requirements For Human Health in
the Okavango River Basin: Country: Namibia


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