EFA Namibia Water Quality
Okavango River Basin Technical
Diagnostic Analysis:
Environmental Flow Module
Specialist Report
Country: Namibia
Discipline: Water Quality
Cynthia L Ortmann
June 2009


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EFA Namibia Water Quality
Okavango River Basin Technical
Diagnostic Analysis:
Environmental Flow Module



Specialist Report

Country: NAMIBIA

Discipline: WATER QUALITY

Author: CYNTHIA L ORTMANN

Date: JUNE 2009


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EFA Namibia Water Quality
EXECUTIVE SUMMARY

This study dealt with the physiochemical characteristics of the Okavango River on
the Namibian side. Two sites were selected as part of an Environmental Flows
Assessment exercise and a thorough literature review was conducted prior to the
actual monitoring and assessment of findings.

The most outstanding finding of the literature review is that the quality of the
Okavango River is generally very good and contains very low concentrations of
nutrients, turbidity and suspended solids (Bethune 1986, Bethune 1991, Cronberg et
al, 1995, Turton, 1999, Hay et al 2000, Trewby 2003 , Anderson 2006) .

The major gaps that were identified are the inability of detecting measurable
concentrations of nutrients by the methods that were used in all the studies and the
absence of monitoring chlorophyll a concentrations in the Namibian waters.

Seven (7) indicators of water quality were identified and monitored at both the
selected EFA sites for the dry season and the wet season. The monitoring was
conducted in the mainstream of the river as well as in the isolated floodplain pools
and backwaters of the river system. The outcome of the results of this monitoring
reflects the findings of the existing studies to a great extent in terms of the seasonal
variations of the water quality throughout the river system.

However, as good as the quality of the river water is at this stage, there are human
and environmental impacts on riverine environments which can compromise this
state of affairs in future. As part of a holistic water management approach, this study
aims to investigate the existing relationships between the river ecosystem and the
riparian peoples' livelihoods and to predict possible development-driven changes to
the flow regime and thus to the water quality of the river.

It is clear from this analysis of linking the different flow regimes and water quality, that
most water quality problems are associated with episodes of low flow.


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EFA Namibia Water Quality
TABLE OF CONTENTS

EXECUTIVE SUMMARY ................................................................................................ 3
LIST OF TABLES ............................................................................................................ 6
LIST OF FIGURES .......................................................................................................... 7
ACKNOWLEDGEMENTS ............................................................................................... 9
1.1 The Analytical Laboratory Services for the chemical analyses of my
water samples .................................................................................................... 9
1.2 The NamWater Laboratory for Chlorophyll a analyses ...................................... 9
1.3 Shishani Nakanwe and Ndina Nashipili for assisting with fieldwork ................... 9
1.4 Kevin Roberts for helping me to access the floodplain sites on the boat
during the wet season ........................................................................................ 9
1.5 Shirley Bethune for guidance with assessment of the results and
compiling this report ........................................................................................... 9
1.6 The entire EFA Process Team and Discipline Specialists for inspiration
and moral support. ............................................................................................. 9
1 INTRODUCTION ...................................................................................................... 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
2 STUDY 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 ........................................................... 14
2.3.2 Site 5: Okavango River at Popa Falls ...................................................... 15
2.4 Discipline-specific description of Namibian sites ­ water quality ..................... 15
2.4.1 Site 4: Kapako .......................................................................................... 15
2.4.2 Site 5: Popa Rapids .................................................................................. 16
3 IDENTIFICATION OF INDICATORS AND FLOW CATEGORIES ....................... 17
3.1 Indicators ............................................................................................................. 17
3.1.2 Indicator list for Water Quality .................................................................. 17
3.1.3 Description and location of indicators ....................................................... 17
4
LITERATURE REVIEW .................................................................................... 21
4.1 Introduction .......................................................................................................... 21
4.9 Summary ........................................................................................................ 25
5. DATA COLLECTION AND ANALYSIS ..................................................................... 27
5.1 Methods for data collection and analysis ............................................................. 27
5.2 Results................................................................................................................. 27


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EFA Namibia Water Quality
5.3.1 Indicator (pH) Predicted response to possible changes in the flow
regime of pH in the Okavango River ecosystem ............................... 33
5.4 Conclusion ........................................................................................................... 40
6. FLOW-RESPONSE RELATIONSHIPS FOR USE IN THE OKAVANGO EF-
DSS ............................................................................................................................... 41
7. REFERENCES ......................................................................................................... 42



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EFA Namibia Water Quality
LIST OF TABLES
Table 2.1
Location of the eight EFA sites ................................................ 14
Table 3.1
List of indicators for Water Quality and those chosen to
represent each site .................................................................. 17
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............................ 20
Table 5. 1:
Field pH measurements ........................................................... 27
Table 5. 2:
Field measurements of water temperature .............................. 28
Table 5. 3:
Field Dissolved Oxygen measurements................................... 29
Table 5. 4:
Field and Laboratory Conductivity measurements ................... 30
Table 5. 5:
Field and Laboratory Turbidity measurements ......................... 30
Table 5. 6:
Laboratory Total Nitrogen measurements................................ 31
Table 5. 7:
Laboratory Total Phosphates measurements .......................... 31
Table 5. 8:
Laboratory Chlorophyll a measurements ................................. 32



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EFA Namibia Water Quality
LIST OF FIGURES
Figure 2.1
Upper Okavango River Basin from 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 3.1
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 .................................................................................... 19
Figure 3.2
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 .................................................................................... 19


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EFA Namibia Water Quality
ABBREVIATIONS

ABBREVIATION
MEANING
DTM
Digital Terrain Model
EFA
Environmental Flows Assessment
DO Dissolved
Oxygen
K-N Kjeldahl
Nitogen



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EFA Namibia Water Quality
ACKNOWLEDGEMENTS

I would like to acknowledge the following people for helping in the information
gathering and analyses of this report:

1.1
The Analytical Laboratory Services for the chemical analyses of my water
samples
1.2
The NamWater Laboratory for Chlorophyll a analyses
1.3
Shishani Nakanwe and Ndina Nashipili for assisting with fieldwork
1.4
Kevin Roberts for helping me to access the floodplain sites on the boat
during the wet season
1.5
Shirley Bethune for guidance with assessment of the results and compiling
this report
1.6
The entire EFA Process Team and Discipline Specialists for inspiration and
moral support.





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EFA Namibia Water Quality
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 socio-economic effects of
such possible developments. OBSC recommended at this meeting that a preliminary
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 Water Quality 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 this preliminary 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 preliminary EFA, due to time constraints, as
input to the TDA and to a future comprehensive EFA.

The specific objectives at this 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;
· 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 these preliminary EFA outputs to enhance biodiversity management of the
Delta.
· To develop skills for conducting EFAs in Angola, Botswana, and Namibia.



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EFA Namibia Water Quality
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. Chapter 3, highlighted the agreed
water quality indicators and flow categories. Literature review pertinent to water quality work
in the Okavango River and other similar systems is given in Chapter 4 and the full indicators
are listed. The field survey work undertaken for the water quality investigation within Namibia
in both the dry season (October 2008) and wet season (February 2009); together with data
collection, analysis and results are outlined in Chapter 5. Chapter 6 is a first attempt to link
water quality to flow and provide information on the flow-response relationships for use in the
Okavango EF-DSS. References are found in Chapter 7. Appendix A contains the raw field
and laboratory data.


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EFA Namibia Water Quality
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 inactive
drainage are of the Omatako Omuramba. Although this ephemeral river still regularly floods
along its southern portion, it has not contributed any flow to the Okavango River. Outflows
from the Okavango Delta are drained through the Thamalakane and then Boteti Rivers, the
latter eventually joining the Makgadikgadi Pans. The Nata River, which drains the western
part of Zimbabwe, also joins the Makgadikgadi Pans. On the basis of topography, the
Okavango River Basin thus includes the Makgadikgadi Pans and Nata River Basin (Figure
2). This study, however, focuses on the active drainage parts of the basin in Angola and
Namibia, and the Okavango delta in Botswana. The Omatako Omuramba, 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
uiri
Permanent swamps
ri
#
Seasonal swamps
Cubango
Cuito
NAMIBIA
Okavango
#
Rundu
#
#
#
0
300 Kilometers
#

Figure 2.1 Upper Okavango River Basin from sources to the northern end of the Delta



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EFA Namibia Water Quality
Okavango River Basin
N
W
E
S
C
u
ta
Cu
#
to
c
h
i#
C
C
ui
ua
#
t
o
nava
#
l
e
C
# Menongue
ub
C
a
u
n
c
g
h
o
i
# Cuito Cuanavale
# Cuebe
C
ANGOLA
uirir
#
i
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. These
representative areas, that are reasonably homogeneous in their ecological characteristics
and can be delineated, were used to choose several sites in which to focus data-collection
and where monitoring can be done. 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; aquatic macroinvertebrates,
vegetation and 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). (See the delineation report for details).

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


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EFA Namibia Water Quality
Botswana: three
sites.
The sites chosen by the national teams are given in Table 2.1.

Table 2.1 Location of the eight EFA sites
EFA Site No
Country
River
Location
1 Angola
Cuebe
Capico
2 Angola
Cubango
Mucundi
3 Angola
Cuito Cuito
Cuanavale
4 Namibia
Okavango
Kapako
5 Namibia
Okavango
Popa
Rapids
Upper Panhandle
6 Botswana
Okavango
around Shakawe
Xakanaka lagoon
7 Botswana
Xakanaka in Delta
and Khwai River
8
Botswana
Boteti Rivers
Maun and Chanoga


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 hotspots 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 as
two of its core conservation areas on either side of the river, the Buffalo core area on the
west bank and the Muhango core area on the east bank.

2.3.1 Site 4: Okavango River at Kapako
The river is at the heart and core of the Okavango Basin, and a variety of aquatic plants and
animals live in and near it and make good use of the river, its water and other wetland
resources. In Namibia most of the river often has broad margins of floodplains on either side
beyond which there are drier, deciduous woodlands. A variety of organisms are specialised
inhabitants of the floodplains.

The fish communities can be divided into two groups based on their food preference and
specialization, those that feed on plant material and those that prey on other fish. Secondly
they can be divided according to the habitats where the different fish occur, some preferring
the mainstream, others the rocky areas and rapids, other groups in the backwaters or


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EFA Namibia Water Quality
permanent swamps and a distinct community found in the floodplains. The floodplains are of
greatest value as places in which most fish breed.

Local people have recognised that the quality of water and fish resources are decreasing in
the Okavango River. Fish and fishing remain a significant feature in the lives of people at
Kapako, who fish for food or to earn incomes by selling their catches as well as by providing
trips for tourists. Fish stocks in the floodplains are estimated to be four times higher than in
the main channel.

The riverine landscape comprises the main Okavango River channel and the annually
flooded floodplains with braided channels. The higher fluvial terrace with alluvial deposits
are flooded less regularly (Mendelsohn and el Obeid 2004).

2.3.2 Site 5: Okavango River at Popa Falls
The southward flowing section from Mukwe to the Popa rapids is rocky without floodplains
and has many sand and rock based islands set in the braided rocky channels. The shore is
wooded with the exception of settled areas mainly on the western bank that have been
largely cleared for settlements and crops. The islands remain well forested and several are
used as burial areas for chiefs.

Popa Rapids are where the river cascades down several meters before resuming its normal
slow and leisurely flow. The rocks were formed from sediments deposited in rift valleys about
900 million years ago, (el Obeid, S., Mendelsohn date). During the focus group discussion
by the socio-economic team, it was mentioned that due to the Popa rapids and rocky areas,
it's difficult for the local fishermen to catch fish as desired. Therefore, only a few individuals
owning local mukoros, hook and line, and gill fish nets have access to fish catches in the
main channel.
Papyrus cyperus, papyrus dominates the deepest water margins alongside the main
channels. Water can seep through the walls of papyrus to the reedbeds behind the papyrus
and in places it exits into backwaters and side channels.
The sandy sediments are confined to the channels. These are flanked by reed beds of
Phragmites, Typha capensis or bulrushes and the sedge Miscanthus junceus in the
shallower waters. The residents do not experience floods as there are no floodplains in this
area. They depend on the main channel for their water and wetland resources (Mendelsohn
and el Obeid 2004).

2.4 Discipline-specific description of Namibian sites ­ water quality
2.4.1 Site 4: Kapako
This site is characterised by the main channel and floodplain areas with isolated pools and
backwaters on the Okavango River. The site is situated about 30 km upstream of Rundu, the
biggest town along the Okavango River on the Namibian side. The floodplain is generally
characterised by good water quality with very low nutrient concentrations in the mainstream
along the stretch from Katwitwi up to Katere at the Cuito river confluence with the Okavango
River. The chemical constituents in the backwaters of this stretch of the river are slightly
more concentrated especially in the dry season with low flow rates. This is due to gradual
drying because of the absence of moving streams in these backwaters.



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EFA Namibia Water Quality
2.4.2 Site 5: Popa Rapids
The Popa Rapids is a protected area with a resort, a community campsite and small scale
local community activities. The river channel here is characterised by shallow, rocky rapids
and backwater channels. The site is situated about 103 km downstream from the Cuito River
confluence with the Okavango River and in terms of water quality, there is a clear trend of
dilution effects of nutrients compared to the sites upstream of the confluence. The confluence
of a river is the meeting of two or more bodies of water. The Cuito River is a tributary which
joins the Okavango River, which is the high order stream in the drainage basin and is
therefore called the mainstream. Dissolved oxygen levels are higher below the Popa Rapids
due to the aeration taking place when water flows over the rocks.








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EFA Namibia Water Quality
3 IDENTIFICATION OF INDICATORS AND FLOW CATEGORIES

3.1 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.

3.1.2 Indicator list for Water Quality
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 ­ Cynthia
Ortmann, Namibia; Wellington Masamba, Botswana, Carlos Andrade, Angola, - and is
provided in Table 3.1. For water quality 8 indicators were initially agreed and later reduced to
7 by combining total Nitrogen and Phosphorus simply as nutrients. Further details of each
indicator are discussed fully in Chapter 4.

Table 3.1 List of indicators for Water Quality and those chosen to represent each site
Sites represented ­ no more than ten indicators
Indicator
Indicator name
per site
Number
1 2 3 4 5 6 7 8
1 pH
X x
2 Temperature
X x
3 Dissolved
Oxygen
X x
4 Electrical
Conductivity
X x
5 Turbidity
X x
Total Nitrogen





6



Nutrients
X
x
Total
Phosphorous

7 Chlorophyll
a
X x


3.1.3 Description and location of indicators
Water Quality Indicator 1: pH


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EFA Namibia Water Quality
Description: The pH value of water refers to its acidity or alkalinity water with a pH of 7 is
considered neutral.

Flow-related location: In relatively shallow flowing water systems, the pH remains relatively
stable close to 7 in the mainstream and site channels.

Water Quality Indicator 2: Temperature
Description: It is a measure of how cold or warm the water is and is an important indicator as
different organisms have different temperature tolerance ranges.

Water Quality Indicator 3: Dissolved Oxygen
Description: Refers to the amount of oxygen dissolved in water and is related to
photosynthesis by water plants and aeration as well as decomposition. It is important to
organisms living in the water.
Flow-related location: Fast flows over rapids increase aeration and thus the concentration of
oxygen in water.

Water Quality Indicator 4: Conductivity
Description: The electrical conductivity of water is directly related to the concentration of the
total dissolved minerals in the water.
Flow-related location: Extended dry periods and low flow conditions can contribute to high
conductivity readings.

Water Quality Indicator 5: Turbidity
Description: Turbidity refers to how clear the water is. The greater the amount of total
suspended solids in the water, the muddier it appears and the higher the measured turbidity.
Flow-related location: During low flow, many rivers have a green color and turbidities are low,
usually less than 10 NTU www.jacksonbottom.org/waterqualityconcepts.htm. In most rivers
turbidity increases after rainfall and flooding because of soil erosion. Settled particles can
accumulate and smother fish eggs, water plants and aquatic insects on the river bottom.

Water Quality Indicators 6: Nutrients
In this report, the total nitrogen and total phosphorous will be addressed as one indicator
called nutrients. Total nitrogen consists of NH4, NO3 and NO2 and total phosphorous includes
organic phosphorous and inorganic phosphate. These nutrients are typically low in
concentration and are difficult to detect accurately by conventional laboratory methods.
Flow-related location: In slow flowing water, decomposition of organic material takes place
faster and the nutrient concentration increases.

Water Quality Indicator 7: Chlorophyll a
Description: Used as a measure of algal productivity
Flow-related location: High concentrations in floodplain pools and backwaters where
decomposition takes place and eutrophication is evident.

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 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


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EFA Namibia Water Quality
Okavango Basin river sites: Dry season, Transitional Season 1, Flood Season,Transitional
Season 2. (Later the transitional stages were dropped for the preliminary survey)
Tentative seasonal divisions for river Sites 4-5 are shown in Figure 3.1 and Figure 3.2.
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.

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 3.1 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
n 1
Trans 2
Dry
1200
1000
Year 3
00
Year 2
800
Year 1
600
400
200
0
O
N
D
J
F
M
A
M
J
J
M
J
A
S

Figure 3.2 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 is initially expected to be nine main questions related
flow seasons (
Table 3.2).


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EFA Namibia Water Quality

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

Question
Season
Response of indicator if:
number
1
Onset is earlier or later than natural mode/average
2
Dry Season
Water levels are higher or lower than natural mode/average
3
Extends longer than natural mode/average
Duration is longer or shorter than natural mode/average - i.e. hydrograph is
4
Transition 1
steeper or shallower
5
Flows are more or less variable than natural mode/average and range
Onset is earlier or later than natural mode/average ­ synchronisation with rain
6
Flood season
may be changed
7
Natural proportion of different types of flood year changed
8
Onset is earlier or later than natural mode/average
Transition 2
Duration is longer or shorter than natural mode/average ­ i.e. hydrograph is
9
steeper or shallower




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EFA Namibia Water Quality
4 LITERATURE
REVIEW
4.1 Introduction
This review gives an overview of water quality within the Namibian section of the Okavango
River Basin and indicates the response of selected water quality indicators to river flow and
water variability as an input to the environmental flow assessment of the river. A few studies
have been conducted for investigating the water quality of the Okavango River system.
However, there is not as wide a range of detailed water quality studies as there exists for the
Okavango Delta in Botswana.

This literature survey looks at data from these studies since 1984 up to currently ongoing
studies. Some of the studies carried out by the Department of Water Affairs are available as
Country Reports in the Library of the Ministry of Agriculture, Water and Forestry. Books were
written as a result of extensive studies in the Okavango River, and the sections pertaining to
the Water Chemistry of the river were studied. There is also a report on the Transboundary
Diagnostic Analyses of the Okavango River which was conducted in 1998. This report does
not have sufficient information on the water chemistry of the river on the Namibian side, only
a summary of chemical concentrations that were measured in some mainstream sites and
backwater sites in 1984. However, for the purposes of this study, the review will concentrate
mostly on the recognized indicators which are pH, Temperature, Dissolved Oxygen (DO),
Turbidity, Conductivity, Nutrients which include Total Nitrogen (TN) and Total Phosphorous
(TP) and Chlorophyll a.

After reviewing the literature, it was found that the water quality of the Okavango River
measured in Namibia remains very good overall. The river has low concentrations of
nutrients, turbidity and suspended solids (Bethune 1986, Bethune 1991, Cronberg et al,
1995, Turton, 1999, Hay et al 2000, Trewby 2003 , Anderson 2006) .

4.2 Indicator 1 (pH)
The pH value of water, on a scale of 0 -14 measures the concentration of hydrogen ions. The
pH represents the balance between hydrogen ions and hydroxide ions in water. Water is
basic if the pH is greater than 7 and considered acidic if the pH is less 7. The pH is also a
useful indicator of the chemical balance in water. A high or low pH will negatively affect the
ability of certain chemicals or nutrients in the water for use by plants. Water with a pH of less
than 4.8 or greater than 9.2 can be harmful to aquatic life, for example most freshwater fish
prefer water with a pH range between 6.5 and 8.4

National data on this indicator in this river system
The pH in the Okavango River is generally stable around neutral throughout the Namibian
stretch of the river in both the mainstream and the backwaters in all seasons and at both
sites.
Cronberg et al. (1995) indicated the pH of the Okavango River generally varied between 5.9
to 7.6. During the study on fish populations, gill net selectivity and artisanal fisheries in the
Okavango River (Hay et al. 2000), the highest pH value of 9.5 was recorded at Bunya just
upstream of the Mupini floodplain during the winter of 1994.

Trewby (2003) found that although the water quality of the Okavango River showed some
temporal and spatial patterns during May to December 2002, the pH did not vary much
between the sampling periods at various sites in the mainstream. The monthly mean across
the stretch of the river for May was 6.84; for July it was 6.84 and for December it was 6.97.



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EFA Namibia Water Quality
Similarly, Anderson (2006) found that pH was fairly stable around neutral for most of sites
throughout the mainstream and channel sites. The mean pH values recorded for Popa
Rapids were in the range of 6.7 ­ 6.9.

In summary the pH of the Okavango River mainstream water is generally within the values of
5.9 and 9.5 with the greatest frequency of values found between 6.5 and 6.9 and can be
compared to most natural waters.

4.3 Indicator 2 (Temperature)
This indicator is significant from the rest of the indicator parameters because many of the
physical, biological and chemical characteristics of surface water are dependent on
temperature. The optimal health of aquatic organisms depends on temperature ­ if the
temperatures are outside the optimal range for a prolonged time, organisms are stressed and
can die. The water temperature also affects the volume of dissolved oxygen it can hold.

National data on this indicator in this river system
Findings of the 1984 ­ 1986 Limnological Baseline Survey of the Okavango River indicated
that water temperature at different mainstream and channel sites along the river measured in
the same season was very similar. The temperatures were usually within a degree of the air
temperature, being relatively high in March (24 - 30°C), decreasing sharply in winter (17 -
19°C) and again increasing towards October (23 - 29°C). (Bethune 1987)

Temperature in shallow flowing waters like the Okavango is determined mostly by solar
radiation and is usually very similar to air temperatures. No stratification occurs in the river
nor in any of the pools (Bethune 1991 - Kavango River Wetlands). The water of this river
system is well mixed and the water temperature is similar with depth and distance
downstream. According to Bethune, the temperatures remained fairly constant with depth
and distance along the river, but changed with the time of the day, especially in shallow
waters. Similar results were recorded during the Hay et al 2000 study on Fish populations,
gill net selectivity and artisanal fisheries in the Okavango River. Immediately upstream of the
Mupini floodplain, at Bunya, the minimum and maximum temperatures recorded in 1993 was
26.50 ­ 29.0°C in autumn, in the winter it was 15.1 ­ 19.7°C and in spring 21 ­ 30.1°C.
Slightly lower temperatures were recorded in the same year and seasons at the Popa
Rapids: 25.1 - 27.1°C in autumn, 15.4 ­ 18.7°C in winter and 24.4 ­ 28.6°C in spring.
Temperatures measured in this river seem to be fairly similar throughout the stretch of the
river during the same season, and is usually within one degree of the air temperature.

4.4 Indicator 3 (Dissolved Oxygen)
Dissolved oxygen refers to the amount of oxygen dissolved in water. This indicator is one of
the most important water quality parameters, as it is an essential element for the
maintenance of healthy rivers and lakes. Most aquatic plants and animals need a certain
amount of oxygen dissolved in water for survival. The sources of dissolved oxygen in rivers
are the atmosphere, algae and vascular aquatic plants and are usually expressed as a
concentration of oxygen in a volume of water (mg/l). Oxygen is also introduced into water
when oxygen from the atmosphere is mixed into the water. Where the water is turbulent, for
example where it is tumbling over rocks, the oxygen and water mix more easily, more
atmospheric oxygen gets dissolved in the water and the result is higher DO concentrations.
There are also higher concentrations of oxygen in cold water compared to warm water. A
concentration of 5 mg l-1 dissolved oxygen is required to maintain a healthy aquatic life in a
river system.

National data on this indicator in this river system


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EFA Namibia Water Quality
In 2003, a study by Fiona Trewby indicated that the DO concentration in the Mupini
floodplain was higher than in the rest of the river system both in the winter (July) and summer
(December). The means were recorded as 8.6 and 7.8 mg l-1 respectively.

During the Limnological Baseline Survey of the Okavango River of 1984 ­ 1986, it was found
that the dissolved oxygen concentration measured within a season was more or less the
same throughout the length of the river at the mainstream and channel sites, with the
exception that below the Popa Rapids, the DO concentration increased slightly due to
aeration. The oxygen concentrations increased from March (5.8 - 8.1 mg l-1 ) to October (7.1
­ 9.4 mg l-1). (Bethune 1987).

A UNDP study by Charles Hocutt in 1997 indicated that the dissolved oxygen throughout the
flowing waters of the Okavango is generally high and near saturation conditions. In contrast,
studies by Cronberg et al 1996 stated that the DO content of the water was substantially
below saturation and therefore reflected stagnant conditions throughout the wetland.
According to the 1998 report on the Transboundary Diagnostic Analyses of the Okavango
River, these variations in results probably reflect the relative stages of flood progression in
the specific areas of study. The levels of oxygen in relation to flow, decreased with increasing
flow.
In the floodplain pools, the oxygen levels are higher by day than at night due to
photosynthesis and decrease with depth in isolated backwaters due to decomposition
(Bethune 1991 - Kavango River Wetlands)

The study of Jafet Anderson, 2006, indicated that dissolved oxygen levels were elevated at
sampling sites below the Cuito River confluence with the Okavango River. It seems that the
Cuito has a diluting effect and carries less dissolved solids and less dissolved oxygen than
the mainstream before the confluence. This situation should be verified with the results from
the samples taken at Popa Rapids.

4.5 Indicator 4 (Conductivity)
The electrical conductivity of water is directly related to the concentration of dissolved solids
in the water. It gives an indication of the dissolved ion concentration which may stem from
elevated pollution levels. Temperature also affects conductivity; warm water has a higher
conductivity. Conductivity is measured in micro-Siemens per centimeter (µS cm-1).

National data on this indicator in this river system
Jafet Andersson 2006 found that concentrations of conductivity and total dissolved solids at
sampling points upstream of the Cuito ­ Okavango confluence are significantly higher than
those downstream of the confluence. The Cuito carries less dissolved solids than the
mainstream therefore, after mixing, there is a decrease in concentration. It can also be due to
the intensive land-use of the Okavango River upstream of the confluence.

Similarly, the data from the Hay et al 2000 study on Fish populations, gill net selectivity and
artisanal fisheries in the Okavango River indicate mean conductivity values of 52.4 µS cm-1
at Bunya and 47.0 µS cm-1 at Popa Rapids for the 1993 / 1994 period.

With relation to flow, the conductivity levels seems to be decreasing with increasing flow at
sites before the confluence and increase with increasing flow below the confluence.

4.6 Indicator 5 (Turbidity / SS)
Turbidity refers to how clear the water is. The greater the amount of total suspended solids in
the water, the muddier it appears and the higher the measured turbidity. In most rivers
turbidity increases after rainfall and flooding because of soil erosion. Settled particles can


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EFA Namibia Water Quality
accumulate and smother fish eggs, submerged macrophytes and aquatic invertebrates on
the river bottom.

National data on this indicator in this river system
During the Limnological Baseline Survey of the Okavango River of 1984 ­ 1986, it was found
that the waters of the Okavango River are clear and the river bottom was visible from the
surface at all mainstream and channel sites. The turbidity was usually below 1 NTU. The
shallow backwater sites were not as clear though. Values of 0 ­ 10 NTU are an indication of
a clear stream. (Bethune 1987).

However, it seems that the turbidity may have increased since this baseline survey. Values
measured in December 1991 ranged from 0.5 to 3.5 NTU and were highest below the dry
floodplain area at the junction of the Omatako Omuramba and the Okavango River (Bethune
1992).

Similar results were recorded during the Hay et al 2000 study. The recorded values at most
of the study sites ranged from 0.4 to 5 NTU during autumn, winter and spring of 1993.
However, exceptionally high values were recorded during autumn 1994 during low water.
Immediately upstream of the Mupini floodplain, at Bunya, the highest turbidity value recorded
was 30 NTU in autumn 1994. The same value of 30 NTU was recorded at the Popa Rapids.
These values were measured at sites where fish nets were set along the margin and thus do
not directly reflect the turbidity in the mainstream.

4.7 Indicator 6 Nutrients
Nitrogen is an essential nutrient for all aquatic organisms. The forms of nitrogen analysed
from a water sample are generally reduced (Kjeldahl) nitrogen which includes ammonium
(NH
-
4) and organic nitrogen (Norg); and oxidized nitrogen which is nitrate (NO3 ) and nitrite
(NO -
2 ). Total nitrogen (Tot ­ N) is a measure of all the forms of nitrogen, dissolved or
particulate that is found in the sample. The main sources of nitrogen in rivers include human
and animal wastes, industrial pollutants and non-point-source runoff from agriculture and
aquaculture activities. In excess amounts, nitrates in water can cause an increase in algal
growth, which can rob the water of dissolved oxygen and can eventually lead to the death of
some forms of aquatic life.

Phosphorous is a key element necessary in water for the growth of plants and animals. Its
concentrations in pure waters are generally low. It is introduced in a waterbody as a natural
element found in rocks and soils and from human activities. Total phosphorous includes
organic phosphorous and inorganic phosphate. Organic phosphorous is a part of living plants
and animals, whereas inorganic phosphate consists of the ions bonded to soil particles and
phosphate present in laundry detergents.

National data on this indicator in this river system
The purity of the Okavango River indicates that it is extremely deficient in nutrients
(Mendelsohn J & Obeid S, 2004).

The oxidized nitrogen, which is the sum of the nitrate and nitrite, was below detection limits in
the first half of 1984. The highest concentration was recorded at 0.8 mg/L in May of 2002
(F. Trewby,2003), but during the latter half of the same year it was again too low to be
detected. This was double the highest concentration that was recorded during the
Limnological Baseline Survey of the Okavango River of 1984 ­ 1986, which was 0.43mg/L in
May 1985. (Bethune 1987).



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EFA Namibia Water Quality
In the same survey, it was found that the ammonia (NH4) concentration ranged from below
detection limits to 1.68 mg/L, whereas the organic nitrogen (Norg) had a much greater range
from below detection limit to 6.72 mg/L

Trewby, 2003 found that the total phosphorous concentration in the Okavango River is an
order of a magnitude lower than the total nitrogen, with its maximum for the entire stretch of
the Namibian side being 0.37mg/L compared to the total nitrogen being 3.8 mg/L.

In 2006, Andersson J found that the phosphorous concentrations were similarly low or even
lower than those quoted by Trewby. This study focused on large scale agricultural farms and
it was evident that there were no significant variations with respect to phosphorous
concentrations at locations above these large-scale agricultural developments and the
locations below these developments.

Bethune, 1986 found that ortho-phosphate concentrations were highest in the mainstream
sites. This can be attributed to human and cattle wastes and detergents used for laundry,
given the fact that most of the sites in this study are at human access points to the river.


4.8 Indicator 7 (Chlorophyll a)

Clorophyll is the green pigment in plant cells that carries out the bulk of energy fixation in the
process of photosynthesis. It is a very important ecological and environmental parameter of
waters mostly used to estimate algal biomass in lakes and streams
(http://dipin.kent.edu/chlorophylll.htm). Chlorophyll itself is not single molecule but a family of
related molecules, designated chlorophyll a, b, c and d. Chlorophyll a is measured as a
unicellular algae. Eutrophication in the system is prominent with increasing concentration of
chlorophyll a in rivers

National data on this indicator
There appear to be no data available for chlorophylll a concentration in the Namibian section
of the River. This study will however include these analyses.

4.9 Summary
As was indicated in the introduction of this literature survey, there is not a wide range of
existing data pertaining to the water quality of the Okavango River on the Namibian side.
However, there are five (5) major and quite detailed water quality studies that were
reviewed in the course of this Environmental Flow Assessment. They are as follows:
· The Limnological Baseline Survey of the Okavango River 1984 ­ 1986 by S
Bethune. A detailed survey done at mainstream and backwater sites at ten locations
seasonally over a three year period.
· The UNDP study of 1997 by Charles Hocutt of the Maryland University
· The
Hay
et al 2000 study on Fish populations, gill net selectivity and artisanal
fisheries in the Okavango River
· The Fiona Trewby, 2003 study on Impact of Land-use on the Okavango River
· The Jafet Andersson, 2006 study on Land Cover Changes in the Okavango River
Basin
As a means of strengthening the existing database on Okavango River Water Quality, there
is currently a project running in the Department of Water Affairs, called "The impact of Land
Use Activities on the Water Quality of the Okavango River". This project is executed by Ms
Cynthia L Ortmann and aims at monitoring the water quality on the Namibian side of the river


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EFA Namibia Water Quality
from Katwitwi up to Mahango Game Park. The monitoring programme started in July 2008,
suveys were continued in October 2008, January 2009, April 2009 and will end in July 2009.

The major gaps identified during this literature survey are the inability of detecting
measurable concentrations of nutrients by the methods that were used in all the studies and
the absence of monitoring chlorophyll a concentrations in the Namibian waters.

More detailed and intensive monitoring surveys like the 1984 ­ 1986 Limnological Baseline
Survey are needed in order to determine if there are real changes in the water quality of the
river system due to industrial and agricultural developments that have taken place since then
in order to help make predictions of how future developments could affect the river's
chemistry.





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EFA Namibia Water Quality
5. DATA COLLECTION AND ANALYSIS
5.1 Methods for data collection and analysis
The two Namibian EFA sites Kapako / Mupini Floodplain and Popa Rapids Resort were
visited during the period of 20 -24 October 2008, during the dry season for data collection.
The Kapako / Mupini Floodplain was visited on 20 October 2008 and the Popa Rapids Resort
was visited on 21 October 2008. During the wet season, the Popa Rapids Resort was visited
on 06 February 2009 and the Kapako / Mupini Floodplain on 08 and 09 February 2009. A
motorboat was used in the wet season to access the actual site that was monitored in the dry
season.

Samples were taken and physical measurements recorded from the mainstream of the river
as well as from the backwaters at both sites. For the physico-chemical water quality data, on-
site measurements were recorded of water temperature, pH, Dissolved Oxygen and
Conductivity using a HACH Multimeter, and turbidity using a 2100P HACH Turbidity meter.
Samples of water were collected in 50 ml polyethylene plastic bottles for Chlorophyll- a
analysis and these were refrigerated and transported overnight by Nampost Courier to the
Namibia Water Corporation (NamWater) Laboratory for analyses. More water samples were
collected in 1000 ml polyethylene plastic bottles for analysing Total Nitrates, Total
Phosphates and Total Dissolved Solids. These samples were preserved by keeping them
about 4°C in a cool box throughout the duration of the sampling period and upon return in
Windhoek, they were submitted to the Analytical Laboratory Services for analyses.

5.2 Results
The full raw data ­ on site measurements as well as laboratory readings are available in
Appendix A. The following is an assessment of the results:

5.2.1 pH
Site: Kapako / Mupini Floodplain and Popa Rapids
Date of visit:
Dry Season ­ 20,21 October 2008 and Wet Season ­ 06, 08 and 09 February 2009


Kapako n=1
Popa Rapids n=1
Dry season (Low flows):


Mainstream 7.99
7.88
Backwaters / Floodplain
7.64 7.69
pools
Wet Season (High flows):


Mainstream 7.1
7.69
Backwaters / Floodplain
6.8 , 6.7
7.62
pools
Table 5. 1: Field pH measurements
At Kapako the pH was recorded at 7.99 in the main channel of the river during the dry
season. This is slightly higher than the pH values for this area recorded during previous
studies. This unusual reading can be due to the fact that it is representative of only one (1)


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EFA Namibia Water Quality
sample and the probe used for this reading could be erroneously calibrated. In a small
isolated floodplain pool, the pH value recorded was 7.64, which is slightly less than in the
main channel. The flow recorded during this time was relatively low. The recorded pH values
are normal, given the low flow period of the river.

In the wet season, the pH of the main channel of the river was recorded as 7.1, which is, as
expected, less than it was in the dry season. This can be attributed to slightly acidic
precipitation in the wet season. The introduction of organic matter during high flows can also
reduce the pH in a river. During this high water period the pH values showed a similarity for
the mainstream and the linked floodplain pools. In a deep pool of 2.5m depth and about 15 m
from the river bank, the pH was 6.8 and in a shallow floodplain pool of 0.55 m depth, the pH
was recorded 6.7.

The river at Popa Rapids is characterized by shallow, rocky rapids and side channels. In the
mainstream, the pH was 7.88 in the dry season. This was slightly higher than historic
records, but more realistic than the reading of 7.99 at Kapako. In the backstream waters at
the campsite of the resort the pH was recorded 7.69.

In the wet season, the mainstream pH was slightly less at 7.69, compared to the dry season.
There was again a similarity with the linked side channel pH which was recorded 7.62.


5.2.2 Temperature
Site: Kapako / Mupini Floodplain and Popa Rapids
Date of visit:
Dry Season ­ 20, 21 October 2008 and Wet Season ­ 06, 08 and 09 February 2009


Kapako n=1
Popa Rapids n=1
Dry season (Low flows):


Mainstream 26.7°C 28.7°C
Backwaters / Floodplain
27.9°C 25.4°C
pools
Wet Season (High flows):


Mainstream 27.1°C 27.4°C
Backwaters / Floodplain
27.4°C 27.5°C
pools
Table 5. 2: Field measurements of water temperature
At Kapako, under low flow conditions in the dry season, the temperatures recorded in the
mainstream and the floodplain pools showed a slight difference of 1.2°C. The water
temperature measured in the mainstream was 26.7°C compared to 27.9°C in a pool in the
floodplain. During the wet season, the temperature of the mainstream water was recorded
27.1°C. The temperature in a linked deep pool of 2.5m depth and about 15 m from the river
bank, was 27.4°C. This trend confirms the findings of the 1984 ­ 1986 Limnological Baseline
Survey of the Okavango River (Bethune 1987), which indicated that the water temperature at
different mainstream and channel sites along the river measured in the same season, were
very similar.

At Popa Rapids, the temperatures varied substantially between the mainstream and the
backwaters during the low flow season. The temperature variation through the day reflected
the time of the day the temperature was measured. In the mainstream of the river, the


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EFA Namibia Water Quality
sampling was done during the noon of the day at about 14h00 and the temperature recorded
was 28.7°C. In the backwaters at the campsite of the resort, the sampling was done in the
morning at about 08h30 and the recorded temperature was 25.4°C.

However, there was a similarity of the temperatures in the mainstream and the backwaters
during the high flow season: the temperature in the main channel was slightly colder
recorded at 27.4°C in the backwater stream it was 27.5°C.
5.2.3 Dissolved Oxygen
Site: Kapako / Mupini Floodplain and Popa Rapids Resort
Date of visit:
Dry Season ­ 20, 21 October 2008 and Wet Season ­ 06, 08 and 09 February 2009


Kapako n=1
Popa Rapids n=1

Dry season (Low flows):


Mainstream 7.06
mg/ 9.76
mg/

Backwaters / Floodplain
7.01 mg/ 6.72
mg/

pools
Wet Season (High flows):


Mainstream 4.91
mg/
6.63mg/

Backwaters / Floodplain
2.15 mg/ 6.50
mg/

pools
Table 5. 3: Field Dissolved Oxygen measurements
The table above reflects the Dissolved Oxygen concentrations at the two EFA sites in
Namibia during the two seasons. At Kapako, the DO concentrations in both the mainstream
and the side channel sites were less than the required 5mg/ during the wet season, which is
necessary for the health of aquatic life. In the dry season the DO concentrations were higher
and showed a similarity in the mainstream and floodplain pools due to mixing of water.

During both seasons, the trend from previous studies that DO levels are higher where water
is tumbling over rough surfaces was confirmed. The DO in the mainstream and backwater
samples at Popa Rapids was higher than at Kapako, with the exception of the floodplain pool
which had a higher concentration. The 3.04 mg/ difference in the DO concentration at Popa
Rapids between the mainstream and the backstream can be due to the time of the day that
readings were recorded for these samples.

5.2.4 Conductivity
Site: Kapako / Mupini Floodplain and Popa Rapids Resort
Date of visit:
Dry Season ­ 20, 21 October 2008 and Wet Season ­ 06, 08 and 09 February 2009


Kapako n=1
Popa Rapids n=1
Dry season (Low flows):
Field Laboratory Field Laboratory
Mainstream
47.8µS/cm n/a
28.3 µS/cm 33 µS/cm
Backwaters / Floodplain
175.5 µS/cm n/a
32.7 µS/cm 32.0 µS/cm
pools
Wet Season (High flows):




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EFA Namibia Water Quality
Mainstream
35.2 µS/cm 38 µS/cm 41.4 µS/cm 44 µS/cm
Backwaters / Floodplain
37.5 µS/cm 62 µS/cm 40.8 µS/cm 44 µS/cm
pools
Table 5. 4: Field and Laboratory Conductivity measurements
The conductivity concentrations in the mainstream and the backwaters / floodplain pools
(33.0 µS/cm - 47.8 µS/cm) showed similarity to the study of Jafet Andersson 2006, who
found that concentrations of conductivity and total dissolved solids at sampling points
upstream of the Cuito­Okavango confluence are significantly higher than those downstream
of the confluence due to the input of low conductivity water of the Cuito river.
During the low flow period, the conductivity of the mainstream river was recorded at
47.8µS/cm at Kapako compared to 28.3 µS/cm at Popa Rapids.

The conductivity in the isolated pool of the Kapako floodplain was as expected, exceptionally
high at 175.5 µS/cm during the low flow period. This high concentration can be a result of the
isolation of pools from the mainstream and the gradual concentration of ions as well as the
role of nutrients resulting from eutrophication. During the high flow period, the conductivity in
a 2.5m deep floodplain pool at Kapako was recorded at 37.5 µS/cm but in the laboratory it
was analysed at 62 µS/cm. This difference can be a result of the unavoidable time delay in
transporting samples from the date of sampling to the laboratory to the actual day of
analysis.

The lower conductivity concentrations at Kapako in both the main channel and the floodplain
pools recorded during the wet season are representative of diluting flows of precipitation.
At Popa Rapids, the conductivity was higher in the backstream site than the mainstream
during the low flow period and was recorded at 32.7 µS/cm. In the high flow season the
mainstream conductivity was slightly higher than the backstream site which was 40.8 µS/cm.
The early flash floods and increase in erosion is the explanation for this increase in
conductivity measurements in the mainstream.

5.2.5 Turbidity
Site: Kapako / Mupini Floodplain and Popa Rapids Resort
Date of visit:
Dry Season ­ 20, 21 October 2008 and Wet Season ­ 06, 08 and 09 February 2009


Kapako n=1
Popa Rapids n=1
Dry season (Low flows):
Field Laboratory
Field Laboratory
Mainstream
4.03 NTU n/a
3.24 NTU 3.6 NTU
Backwaters / Floodplain
84.2 NTU n/a
10.5 NTU 22 NTU
pools
Wet Season (High flows):


Mainstream
3.89 NTU 3.2 NTU
3.17 NTU 2.0 NTU
Backwaters / Floodplain
14.9 NTU 11.4 NTU
3.42 NTU 2.2 NTU
pools
Table 5. 5: Field and Laboratory Turbidity measurements
The highest turbidity value (84 NTU) was as expected recorded in the floodplain pool at
Kapako during the low flow season. This can be a result from the decay of vegetation in
standing water. Much lower levels of suspended solids were recorded in floodplain pools in
the wet season, but values were still higher than in the mainstream.


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Lower turbidity readings (less than 10 NTU) were recorded in the mainstream of Kapako and
both the mainstream and backwater sites at Popa Rapids during both seasons. This trend
confirms the finding of the 1984 -1986 Limnological Baseline Study of the Okavango River,
that the waters of the river are generally clear (Bethune 1997).

5.2.6 Nutrients
Total Nitrogen
Site: Kapako / Mupini Floodplain and Popa Rapids Resort
Date of visit:
Dry Season ­ 20, 21 October 2008 and Wet Season ­ 06, 08 and 09 February 2009


Kapako Popa
Rapids
Dry season (Low flows):


Mainstream
Nitrate <0.5 mg / dm³
Nitrate <0.5 mg / dm³
NH4 0.02 mg / dm³
NH4 0.02 mg / dm³
K-N <0.5mg / dm³
K-N <0.5mg / dm³
Backwaters / Floodplain
Nitrate <0.5 mg / dm³
Nitrate <0.5 mg / dm³
pools
NH4 0.6 mg / dm³
NH4 0.04 mg / dm³
K-N 1.7 mg / dm³
K-N <0.6mg / dm³
Wet Season (High flows):


Mainstream
Nitrate <0.02 mg / dm³
Nitrate <0.02 mg / dm³
NH4 0.2 mg / dm³
NH4 <0.2 mg / dm³
K-N <0.2mg / dm³
K-N <0.2mg / dm
Backwaters / Floodplain
Nitrate <0.02 mg / dm³
Nitrate <0.02 mg / dm³
pools
NH4 <0.2 mg / dm³
NH4 0.4 mg / dm³
K-N <0.2mg / dm³
K-N <0.2mg / dm
Table 5. 6: Laboratory Total Nitrogen measurements
Total Phosphates


Kapako Popa
Rapids
Dry season (Low flows):


Mainstream
<0.2 mg/dm³
<0.2 mg/dm³
Backwaters / Floodplain
0.3 mg/dm³
0.2 mg/dm³
pools
Wet Season (High flows):


Mainstream <0.2
mg/dm³
<0.2 mg/dm³
Backwaters / Floodplain
<0.2 mg/dm³
<0.2 mg/dm³
pools
Table 5. 7: Laboratory Total Phosphates measurements
The nutrients in the waters of the Okavango River were very low or undetectable, as was
expected. Especially during the wet season, there was no difference in the undetectable
nutrient concentrations in both the mainstream and the backwater of both sites.
A slightly higher concentration of total nitrogen was recorded in the isolated floodplain pool at
Kapako during the dry season. The total phosphates were also mostly undetectable during


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EFA Namibia Water Quality
the wet season at both sites with a slightly higher concentration in the Kapako floodplain pool
during the dry season.

The nutrient richness or trophic level of the Okavango River is therefore classified as
oligotrophic in the wet season since all the recorded N03-N values were less than 0.3 mg/
dm³ ( Massachusetts Water Watch Partnership) in the mainstream and backwater sites.
In the dry season a slight increase in nutrient concentration of less than 0.5 mg/ dm³ is
measured in the mainstream of both sites, suggesting a mesotrophic state. The backstream
and floodplain pools indicate a temporary eutrophic state with nutrient levels higher than 1.5
mg/ dm³.



5.2.7 Chlorophyll a
Site: Kapako / Mupini Floodplain and Popa Rapids Resort
Date of visit:
Dry Season ­ 20, 21 October 2008 and Wet Season ­ 06, 08 and 09 February 2009


Kapako Popa
Rapids
Dry season (Low flows):


Mainstream 0.69µg/
0.92µg/

Backwaters / Floodplain
8.60µg/ 0.69
µg/

pools
Wet Season (High flows):


Mainstream 0.11µg/

0.23 µg/
Backwaters / Floodplain
0.11µg/ , 0.69µg/ in shallow 0.34µg/
pools
pool about 8m from riverbank
Table 5. 8:Laboratory Chlorophyll a measurements
The chlorophyll a concentrations recorded in the river during the dry and wet seasons at both
study sites were very low, thus showing an oligotrophic system. Oligotrophic systems
typically have an average value of 1.7 mg/m³ with the most common values in the range of
0.3 ­ 4.5 mg/m³ whereas a eutrophic river system often has chlorophyll a concentrations
averaging about 14 mg/m³ or higher (Wetzel (1983). As with the nutrients, a slight peak was
observed at the isolated floodplain pool during the dry season.

Slightly higher concentrations were recorded during both seasons, for mainstream samples
after Cuito / Okavango confluence ­ Popa Rapids compared to Kapako


5.3 A summary of present understanding of the predicted responses of all water
quality indicators to potential changes in the flow regime

The following tables indicate predicted responses, if at all by the indictors to changes in flow


32

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EFA Namibia Water Quality
5.3.1 Indicator (pH) Predicted response to possible changes in the flow regime of pH in the Okavango River ecosystem
Confidence in
Question
prediction (very
Season
Possible flow change
Predicted response of indicator
number
low, low, medium,
high)
Onset is earlier or later than
Nil
1

natural
Dry Season
Water levels are higher or

2

lower than natural
3
Extends longer than natural
Nil

Duration is longer or shorter

4
than natural - i.e. hydrograph

Transition 1
is steeper or shallower
Flows are more or less
Addition of organic matter during high flow periods can reduce pH
5
Medium
variable than natural
Onset is earlier or later than
Nil
6
natural ­ synchronisation with

Flood
rain may be changed
season
Natural proportion of different
Nil
7

types of flood year changed
Onset is earlier or later than
Nil
8

natural
Transition 2
Duration is longer or shorter
Nil
9
than natural ­ i.e. hydrograph

is steeper or shallower



33

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EFA Namibia Water Quality
5.3.2 Indicator (Temperature) Predicted response to possible changes in the flow regime of Temperature in the Okavango River ecosystem
Confidence in
Question
prediction (very
Season
Possible flow change
Predicted response of indicator
number
low, low, medium,
high)
Onset is earlier or later than

1

natural
Water levels are higher or
The waters are well mixed and the pools too shallow to stratify.
2
Dry Season
medium
lower than natural
Extended higher temperatures during dry season lowers oxygen content and can make
3
Extends longer than natural
medium
contaminants more toxic
Duration is longer or shorter
Nil
4
than natural - i.e. hydrograph
low
Transition 1
is steeper or shallower
Flows are more or less
Nil
5
low
variable than natural
Onset is earlier or later than
Nil
6
natural ­ synchronisation with
low
Flood
rain may be changed
season
Natural proportion of different
Nil
7
low
types of flood year changed
Onset is earlier or later than
Nil
8
low
natural
Transition 2
Duration is longer or shorter
Nil
9
than natural ­ i.e. hydrograph
low
is steeper or shallower


34

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EFA Namibia Water Quality
5.3.3 Indicator (Dissolved Oxygen) Predicted response to possible changes in the flow regime of Dissolved Oxygen in the Okavango River
ecosystem
Confidence in
Question
prediction (very
Season
Possible flow change
Predicted response of indicator
number
low, low, medium,
high)
Onset is earlier or later than
Nil
1
Low
natural
Dry Season
Water levels are higher or
Nil
2
Low
lower than natural
3
Extends longer than natural
Decrease in oxygen concentration
medium
Duration is longer or shorter
Nil
4
than natural - i.e. hydrograph

Transition 1
is steeper or shallower
Flows are more or less
Nil
5

variable than natural
Onset is earlier or later than
Nil
6
natural ­ synchronisation with

Flood
rain may be changed
season
Natural proportion of different
Nil
7

types of flood year changed
Onset is earlier or later than
Nil
8

natural
Transition 2
Duration is longer or shorter
Nil
9
than natural ­ i.e. hydrograph

is steeper or shallower



35

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EFA Namibia Water Quality
5.3.4 Indicator ( Conductivity) Predicted response to possible changes in the flow regime of Conductivity in the Okavango River ecosystem
Confidence in
Question
prediction (very
Season
Possible flow change
Predicted response of indicator
number
low, low, medium,
high)
Onset is earlier or later than
Nil
1
Low
natural
Water levels are higher or
Nil
2
Dry Season
Low
lower than natural
Conductivity may increase with increasing evaporation and decomposition especially in
3
Extends longer than natural
medium
floodplain pools
Duration is longer or shorter
Longer period of change may lead to decreases conductivity
4
than natural - i.e. hydrograph
Low
Transition 1
is steeper or shallower
Flows are more or less
Nil
5
Low
variable than natural
Onset is earlier or later than
Nil
6
natural ­ synchronisation with
Low
Flood
rain may be changed
season
Natural proportion of different
Nil
7
Low
types of flood year changed
Onset is earlier or later than
Nill
8
Low
natural
Transition 2
Duration is longer or shorter
Nil
9
than natural ­ i.e. hydrograph
Low
is steeper or shallower



36

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EFA Namibia Water Quality

5.3.5 Indicator (Turbidity) Predicted response to possible changes in the flow regime of Turbidity in the Okavango River ecosystem
Confidence in
Question
prediction (very
Season
Possible flow change
Predicted response of indicator
number
low, low, medium,
high)
Onset is earlier or later than
Nil
1
Medium
natural
Dry Season
Water levels are higher or
Nil
2
Medium
lower than natural
3
Extends longer than natural
Higher turbidity as a result of pollution, especially in floodplain pools
Medium
Duration is longer or shorter
If hydrograph gets steeper, there will be changes in turbidity because of flushing
4
than natural - i.e. hydrograph
Medium
Transition 1
is steeper or shallower
Flows are more or less
Nil
5
Medium
variable than natural
Onset is earlier or later than
Nil
6
natural ­ synchronisation with
Medium
Flood
rain may be changed
season
Natural proportion of different
Considerable addition of sediments can increase turbidity
7
Medium
types of flood year changed
Onset is earlier or later than
Nil
8

natural
Transition 2
Duration is longer or shorter
Increased turbidity due to sediment addition may increase acidity and threaten aquatic life
9
than natural ­ i.e. hydrograph
Medium
is steeper or shallower



37

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EFA Namibia Water Quality
5.3.6 Indicator ( Nutrients) Predicted response to possible changes in the flow regime of Total Nitrogen and Total Phosphorous in the Okavango
River ecosystem
Confidence in
Question
prediction (very
Season
Possible flow change
Predicted response of indicator
number
low, low, medium,
high)
Onset is earlier or later than
Nil
1
Low
natural
Dry Season
Water levels are higher or
Nil
2
Low
lower than natural
3
Extends longer than natural
Concentrations can reach toxic levels
Medium
Duration is longer or shorter
Nil
4
than natural - i.e. hydrograph
Low
Transition 1
is steeper or shallower
Flows are more or less
Less flushing can lead to increased nutrient concentration and eutrophication
5
Medium
variable than natural
Onset is earlier or later than
Nil
6
natural ­ synchronisation with
Medium
Flood
rain may be changed
season
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
Nil
9
than natural ­ i.e. hydrograph
Medium
is steeper or shallower



38

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EFA Namibia Water Quality
5.3.7 Indicator (Chlorophyll a) Predicted response to possible changes in the flow regime of Chlorophylll a in the Okavango River ecosystem
Confidence in
Question
prediction (very
Season
Possible flow change
Predicted response of indicator
number
low, low, medium,
high)
Onset is earlier or later than
Nil
1

natural
Dry Season
Water levels are higher or
Nil
2

lower than natural
3
Extends longer than natural
Nil

Duration is longer or shorter
Nil
4
than natural - i.e. hydrograph

Transition 1
is steeper or shallower
Flows are more or less
Nil
5

variable than natural
Onset is earlier or later than
Nil
6
natural ­ synchronisation with

Flood
rain may be changed
season
Natural proportion of different
Nil
7

types of flood year changed
Onset is earlier or later than

8

natural
Transition 2
Duration is longer or shorter

9
than natural ­ i.e. hydrograph

is steeper or shallower




39

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EFA Namibia Water Quality
5.4 Conclusion
After reviewing literature and conducting the physiochemical quality survey for the
two Environmental Flow Assessment (EFA) sites, it is clear that the water quality of
this system remains very good. Although there is not a very wide range of detailed
water quality surveys for the Namibian section of the river, the existing data provided
a stable baseline and the water quality results obtained for this EFA confirmed the
state of affairs for the system. However, there is a gap pertaining to information about
chlorophyll a concentrations in this river.

The very low or undetectable nutrient concentrations in the river system or the
inadequacy of the methods used to measure these is also a major area that needs
future in depth investigations, in order to establish the exact nature and status of
nutrient concentrations as well as to predict their responses to the different flow
regimes of the system.




40

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EFA Namibia Water Quality
6. FLOW-RESPONSE RELATIONSHIPS FOR USE IN THE OKAVANGO EF-DSS
The response curves were developed during a workshop held in Windhoek from 30
March 2009 to 04 April 2009. The final Respose Curves from all the disciplines are
captured on a CD which is attached to this report.




41

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EFA Namibia Water Quality
7. REFERENCES
1. Bethune S, 1987 -The Limnological Baseline Survey of the Okavango River 1984 - 1986
2. Charles Hocutt, 1997 - The UNDP study - Maryland University
3. Bethune S, 1991 ­ Kavango River Wetlands
4. Clinton Hay et al, 2000 - Fish populations, gill net selectivity and artisanal fisheries in the
Okavango River
5. Fiona Trewby, 2003 - The effect of Land-use / Land Cover Change on the Water Quality
of the Okavango River, Namibia
6. Mendelsohn, J & Obeid S, 2003 ­ Sand and Water, A profile of the Okavango River
7. Mendelsohn, J & Obeid S, 2004 ­ Okavango River, The flow of a lifeline
8. Schemel L.E et al , 2004 ­ Hydrologic variability, water chemistry and phytoplankton
biomass in a large floodplain of the Sacramento River, CA, USA
9. Jafet Andersson, 2006 - Land Cover Change in the Okavango River Basin
10. www.riverkeepers.org/pdf/water_quality_manual01.pdf - Red River Basin Water
Quality Monitoring Volunteer Manual
11 http://www.jacksonbottom.org/waterquality_concepts.htm - Water Quality Concepts
12. http://www.lcra.org/water/quality/crwn/indicators.html - Water Quality Indicators
13. NSW Government No 11 ­ Integrating water quality and river flow objectives in water
sharing plans
14. Nisson C & Renöfält , 2008 ­ Linking Flow Regime and Water Quality in Rivers: a
Challenge to Adaptive Catchment Management
15. http://www.umass.edu/tei/mwwp/factsheets.html - Massachusetts Water Watch
Partnership Fact Sheets
16. Wetzel R.G, 1983 ­ Limnology. Philadelphia, W.B. Saunders Co., 767pp



42

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EFA Namibia Water Quality
APPENDIX A: RAW DATA FOR KAPAKO FLOODPLAIN ­ DRY SEASON

DRY SEASON
KAPAKO FLOODPLAIN

MAINSTREAM

Origin


Kavango Region,Mupini/Kapako Floodplain




Description
Water from main channel(EFA site)













S


17o51.954





E
19o34.805





Date of sampling

2008/10/20





Date received

2008/10/28





DWA number

7162




Test item number

08/7162











Parameter

Value
Unit General
standard
















Total Dissolved Solids (det.)
79

mg/dm3











Nitrate as N
<0.5

mg/dm3


Ammonia Nitrogen as N
0.02

mg/dm3
10
Kjeldahl Nitrogen as N
<0.5

mg/dm3











Total Phosphate as P
<0.2

mg/dm3






















Physical on site measurements:


pH


7.99








Temperature
26.7°C






Dissolved Oxygen
7.06mg/






Electrical Conductivity 47.8S/cm






Turbidity

4.03 NTU











Chlorophyll a concentration:

0.69 µg/l



43

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EFA Namibia Water Quality





FLOODPLAIN POOL
Origin


Kavango Region,Mupini/Kapako Floodplain





Description
Smallpool in Floodplain(EFA site)















S


17o57.055






E
20o28.387






Date of sampling

2008/10/20






Date received

2008/10/28






DWA number

7160




Test item number

08/7160












Parameter

Value

Unit

















Total Dissolved Solids (det.)
122

mg/dm3












Nitrate as N
<0.5

mg/dm3


Ammonia Nitrogen as N
0.6

mg/dm3


Kjeldahl Nitrogen as N
1.7

mg/dm3












Total Phosphate as P
0.3

mg/dm3














Physical on site measurements:

pH


7.64






Temperature
27.9°C




Dissolved Oxygen
9.76mg/




Electrical Conductivity 175.5S/cm




Turbidity

84.2 NTU


Chlorophyll a concentration:
8.60 µg/l





44

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EFA Namibia Water Quality
APPENDIX B: RAW DATA FOR KAPAKO FLOODPLAIN ­ WET SEASON

WET SEASON
KAPAKO FLOODPLAIN

MAINSTREAM

Origin

Kavango Region, Kapako Village




Description


Mainstream of river













S


17o51,936'





E

19o34,819'





Date of sampling

9/2/2009





Date received

12/2/2009





DWA number

7304





Test item number

7304











Parameter

Value

Unit







Ammonium as N
<0.02

mg/dm3
Kjeldahl Nitrogen as N
0.2

mg/dm3
Total Phosphate as P <0.2

mg/dm3













Physical on site measurements:
pH


7.1






Temperature
27.1°C




Dissolved Oxygen
4.91 mg/




Electrical Conductivity 35.2S/cm




Turbidity

3.89 NTU


Chlorophyll a concentration:
0.11 g/l








45

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EFA Namibia Water Quality


FLOODPLAIN POOL


Origin


Kavango Region, Kapako Floodplain




Description

Floodplain pool - sampled at 15m from riverbank





at depth of 2.5m




S


17o52,661'




E
19o34,981'




Date of sampling

8/2/2009




Date received

12/2/2009




DWA number

7303




Test item number

7303










Parameter

Value

Unit







Ammonium as N
<0.02

mg/dm3
Kjeldahl Nitrogen as N
<0.2

mg/dm3
Total Phosphate as P <0.2

mg/dm3













Physical on site measurements:

pH


6.77





Temperature

27.4°C





Dissolved Oxygen

2.15 mg/L





Electrical Conductivity
37.5S/cm





Turbidity

14.9 NTU


Chlorophyll a concentration:
0.11 g/l








46

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EFA Namibia Water Quality
APPENDIX C: RAW DATA FOR POPA RAPIDS ­ DRY SEASON

DRY SEASON POPA
RAPIDS
MAINSTREAM Full Group II analyses:
Kavango
Region,Po
pa Falls
Communit
Origin


y
Camp


Descripti
on
water from rapids behind community camp (past the prison) (EFA site)



S


18o06.734








E


21o34.968








2008/10/2
Date of sampling

1








2008/10/2
Date received

8








DWA number

7163



Recommended max. limits

Test item number

08/7163



(according to tender specification)

Livestoc









k-

Classificati
Grou
Grou
Grou
Parameter

Value
me
Unit
on
p A
p B
p C
watering












5.5 -
4.0-
P H

8.0

A
6-9
9.5
11.0 4.0-11.0
Conductivity
3.3
mS/m A 150 300 400


mg/d
TDS (determined)
58
m3

6000

Turbidity
3.6
NTU B 1 5 10
Colour
<10
Pt A 20

0.0
mg/d
Sulphate as SO4
<1
2
m3 A 200 600 1200 1500
0.0
mg/d
Chloride as Cl
1
3
m3 A 250 600 1200 3000
0.0
mg/d
Fluoride as F
<0.1
1
m3 A 1.5 2.0 3.0 6.0
0.0
mg/d
Nitrate as N
<0.5
4
m3 A 10 20 40 100
0.0
mg/d
Nitrite as N
<0.1
1
m3




10

mg/d
Silica as SiO2
13
m3






P-Alkalinity as
mg/d
CaCO3
0
m3






T-Alkalinity as
0.3
mg/d
CaCO3
<20
0
m3






mg/d
T-Hardness as CaCO3, cal.
17
m3 A 300 650 1300


0.2
mg/d
Calcium as Ca
5
5
m3 A 150 200 400 1000
0.0
mg/d
Magnesium as Mg
1
8
m3 A 70 100 200 500
0.0
mg/d
Sodium as Na
2
9
m3 A 100 400 800 2000
0.0
mg/d
Potassium as K
1
3
m3 A 200 400 800


mg/d
Iron as Fe
0.1
m3 A 0.1 1 2 10
mg/d
Manganese as Mn
<0.01
m3 A
0.05 1 2
10


47

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EFA Namibia Water Quality












Langelier Index

-1.5
corrosive

>0=scaling, <0=corrosive, 0=stable

<6.5=scaling, >7,5=corrosive, >6.5 and
Ryznar Index

11.0
corrosive

<7.5=stable
Corrosivity ratio

0.2
no corrosive properties
Applies to water in the pH range 7-8

Stability pH

9.5



which also contains dissolved oxygen








ratios <0.2 no corrosive properties








ratios >0.2 increasing corrosive tendency












Remark:
Overall classification of water considering only constituents that have been tested for:


Group B, good quality water








Nutrient analyses:
Parameter


Value


Unit







Total Dissolved Solids (det.)
58

mg/dm3







Nitrate as
N
<0.5
mg/dm3
Ammonia Nitrogen as N
0.02
mg/dm3
Kjeldahl Nitrogen as N
<0.5
mg/dm3







Total Phosphate as P
<0.2
mg/dm3


Physical on site measurements:
pH


7.88





Temperature

28.7°C





Dissolved Oxygen

7.01mg/L





Electrical Conductivity
28.3S/cm





Turbidity

3.24 NTU






Chlorophyll a concentration:
0.92 g/l









48

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EFA Namibia Water Quality

BACKSTREAM AT CAMPSITE
Full Group II analyses:
Kavango Region,
Origin


Popa Falls Resort







Backstream at
Description
campsite of Lodge


















Lat










Long










Date of
sampling ######







Date received

######







DWA number

7301



Recommended max. limits
Test item
number
7301



(according to tender specification)





Livestock-
Group Group Group
Parameter
Value me
Unit
Classification
A
B
C watering











5.5 -
4.0-
p H

7.9

A
6-9
9.5
11.0 4.0-11.0
Conductivity
4.4
mS/m
A
150 300 400

TDS
(determined)
80
mg/dm3

6000
Turbidity
2.2
NTU
B 1 5 10
Colour
24.0
Pt B 20

Sulphate as SO4
2.9
0.06
mg/dm3 A 200 600 1200 1500
Chloride as Cl
1
0.03
mg/dm3 A 250 600 1200 3000
Fluoride as F
<0.1
0.01
mg/dm3

1.5 2.0 3.0 6.0
Nitrate as N
<0.5
0.04
mg/dm3 A 10 20 40 100
Nitrite as N
<0.02
0.00
mg/dm3




10
Silica as SiO2
16
mg/dm3





P-Alkalinity as
CaCO3
0
mg/dm3





T-Alkalinity as
CaCO3
21
0.42
mg/dm3





T-Hardness as CaCO3,
cal.
0
mg/dm3

300 650 1300

Calcium as Ca

0.00
mg/dm3

150 200 400 1000
Magnesium as
Mg

0.00
mg/dm3

70 100 200 500
Sodium as Na

0.00
mg/dm3

100 400 800 2000
Potassium as K

0.00
mg/dm3

200 400 800

Iron as
Fe
mg/dm3

0.1 1 2
10
Manganese as
Mn

mg/dm3

0.05 1 2
10











Langelier Index

#NUM!
####

>0=scaling, <0=corrosive, 0=stable
<6.5=scaling, >7,5=corrosive, >6.5 and
Ryznar Index

#NUM!
####

<7.5=stable
Corrosivity ratio

0.2
increasing corrosive tendency
Applies to water in the pH range 7-8
Stability pH

#NUM!



which also contains dissolved oxygen







ratios <0.2 no corrosive properties







ratios >0.2 increasing corrosive tendency



49

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EFA Namibia Water Quality


Nutrient analyses:
Parameter

Value


Unit







Total Dissolved Solids (det.)
59

mg/dm3







Nitrate as N
<0.5
mg/dm3
Ammonia Nitrogen as N
0.04
mg/dm3
Kjeldahl Nitrogen as N
0.6
mg/dm3







Total Phosphate as
P
0.2
mg/dm3

Physical on site measurements:
pH


7.69





Temperature

25.4°C





Dissolved Oxygen

6.72 mg/L





Electrical Conductivity
32.7S/cm





Turbidity

10.5 NTU


Chlorophyll a concentration:
0.69 g/l
















50

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EFA Namibia Water Quality

APPENDIX D: RAW DATA FOR POPA RAPIDS ­ WET SEASON

WET SEASON POPA
RAPIDS

MAINSTREAM
Full Group II Analyses:

Kavango Region,
Origin


Popa Falls








Mainstream behind
Community
Description Campsite











(EFA site)








Lat


18°06.734








Long


21°34.968








Date of
sampling ######








Date received

######








DWA number

7300



Recommended max. limits

Test item
number
7300



(according to tender specification)






Livestock-

Group Group Group
Parameter


Value
me
Unit
Classification
A
B
C watering













5.5 -
4.0-
p H

7.9

A
6-9
9.5
11.0 4.0-11.0
Conductivity
4.4
mS/m
A
150 300 400


TDS
(determined)
104
mg/dm3

6000

Turbidity 2.0
NTU
B 1 5 10
Colour 24.0
Pt B 20

Sulphate as
SO4
2.6 0.05
mg/dm3 A 200 600 1200 1500
Chloride as Cl
1 0.03
mg/dm3 A 250 600 1200 3000
Fluoride as F
<0.1 0.01
mg/dm3

1.5 2.0 3.0 6.0
Nitrate as N
<0.5 0.04
mg/dm3 A 10 20 40 100
Nitrite as
N
<0.02 0.00
mg/dm3

10

Silica as SiO2
16
mg/dm3






P-Alkalinity as
CaCO3
0
mg/dm3






T-Alkalinity as
CaCO3
21 0.42
mg/dm3






T-Hardness as
CaCO3, cal.
0
mg/dm3

300 650 1300


Calcium as Ca
0.00
mg/dm3

150 200 400 1000
Magnesium as
Mg
0.00
mg/dm3

70 100 200 500
Sodium as Na
0.00
mg/dm3

100 400 800 2000
Potassium as K
0.00
mg/dm3

200 400 800


Iron as Fe


mg/dm3

0.1 1 2 10
Manganese as
Mn

mg/dm3

0.05 1 2
10












Langelier Index

#NUM!
####

>0=scaling, <0=corrosive, 0=stable

<6.5=scaling, >7,5=corrosive, >6.5 and
Ryznar Index

#NUM!
####

<7.5=stable


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EFA Namibia Water Quality
Corrosivity ratio

0.2
no corrosive properties
Applies to water in the pH range 7-8

Stability
pH
#NUM!



which also contains dissolved oxygen








ratios <0.2 no corrosive properties








ratios >0.2 increasing corrosive tendency













Nutrient analyses:

Parameter

Value


Unit







Ammonium as N
<0.02

mg/dm3
Kjeldahl Nitrogen as N
0.2 mg/dm3
Total Phosphate as P
<0.2
mg/dm3


Physical on site measurements:
pH


7.69





Temperature

27.4°C





Dissolved Oxygen

6.63 mg/L





Electrical Conductivity
41.4S/cm





Turbidity

3.17 NTU


Chlorophyll a concentration:
0.23 g/l

















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EFA Namibia Water Quality
BACKSTREAM AT CAMPSITE
Full Group II analyses:
Kavango Region,
Origin

Popa Falls Resort








Backstream at
Description campsite of Lodge




















Lat


18º07.310








Long


20º34.970








Date of sampling
06/02/2009








Date received
12/02/2009








DWA number
7301



Recommended max. limits

Test item number
7301



(according to tender specification)






Livestock-

Group Group Group
Parameter

Value
me
Unit
Classification
A
B
C watering













5.5 -
4.0-
p H

7.9

A
6-9
9.5
11.0 4.0-11.0
Conductivity
4.4
mS/m
A
150 300 400


TDS (determined)
80
mg/dm3

6000

Turbidity
2.2
NTU
B
1 5 10
Colour
24.0
Pt
B
20

Sulphate as SO4
2.9 0.06
mg/dm3 A 200 600 1200 1500
Chloride as Cl
1 0.03
mg/dm3 A 250 600 1200 3000
Fluoride as
F
<0.1
0.01
mg/dm3

1.5 2.0 3.0 6.0
Nitrate as N
<0.5
0.04
mg/dm3 A 10 20 40 100
Nitrite as N
<0.02
0.00
mg/dm3




10

Silica as SiO2
16
mg/dm3






P-Alkalinity as
CaCO3
0
mg/dm3






T-Alkalinity as
CaCO3
21 0.42
mg/dm3






T-Hardness as
CaCO3, cal.
0
mg/dm3

300 650 1300


Calcium as Ca
0.00
mg/dm3

150 200 400 1000
Magnesium as Mg
0.00
mg/dm3

70 100 200 500
Sodium as Na
0.00
mg/dm3

100 400 800 2000
Potassium as K
0.00
mg/dm3

200 400 800


Iron as Fe

mg/dm3

0.1 1 2
10
Manganese as Mn

mg/dm3

0.05 1 2
10












Langelier Index
#NUM!
####

>0=scaling, <0=corrosive, 0=stable

Ryznar
<6.5=scaling, >7,5=corrosive, >6.5 and
Index
#NUM!
####

<7.5=stable
Corrosivity ratio
0.2
increasing corrosive tendency
Applies to water in the pH range 7-8

Stability pH

#NUM!



which also contains dissolved oxygen







ratios <0.2 no corrosive properties







ratios >0.2 increasing corrosive tendency






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EFA Namibia Water Quality

Nutrient analyses:

Parameter


Value


Unit







Ammonium as N
<0.02

mg/dm3
Kjeldahl Nitrogen as N
0.4
mg/dm3
Total Phosphate as P
<0.2
mg/dm3

Physical on site measurements:

pH


7.62





Temperature

27.5°C





Dissolved Oxygen

6.50 mg/L





Electrical Conductivity
40.8S/cm





Turbidity

3.42 NTU








Chlorophyll a concentration:
0.34 g/l




















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EFA Namibia Water Quality
APPENDIX E: KAPAKO SITE A MAP INDICATING WATER DEPTH
READINGS FOR WATER QUALITY SAMPLING IN MAINSTREAM DURING
WET SEASON


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APPENDIX F: KAPAKO SITE B MAP INDICATING WATER DEPTH READINGS
FOR WATER QUALITY SAMPLING IN A POOL DURING WET SEASON




57

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APPENDIX G: KAPAKO SITE A MAP INDICATING WATER DEPTH READINGS
FOR WATER QUALITY SAMPLING IN THE MAINSTREAM DURING DRY SEASON




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APPENDIX H: POPA RAPIDS SITE B MAP INDICATING WATER DEPTH
READINGS FOR WATER QUALITY SAMPLING IN THE MAINSTREAM BEHIND
COMMUNITY CAMP IN THE WET SEASON








































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APPENDIX I: POPA RAPIDS SITE A MAP INDICATING WATER DEPTH
READINGS FOR WATER QUALITY SAMPLING IN THE BACKSTREAM AT
CAMPING SITE IN THE WET SEASON






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APPENDIX J: POPA RAPIDS SITE B MAP INDICATING WATER DEPTH
READINGS FOR WATER QUALITY SAMPLING IN THE MAINSTREAM BEHIND
THE COMMUNITY CAMP IN THE DRY SEASON




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APPENDIX K: POPA RAPIDS SITE A MAP INDICATING WATER DEPTH
READINGS FOR WATER QUALITY SAMPLING IN A BACKSTREAM AT THE
CAMPING SITE IN THE DRY SEASON



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EFA Namibia Water Quality

The Okavango River Basin Transboundary Diagnostic Analysis
Technical Reports

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

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

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


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


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


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


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


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

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


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

Beuster,
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)


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EFA Namibia Water Quality


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 &
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


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EFA Namibia Water Quality
Series
Cubango: Relatório Final

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


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


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

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

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


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

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


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

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


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

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


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

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

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


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


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


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


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

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



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