African Journal of Tropical Hydrobiology and Fisheries 15: 25-36 (2017)

© Lake Victoria Fisheries Organization

Effects of the Bujagali Hydropower Project on Major Physico-Chemical Parameters of

the Upper Victoria Nile Water in Uganda, East Africa

WANDA FRED MASIFWA1*, AMONDITO BRENDA1, MOUREEN MATUHA1, HENRY OCAYA1,

GODFREY MAGEZI1
1
National Fisheries Resources Research Institute (NaFIRRI), Plot 39-45 Nile Crescent, P. O. Box 343, Jinja,
Uganda.

*Corresponding author e-mail: mwandaless2009@gmail.com

Abstract
The Bujagali hydropower project is a 250 megawatt facility that was set up to alleviate power shortages in
Uganda. The project was perceived to have negative effects on major physico-chemical characteristics of the
upper Victoria Nile water. Key water physico-chemical parameters monitored biannually in April and
September from 2006 to 2015 at the upstream and downstream transects and in the reservoir were dissolved
oxygen, pH, temperature, TSS, oil/grease, conductivity and water clarity. Triplicate water samples for TSS plus
oil and grease were analyzed from the laboratory following standard procedures. The rest of the parameters
were determined in-situ using a CTD profiler. Reference for environmental compliance was made to NEMA
and EU/WHO environmental discharge standards. All parameters were within acceptable limits i.e. dissolved
oxygen (>3 mgl-1); temperature (20 to 35 °C); TSS (<100 mgl-1); oil and grease (<10 mgl-1), and pH (6 to 8.5).
Thus, the Bujagali hydropower project had so far had no significant negative effects on the major
physico-chemical parameters of the upper Victoria Nile water. Continued monitoring is recommended to enable
detection of any deviations, if any, from the observed trends.

Keywords: Bujagali, Environmental standards, Hydropower, Physico-chemical parameters

Introduction 1992; Bullock and Acreman, 2003; Narasimhan 2009;

From the beginning of the twentieth century, Seager et al., 2010; Wild and Liepert, 2010; Zhou et
technological progress and a greater need for energy, al., 2011). While there are many benefits to using
water supply, and flood control have motivated an hydropower as a renewable source of energy, there are
increase in the number of hydropower plants and dams also environmental impacts that relate to how a
constructed all over the world (Horlacher et al., 2012). hydropower project affects a river’s ecosystem and
The world over, hydropower has traditionally been associated habitats (Baxter, 1977; Anderson et al.,
considered environmentally friendly because it 2006; Klaver et al., 2007; Rehn, 2009; Räsänen et al.
represents a clean and renewable source of energy 2012). For example, reservoirs alter riverine dynamics
(Birgitta et al., 2010; Kothari et al., 2010; Panwar et and can impact the water quality of the natural system
al., 2011; Abanda, 2012). This is because production (Ashby, 2009).
of this form of energy does not significantly contribute Hydropower dams may be a significant source of
to acid rain that results into alteration of water quality water pollution (Berkun, 2010; Zhang et al., 2014;
characteristics. This form of energy is renewable in Chen et al., 2015). Various scholars have long
that the hydrologic cycle circulates water back to acknowledged that hydropower dams cause ecosystem
wetlands, rivers, streams, lakes and oceans (Chahine, pollution by altering the temperature and other
25
physico-chemical characteristics of water that is Water flowing out of Lake Victoria passes through the
impounded behind and released through dams, Nalubaale and Kiira Hydropower dams which are
harming the biological integrity of river ecosystems upstream of the Bujagali Dam. The dam created a
(Gore et al., 1989; Hasler et al., 2009; Rehn, 2009; reservoir that extends upstream to the tailrace of the
Xiaoyan et al., 2010; Pandit and Grumbine, 2012; Li Nalubaale and Kiira facilities. The Bujagali
et al., 2013; Skalak et al., 2013). Worse still, the Hydropower Dam is therefore part of the upstream
cumulative impacts of multiple hydropower dams are series of Nalubaale and Kiira dams. Effects of the
often much greater than the simple sum of their direct hydropower project on major physico-chemical
impacts (Gergel, 2002; Berkun, 2010; Birkel et al., parameters was the thrust of this study because these
2014). A series of dams can severely impact an entire parameters show immediate responses to any form of
watershed (Kibler and Tullos, 2013), even if each of perturbation right from the time of project
the individual dams may have a relatively low impact implementation.
when considered in isolation. The extent of this
damage can be much greater when combined with a Materials and Methods
whole host of other threats to rivers such as poor water Bujagali Energy Limited (BEL) was constructed on
quality, a growing demand for scarce water, the section of the Victoria Nile that lies between the
encroaching urbanization, and poor land management upstream transect (Kalange-Makwanzi) and the
practices (Nel et al., 2007; Tockner et al., 2010). It downstream transect (Buyala-Kikubamutwe) (Figure
should also be noted that the main environmental 1). This section of the Victoria Nile was characterized
effect on the river system for hydropower operations is by strong waterfalls, rapids, rocky outcrops and river
the alteration of flow regime which affects the water bends. The hinterland along the banks of the study
quality and cause impacts on aquatic ecosystems area had been transformed by human activities from
(Bhatt and Khanal, 2012). the originally wooded savannah landscape to one
The Bujagali Hydropower Project is a scheme that dominated by small farm holdings of a variety of
was set up to create substantial benefits to Ugandans crops. Perennial crops especially coffee and bananas,
such as increased supply of reliable hydroelectricity and annual crops such as maize used to cover the river
and reduced power tariffs. The power plant and its banks and islands. Similarly in the more northerly
associated dam were constructed on Dumbell Island downstream sections, the river banks had been
which is approximately 8 kilometers downstream from transformed into sparse human settlements and small
where the river leaves Lake Victoria (Figure 1). holder farmer fields.
Construction of the dam and power house at Bujagali
started in June 2007 and was completed in 2012.

26
Figure 1: Map showing location of the hydropower project at Bujagali on River Nile in Uganda

The BEL reservoir is approximately 388 ha in surface year by sampling on a quarterly basis, but this was not
area comprising of the then existing 308 ha surface of feasible due to logistical constraints that dictated
the Victoria Nile, and 80 ha of newly inundated land limiting data collection to the months of April and
that is comparatively small as the reservoir water is September of each subsequent year. These two months
contained within the steeply incised banks of the river. however, only cover the rain seasons, thus missing out
The reservoir has a maximum depth of 30 m with a the dry season data that would probably reveal
mean depth of 9.3 m. This hydropower dam has a seasonality effects. Thus, data was collected
residence time of 16 hours and the reservoir’s daily biannually from 2006 to 2015 during the months of
fluctuation was between 2 and 2.5 m. The project site April and September from the upstream and
is in the zone characterized by a long wet season downstream of the reservoir (Figure 1). For each of
(February to May), a short dry season (June to July), a the two transects (upstream and downstream), there
short wet season (August to October) and a long dry were 153 samples i.e. 17 sampling events x 3 sites per
season (November to January). Originally, field data transect x 3 (triplicates). After completing and filling
collection was expected to cover all seasons in the the reservoir, collection of water physico-chemical

27
data from this reservoir commenced in April 2012. Oil and grease
Thus from the reservoir, there were 8 sampling events Water samples for oil and grease were collected in the
at 3 sites in triplicate, resulting into 72 samples. Major same way as those for TSS and a known volume
physico-chemical parameters were determined in three preserved in glass bottles using hydrochloric acid and
triplicates (i.e. east, middle & west of the river & kept on ice in a cool box. Preserved water samples
reservoir) in-situ at the sub-surface between 0.5 and were delivered the same day to the National Water and
1.0 m depth at each of the two transects, and Sewerage Corporation (NWSC) Laboratory in
integrated samples from the reservoir, using a CTD Kampala for analysis using the partio-gravimetric
profiler (Seabird Electronics Model 19-03). In total, method as described in Greenberg et al. (1992).
153 samplings (i.e. 3 sites per transect x 3 sub-samples The major objective of this study was therefore to
x 17 months) were done at each of the transects, and determine the effects of the Bujagali Hydropower
72 samplings (i.e. 3 sites x 3 sub-samples x 8 months) Project on the major physico-chemical parameters of
in the reservoir. Parameters determined in-situ using a the upper Victoria Nile water. Results from this study
CTD profiler were dissolved oxygen, pH, temperature were expected to guide management in case of need
and water conductance. Water clarity (or secchi depth) for mitigation against significant negative effects of
was also determined in-situ from the shaded side of the project on the water environment. It was hence
the canoe using a 25 cm diameter white Secchi Disc hypothesized that the BEL project would not have any
(Model KC Denmark A/S) following standard significant negative effects on major physico-chemical
methods. However, Total Suspended Solids (TSS) parameters of the water of the upper Victoria Nile.
plus oil and grease were determined in the laboratory
as detailed below. All samples were well labeled with Data Analyses
respect to site, transect and date of sampling. Data were imported from excel into SPSS Statistics
Data Editor Version 20.0, and analyzed using “Paired
Total suspended solids (TSS) Samples T-Test” for comparison of means. In all
Water samples for TSS were collected as an integrated analyses, the level of statistical significance was
sample from the water column using a 3 L Van Dorn determined at 95% (p = 0.05) Confidence Interval.
sampler (Wildlife Supply Company Model KC
Denmark A/S) from the respective transects. 1,000 ml Trends in major physico-chemical parameters are
of each sample was put in Nalgene plastic bottles for provided for the upstream and downstream transects
determination of TSS concentration. Final (April and September, 2006 to 2015), and for the
concentrations of TSS were determined by weight reservoir (April and September, 2012 to 2015) as
difference. Here, the initial weight of an oven dried compared with permissible environmental discharge
0.45 µm GF/C Whatman filter paper was obtained standards by Uganda’s National Environmental
before filtering a known volume of water. After Management Authority (NEMA, 1999), the World
filtration, the filter papers were oven dried for 1 hour Health Organization (WHO, 1993) and the European
at 105 ºC, left to cool to constant room temperature, Union (EU, 1998) (Table 1).
and reweighed. The weight difference per volume of
water filtered represented the concentration of TSS.

Table 1: NEMA, WHO and EU permissible environmental discharge standards

Parameter NEMA Standard1 WHO Standard2 EU Standard2

Water conductance (µS cm-1) - ≤250 ≤ 250
Dissolved oxygen (mgl-1) - - 5.0
pH 6.0 – 8.0 6.5 – 8.5 6.5 – 8.5
Temperature (°C) 20 - 35 - -
Water clarity (cm) - - -
TSS (mgl-1) ≤ 100 - -
Oil & Grease (mgl-1) ≤ 10 - -

28
 compared to the upstream transect (M = 5.80 mgl-1,
10
SD = .92), t(16) = 5.00, p < 0.05. However, there were
Upstream no significant differences between the upstream
9 Downstream
Reservoir
transect (M = 5.80 mgl-1, SD = 0.92) and the reservoir
8 Lower_NEMA Std (M = 6.06 mgl-1, SD =.68), t(7) = 0.31, p > 0.05; and
Dissolved Oxygen (mg/l)

7 between the reservoir (M = 6.06 mgl-1, SD = 0.68) and

6 the downstream transect (M = 7.01 mgl-1, SD = 0.89),
t(7) = 1.31, p > 0.05. At all sites, dissolved oxygen
5
concentrations were significantly higher, t(16), p <
4
0.05, compared to the minimum environmental
3 discharge standard of 3 mgl-1. Trends in pH (Figure 3)
2 were such that most of the sampling period other than
1
that in the reservoir in September 2015 whose mean
value was above the upper permissible limit, this
0
remained within the NEMA and WHO/EU permissible
Se 06

Ap 8
Se 09

Se 10

Se 11

Se 12

Se 13

Se 14

Ap 5
16
Ap 7

Ap 9

Ap 0

Ap 11

Ap 2

Ap 13

Ap 4
0

1
_0

_0

_1

_1

_1
range of 6 to 8.5 even before and after completion of
r_

r_
r_

r_

r_

r_

r_

r_

r_
r_
_

_
pt

pt

pt

pt

pt

pt

pt
Ap

Sampling Period the dam. Despite this, there were no significant

Figure 2: Trends in concentration of dissolved oxygen differences in pH between the upstream (M = 7.28, SD
compared to NEMA permissible lower limit = 0.47) and downstream (M = 7.43, SD = 0.49)
transects, t(16) = 1.29, p > 0.05; between the upstream
12 transect (M = 7.28, SD = 0.47) and the reservoir (M =
Upstream 7.60, SD = 0.66), t(7), = 1.33, p > 0.05; and between
Downstream
Reservoir the reservoir (M = 7.60, SD = 0.66) and the
10 Upper_NEMA Std
Lower_NEMA Std
downstream transect (M = 7.43, SD = .49), t(7) = 0.13,
p > 0.05.
8
pH

45
Upstream
6 Downstream
40 Reservoir
Upper_NEMA Std
Lower_NEMA Std
4
Temperature (°C)

35

2 30
Se 06

Ap 8
Se 09

Se 10

Se 11

Se 12

Se 13

Se 14

Ap 5
16
Ap 7

Ap 9

Ap 0

Ap 11

Ap 2

Ap 13

Ap 4
0

1
_0

_0

_1

_1

_1
r_

r_
r_

r_

r_

r_

r_

r_

r_
r_
_

_
pt

pt

pt

pt

pt

pt

pt
Ap

25
Sampling Period

20
Figure 3: Trends in pH compared to NEMA
permissible range
15
Se 06

Ap 8
Se 09

Se 10

Se 11

Se 12

Se 13

Se 14

Ap 5
16
Ap 7

Ap 9

Ap 0

Ap 11

Ap 2

Ap 13

Ap 4
0

1
_0

_0

_1

_1

_1
r_

r_
r_

r_

r_

r_

r_

r_

r_
r_
_

Results
pt

pt

pt

pt

pt

pt

pt
Ap

Figure 2 shows trends in average values of dissolved Sampling Period

oxygen. The lowest mean dissolved oxygen

concentration was 4.2 mgl-1at the upstream transect in Figure 4: Trends in water temperature compared to
April 2006 and was above the NEMA minimum NEMA permissible range
environmental standard of 3 mgl-1. There was a
significant difference in average dissolved oxygen
concentrations before and after completion of the dam,
with significantly higher concentration at the
downstream transect (M = 7.01 mgl-1, SD =0.89)
29
 Average values of water conductivity were below
110 the WHO/EU permissible discharge upper limit of 250
100
µS.cm-1, and were comparable to what was known for
90 Upstream unpolluted sites of Lake Victoria whose field data
Downstream
Reservoir
fluctuated between 90 and 130 µS.cm-1 (Wanda:
80
Upper_NEMA Std unpublished data). There were however, no significant
70
differences in water conductivity between the
TSS (mg/l)

60
upstream (M = 100.15 µS.cm-1, SD = 10.64) and
50
downstream (M = 101.89 µS.cm-1, SD = 11.58)
40 transects t(16), p > 0.05; between the upstream
30 transect (M = 100.15 µS.cm-1, SD = 10.64) and the
20 reservoir (M = 100.73 µS.cm-1, SD = 4.56), t(7), p >
10 0.05; and between the reservoir (M = 100.73 µS.cm-1,
0 SD = 4.56), and the downstream transect (M = 101.89
µS.cm-1, SD = 11.58), t(7), p > 0.05.
Se 06

Ap 8
Se 09

Se 10

Se 11

Se 12

Se 13

Se 14

Ap 5
16
Ap 7

Ap 9

Ap 0

Ap 11

Ap 2

Ap 13

Ap 4
0

1
_0

_0

_1

_1

_1
r_

r_
r_

r_

r_

r_

r_

r_

r_
r_
_

_
pt

pt

pt

pt

pt

pt

pt
Ap

Sampling Period Although there was no NEMA/EU/WHO

environmental standard for water column clarity, this
Figure 5: Trends in concentration of TSS compared to parameter was comparable to that of Lake Victoria’s
NEMA permissible upper limit unpolluted sites (Wanda: unpublished data). Water
clarity ranged between 1.3 and 2.4 m at the upstream;
Trends in average water temperature are shown in 1.3 and 2.5 m at the downstream; and 1.4 and 2.3 m in
Figure 4. Although water temperatures varied slightly the reservoir. A significant difference in mean water
among sites, mean values remained within the column clarity was noted between the upstream (M =
permissible NEMA range of 20 to 35°C. While minor 1.91 m, SD = 0.33) and downstream (M = 1.79 m, SD
variations were noted, there were no significant = 0.34) transects, t(17), p < 0.05, with the upstream
differences in water temperatures between the having a significantly higher mean value; and between
upstream (M = 25.88°C, SD = 0.72) and downstream the downstream transect (M = 1.79 m, SD = 0.34) and
(M = 26.13°C, SD = 0.74) transects, t(16) = 0.40, p > the reservoir (M = 1.84 m, SD = 0.34), t(7), p < 0.05,
0.05; between the upstream transect (M = 25.88°C, SD with the reservoir having a significantly higher water
= 0.72) and the reservoir (M = 25.95°C, SD = 0.74), column clarity. However, no significant differences in
t(7) = 1.57, p > 0.05; and between the reservoir (M = water column clarity were noted between the upstream
25.95°C, SD = 0.74) and the downstream transect (M transect (M = 1.91 m, SD = 0.33) and the reservoir (M
= 26.13°C, SD = 0.74), t(7) = 1.48, p > 0.05. While = 1.84 m, SD = .34), t(7), p = 0.05. Throughout the
this was so for water temperature, the concentration of sampling period, the mean concentrations of oil and
TSS showed minimal variability over the sampling grease were below the permissible NEMA upper limit
period and was far below the permissible upper of 10 mgl-1 and ranged between 0.0 and 0.60 mgl-1 at
NEMA environmental discharge standard of 100 mgl-1 the upstream transect; 0.0 and 0.90 mgl-1 at the
(Figure 5). No significant differences in TSS were downstream transect; and 0.08 and 0.23 mgl-1 in the
noted between the upstream (M = 3.08 mgl-1, SD = reservoir (Figure 6). The concentration of oil and
1.54) and downstream (M = 3.27 mgl-1, SD = 1.15) grease was however, significantly different between
transects, t(16) = 0.68, p > 0.05; and between the the upstream (M = 0.13 mgl-1, SD = 0.01) and the
upstream transect (M = 3.08 mgl-1, SD = 1.54) and the downstream (M = .24 mgl-1, SD = .06), t(16), p < 0.05;
reservoir (M = 3.52 mgl-1, SD = 1.19), t(7) = 2.04, p > and between the upstream transect (M = 13 mgl-1, SD
0.05. However, there was a significant different in the = .01) and the reservoir (M = .18 mgl-1, SD = 0.05),
concentration of TSS between the reservoir (M = 3.52 t(7), p < 0.05. Oil and grease concentration was
mgl-1, SD = 1.19) and the downstream transect (M = however, not significantly different between the
3.27 mgl-1, SD = 1.15), t(7) = 3.12, p < 0.05, with the upstream transect (M = 0.13 mgl-1, SD = 0.01) and the
reservoir having a significantly higher mean reservoir (M = 0.18 mgl-1, SD = 0.05), t(7), p > 0.05.
concentration of TSS.

30
 Water low in dissolved oxygen can “suffocate” some
12
aquatic organisms and make such water unfit for
various uses including human consumption. Dissolved
10
oxygen is also vital for bacteria-mediated break down
of organic detritus and pollution (Young et al., 2008).
Upstream
At all sites, dissolved oxygen was above the lower
Oil & Grease (mg/l)

8 Downstream
Reservoir
Upper_NEMA Std
NEMA and EU permissible limits of 3 and 5 mg L-1,
6
respectively, a situation that rendered the project area
suitable for supporting low oxygen intolerant aquatic
4
life including most fish species. Before April 2012
when the reservoir was not filled, the flow-through of
2
the water was reflected in terms of the relatively high
but similar concentration of dissolved oxygen at the
0
upstream and downstream transects. However, after
filling the reservoir, the concentration of dissolved
Se 06

Ap 8
Se 09

Se 10

Se 11

Se 12

Se 13

Se 14

Ap 5
16
Ap 7

Ap 9

Ap 0

Ap 11

Ap 2

Ap 13

Ap 4
0

1
_0

_0

_1

_1

_1
r_

r_
r_

r_

r_

r_

r_

r_

r_
r_
_

_
pt

pt

pt

pt

pt

pt

pt
oxygen reduced in similar proportions, but with the
Ap

Sampling Period
downstream transect having a significantly high
concentration. The significantly higher dissolved
Figure 6: Trends in concentration of oil and grease oxygen at the downstream transect was attributed to
compared to NEMA permissible upper limit the enhanced residence time of 16 hours that probably
allowed ample time for algae, through photosynthesis,
Discussion to yield more oxygen such that by the time the
Reservoirs, like lakes, are created when water storage reservoir water was released, there was relatively high
projects are built. Dams and their reservoirs can as concentration of the dissolved oxygen. Additionally,
such significantly slow down the rate at which the decomposition of organic matter results into
water flows downstream (Ligon et al., 1995; Kondolf, accumulation of gases such as carbon dioxide which,
1997; Nilsson et al., 2005). When the Bujagali in aqueous states, lower pH of the water. Despite this,
reservoir was established, riparian areas became water pH fluctuated within the permissible NEMA and
inundated, habitat conditions changed and over time, EU/WHO environmental limits of 6 to 8, and 6.5 to
this probably resulted into a new equilibrium of the 8.5, respectively. This relatively constant pH, coupled
reservoir (Soares et al., 2008). with the short residence time of 16 hours, indicated no
During the first years after a reservoir is filled, the extreme effects of the project on the pH of the upper
decomposition of submerged vegetation and soil Victoria Nile water.
organic matter can drastically deplete the level of Water temperature has a major effect on the
oxygen in the water (Tank et al., 2010; Zhu et al., metabolic rates and physiological responses of aquatic
2011). Reservoirs often “mature” within a decade or biota and on the rates of chemical, biochemical and
so, although in the tropics, it may take many decades biogeochemical reactions in a reservoir (Dallas, 2008).
or even centuries for most of the organic matter to The trend in water temperature indicated minimal
decompose (Hamilton and Schladow, 1997; Soares et variations before and after the dam was completed.
al., 2008). Since much of the site was steep-sloped, However, the relatively low water temperature at the
the amount of submerged macrophytes was limited to upstream transect was partly attributed to the slightly
the few sheltered bays hence their contribution to the low concentration of TSS that likely trapped less solar
organic matter load in the inundated area was assumed energy compared to what was noted in the reservoir.
to be minimal. When algae in a reservoir senescence Since there is a strong correlation between TSS and
and die, they sink to the hypolimnion, where they turbidity (Packman et al., 1999; Paaijmans et al.,
decay and in doing so, consume the already limited 2008; Hui et al., 2011), turbid waters tend to absorb
hypolimnetic oxygen (Nürnberg, 2004). However, more solar energy than clear water. The differences in
presence of adequate concentrations of dissolved water temperature, though insignificant, were
oxygen in a river is one of the main indicators of good therefore partly attributed to differences in the
water quality (Best et al., 2007; Carsten et al., 2007). concentration of TSS. Additionally, water turbidity
31
affects water temperature as suspended particles in a situation that indicated that the project did not have
water column absorb and scatter sunlight and hence negative significant effects on the concentration of oil
determine the extinction of solar radiation (Paaijmans and grease in the upper Victoria Nile water.
et al., 2008). This also had a bearing on the While the above observations indicated no
significantly high water clarity at the upstream transect significant impacts of the BEL project on the major
compared to that at the downstream transect. Surface water physico-chemical characteristics, elsewhere
waters tend to become warmer as the slack water other scholars have documented alterations by similar
absorbs more heat from the sun. Warming or cooling projects on water physico-chemical characteristics that
the natural river affects the amount of dissolved profoundly affect the ecology of river systems
oxygen and suspended solids it contains, and (Goodwin et al., 2006; Horlacher et al., 2012).
influences the biogeochemical reactions which take Moreover, Berkun (2010) reaffirmed that urbanization
place in it. and industrialization that are fueled by the relatively
While there were no significant differences in the affordable hydropower, result into social and
concentration of TSS between the upstream and economic development, but bring about increased
downstream transects, and between the upstream pollution levels that degrade water quality. Thus,
transect and the reservoir, the significant difference in water quality is not only impaired by hydropower
TSS concentration between the downstream transect projects but also by other factors such as urbanization
and the reservoir, with the reservoir having a and industrialization, among others. The effect of
significantly higher concentration was a result of seasonality was not realized because data collection
release of accumulated TSS from the latter. However, was done in April and September which are in the
the significantly low concentration of TSS before and bracket of the long (February to May) and short
after completion of the dam compared to the NEMA (August to October) rains, respectively. Thus, lack of
permissible environmental upper limit of 100 mgl-1 the dry season data which could be compared with that
was an indicator that the project had so far had no of wet season, could have influenced the trends that
significant negative effect on the water environment of were observed during this study.
this area in relation to TSS. This study has demonstrated that more than ten
Water conductance quantitatively reflects the status years since the project was initiated, there has so far
of inorganic pollution and is a measure of total been no significant negative effect of the BEL project
dissolved solids and ionized species in waters on the major water physico-chemical parameters of the
(Jonnalagadda and Mhere, 2001). Although it was upper Victoria Nile water. This was probably due to
anticipated that the submerged vegetation and soil the short residence time of 16 hours which was
organic matter would decompose and products of probably not long enough to impact on the various
decomposition alter water conductivity, this parameter physico-chemical changes of the water. Additionally,
varied minimally at all sites. While there was no since data collection was done only during the rainy
NEMA environmental standard for water conductivity, seasons (April and September), the effect of
reference to the WHO/EU environmental discharge seasonality could not be realized due to lack of
standard indicated that water in the project area was comparable data if sampling was also done during the
not significantly affected by the project since even the dry season.
highest recorded water conductivity was less than half
of the upper WHO/EU permissible environmental
Acknowledgement
standard of 250 µS cm-1. While this was so for water
conductivity, the significantly low water column Financial support for data collection was provided by
clarity at the downstream transect was a result of the Bujagali Energy Limited (BEL), while the
release of the accumulated TSS from the reservoir. National Fisheries Resources Research Institute
Despite the observed trends in water column clarity, (NaFIRRI) provided field and laboratory logistics.
mean values were not very different from what was
recorded for unpolluted sites of Lake Victoria (Wanda,
unpublished data). Additionally, the concentrations of
oil and grease were far below the permissible
environmental discharge standard of 10 mgl-1, a
32
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