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Monitoring the Effects of Anthropogenic Activities on Water Quality: Von Bach Dam, Namibia

Authors:
  • Namibia Water Corporation

Abstract and Figures

This chapter is based on research carried out to examine the effects of human activities on the quality of water flowing into Von Bach Dam, the water in the dam as well as water flowing out of the dam during different seasons. The specific objectives of the study were to determine water quality at different points around the Von Bach Dam during different seasons of the year. The study involved bacteriological testing, turbidity determination and temperature variation within the water body. Other tests carried out include dissolved oxygen content and pH levels. Bacteriological analysis showed high presence of E. coli which is a strong indication of pollution emanating from human activities. High values for soil and other organic matter were found to be the major contributing factors in raising the dam water turbidity which was responsible for algal blooms in the dam. The pH of the water during summer and winter did not indicate potential harmful effects to human health as these were within the limits of the NAMWATER standards for drinking water.
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Chapter 4
Monitoring the Effects of Anthropogenic
Activities on Water Quality: Von Bach
Dam, Namibia
J. J. Sirunda and J. P. Msangi
Abstract This chapter is based on research carried out to examine the effects of
human activities on the quality of water flowing into Von Bach Dam, the water in
the dam as well as water flowing out of the dam during different seasons. The
specific objectives of the study were to determine water quality at different points
around the Von Bach Dam during different seasons of the year. The study involved
bacteriological testing, turbidity determination and temperature variation within
the water body. Other tests carried out include dissolved oxygen content and pH
levels. Bacteriological analysis showed high presence of E. coli which is a strong
indication of pollution emanating from human activities. High values for soil and
other organic matter were found to be the major contributing factors in raising the
dam water turbidity which was responsible for algal blooms in the dam. The pH of
the water during summer and winter did not indicate potential harmful effects to
human health as these were within the limits of the NAMWATER standards for
drinking water.
Keywords Eutrophication Anthropogenic activities Inflow and outflow
discharge Turbidity Coliform bacteria E.coli Dissolved oxygen PH levels
Introduction
Namibia is the second driest country in Sub-Sahara Africa and water scarcity is the
norm for most of the country. Surface water is almost non-existent with the
exception of the five trans-boundary rivers marking its political boundaries with
J. J. Sirunda (&)
Water Quality and Environmental Services, NamWater, P Bag 13389, Windhoek, Namibia
e-mail: SirundaJ@namwater.com.na
J. P. Msangi
WELER Consulting Services, PO Box 98138, Pelican Square, Hochland Park,
Windhoek, Namibia
e-mail: jpmsangi@iway.na
J. P. Msangi (ed.), Combating Water Scarcity in Southern Africa,
SpringerBriefs in Environmental Science, DOI: 10.1007/978-94-007-7097-3_4,
ÓThe Author(s) 2014
61
Botswana, Angola, Zambia and South Africa. These include Kwando-Linyati-
Chobe, Okavango, Kunene, Zambezi and the Orange Rivers. Most of the other
rivers are ephemeral carrying water only during and soon after the rains.
Namibia has great temperature variations, the average annual temperature along
the coast being less than 16 °C, about 18–20 °C in the central area, 20–22 °Cin
the south, and more than 22 °C in the northern-eastern parts. However during the
hottest months (i.e., October–February), the temperature at the coast remains less
than 20 °C, it rises to over 30 °C in the centre, over 36 °C in the southern and over
32 °C in the northern-eastern parts of the country.
In Namibia, annual rainfall varies across the country, where the coastal areas on
average receive less than 50 mm per year, the southern part 50–200 mm per year,
the central parts 200–400 mm per year and the northern part receives 400–550 mm
per year (Mendelsohn et al. 2002). The eastern Caprivi receives the highest
average rainfall of about 650 mm per year while some areas in the central part like
Tsumeb receive 510 mm per year, Otavi 540 mm per year, and Grootfontein
550 mm per year. Most parts of the country receive rainfall during the summer
months (November–March) with the exception of the south–western corner of
Namibia which receives winter rainfall during June–August.
The country is characterized by very high evaporation losses (southern areas
2380–2660 mm per year; north-eastern parts 1680–1820 mm per year and less
than 1680 mm per year along the coastal area. The highest rates occur during
October–January (Mendelsohn et al. 2002).
Overview
This chapter is based on research carried out to examine the effects of human
activities on the quality of water flowing into Von Bach Dam, the water in the dam
as well as water flowing out of the dam during different seasons. The specific
objectives of the study were to determine water quality at different points around
the Von Bach Dam including inflow and outflow points at different depths. The
study set out to compare quality of water collected at different points in order to
determine the effects of human activities on the water quality of the dam. The main
research question of the study was to determine the season during when human
activities affect the water quality of Von Bach dam the most. Therefore the study
involved bacteriological testing, turbidity determination and temperature variation
within the water body. Other tests carried out included dissolved oxygen content
and pH levels. Three sampling stations were selected randomly: one for testing
inflow discharge, one for assessing effects of intense human activities and the last
one for assessing the outflow discharge. A total of thirty eight (38) water samples
were collected at different depths during winter and summer months.
The driving force behind the choice of Von Bach dam is the fact that there are
very few fresh water sources available to meet the ever increasing demands of the
country’s growing population and industrial activities. These few sources are also
62 J. J. Sirunda and J. P. Msangi
at risk from pollution resulting from uncontrolled waste dumping, poorly managed
agricultural lands, industrial effluents and air borne pollutants. Von Bach Dam,
located on Swakop River seven kilometers from Okahandja, town is the main
source of fresh water for the largest town and capital city of the country,
Windhoek. The dam is a recreation facility which also serves as a water source not
just for Windhoek but also for the nearby Okahandja town.
Von Bach Dam has a capacity 48.5 Mm
3
. It is a popular venue for aquatic
recreation for activities such as water skiing, yachting, windsurfing, boating as
well as angling. At Von Bach Dam there are bungalows and camping facilities on
the south eastern banks of the dam. Wild animals including kudu provide added
attraction. The catchment area of Von Bach Dam, used mainly for livestock
farming and small-scale crop cultivation to produce food for family and friends,
has seasonal rivers which cut off villages such as Ovitoto during the rainy season
when they are in flood.
Anthropogenic activities which take place in a catchment area are assumed to
affect the quality of the water in rivers and storage dams. Human activities are
considered to be the highest contributing factor in water pollution of water bodies
all over the world. In any given river basin, human activities emanating from
different sources affect water characteristics particularly those taking place in the
upper catchment area.
Overall assessment of drinking water system should take into consideration any
historical water quality data that assists in understanding sources of water char-
acteristics and drinking water system performance both over time and following
specific events like excessively high rainfall. The efficiency in managing water
resources and potentially polluting human activities in the catchment will influ-
ence water quality downstream as well as groundwater aquifers.
Turbidity of the water is important in quality monitoring because this is related
to cleanliness (aesthetically) of the water. Turbidity is caused mainly by high
concentrations of biota such as phytoplankton and sediments. Waters with low
concentrations of total suspended solids are clearer and less turbid than those with
high total suspended solids. Turbidity as a water quality parameter affects the
aquatic system as it can alter light intensities in a water column thus potentially
altering potential rates of photosynthesis and the distribution of organisms within
the water column. Lowered rates of photosynthesis may in turn affect the levels of
dissolved oxygen available in a water body, thus affecting large organisms such as
fish. Sedimentation increases the turbidity of water in a reservoir (dam). Some
sediments originating from the catchment’s top soil following bad cultivation
practices introduce nutrients into the river and eventually into a reservoir, dam or
lake and thus affect primary producers in the plankton by reducing light pene-
tration to the lower layers. Eventually this alters the composition of benthic
communities.
Dissolved oxygen analysis is a key test in water pollution and waste water
treatment process control since it is a key determinant of survival of most aquatic
organisms. It is vital in the process of cellular respiration and without sufficient
dissolved oxygen most aquatic life would not survive. Some organisms require
4 Monitoring the Effects of Anthropogenic Activities on Water Quality 63
high amounts of dissolved oxygen than others. Aquatic plant populations, rainfalls,
rocks on the river bed, time of day, water velocity and water temperature are
contributors to total dissolved oxygen. It is documented that dissolved oxygen in a
water body should not exceed 110 % of the concentration of oxygen in the air
because at certain concentrations it could be harmful to aquatic life.
Water pH in a body of water is affected by the age of the water body because of the
chemicals discharged into it over time by communities and industries. Most lakes and
dams/reservoirs are basic when they are first formed and become acidic with time due
the buildup of organic materials. Surface waters receive a variety of organisms
discharged in municipal wastewater effluents, industrial wastes and agricultural
activities. Water temperature affects and accelerates the growth of adapted organ-
isms in the water body. Microbial growth is not only keyed to bacterial strains that
quickly adjust to limited nutrient sources, but also to water temperature.
Coliform bacteria are used as indicator organism in assessing the quality of the
water and the presence of these bacteria indicates that pollution has occurred
which can be associated with fecal contamination from man or other warm
blooded animals (Gronewold and Wolper 2008). The characteristics of these
bacteria include all aerobic and facultative anaerobic gram-negative, non-spore
forming, rod-shape bacteria. This bacteria ferment lactose to produce a dark col-
ony with a metallic sheen. The sheen may cover the entire colony and may appear
only in the central area or on the periphery.
Testing water for all possible pathogens is complex, time-consuming, and
expensive. However it is relatively easy and inexpensive to test for coliform
bacteria. There are three different groups of coliform bacteria; each has a different
level of risk. Total coliform, fecal coliform, and E. coli are all indicators of
drinking water quality. The total coliform group is a large collection of different
kinds of bacteria. Fecal coliforms are types of total coliform that mostly exist in
feces. E. coli is a sub-group of fecal coliform. When a water sample is sent to a lab,
it is tested for total coliform and if it appears that total coliform is present, the
sample will also be tested for either fecal coliform or E. coli, depending on the lab
testing method.
Reviewed Literature
Nowadays most river basins are to some extent subjected to the effect of the
human economic activity (Ismaiylov et al. 2007). The changes in their runoff can
be caused by both a direct impact on it and changes in the conditions of its
formation resulting from an impact on the physiographic conditions (topography,
soils, vegetation, etc.). It is generally true that a minimum quality of surface water
must be ensured in order to maintain property self-purification (Rump and Krest
1992). In this report it is stated that the degree of pollution always parallels
changes in the ecological situation.
64 J. J. Sirunda and J. P. Msangi
Water quality in adjacent streams or upper or lower reaches of the same stream
typically exhibit similar trends (Chang 2008). In this study Chang shows that the
spatial patterns of nutrient concentrations confirm the influence of urban land
cover on stream water quality. He stated that, watersheds that have been disturbed
by deforestation and urbanization are less able to process these pollutants because
of a reduction in microbes and processes that naturally work to immobilize
nutrients. He reports that, some forms of nitrogen or phosphorus show elevated
concentrations as flow rises due to a flushing effect.
The environmental state of water bodies is affected not so much by particular
chemical elements as by complexes of elements that are simultaneously present in
water and bottom sediments (BS) (Klenkin et al. 2008). Their research found out
that the comparative assessment of BS pollution in different regions of aquatic
ecosystems and the investigation of sources of the increased anthropogenic pol-
lution are only possible with the compensation for differences in the granulometric
composition of BS. River water runoff is regarded as the most available resource
that renews every year (Magritskii 2008). Magritskii suggested that this property
of river water makes it most significant for practice as compared with water
resources that renew more slowly or groundwater that renew annually.
In his analysis, Magritskii found out that, the effect of economic activity on the
river basins of North European and Asian parts of Russia is much weaker. He
stated that the rate of intensification of sulfate reduction in water bodies is a sign of
a stronger anthropogenic impact on the environment and natural water bodies. On
the other hand, other researchers including Chicherina and Leonov in their work
dated 2008, state that the rate of sulfate reduction (SRR) is a representative
characteristic allowing one to control anthropogenic pollution and eutrophication
processes in water bodies (Leonov and Chicherina 2007).
The productivity growth of a water body is affected by an increase in phos-
phorus release from bottom sediments (Martynova 2008). According to Martynova
it is believed that the main reason for the increase of the internal phosphorus load
in a eutrophic water body is the expansion of the area under anaerobic sediments,
from which phosphates absorbed by iron compounds under aerobic conditions are
released. Additionally, biogenic substances (N and P compounds), which are
present in natural waters, play a very important role in the processes taking place
in streams and largely effect the chemical composition and physical properties of
water (Samarina 2008). In this report it is stated that on one hand, the need to
restrict eutrophication requires the identification of links between biogenic sub-
stances flow formed at the watershed and on the other hand, the dynamics of the
water body eutrophication.
According to the study conducted by Samarina in (2008), the destruction of
high-molecular organic compounds of natural and anthropogenic origin intensifies
the contamination of a water body and disturbs the normal vital activity of animal
and plant organisms. In this study, it is stated that, analyzing the anthropogenic
factors resulting in the appearance of phosphorus and different mineral forms of
nitrogen in the streams in industrially developed areas of Central Chernozem
region, the following factors could be identified: the intense development of
4 Monitoring the Effects of Anthropogenic Activities on Water Quality 65
national economy, accompanied by an increase in the number of settlements in the
region, points to an abrupt increase in the amount of domestic and industrial
effluents, as well as uncontrolled washes off from settlements and industrial zones
within the watershed area. Meanwhile in his study conducted in 2007, Jing Zhang
argues that industrialization and urbanization along the coastal population centers
have brought great changes in the land cover and natural material fluxes from
watersheds to receiving bays and estuaries.
Generally, the temperature of the water under treatment is another factor to
consider in the operation of a sedimentation basin (Goula et al. 2008). It is stated
that, usually, a wastewater treatment plant has the highest flow demand in the
summer, whereas when the water is colder, the flow in the plant is at its lowest. As
ecosystems with slow water circulation, lakes and reservoirs (dams) have similar
formation and development regularities (Martynova 2006). Martynova argues that,
as compared to natural lakes, reservoirs have larger catchment area and higher rate
of water circulation; they are subjected to a higher pollutant load and have a higher
capacity of retaining all sorts of human-induced contaminants.
Elsewhere, the environments receiving runoff from urban areas have been
reported to experience an increase in their concentrations of suspended sediments,
nutrients and metals (Pecorari et al. 2006). According to them, rivers, lakes and
other water bodies are frequently located in urbanized areas and such waters are
not only used for recreational purposes, but usually act as collectors of diverse
types of effluents. Pecorari et al. stated that traditionally, few limnologists have
paid attention to the effects of urbanization on the ecology of these impacted
aquatic systems. However, it is a well-known fact that urbanization causes great
changes in the hydrology, geomorphology and water quality, which can be
stronger than the impacts caused by other uses of the land such as agriculture and
forestation.
Data Collection and Analysis
Non-probability sampling techniques were used, where the probability of any
particular member of the population being chosen is unknown. The selection of
sampling units is arbitrary as researchers rely heavily on personal judgment. In this
study, the sample size was selected in such a way that it represented the charac-
teristic of the total population. Nineteen (19) water samples were collected on each
trip, the first samples were collected during winter (June 2008) and the second
samples were collected during summer (September 2008).
Water samples were collected at each of the three selected stations, two at each
depth using a niskin bottle with a depth finder and an attached weight. Water from
the niskin bottle was poured into sampling bottles (glass bottle 250 ml) and the
sample bottles were labeled before they were stored in the cooler box at a tem-
perature below 10 °C. Samples in the cooler box were taken to the laboratory
where they were refrigerated at a temperature below 10 °C and analyzed within
66 J. J. Sirunda and J. P. Msangi
24 h to test for total coilforms, fecal coilforms, and pH. Parameters such as,
dissolved oxygen, turbidity and temperature were measured and recorded in the
field. To measure Temperature and Dissolved oxygen, an oxygen meter was used
after calibration and a secchi disk was used to determine turbidity.
The data was subjected to statistical analysis using a two way-ANOVA. This
analysis revealed that there was a significant difference in temperature readings at
all the stations in both winter and summer at 5 % significance level. The analysis
also revealed that the water temperature readings were significantly different at
5 % significance level. Dissolved Oxygen level analysis revealed that there was no
significant difference in dissolved oxygen levels for winter and summer months.
Collected data on turbidity, pH and heterotrophic counts bacteria at all the three
stations were also subjected to statistical analysis using ANOVA. The analysis
showed that there was no statistical difference in turbidity of the dam water at all
stations during winter and summer at 5 % significance level. Similarly, no sta-
tistical difference in pH of the water was recorded for all the stations for winter and
summer months at 5 % significance level and that the heterotrophic plate bacteria
count were the same in both winter and summer. Statistical analysis for total
coliform counts bacteria from all the stations were not statistically different from
each other at 5 % significance level.
However, statistical analysis of fecal coliform counts revealed that there was a
marked difference on samples collected from the three stations during winter and
summer at 5 % significance level. Samples from the inflow water station for both
winter and summer contained E. coli while the water for the other two stations
showed presence of E. coli only during summer months (Table 4.1).
Heterotrophic Plate Count Bacteria (CFU/1 ml)
The average density of the heterotrophic plate counts bacteria are shown in
Tables 4.1 and 4.2. The winter results show that the average density was higher at
the Ski Club station at 0 m depth compared to the Inflow and Outflow stations at
Table 4.1 Average bacteria density for summer season
Station Depth
(m)
Heterotrophic plate
count (CFU/1 ml)
Total coliform
(CFU/100 ml)
Fecal coliform
(CFU/100 ml)
E. coli
presence/
absence
Inflow 0 2026.5 146.7 184.3 Present
Ski club 0 736 30.7 1.7 Present
Outflow 0 362.5 27.3 0.7 Present
9 373.5 79 1.3 Present
18 395 36.7 0.7 Present
Total
average
778.7 64.1 37.7
4 Monitoring the Effects of Anthropogenic Activities on Water Quality 67
the same depth. On the other hand, in Table 4.2 the average heterotrophic plate
count bacteria were higher at the Inflow Station at 0 m depth.
The inflow station in Table 4.2 shows higher total coliform counts bacteria
compared to the other two stations. The temperature differences during winter and
summer affects the average total coliforms as indicated in the two tables where the
total coliform counts are more in winter than in summer. Despite the low tem-
peratures in winter, the population of bacteria is one to one and half orders of
magnitude than in summer. The Inflow station had a higher count of fecal coli-
forms in both winter and summer. The total average of coliform counts was higher
in summer than in winter giving an inverse proportion relationship between total
coliform and fecal coliform. E. coli was confirmed at all stations during summer at
all depths except at the Outflow during winter.
As expected the water temperature was higher during summer than during
winter at the Outflow Station, however the rate of decrease with depth was faster in
summer than during winter (Fig. 4.1). The water temperature at the Inflow and Ski
Club Stations showed low variations with depth and as such had no significant
bearing on the water of Von Bach dam.
The Outflow Station recorded higher levels of dissolved oxygen at the surface
water in summer than in winter. The dissolved oxygen dropped rapidly with depth
during the season. Comparatively, in winter the water dissolved oxygen decreased
more slowly with depth than during summer (Fig. 4.2).
The effect of water temperature on bacteria counts was clearly demonstrated by
the bacteria average density which was much lower at the surface during summer
compared to the winter season when there was a rapid increase of bacteria count
with depth. This supports the fact that the higher the temperature the lower the
bacteria replication process (Dolgonosov et al. 2006).
The Outflow Station experienced rapid drop of dissolved oxygen with depth
during summer and a more gradual drop during winter. This difference can be
explained by the fact that low surface water temperatures in winter supports fast
growth in bacteria in all depths as compared to summer scenario when tempera-
tures are high at the surface but drop rapidly with depth thus supporting fast
growth of bacteria at greater depths (Fig. 4.3). The dissolved Oxygen levels at the
Table 4.2 Average bacterial density for winter season
Station Depth
(m)
Heterotrophic plate
count (CFU/1 ml)
Total coliform
(CFU/100 ml)
Fecal coliform
(CFU/100 ml)
E. coli
presence/
absence
Inflow 0 850 87.7 9.7 Present
Ski
club
0 1400 70.3 1.7 Present
Outflow 0 750 118 0 Absent
9 450 102 4 Present
18 350 116.3 4.3 Present
Total 760 98.9 3.9
68 J. J. Sirunda and J. P. Msangi
Inflow and Ski Club stations in both summer and winter showed fewer constant
variations with depth (Figs. 4.3 and 4.4).
Turbidity levels were higher at the Inflow Station during winter than other
stations. This was caused mainly by in flowing water from the catchment area
which suffers from overgrazing and is characterized by high losses of top soil
loosed by continuous trampling by large herds of livestock. This high sediment
Temperature profile "Outflow"
0
5
10
15
20
25
0 5 10 15 20
Temperature "degree celsius"
Depth m
winter "t emp"
summer "temp"
Fig. 4.1 Winter and summer temperature profile at the outflow station
Diss olved Oxyge n profile "Outflow Station"
0
5
10
15
20
25
012345678
DO mg/l
Depth m
summer "DO"
winte r "DO"
Fig. 4.2 Winter and summer dissolved oxygen at the outflow station
4 Monitoring the Effects of Anthropogenic Activities on Water Quality 69
concentration can be linked with the low counts of coliform bacteria at the Inflow
Station because when the level of turbidity increases, the water loses its ability to
support a diversity of aquatic organisms. Water turbidity has a direct relationship
with temperature and dissolved oxygen because when turbidity level is high, the
suspended particles absorb more heat from the sunlight and lead to an increase in
Temperature profile "Inflow and Ski club Station"
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25
Temperature " degree celsius"
Depth m
winter Inflow "tem p"
summer Inflow "temp"
Wint er Sk i cl ub "tem p"
Summre Ski club
"tem p"
Fig. 4.3 Summer and winter temperature profiles at the inflow and ski club stations
Oxygen profile "Inflow and Ski club Station"
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15
DO mg/l
Depth m
Wint er Inflow "DO"
Sum mer Infl ow " DO"
Wint er Sk i cl ub "DO"
Summer S ki club " DO"
Fig. 4.4 Summer and winter oxygen profiles at the inflow and ski club stations
70 J. J. Sirunda and J. P. Msangi
water temperature which results in lower dissolved oxygen in the water. Hence the
higher the turbidity the lower the bacterial counts.
The water turbidity level was higher during winter at the inflow station as the
secchi disk’s color disappeared at 31 cm deep compared to that of summer when
the color disappeared at 46 cm deep; a difference of 15 cm. The Outflow Station
showed turbidity content at 72 cm and Ski Club showed turbidity at 87 cm while
during summer the turbidity content was observed at 38 and 50 cm at the Outflow
and Ski Club stations respectively.
The pH values of the water at the Inflow Station in winter and summer were
constant while at the Ski Club and Outflow Stations some variations were
observed. This is explained by the effluents from the residential and resort bun-
galows at the Ski Club Station.
According to water classifications based on NAMWATER standard guidelines
for drinking water, water at the Ski Club Station is fit for human consumption
during all seasons. However water at the Inflow Station is fit for human con-
sumption during summer because the bacterial counts were in group B and C
(Appendix 4.1).
Discussion
The major sources of microbial pollution to the dam water emanate from human
and warm-blooded animal excrements that enter into water bodies with municipal
wastewaters and drains from cattle farms and areas polluted by manure
(Dolgonosov et al. 2006). Heterotrophic plate count consists of diverse groups of
microorganisms that have wide range of metabolic capabilities and culture
requirements and constitute a wide range of risks to public health (Lechevallier
and Mcfeters 1985). The growth of many heterotrophic is more pronounced than
the coliform subset of this population, often providing abrupt surges in density
during summer (Geldreich et al. 1977). Heterotrophic plate counts bacteria cause
health risk in patients who are in hospitals, clinics as well as at home. Some
species and strains of Psedomonas, Bacillus and sarcina suppress coliform bacteria
detection in water; this suppression is due to the increase in heterotrophic plate
counts bacteria. Fecal and total coliform bacteria are indicators of potential fecal
pollution and water-borne pathogenic threats to human health.
In this study, high coliform bacteria counts recorded at the Inflow Station
during both seasons is an indicator of pollutants gathered by rain water from the
catchment area and delivered to the streams flowing into Von Bach dam. The
presence of the bacteria at the other two stations can be explained by the discharge
from the resort bungalows and directly from the people who swim and bathe in the
water body. Animals who are watered directly from the dam could also be a
contributor to this direct pollution through their droppings.
Studies done elsewhere have demonstrated that there are low population of
microorganisms in summer and autumn which can be due to phytoplankton
4 Monitoring the Effects of Anthropogenic Activities on Water Quality 71
blooming bringing about an increase in pH values. Raised pH values suppress vital
activity of bacteria flora (Dolgonosov et al. 2006). The observed high pH value
(close to 10) at both the Ski Club and the Outflow Stations in summer confirms this
observation documented in the report by Dolgonosov et al. Combined with high
temperatures and high turbidity, such an occurrence could have contributed to the
low summer coliform counts at the two stations at 0 m depth. E. coli was con-
firmed at the Inflow Station in both seasons and at the Ski Club Station during
summer.
Bacterial count for heterotrophic plate counts, total coliform, and fecal coliform
shows high counts in summer at the Inflow Station with lower content of turbidity
than it was in winter with highly turbid water. This shows that, turbidity plays a
very important role in bacterial growth and they are inversely related. According to
the study conducted by Martynova in 2006 it was confirmed that the higher the
plankton production (and the higher the rate of its destruction in the water column,
which lags behind the increase in the productivity), the higher the rate of organic
matter accumulation, and, respectively, the higher the sedimentation rate. The high
population of coliforms in winter could be explained by high release of organic
matter at the catchment surface because of decay of dead plant material accu-
mulated in summer and delivered by surface waters into the estuary. This obser-
vation is well indicated in this study, whereby coliform counts at the Inflow Station
was high in summer compared to the counts during winter. The reason could be
that, the decay of dead plant material was taking place in summer while the water
has already reached the inflow station from the catchment area. During winter the
outflow station was inundated by dead plant material and since the decay process is
very slow in winter, few counts of coliform (fecal and total) were found.
Dissolved Oxygen is used by bacteria during the decaying process of organic
matter in the aquatic system. Dissolved Oxygen is also produced during the
photosynthesis process by phytoplankton in the aquatic system as a by-product.
Possible increase in organic matter in the Von Bach dam could be through soil
losses resulting from poor agricultural practices in the catchment area, land
clearing for building structures around the dam and through direct disposal of
organic matter by people frequenting the dam to engage in recreational activities.
The consequences of these activities may have contributed towards lowering
oxygen levels in the dam water. Elsewhere, it has been documented that aquatic
ecosystems changes were brought about by the changes in the relative contribution
of major water pathways and biotic concentrations originating from human
activities in the watershed (Zhang 2007).
Turbidity which depicts clear state of the water is mainly caused by the sedi-
ment released from the catchment area and from activities around the dam. This
sediment carries nutrients into the water body resulting in rapid bacteria growths.
On the other hand, an increase in the pH of water lowers the growth of micro-
organisms such as bacteria. The rise in pH values is caused by the increase in
organic material within the water body because when these materials decompose,
carbon dioxide is released and the carbon dioxide combines with water to form
carbon acid. Even though the acid formed is weak, large amount of this can lower
72 J. J. Sirunda and J. P. Msangi
the water pH. Dumping of chemicals into the water by individuals, industries and
communities in the watershed can affect the water pH as well. Chemicals con-
tained in shampoos can affect the water quality; these chemicals are frequently
used by residents occupying holiday bungalows around the dam and those using
the ablution facilities of the recreational infrastructure. Daily visitors to the dam
can also contribute to this through dumping. This explains the variations of the pH
values at the Ski Club and Outflow Stations throughout the two seasons against the
constant pH values at the Inflow Station over the two seasons.
Conclusions
Natural waters become polluted when the polluting material upsets the natural
balance of microorganisms, plants and animals living near or in the water body or
makes the water unsafe for human consumption or for recreation. In this article,
Chan et al. also stated that natural water may contain a wide variety of microor-
ganisms; in fact it is not unlikely that one might find representatives of many of the
major categories of microorganisms in a specimen from such sources. Therefore
monitoring the water quality overtime being it seasonal, monthly or even weekly
may give conclusive evidence on the quality of the water.
In this study on Von Bach Dam, the bacteriological analysis of fecal coliform
indicates that there is pollution emanating from human activities since the results
from some of the water samples tested for E. coli confirmed the presence of these
microorganisms. It is assumed that water at these stations was contaminated by
human activities both in the catchment area and around the dam. However, it
should be noted that, not all the fecal coliform counts were from human and
animal intestines as it was observed in the entire confirmation test for E. coli where
some of the samples were negative results (brown and orange color). The higher
detection of coliform bacteria at the Inflow Station could be attributed to the
increase in nutrients load coming into the dam from the catchment area.
Heterotrophic plate count is not sensitive to human activities, as this test is for
diverse groups of microorganisms but the water with higher level of heterotrophic
plate count when consumed can cause illness or spoil food. The results from this
test indicated that, the water at all the stations were of little risk to human health,
since the counts were within the limits stipulated by NAMWATER as of little risk
to human health. The pH of the water during summer and winter did not indicate
potential harmful effects to human health because the pH levels results were within
the limits of the NAMWATER standards for drinking water. Organic matter and
soil sediments reaching the dam from the catchment area and from construction
around the dam were the main indicators of anthropogenic activities affecting the
water quality in Von Bach Dam.
Organic matter in the dam affects aquatic organisms by altering the temperature
and dissolved oxygen levels upon which the aquatic organisms depend on for growth .
Soil sediments and the organic matter values were found to be the major contributing
4 Monitoring the Effects of Anthropogenic Activities on Water Quality 73
factors in raising the dam water turbidity. Chemicals from shampoos and other
cosmetics used by frequent visitors to the dam for recreational activities were found
to be responsible for the elevated pH values particularly during summer months.
Recommendations
While this study generated some useful data which pointed to an indication of
possible pollution to Von Bach Dam, it is recommended that for effective
assessment of the impacts of anthropogenic activities on the dam water, more
intensive testing should be carried out where more sampling stations would be
established and more water samples collected using more sophisticated and
accurate instruments that will afford higher precision.
It is also recommended that NAMWATER as the managing agent charged with
providing potable drinking water to the country’s population, should carefully
address the dangers of waste water disposal particularly that which contain
chemicals found in cosmetics. Over time these chemicals would accumulate to be
a major threat to the balance of the aquatic ecosystem. These imbalances may
affect the water quality in the long run so as to increase water purification costs.
Furthermore, it is recommended that more effective disposal methods of refuse
from building construction around the dam should be put in place so as to prevent
accumulation of shrubs and grass in the dam water which then lowers the amount
of light penetrating the water body which deprives the light and energy required by
phytoplankton for photosynthesis; it also increased the temperature of the surface
water.
Lastly, it is recommended that periodic cleaning to remove debris should be
instituted. Debris and organic matter reaching the dam from the catchment area
accumulates at the Outflow Station which raises nutrients load that is likely to lead
to an increase in the growth of phytoplankton. Rapid phytoplankton growth leads
to algal blooms which affects the appearance of the water and kills aquatic
organisms by preventing light penetration to the benthic layer of the water body.
Debris affects the aquatic ecosystem by altering the pH of the water, temperature,
dissolved oxygen, light intensity and turbidity. Thus filtration structures should be
installed just above the inflow points to minimize the quantity of debris entering
the water body from the catchment area.
Appendix 4.1: Water Classifications Based on NAMWATER
Standard Guidelines for Drinking Water
The classification Consists of four groups:
Group A Water with an excellent quality
Group B water with good quality
74 J. J. Sirunda and J. P. Msangi
Group C Water with low health risk
Group D Water with high risk, which is unsuitable for human consumption.
Summer standards
Stations (summer) Inflow Ski club Outflow
Limits to groups A B C D A B C D A B C D
pH 8.6 9.6 9.3
Turbidity (Secchi cm) * * * * * * * * * * * *
Dissolved oxygen (mg/l) * * * * * * * * * * * *
Temp (°C) * ** *** * *** * *
Heterotrophic plate count (cfu/1 ml) 2027 736 362.5
Total Coliform (cfu/100 ml) Beyond limits 30.3 24
Fecal Coliform (cfu/100 ml) Beyond limits 1.7 0.7
E. coli (presence or absence) * * * * * * * * * * * *
Star (*) indicate water quality parameters which are not in NAMWATER standard guidelines
Winter standards
Stations (winter) Inflow Ski club Outflow
Limits to groups A B C D A B C D A B C D
pH 8.5 8 7.5
Turbidity (Secchi cm) * * * * * * * * * * * *
Dissolved oxygen (mg/l) * * * * * * * * * * * *
Temp (°C) ** * *** * *** **
Heterotrophic plate count (cfu/1 ml) 850 1400 750
Total Coliform (cfu/100 ml) 87.7 70.3 Beyond Limits
Fecal Coliform (cfu/100 ml) 9.67 1.67 0
E. coli (presence or absence) * * * * * * * * * * * *
Star (*) indicate water quality parameters which are not in NAMWATER standard guidelines.
Water at the ski club station meets the NAMWATER standards in all seasons because all the
measured parameters fall in groups which are less health-risk to human beings. The inflow station
water was also less risky to human health because the bacteria counts were in groups B and C
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4 Monitoring the Effects of Anthropogenic Activities on Water Quality 77
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