| dc.description.abstract | River Kisat is a perennial river draining the Mamboleo - Kisumu basin between Latitude
0°04'12.42" S and Longitude 34°46'33.86" E to the North and Latitude 0°05' 13.52" S and
34°45'00.15" E to the South. It drains a distance of about 10 Kms through Industrial, Slums
and Sewerage Treatment Plant (STP) areas into Winam Gulf. The river is polluted from various
sources of pollutants ranging from non-point to point sources. This has resulted in changes in
the trophic status of the lake at Winam Gulf from mesotrophic to hypertrophic. Pollution in the
lake has reduced biotic abundance and diversity. A study was therefore designed on River
Kisat, which is believed by many researchers as one of the major source of pollution into Lake
Victoria, to generate data and results that will aid in the management of Lake Victoria water
pollution and its probable source River Kisat. The specific objectives of this study were; to
identify main point and non-point sources of pollution to River Kisat, to determine the
pollution status of River Kisat through measurement of Nitrogen and Phosphorus nutrient
concentration levels, and to establish the amount of Nitrogen and Phosphorus discharge loads
into Winam gulf from River Kisat. The study was conducted during wet and dry seasons for a
period of one year (2009) in order to capture the seasonality and was confined to 8 stations
(STN 1, 2, 3, 4, 5, 6, 7 & 8) within the course of River Kisat, located at probable sources of
pollution. The samples were collected from the middle of the channel through scoop method
while sediments were collected using grab method. Samples from selected run-offs causes,
during rainy season, were also collected. Sampling containers were first cleaned and samples
pretreated using 0.02N HCl. The samples were then stored under refrigeration at temperatures
of 4°C before analyses. The data obtained from the analyses were then subjected to statistical
analyses using Excel spreadsheet by comparing variations between stations and between
months through line graphs, bar charts, and descriptive statistics and ANOVA. The DO
concentration levels between stations ranged between 1.33,(STN 6) and 4.11 mg/l (STN 8).
The pH levels ranged between 7.00 (STN 6) and 7.41 (STN 3). In terms of nutrient (N & P)
concentrations at STN 6 exhibited low concentrations but probably one of the main pollutant of
the river. The NH4+ concentrations within the river course between stations ranged between
0.15 (STN 7) and 1.89 mg/l (STN 4) with a maximum in STN 4. The NH/ concentration is
high during dry season but low during wet season. The N02- concentrations between stations
ranged between 0.04 (STN 7 & 8) and 0.23 mg/l (STN 5). N03- ranged between 0.35 (STN 8)
and 0.96 mg/l (STN 5). The N03- concentrations increases with increase in discharge. SRP and
TP concentrations ranged from 0.16 to 1.04 mg/l and 0.21to 1.39 mg/l respectively. STN 4 is
the main contributor of SRP. The total discharge load in a year during the study period is
estimated at 140.5 tons/year. The TN concentrations shoot with increasing discharge rates. TP
load per year is estimated at 155.8 tons/year. The TP also increases with discharge rates but at a
lower scale compared to TN. The DO concentrations are low compared to standard guidelines
for drinking and aquatic life. The nitrogen species concentration levels for both fisheries and
domestic use falls within recommendable levels except for NH/. The concentration levels of
nitrogen species tend to increase with decreasing discharges except for N03- and to some extent
N02-. The phosphorus levels are very high compared to water quality standard for fisheries but
within recommendable levels for drinking. The major pollution sources, both point and nonpoint,
lies between STN's 1-6. STN 7 and 8 are near the river source devoid of major
developments and are therefore less polluted. The government should therefore introduce a
policy of Polluter Pays Principle (PPP) with the revenue collected plowed back into cleaning
the river. These data would be important to policy makers like Municipal Council of Kisumu
(MCK),National Environmental Management Authority (NEMA), Kenya Marine and Ministry
of Public Health, Lake Basin Development Authority (LBDA). | en_US |
