The Effects of Hydrological Characteristics of River Nyakomisaro on the Water Supply of Kisii Municipality, Kenya
Kebaso, Bisley Mokaya
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A research was carried to explain the variation in the hydrological characteristics of river Nyakomisaro and its effect on water supply in the Kisii Municipality. The study determined the variability in rainfall and river discharge in the Nyakomisaro sub Catchment, established the relationship between rainfall and streamflow in the sub catchment, examined the extent for which River Nyakomisaro water was used in supplying water to the Kisii Municipality and examined the streamflow management status in the sub catchment. Secondary data for river discharge, rainfall and water supply data were used. Structured questionnaires were used to obtain information on water supply and storm water management in the sub catchment. Annual variability of river flow was calculated using annual peak and minimum flows and plotting them against time. Flood frequency analysis of stream flow was based on the linear regression model. The relationship between river flow and rainfall was established by calculating coefficient of determination (r2) and the correlation coefficient (r) in the regression model. Water supply data was analyzed by calculating mean, mode, frequency and percentages. Storm water management data was subjected to qualitative analysis by computing frequencies, totals and percentages. The study showed linear correlations between the variables; correlation between water supply and rainfall was 0.63, between rainfall and streamflow was 0.5779, and between water supply and streamflow is 0.9087. Rainfall in the catchment appears generally to be varying in the past eighteen years with a coefficient of variation of 0.8366. The study established that river Nyakomisaro is over utilized to provide water to Kisii municipality where 66.55% of population depend on it. Dumping of solid wastes along the river, road and house construction, fish farming, planting of eucalyptus trees along the river diverted flow of water in the river and affected its flow. The study indicates that when dry spells lasts for just one week, there is severe shortage of water and people travel more than 200 m in search of water. 65% of the respondents agree that water is expensive and its shortage limits domestic and commercial activities in the sub catchment. The study shows that there is no clear and proper drainage systems installed in the Nyakomisaro sub catchment. Study recommends to Kisii municipality to upgrade over 70 % of bridges and manage the number of houses constructed to reduce chances of houses collapsing and allowing waste materials of these houses to the River, make deliberate attempts to clean up River Nyakomisaro to enhance free movement of water in the stream and to control hazardous nature of destroying property and killing people. Initiative to revive the river to its original status by involving WRUA’s and WRMA and efforts should be made to involve the community in water management and to provide sufficient information on how they can improve river health. GWASCO which is mandated in supplying water to Kisii municipality should replace dilapidated system to reduce water wastage.