Hydrometeorological Analysis of the Mara River Basin, Kenya/Tanzania

Flowing from the high mountains of the Mau escarpment in Kenya to the Mara bay of Lake Victoria in Tanzania, Mara River is one of the most ecologically significant rivers in the region. Meeting the water demands of the different sectors while maintaining a healthy environment requires understanding of the hydrology (water flux) and the major hydrometeorological processes responsible for the changes in the water balance. A study to understand the hydrometeorological trends of the basin's precipitation and flow is reported. Low flow and flood frequency analysis for three selected sub-basins with distinct land-use change and precipitation regimes was studied. Historical analysis of the rainfall information has shown that the annual rainfall amount did not change significantly but the seasonal and monthly distribution varied over the study period. The upper basin has shown little variability in the monthly average rainfall amount. Analysis of the flow records during the month of March, one of the low flow months of the basin, has indicated that the minimum flow at the Amala gauging station has declined over the period of time. On the other hand, flows at the Nyangores gauging station did not show any significant changes for the available records. Maximum flows at Amala were much higher than the adjacent Nyangores basin of a similar drainage area. Low dry flows and high wet season flows can be attributed to less vegetation cover and reduction in recharge in the head water of the river system.