Development of a Hydrodynamic Model for River Sosiani

Abstract

River Sosiani’s catchment is a sub-catchment of the larger river Nzoia sub-basin which drains into Lake Victoria. River Sosiani drains rich agricultural lands and is the source of water for Eldoret town. The river is also the receiving body of effluent discharges from Eldoret town. It, therefore, has a major economic and environmental value in the western region of Kenya. For effective and sustainable management of river Sosaini it is important, among other things, to understand the hydrology and hydraulics of the river. MIKE 11 HD software was applied to simulate river Sosiani’s discharge. The river’s catchment was delineated from topographical map sheets after digitization using ArcView 3.3 GIS software. Geometrical parameters of the river were obtained by physical survey. In total seventeen cross-sections were surveyed. The model was calibrated using measured streamflow at the catchment outlet for three years and then validated for additional three years. The reliability of the MIKE 11 HD module was evaluated based on the Efficiency Index (EI) and Root Mean Square Error (RMSE). The EI and RMSE obtained are 0.75 and 0.050 m³s^-1, respectively. This model can be used for various watershed management purposes, including construction of the river’s water quality model.

Keywords: River Sosiani; Hydrodynamic model; MIKE 11; model calibration, model validation