Optimum water allocation planning in the lake Kochobo sub-catchment, Uganda.

Abstract

Given Uganda's per capita water availability (1004 m') as of2014, basin hydrologic modelling can sustainably help in: planning for the anthropogenic actions and changing climate effect on scarce water resources and reviving ecologically sensitive areas. The competing water uses within the Lake Kochobo Sub-Catchment (LKSC) has resulted into increased water demand on River Awoja. Previous studies within the Lake Kochobo Sub-Catchment focused on the precipitation trend and climate change scenarios analysis, impact of land use and climate change on soil fertility among other studies. There are no hydrologic studies evaluating the combined impacts of land use and other human activities within the Sub-Catchment and thus affecting water allocation among competing users. This research aimed at investigating and evaluating optimum Water Allocation Planning in the LKSC (974 km") where unsustainable water abstractions have impacted, using Water Evaluation and Allocation Planning (WEAP21) system. In a bid to assess the impact of possible mitigation measures for future, the research study considered quantifying catchment water uses in regards to their current uses and demands. This aimed at establishing a baseline for future forecasts. The Parameter Estimation Tool (PESn was used in system calibration. Calibration focused on reproducing daily-observed runoffhydrographs for the 2007-2017 period. To evaluate the model performance for calibration, the Coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE), Root Mean Square Error (RSR) and Percent Bias (PBIAS) criteria were exploited. The year 2007 was used as a base year for scenario simulations due to minimal data gaps in the available data. The projections of the current study stretch up to the year 2050. The study aimed at estimating the water demand within the catchment under the reference, current and future scenarios through scenario building and analysis. As a result, sustainable management strategies were recommended to the decision makers for implementation. It was concluded that the basin's hydrologic behavior basing on the current and proposed future demand sites is significant to both positive and negative scenarios. The results give an insight into the water demand and supply implications and can guide in developing ecologically sound Sub-Catcbment management and development strategies. Keywords: Lake Kochobo Sub-catchment, WEAP, Water Resources Allocation, Water Demand, Uganda