Water Demand Simulation Using WEAP 21: A Case Study of the Mara Basin, Kenya

Abstract

The competing water uses within the Mara Basin has resulted into increased water demand on the mara river. The water evaluation and planning system (WEAP) was utilized to assess various ways to alleviate the river stress. In a bid to assess the impact of possible alleviation measures, diverse demand management strategies such as water reuse, use of more efficient equipments and policies were analysed. Water uses in the basin were quantified, mapped in regards to their current uses and demands. This established the baseline for future forecasts. The Parameter Estimation Tool (PEST) was used in model calibration. The year 2010 was used as a base year for scenario simulations up to the year 2045 due to few data gaps in the data available. From the results, the water demand within the basin under the reference scenario is 49.1 BCM, the demand drops to 4.1 BCM under the DMS scenario and to 3.5 BCM under the enhanced policy implementation and DMS scenario. The unmet demand under the reference scenario is 13.0 BCM mostly at the irrigation nodes at Nyangores and the downstream large scale farms. By embracing the proposed demand management strategies explored, the sector specific total water demand is projected to decline by 92.87% by the year 2045.