Optimal surface water allocation under various scenarios in the Central Rift Valley basin in Ethiopia

Lack of sufficient knowledge about available water resources, unbalanced supply and demand collaboration in water resource management, conflicts among different water use sectors, and improper allocation of available water resources in river basins are still major issues around the world, including Ethiopia. This will allow us to establish water allocation strategies and principles for current and future development planning. Therefore, the overall objective of this study was to allocate surface water resources within the Central Rift Valley basin, Ethiopia, sustainably for social, economic, and environmental benefits. The future water demand was projected using three future development scenarios: short-term, medium-term, and long-term. The water Evaluation and planning model (WEAP) was used to assess water supply and demand. The parameter estimation tool (PEST) was used to evaluate the model's performance in simulating water availability, and the model accurately addressed surface water flow. According to the model findings, total estimated mean annual surface runoff leaving the watershed is 289.61 MCM. The estimated mean annual actual evapotranspiration, interflow, and baseflow were 2649.72 MCM, 78.74 MCM, and 77.60 MCM, respectively, whereas the estimated mean annual precipitation was 3095.67 MCM. The total available yearly streamflow at the outlet point is 445.95 MCM. The current domestic, industrial, livestock, and irrigation water consumption was 45.13 MCM. The present water demand result indicates that there is no shortage of water. Three basic scenarios were developed to forecast water demand up to the year 2050. The first, short-term scenario has little impact on future water demand. In the medium and long term, irrigation activities and the expansion of industry in the basin were implemented. In the medium and long run, there will be a shortfall of water demand in the industrial and agricultural sectors in upcoming years. Based on the findings of this study, it is advised that both water supply and demand side management strategies be adequately implemented and integrated in the Central Rift Valley basin in Ethiopia.