Assessment of water resource and forecasting water demand using WEAP model in Beles river, Abbay river basin, Ethiopia

Since water is essential for life, it is important to analyze the supply and demand of water in the basin. This will allow the development of strategies for water allocation and allocation concepts for current and future planning. The Water Evaluation and Planning model was used to model the assessment of water supply and demand in this study. To calibrate and validate the model, the Parameter Estimation Tool (PEST) was used. Future water demand was estimated using four different scenarios, namely Scenario-I: high population growth, Scenario-II: Dangur hydropower, Scenario-III: Expansion of irrigation activities and Industries in Beles basin, and Scenario-IV: combination of Scenario-I, Scenario-II and Scenario-III Simultaneously. According to the result obtained from the model, the total estimated mean annual surface runoff that leaves the basin is 5858.6 MCM, the estimated mean annual actual evapotranspiration is 10017.13 MCM, the estimated mean annual precipitation is 17525.33 MCM, mean annual interflow is 962.37 MCM and mean annual Base flow is 480.82 MCM. Total available streamflow of Beles basin including the Tana-Beles hydropower scheme is 10.03 BCM. Current water demand for Domestic, Industrial, Livestock, and Irrigation was 880.91MCM. The water demand result shows there is no shortage of water in the current situation. The first two scenarios, Scenario-I and Scenario-II have not much effect on future water demand. In the third scenario, Scenario-III, the shortage of water demand will happen in Upper and Lower Beles irrigation. Scenario-IV evaluates the water demand after Dangur hydropower is in operation. In this scenario, the water resource of the basin satisfies all demand sites in the basin.