Integrating SWAT‐WEAP Models for Surface Water Availability and Demand Analysis in Gumara Watershed, Upper Blue Nile Basin, Ethiopia

Reliable information on the water resource’s potential and its demand in a watershed helps to plan for efficient management and utilization. This study was carried out to assess surface water potential and water demands in the Gumara watershed of the Upper Blue Nile basin by integrating the SWAT and WEAP hydrological models. The SWAT model was employed to simulate the surface water potential while the WEAP model was used for the optimal allocation of the available potential under current and future scenarios. The annual water yield in the watershed was found to be 1251.60 MCM. Based on this potential, the current water demand allocation in the watershed for domestic, irrigation, livestock, and environmental flow requirements was estimated as 28.28 MCM, 949.08 MCM, 23.81 MCM, and 250.32 MCM, respectively. The future water demands up to 2050 were further assessed under a reference scenario and four changing future scenarios including increasing population growth (scenario one), use of efficient irrigation technologies (scenario two), improved living standards (scenario three), a combination of population growth, and improved irrigation efficiency (scenario four). The results revealed that the domestic demand will need 3.8%‐fold in scenario one, 4.7%‐fold in scenario two, 5.7%‐fold in scenario three, and 6.3%‐fold in scenario four from the current situation. The available water surface water potential was not found to satisfy the demands of all the water users. The irrigation demand in all cases covers more than 76% of the total annual water demand which will press high pressure on the available water surface water resources. This warrants a more efficient utilization of water for irrigation. Furthermore, to augment the resource and meet at least some of the demands, a groundwater potential assessment in the area ought to be assessed which was not covered in this study and the construction of a reservoir is another option to augment water resources in the watershed.