Assessment of surface water potential and irrigation water requirements for selected crops: the case of the Zenti River catchment, Omo Gibe River Basin, Ethiopia

Abstract Irrigation potential assessment has enormous use for smallholder farmers, who are largely dependent on subsistence farming systems. Due to rising agricultural production demands and the scarcity of irrigation water resources, assessing irrigation potential is very important for the planning, management, and irrigation development of an area. However, there were very limited studies available in the study area that indicated irrigation water potential, and crop water demand in the area. Therefore, the main objective of this study was to assess the surface water potential and irrigation water requirements for selected crops in the Zenti River catchment, Omo Gibe River Basin, Ethiopia. To achieve the objectives, hydro-meteorological data and physiographic characteristics were used. This was accomplished using the CROPWAT model, FDC2.1 software, and GIS-based tools. The CROPWAT models to estimate the amount of irrigation water needed for major crops growing in the area, as well as FDC 2.1, were used. The FDC 2.1 software result revealed that the overall long-term monthly minimum available stream flow of the Zenti River is 0.11m3/s. According to the CROPWAT model result, the seasonal net irrigation requirements for sugarcane, maize, cabbage, and onion (60% field efficiency) were 640.66mm, 260mm, 251.66mm, and 233.17mm, respectively. The result indicated that although the need for irrigation water varies depending on the season, the potential irrigation area of the River catchment is in the order of 0.1% of the watershed. The results from this study could enable decision-makers and smallholder farmers to further use surface water for irrigation purposes with a proper management system.