Assessment of surface water potential for sustainable irrigation development in the Muga watershed, Abbay Basin, Ethiopia using ArcSWAT model

Abstract

Agriculture in Ethiopia is mainly rainfed. Thus, the sector is highly vulnerable to climate variability. Enhancing sustainable surface water irrigation is essential to ensuring food security. Based on this, this study aims at assessing the surface irrigation potential using the integrated approach of a GIS, SWAT hydrological model, and CROPWAT in the Muga watershed, Abbay Basin. Key inputs used were a 30 m SRTM DEM; land use/land cover and soil maps; and long-term hydro-meteorological data from 1994 to 2018. In these aspects, the performance of the SWAT model is very good both during calibration, Nash–Sutcliffe Efficiency (NSE = 0.83, coefficient of determination (R2 = 0.88) and validation (NSE = 0.81, R2 = 0.86). The modelling results indicated that there was a huge spatial and temporal variability in water availability and the average monthly flow varied between 0.18 m3/s in April and 17.67 m3/s in September. The irrigation water requirements were estimated by the CROPWAT 8.0 for dominant crops, namely maize, onion, and potato. By comparing the water availability with demand, it is deduced that the Bora, Gibstawit, and Genet subbasins have sufficient water for irrigation at any time of the year. However, whereas the Enat Muga and Gilgel Muga have seasonal deficits between January and April, the total potentially irrigable area is identified as 3443 ha, equivalent to 5.1% of the entire watershed, and this varies but has its maximum potential in the Enat Muga sub-basins, covering an area of 1882–2509 ha. The finding provides scientific evidence which supports irrigation planning and sustainable water resource management efforts in areas with limited data availability.