SURFACE IRRIGATION POTENTIAL ASSESSMENT AT MILLE RIVER CATCHMENT, LOWER AWASH BASIN, NORTH ETHIOPIA

Abstract

Irrigation plays a vital role to increase agricultural output and enhance the livelihoods of the communities. Since identification of suitable areas is essential for the planning irrigation schemes and also sustainable use of resources. However, there is limited explicit knowledge regarding to irrigation potential of the study area. So, the research aims to assess surface irrigation potential in the Mille River catchment. Identification of suitable irrigable land was carried out by using an integration of geographical information system and analytical hierarchy process technique by considering criterions incase soil properties, slope, landuse landcover, and river proximity. Estimation of surface water availability of the catchment was done using soil and water assessment tool. And also, the gross irrigation requirement of selected crops (Maize, Onion, and Tomato) was determined using CropWAT model. Potential irrigable land was identified through weighted overlying of criterions. Out of the total area of the catchment (4426 km2), highly suitable moderately suitable and marginally suitable 3672 km2 (83%) was suitable and the rest 753 km2 (17%) was not suitable for defined land use. The SWAT performance was evaluated as a better comparison between measured and simulated stream flow, as verified by 0.83 and 0.81 of R2, 0.79 and 0.78 of NSE, and 3.3 %, and 4.8 % of PBIAS during calibration and validation respectively. The catchment generates annual volume of 410.91 MCM. The gross irrigation requirement of selected crops (Maize, Onion, and Tomato) was determined using CropWAT model. So, gross water irrigation requirement of the irrigable land is 1439 MCM in one irrigation season. Lastly, the irrigation potential of the Mille River catchment was estimated to be 163.19 km2 (3.7 % of total land) of areal coverage under the surface irrigation method through a comparison of surface water and crop requirements of the catchment. Since, it is small relative to suitable land due to the scarcity of water in the dry season. Hence, construction of storage structures (pond and reservoir) and deficit irrigation practices will be necessary to increase irrigable land.