GIS-BASED MULTI CRITERIA APPROACH SURFACE IRRIGATION POTENTIAL ASSESSMENT FOR ETHIOPIAN RIVER BASIN

Abstract

Agriculture plays a significant role in the economy of Ethiopia. However, Ethiopian agriculture is vulnerable to rainfall, with the use of irrigation for agricultural production is highly limited. The primary issue associated with rainfall-dependent agriculture is the instability and unreliability of rains. Consequently, droughts and crop failure occur frequently. This results in food uncertainty, famine, leading to the slightest adverse climatic incident, affecting the rural peoples' livelihoods. The main problem in this study area is available water resources, potentially irrigable sites, and irrigation water demand for crops grown are not explicitly known. Looking to the above, assessment of the potentially irrigable area, available river flow, and the Gross irrigation water requirement for dominant crops are estimated. The main essential factors assessed in surface irrigation potential assessment are land slope, soil characteristics, distance from the water source, land use land cover, and weighted using ArcGIS. Soil suitability was examined in terms of soil texture, depth, and drainage for surface irrigation using GIS. The study area is dominated mainly by moderately suitable, which covers 488337.1ha (48.4) from the total area. The highly suitable area covers 284220.31ha (28.17%), the marginally suitable area covers 147221.205 (14.6%), and not a suitable area covers 89121.23ha (8.83%) for surface irrigation. Generally, the area of land suitability for surface irrigation within the upper Awash watershed is 919778.6201ha (91.17%) from the total area. Irrigation water demand was assessed by using metrological station data using CROPWAT8.0 software. Crops that are identified in the study area are Potato and Tomato. Physical surface irrigation potential was determined by comparing available stream flow and gross irrigation water requirements. Almost in all sub-watersheds, the gross irrigation water demand was greater than the available stream flow. Using the CLIMWAT 2.0 climate reanalysis data set and depending on the available average stream flow of 32.848m3/s, the study area's potential irrigable area is 49897.936ha from the total irrigable area of 919778.2ha. However, based on CLIMWAT 2.0 climate reanalysis data set, the study area's potential irrigable area is 47359.31ha out of the total irrigable area of 919778.2ha.