TARIKU TUNSISA TULICHA MAJOR ADVISOR: DEMELASH WENDEMENEH (PhD) CO-ADVISOR: DEMELASH WENDIMAGEGNEHU (PhD)

Abstract

Planning and managing new irrigation expansion projects necessitates a systematic assessment of irrigable land, which is typically linked to available water supplies. The objective of this study was to assess the Kola river water resources availability and surface irrigation potential using integration of Soil Water Assessment Tool (SWAT) and geographic information system (GIS). A CROPWAT model was used to determine crop water requirements of important crops that grow in the area. The identification of potentially irrigable land was assess using Analytic Hierarchy process (AHP) along with GIS and Arc SWAT model was used to estimate the water resources available in the watershed. When identifying potentially suitable irrigable land, irrigation suitability characteristics such as soil physical features, slope, land use/land cover, and distances from the water supply (sources) are considered. According to the irrigation suitability analysis show that; 93.97% of the soil in the study area, 94.81% of the LULC, 93.5% of the slope, and 90.02% of the river proximity are highly to marginally suitable for irrigation. According to the final irrigation land suitability results, 69.2% of the land is highly suitable (S1), 28.2% of the land is moderately suitable (S2), and 2.6% of the land is unsuitable (N) for surface irrigation development. The calibrated and validated SWAT model show that; 26.23m3/s per annual/month the minimum simulated stream flow and to determine water availability for irrigation. The irrigation water demand, for five major crops grown in the study area, was determined to be 64.19m3/s throughout the growing season. The available water could irrigate 3287 ha (23%) of highly suitable land.