GIS BASED SURFACE IRRIGATION POTENTIAL ASSESSMENT OF GOLOLCHA RIVER WATERSHED, AWASH BASIN, ETHIOPIA

Abstract

Management of land and water resources are very important through assesment practice for future irrigation development. However, the irrigation potential of Gololcha river watershed has not been assessed yet. Thus, it was difficult to identify and know land and water resources potential of the watershed for sustainable management. The current study was conducted to assess the potential of land and available water of river for surface irrigation in Gololcha river watershed for the development of surface irrigation. The study employed Geographical information System_based multi criteria analysis method considering seven factors such as soil texture, soil drainage, soil depth, Slope, LULC, distance from the main river and road to find suitable land for surface irrigation. Using the Analytical Hierarcy process, the values of each dataset were weighted and combined to find the most suitable land for irrigation using the ArcGIS environment. The results of the study revealed that about 2508ha (7.27 % of the watershed area) highly suitable, 16420 ha (47.65 % of the watershed area) moderately suitable, 1502 ha (4.35 % of the watershed area) marginally suitable and 14029 ha (40.71 % of the watershed area) not suitable. Three (Maize, Wheat and Potato ) major crops which are mainly grown in the area were selected under identified irrigable area and their gross irrigation demand were calculated by using nearby climatic stations. The results revealed that irrigation requirements of identified command area varies according to nearby climatic stations and type of crops selected. The discharges at un-gauged sites were estimated from gauged sites on the same river by applying area-ratio method and results were obtained on monthly bases. By associating gross irrigation demand of irrigable land with available flow in rivers, the total surface irrigation potential of the study area was obtained as 4872.58ha. Potential suitable land for surface irrigation is very small due to the scarcity of water. Therefore, it is possible to increase surface irrigation potential by increasing available water using storage structure.