Gis Based Multi Criteria Decision Analysis Of Land Suitability Evalution For Surface Irrigation Method: (A Case Study Of Chemoga Watershed)

Abstract

Ethiopia depends on rain fed agriculture with limited use of irrigation for agricultural production. Evaluation of land suitability and water resources availability is very important for irrigation and planning water resources projects. Chemoga River has not been used for irrigation purpose due to this fact agricultural production is very low in this area. This study is initiated with the objective of evaluate the land resources potential of Chemoga watershed for surface irrigation development by using Geographic Information System with multi criteria dissection evaluation and analytical hierarchy process. Irrigation suitability of each land parameters was classified based on the Food and Agricultural Organization guideline for land evaluation in to highly suitable (S1), moderately suitable (S2), marginally suitable (S3) and marginally not suitable (N) suitability classes independently. The factors that were considered for evaluation of the land suitability for surface irrigation were slope, land use/cover, soil depth, soil drainage, soil texture, road access and distance of the river. After evaluating the land capability of surface irrigation, irrigation suitability map was developed. Analytical hierarchy process method was utilized to identify the weight of each criterion from the pair wise comparison matrix. The weighted sum overlay analysis was used to generate the suitability map in a geographic information system environment and the map was classified in to four suitability classes. Land suitability potential was evaluated by overlying the parameters indicate that 42.67 % of slope, 90.68 % of land use/ land cover, 69.08 % of soil depth, 60.98% of soil drainage, 68.02% of soil texture, 89.70% of river proximity and 87.4% of road proximity of the study area were identified to be in the range of highly suitable to marginally suitable for surface irrigation. By weighting analysis of all parameters 15.91% of the study area was found to be highly suitable, 31.94% moderately suitable, 21.20% marginally suitable and 30.95% were not suitable. By comparing the irrigation water demand and available dry months stream flow of the river, irrigation water demand was greater than available stream flow of the dry months. The overall result indicates that most of the Chemoga river watershed was (80093.09 ha) potentially suitable for irrigation development from the total study area for potato, tomato, cabbage and onion. To irrigate this land 118.76m3/s gross irrigation water is supplied to the field for these crops resulted from CropWat software and to irrigate all the identified irrigable area, the decision maker should take the mitigation measure by expand irrigation technology, construct storage structures across a river, exploring water from ground has to be implemented in the sub basin of river