Assessment of Physical Land Resource Potential For Surface Irrigation: (A Case Study of Muga Watershed)

Abstract

Assessing available land and water resources for irrigation is important for planning water resources projects. This study is initiated with the objective of assessing the land resources potential of Muga watershed for surface irrigation development by using Geographic Information System and analytical hierarchy process with multi criteria analysis. The evaluation of land in terms of the suitability classes for surface irrigation is based on the method as described in FAO (food and agricultural organization) guideline for land evaluation. The factors that were considered for evaluation of the land for surface irrigation were slope, soil drainage, soil texture, soil depth, land use/cover and distance to water sources. After evaluating the physical land capability for surface irrigation, irrigation suitability map was developed AHP method was utilized to identify the weight of each criterion from the pair wise comparison matrix. The weighted sum overlay analysis was then used to generate the suitability map in a GIS environment. This map was classified in to four suitability classes as highly suitable (S1), moderately suitable (S2), marginally suitable (S3) and not suitable (N) suitability classes independently and the final potentially irrigable land was identified by weighting the factors of suitability. The suitability analysis of the parameters with the method of multi criteria analysis indicates that 20.19% slope (covering an area of 14905.03 ha), 83.93%(61961.08 ha) soil texture, 40.37%(29801.64 ha)soil depth, 85.98% (63478 ha)soil drainage and 64.78%(47825.92 ha) land use/cover of the study area were classified as potentially suitable for irrigation development in the study area. By weighting analysis of all parameters 2.99 %( 2191.04 hectare) of the study area was found to be highly suitable whereas about 24658.80 hectare (33.63%) was restricted for irrigation developments. Resulted from CropWat software the annual total gross irrigation water requirement was found to be 74.78 m3/s and the the annual total minimum flow of the river was 35.78m 3 /s. this result indicates that the annual minimum flow of river couldn’t fulfill the water requirements of the crop commonly grown in the area so construction of any storage structure is necessary.