GIS BASED LAND SUITABILITY ASSESSMENT FOR SURFACE IRRIGATION: CASE STUDY IN KOBO VALLEY,EASTERN AMHARA

Abstract

The main objective of this research is to evaluate land suitability for surface irrigation method based upon a parametric evaluation system in an area of 33,383.09 ha in the Kobo Valley, Eastern Amhara. Key factors that significantly affect irrigation suitability evaluated in this study include physical land features (land use, soil, and slope). These factors were analyzed and evaluated based on rating table values, then reclassified and overlaid to identify suitability maps for surface irrigation methods using Geographic Information System (GIS). Groundwater and climate (rainfall and evapotranspiration) data were used to estimate the groundwater potential, which indicates the corresponding irrigation potential for major crop. The obtained results showed that 77.7 % (25,934.08 ha) of study area was highly suitable (S1), 15.5 % (5,176.84 ha) of the study area was moderately suitable (S2), 6.1 % (2,033.75 ha) of the study area was marginally suitable (S3), 0.4 % (124.32 ha) of the study area was currently not suitable (N1) and 0.3% (114.11ha) of the study area was permanently not suitable (N2) for surface irrigation purpose. In this particular study drainage was the major limiting factor and the cause for the area to be moderately suitable (S2); drainage and texture were the major limiting factor and the cause for the area to be marginally suitable (S3). Irrigation well yield potential using ground water assessment result showed that a yield can satisfy the crop water need of the study area two times beyond net irrigation requirement, indicating that Kobo valley has high amount of ground water resource to fulfill maximum crop water need in the area using surface irrigation method. Hence, the majority of the study area was highly suitable and potential in terms of surface irrigation and ground water resource.