GIS BASED SURFACE IRRIGATION POTENTIAL ASSESSMENT IN JIDO RIVER CATCHMENT CENTRAL RIFT VALLEY, ETHIOPIA

Abstract

The rainfall-dependent agriculture in the country is affected by the high degree of rainfall variability and unreliability. Irrigation plays a vital role to increase agricultural productivity and improve the livelihoods of the communities specifically and the economy of Ethiopia in general. However, surface irrigation development in the study area is constrained due to lack of consistent data of suitable land and available water potential. Therefore, this study is conducted to assess the land and water resource of the Jido river catchment in rift valley, Ethiopia using geographic information system (GIS) to identify suitable land and available water potential for surface irrigation. Slope, Land use land cover, soil, and proximity to river are factors used to assess land suitability for surface irrigation. Delineation of watershed, estimation of crop water requirement for selected crops and estimation of surface water resource availability and mapping of potentially irrigable land were the major steps followed in this study. ARC SWAT model is used to estimation of surface water resource. While AHP is used to reclassify suitability of land. The weighted overlay analysis indicated that 65.09% (113,448.13ha) of land in the watershed were in the range of highly suitable (S1) to moderately suitable (S2) and the remaining 34.91% (60,852.82ha) of the river basin were in the range of marginally suitable to none suitable for surface irrigation development. Crop water requirement of selected crops in the study area was estimated by CROPWATT 8.0 model. The gross irrigation water requirement of Wheat, Maize, Potato and Tomato crops grown in the study area throughout the growing season in 11 sub-watersheds of the watershed was 256.11 m3/s and the monthly dependable simulated stream flow throughout irrigation period was 197.2 m3/s. The simulated available flow could irrigate 47,044.65ha for highly to moderately suitable area. To irrigate the remained 66,403.48ha of potentially suitable land, additional water should be added through construction of water storage structure or assessment of other water saving irrigation methods such as drip/trickle and sprinkler irrigation systems in the study area