SPATE IRRIGATION POTENTIAL ASSESSMENT THE CASE OF HARGETI RIVER WATERSHED

Abstract

Assessing availability of water source and land for irrigated agriculture is very important to reach at a proper decision on the demand and supply of irrigation development. This study was initiated with the objective of assessing surface runoff potential , land suitability evaluation for irrigation and crop water demand of Hargeti river watershed for spate irrigation development .The surface runoff potential was calculated by the soil Conservation Service Curve Number ( SCS - CN) method.Crop water demand was estimated using Hargreaves method. To identify potential irrigable land , irrigation suitability factors such as soil type, slope, and land cover/use, were taken into account. The surface runoff potential Hargeti sub catchment was assessed monthly based, the result shows there is high tempora l variability of runoff observed. The irrigation suitability analysis o f these factors indicates that 54 % of soil is marginally suitable. whereas based on slope suitability 7 % and 31% of the study area is in the range of highly to marginally suitable for surface irrigation system respectively. In terms of land cover /use, 63 % and 35% of land cover/ use is in the range of highly to marginally suitable. The overall analysis of these factors gave 29,200 ha of irrigable land by surface irrigation system. Based on analysis of surface runoff potential and water demand for selected crop, the potential irrigable land by spate irrigation is 3682 ha, thus the potential can be enhanced through additional water harvesting activities.