IRRIGATION POTENTIAL ASSESSMENT USING GIS AND REMOTE SENSING TECHNIQUES

Abstract

Ethiopian agriculture is dependent on rain fed system with limited use of irrigation. Highly variable and erratic rain fall and lack of means to store water causes risk of draught and chronic food shortages. Recently, emphasis is given to the development of large and medium-scale irrigation schemes in the medium to long-term planning periods. The Megech River is one of the · irrigation projects planned to be developed and traditional irrigation under the river system is increasing progressively. The expansion of irrigation development without the knowledge of water resource availability and land suitability will have the outcome of water stress and agricultural yield reduction. Thus, assessment of land and water for irrigation has a paramount importance for planning and economic development. The main objective of this study is to assess irrigation potential of the Megech River watershed using� and �S. The approach followed in this work �as: - Delineating thB a_nd'w��g Arc-SWAT, identification of land suitable for irrigation using sotl, slope and land use/cover as evaluation factors, estimation irrigation water demand using CROP_y//\T·8 model and estimation of water resources avaiiability, at the dam site usin� Future irrigation development scenarios were also evaluated to assess the future water requirement of crops commonly grown in the command area and future water availability at the dam site. Results of the watershed and command area delineation gave 416 km 2 and 248.8 km 2 respectively. The overall land suitability analysis of those factors indicated that 15,888.4 ha of land are in the range of highly suitable to marginally suitable for surface irrigation. This land was evaluated with the water availability at the proposed dam site based on the gross water requirement of c rops commonly g rown in the area. The N et available water for irrigation at the dam o _ ut let was 69.l Mm 3 .By matching the gross irrigation demand under th e current cropping intensity and irrigation effi ciency, the total i rr igation p otential estimated was 7250 ha. The stu d y also provide s fu t ure irrigation r e q uirement in the command area and future water availa b ility at the dam outlet. This asse ssment of available land and water resources for irrigation is important for future p lanning. I n conclusion, irrigation potential from this fi gure can b e increased by improving i rr igation e ffi ciency or by shi ft ing irrigation methods.