ASSESSEMENT OF SURFACE WATER AND LAND RESOURCE POTENTIAL FOR SURFACE IRRIGATION: CASE STUDY OF GUMARA WATERSHED TANA SUB BASIN NORTH GONDAR

Abstract

Irrigation development is one of the key strategies to increase agricultural production to generate profit. One of the main factor rain fed dependent agriculture is rainfall variability and unreliability occurrences. Due to this effect, crops are failed and consequence, food insecurity often turns into famine. Surface water and land resource potential for surface irrigation was assessed before any structure is lunched. The main problem on this area, potential of irrigable area, available water and irrigation water demand for some selected crop were not known. In order to alleviate this problem, assessment of surface water and land resource potential for surface irrigation was assessed. To meet the main objective, land suitability, available water and irrigation water demand was assessed in this thesis. Materials used to assessing surface irrigation potential were GIS, CROPWAT8.0, and PCP. Land suitability was assessed by using GIS model. The most determinant factors of surface irrigation were land use/cover, slope and soil suitability was assessed for this study. Soil suitability was examined in terms of soil depth; texture and drainage for surface irrigation using GIS model. Overall soil suitability for surface irrigation was obtained two suitability class namely moderately suitable and marginal suitable. The area of each suitability 7040ha (19.31%) is covered by moderately suitable and29, 410ha (80.69%) is covered by marginal suitable for surface irrigation. Land suitability potential was evaluated by overlying soil, slope and land use/cover. Based on this analysis suitability area of surface irrigation is 34950ha from marginal to highly suitable and the rest of the study area 1500ha is not suitable for surface irrigation. On average, to irrigate this irrigable area 2,558.5mm/growing period of water is needed for wheat, sunflower, barely, pepper and maize. Physical irrigation potential was identified by comparing irrigation water demand and available stream flow. Throughout the season irrigation water demand was greater than available stream flow. The total irrigable area due to the available stream flow was about 813.98ha (2.33%) of the total identified irrigable area for wheat, sunflower, barely, pepper and maize. To irrigate this land 129.75m 3 /s gross irrigation water is supplied to the field for these crops. Hence, irrigation water demand is greater than the available stream flow the decision maker should be decide to construct storage structure rather than diversion structure.