Potential Water Harvesting Site Identification for Micro-Dam Using SCS-GIS Approach: The Case of Genfel River Catchment, the Eastern Zone of Tigray, Ethiopia

Abstract

Potential water harvesting area assessment in the country particularly in the Study area are essential for increasing agricultural production. This study integrated SCS CN-GIS with Analytic Hierarchy Process (AHP) in Genfel Watershed Eastern Zone of Tigray, Northern Ethiopia with the objective to identify potential water harvesting area for micro-dam. The Required data sets are; Digital Elevation Model to generate physiographic characteristics of the Watershed, a remotely sensed land sat 7 image, to classify the land cover types, and Daily rainfall data to estimate annual runoff. The causative factors for water harvesting site for micro-Dam in the watershed are taken into account as runoff volume, Soil, slope, drainage density, Land use land cover and Geology. Questionnaires were distributed to experts to score each, water harvesting potential site contributing factor used as criterion separately in their order of significance. SCS-CN method was used to estimate runoff volume of the watershed, Multi-criteria analysis hierarchy process method was used to compute the priority weights of each criterion and GIS was used to map. The result showed only a small portion of the watershed 3% where found very high potential water harvesting zone for micro dam site whereas the identified very high potential water harvesting area had a direct runoff volume of 50818.5m3/year to 47469.4m3/year. The identified area were verified and found a correlation coefficient of 0.64 which shows a strong positive linear value. Thus the methodology employed can be an alternative way for water harvesting mapping and better decision making.