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

Abstract

Potential water harvesting area assessment in the country particularly in the Study area is essential for increasing agricultural production. This study was, therefore, very important to identify potential water harvesting areas for Micro Dam construction. In SCS CN-GIS with Analytic Hierarchy Process (AHP) method in Genfel Watershed Eastern Zone of Tigray, Northern Ethiopia to select potential water harvesting area. Digital Elevation Model, 30m resolutions to generate physiographic characteristics of the Watershed were downloaded from united states geological survey, Required data set, a remotely sensed land sat 7 image of march 2016 with a spatial resolution of 30m to classified the land cover types, and Daily rainfall data were collected from six metrological stations (2000 – 2015) from National Metrological Agency to estimate annual runoff. The causative factors for water harvesting sites 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 map. estimation of direct run-off depth of the watershed showed that an average runoff volume of 35902.6m3/year was generated basin slope (C1) and Geology (C2) were the most water harvesting potential contributing factors of the area based on the decision-makers’ preferences. The Reclassified potential water harvesting zones depicted that Small portion of the watershed 3% were 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 potential water harvesting areas were compared with micro dam areas to verified and check the validity and reliability of the results. The result shows that SCS CN-GIS with Analytic Hierarchy Process (AHP) method integration with Analytic Hierarchy Process can be used to map potential water harvesting areas to assist decision-makers on the selection of micro dam site.

Keywords: SCS CN; Analytical Hierarchy Process; GIS; runoff volume.

DOI: 10.7176/JEES/10-9-02

Publication date:September 30^th 2020