GIS-Based Assessment of Suitability Area of Rainwater Harvesting in Daro Labu District, Oromia, Ethiopia

Abstract

Rainwater harvesting is the process of intercepting, conveying and storing rainfall for future use as an alternative source of water in the drought prone areas of Ethiopia especially eastern Oromia. The aim of the research was to assess and mapping suitability area of water harvesting site in Daro Labu District. There are various methodologies and criteria to identify suitable sites and techniques for rainwater harvesting (RWH). Determining the best method or guidelines for site selection, however, is difficult. GIS is the recent technology of spatiotemporal data used to assess the factor of influences for rainfall and runoff depth estimation for identification of potential area of RWH for crop production and mapping of the potential site. The influence factors for consideration of the assessment was climate data, soil texture and depth, land use and land cover (LULC) type, slope difference were used. The total area of the catchment was about 156064.72 ha. The SCS–CN for rainfall used to runoff depth estimation compute runoff and volume from the land surface depend on the level of antecedent moisture condition (AMC.) The length of wet and dry season of the study area were known with antecedent moisture condition (AMC) of II, I III by having the values of 82, 67 and 91 respectively. The annual of 20 years average rainfall was 925.2 mm with maximum and minimum of 1134 mm and 737.3 mm respectively with average annual runoff depth of estimate was 185.3 mm. From the estimated annual runoff the volume of water harvested was about 2.89 × 10⁸ m³. The suitability map of the study area shows extremely potential, highly potential, potential and not potential accounts by coverage areas about (12,797.3 ha) 8.2%, (25,906.7 ha) 16.6%, (98,302.8 ha) 63.5%, and (19,040 ha) 7.5% respectively. The runoff in the study area was affected by geomorphological factors, particularly, land use change, topography, soil texture and depth, drainage density, and population density affects the runoff rate and volume significantly.