GIS BASED ASSESSMENT OF POTENTIAL AREA OF RAIN WATER HARVESTING FOR CROP PRODUCTION AT DARO-LABU DISTRICT, WEST HARARGHE, 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 potential 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 was used. The SCS–CN for rainfall runoff depth estimation was used to compute runoff and volume from the land surface depend on the level of antecedent moisture condition (AMC) and length of wet and dry season of the study area. The total area of the catchment was about 156064.72 ha with antecedent moisture condition (AMC) of II, I III by having the values of 82, 67, and 91 respectively. The annual average rainfall of 20 years was 925.2 mm with maximum and minimum of 1134 mm and 737.3 mm, with average annual runoff depth estimate of185.3 mm. From the estimated annual runoff the volume of water harvested was about 289.14 x 106 m 3 . The suitability map of the study area shows that, extremely potential, highly potential, moderately potential, marginal and not potential accounts by coverage areas about (12,828.52 ha) 8.22%, (25,220.05 ha) 16.6%, (99,038.67 ha) 63.5%, (11,777.28 ha) 7.54%, and (7120.20) 4.62% respectively. The runoff in the study area was affected by geomorphological factors, particularly, land use change, topography, soil texture and depth, slope, and affects the runoff rate and volume significantly. In order to change the water harvested for crop production and meet the irrigation requirements of selected crop (tomato, onion, and maize) was 528 mm, 354.3 mm and 558.5 mm respectively was taken. The total cultivated area was about 58.6% and the area can be irrigated using the volume of water harvested was about 63% of the total cultivated area for single crop season of the study area. Thus, Rainwater harvesting can be considered as livelihood income generation and increases with production and productivity of the communities as well.