Potential Sites Selection For Rainwater Harvesting Using Mce And Gis Techniques: Adama Subwatersheds, Ethiopia.

Abstract

Rainwater harvesting (RWH) is collection and storage of rainfall by runoff for differentpurposes such as agriculture, livestock, domestic use, industry and groundwaterrecharge as well as flood control. This study was aimed to Potential Sites Selection forRWH in Adama Subwatersheds using MCE and GIS techniques and specifically To drivethe suitability maps for pond and Insitu RWHTs in the study area, to evaluate existingRWH structures based on the proposed suitability map and observed data of the study areaand to quantify the water balance components of the watersheds using ArcSWAT model.Thematic maps of the dominant factors were developed and reclassified based on theimportance to identify the potential areas for RWH using MCE and GIS techniques in theArcGIS software version 10.3. These were: slope, soil texture, soil depth and LULC maps.Weighted overlay analysis was carried out by combing each reclassified raster maps forpond and in-situ RWHTs factors with their corresponding weights developed in IDRISISelva 17.0 software for each parameter of pond and in-situ RWHTs using ArcGIS overlayspatial analysis tools. The results obtained for pond RWHT were: the very highly suitableareas with 58.14 km2 (9.63 %) and the very suitable area was 423.92 km2 (70.2 %)followed by suitable area of 121.82km2(20.17 %) in the study area. In the meanwhilesuitability map for in-situ was covered by 20.06 km2 (3.32 %), 458.07 km2 (75.86 %) and125.75 km2 (20.82 %) with the suitability levels of very highly suitable, very suitable, andsuitable area respectively. The majority or 91% of existing pond structures were found notfunctioning during evaluation due to seepage, evaporation and silting. The outputs in theanalysis of SWAT model simulation, the lowest runoff was occurred in the year of 2015amounted to 6.58mm, 3.98mm and 10.72mm for Northern, Northwest and Southernwatersheds. While the highest runoff occurred in the year 2012 rose to159.25mm,124.91mm and 197.69mm respectively for each watershed in the study area. Suitabilitymaps for RWHTs were depicted that the majority parts of the study area had the potentialof RWH for agriculture activities. SWAT modeling proved that how different water balancecomponents, such as recharge and runoff, vary significantly both spatially throughout thewatersheds and temporarily through time.Finally, MCE approach in ArcGIS environment and the hydrological modelling with SWATsoftware had a potential to select suitable areas for RWH and to quantify water balancecomponents for planning and managing rainwater resource in the study area and wherewith water shortage areas.