Identification of suitable indices for identification of potential sites for rainwater harvesting

Tanzania Journal of Agricultural Sciences 2014),Vol. 12(2): 35-46Although indigenous and scientific knowledge for locating potential sites for water harvesting technologies do exist, a simple and integrated tool to assist farmers’ support agencies, is missing. A geographic information system (GIS)-based decision support system (DSS) can be a valuable tool for such a task. However, key to such DSS are the factors and their suitability levels, which are not well developed. This study therefore focused on the development of suitability levels for most important factors/parameters for identification of such sites. The factors included rainfall, soil texture, soil depth, drainage, topography and land use or cover. Specific suitability levels were derived from analysis of existing RWH technologies in Makanya river catchment. Results showed that suitability levels of factors differ with different RWH technologies. Suitable areas for ndiva is on steep slopes (18o-30o) with clay soils, stone terraces is on moderately steep slopes (10o – 18o) with sandy clay loam soils, bench terraces (5o-18o slopes, clay or silt clay soils) and “boda” (2o-5o slopes, slit clay or clay soils). It was also found that ndiva, “boda”, stone terrace and bench terrace are located at a distance within 125m from cropland. Testing of the developed parameters using ArcView-based DSS framework showed that 81.4% RWH technologies were located in the very high and high suitability levels, indicating the usefulness of the developed parameters and their suitability levels