Tanzania Journal of Agricultural Sciences 2014),Vol. 12(2): 35-46
Although 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.