Integrating a GIS-based approach and a SWAT model to identify potential suitable sites for rainwater harvesting in Rwanda

The increasing demand of water results in the overexploitation of water resources. This situation calls for more effective water management alternatives including rainwater harvesting (RWH) systems. Due to the lack of biophysical data and infrastructure, the identification of suitable sites for various RWH systems is a challenging issue. However, integrating geospatial analysis and modeling approaches has become a promising tool to identify suitable sites for RWH. Thus, this study aimed at identifying suitable sites for RWH in the Nyabugogo catchment located in Rwanda by integrating a geo-information-based multi-criteria decision-making (MCDM) and SWAT (Soil and Water Assessment Tool) model. Moreover, the sediment yield was compared to the soil erosion evaluated using the Revised Universal Soil Loss Equation (RUSLE) owing to the lack of sediment concentration measured data. The results revealed that about 4.8 and 16.35% of the study area are classified as highly suitable and suitable areas for RWH, respectively. Around 6% of the study area (98.5 km2) was found to be suitable for farm ponds, whereas 1.6% (26.1 km2) suitable for check dams, and 25.9% (423 km2) suitable for bench terraces. Among 50 proposed sites for the RWH structures, 29 are located in the most suitable area for RWH. The results implicated that the surface runoff, sediment yield, and topography are essential factors in identifying the suitability of RWH areas. It is concluded that the integrated geospatial and MCDM techniques provide a useful and efficient method for planning RWH at a basin scale in the study area.