RS- and GIS-based modeling for optimum site selection in rain water harvesting system: an SCS-CN approach

In this study, an integrated approach has been adopted for optimum selection of locations for rain water harvesting (RWH) in Kohat district of Pakistan. Various thematic layers including runoff depth, land cover/land use, slope and drainage density have been incorporated as input to the analysis. Other biophysical criteria such as geological setup, soil texture and drainage streams characteristics were also taken into account. Drainage density and slope were derived from digital elevation model, and map of land use/land cover was prepared using supervised classification of multi-spectral Sentinel-2 images of the area. Aforementioned thematic layers are assigned respective weights of their importance and combined in GIS environment to form a RWH potential map of the region. The generated suitability map is classified into three potential zones: high, moderate and low suitability zones consisting of area 638 km2 (21%), 1859 km2 (62%) and 519 km2 (17%), respectively. The suitability map has been used to mark accumulation points on the down streams as potential spots of water storage. In addition, site suitability of artificial structures for RWH consisting of farm ponds, check dams and percolation tanks has also been assessed, showing 3.2%, 3% and 4.5% of the total area as a fit for each of the structure, respectively. The derived suitability will aid policy makers to easily determine potential sites for RWH structures to store water and tackle acute paucity of water in the area.