Assessment of Geospatial and Multicriteria Decision Method to Evaluate Site Suitability for Rainwater Harvesting

The Sri Sathya Sai District of Andhra Pradesh is a drought-prone area. To plan for the development of irrigational water resources in this area, a scientific study of various variables, viz., land use/land cover, soil texture, rainfall, slope, and drainage density that determine the availability of water for the purpose of developing rainwater harvesting (RWH) sites is necessary. Geographical Information Systems (GIS), along with multicriteria decision methods (MCDM), have been useful for identifying suitable RWH sites. This chapter attempts to identify suitable RWH sites using GIS and multicriteria decision method for Sri Sathya Sai district. An attempt is also made to evaluate this method in RWH site suitability studies. To achieve the objectives, various government and nongovernmental websites were used to download datasets from which thematic layers were created and reclassified in a GIS environment with ranking from 1 to 5 to indicate ‘unsuitable’ to ‘very high suitability’ classes, respectively. The weightages for variables were determined by an analytical hierarchical process (AHP), and the same were used to perform a weighted overlay analysis (WOA). The findings indicated that only 1% was under ‘very high suitability,’ while 51%, 43%, 5%, and 0.0001% of the study areas fell under ‘high,’ ‘medium,’ ‘low,’ and ‘unsuitable’ categories, respectively, for RWH. Finally, top two and bottom two categories were merged to get three relatively homogenous zones under high, medium, and low RWH suitability. Thematic layers of roads, railway tracks,, and major towns were overlaid upon the resultant map and were masked using the buffer function in GIS to exclude those areas. The findings of the study were validated by overlaying the existing RWH structures on the resultant RWH suitability map. The study revealed that 71% of the existing structures are in the ‘high suitability’ zone. Thus, this method gave reliable results and may be followed to identify RWH site suitability zones for other drought-prone areas, also where the stakeholders are looking forward to harvesting rainwater for irrigation to be utilized during dry periods.