Potential assessment of water harvesting in arid and semi-arid watersheds using multi-criteria hierarchy decision making (Case study: Roodsarab watershed, Khooshab, Iran)

Water shortage has led to a fragile living condition in arid and semi-arid regions of the globe. Due to the limited time and amount of rainfall in these areas, presenting solutions for the utilization of rain water is the main concern of many residents and managers of these areas. There are some criteria to select the appropriate method of water harvesting and also site selection according to environmental conditions. In this study, to site selection of the projects Pitting, Furrowing, and Terracing, several types of spatial data, i.e. plant cover, soil, topography and climate were overlaid within a GIS framework through the Analytic Hierarchy Process (AHP) in a three step approach. In the first step, the hierarchical level was formed using the objectives, criteria and sub-criteria. During the second step, pair wise comparisons were implemented and consistency ratio was computed. Inconsistency ratio of the judgments for the projects Furrowing, Pitting and Terracing were determined to be 0.07, 0.03, and 0.04, respectively. These ratios were lower than the standard level of 0.1. Therefore the calculated weights were desired to be validated. Results showed that the criteria topography and climate with a normal weight of 0.563 and 0.055 respectively had the highest and the lowest impact on the site selection of Pitting. The same situation was happened for the projects Furrowing and Terracing with the normal weights 0.563, 0.055 and 0.566, 0.081, respectively. In the third step, all layers were overlaid to extract the suitability maps of the defined projects. Validation analysis of the suitability maps revealed that the suitability map of the Pitting project with the accuracy level of 79% was in the highest level of accuracy among the extracted suitability maps.