Determination of suitable locations for rainwater harvesting using analytic hierarchy process in GIS framework (Case study: Roodsarab watershed, Khooshab, Khorasan Razavi, Iran)

Water shortage in arid and semi-arid world results in fragile environmental conditions. Therefore, the implementation of rainwater harvesting system is an important step in order to maximize water availability for agriculture and other uses. However, choosing the appropriate location for implementation of various systems to collect rainwater on a large scale is being a great challenge due to the need for environmental data and infrastructure. In this study, the most influential factors affecting the rainwater storage in the soil profile and runoff production in the Rudsarab watershed were fed into the analytic hierarchy process (AHP). The weights for six criteria, i.e. land use, slope, permeability, soil texture, soil depth and rainfall using ext-AHP application within the Arc GIS9.3 environment were determined as 0.4281, 0.1930, 0.0724, 0.0725, 0.0414, 0.1924, respectively for the objective of runoff production. However, based on the objective of runoff storage, the weights for criteria land use, slope, permeability, soil texture and soil depth were respectively determined as 0.102, 0.0458, 0.102, 0.504, 0.0245. Thus, in terms of runoff storage, the effect of soil texture and based on the aim of runoff production the effect of land use was more than the others for site selection in the study area. Then rain water harvesting potential map for both objectives, i.e. runoff storage and runoff production was extracted using a weighted linear combination in the GIS environment. The extracted map was classified into five suitability groups, i.e. very good, good, average, poor and very poor using the natural breaks approach. In general, it can be revealed that about 58% and 19% of the watershed area had very good and good potential for rainwater harvesting, in terms of the objectives runoff storage and runoff production, respectively. This established a more significant potential of the watershed for runoff storage, as compared with runoff production (efficiency).