A hydro-spatial hierarchical method for siting water harvesting reservoirsin dry areas

Water availability is the main limiting factor in dry-land agriculture, thr oughout arid and semi-arid regions, due to low annual rainfall depth and it s non-uniform temporal and spatial distribution. Water harvesting has been used for thousands of years to supplement scarce water resources in dry are as. Surface reservoirs are used to collect and store precipitation surface runoff so that stored water can be used for supplemental irrigation during long dry seasons. This article presents Hydro-Spatial AHP, a method for sit ing small water harvesting reservoirs. This method is used to rank potentia l sites for such reservoirs based on a Reservoir Suitability Index (RSI) de termined for each one of these sites. The RSI is calculated using Geographi c Information Systems (GIS) along with hydrologic modeling and the Analytic Hierarchy Process (AHP). This method was applied to Irsal, a dry-land agri cultural region in Lebanon. results reveal that Hydro-Spatial AHP works wel l in that area. This article also shows the flexibility of the method with respect to the criteria used for ranking the candidate sites.