Developing a Spatial Modeling Approach to Integrate Water Sustainability Map for the West Bank Aquifers, Palestine

The goal of this paper is to present a Spatial Modeling Approach (SMA) developed to integrate a Water Sustainability Map (WSM) for the West Bank aquifers. This SMA is based on interpolating physical and hydrometeorological data from point stations into GIS raster grids and then using the various GIS geo-processing tools to create feature spatial maps with tables of attributes representing the various estimated parameters within the boundary of the study area. Because groundwater is the only accessible water in the West Bank, the WSM is defined as the total annual renewable recharge classified by various groundwater basins and related aquifers and so it is equivalent to the West Bank Aquifer Sustainable Yield (ASY). The SMA used a 25-meter topographic contour map to construct a digital elevation model that was then used to delineate the surface water drainage and 72 watersheds for the West Bank boundary. The 72 created watersheds represent the spatial boundary of the model. Of these, 14 watersheds have their stream outlets draining their surface water out of the West Bank boundary. The SMA used a 10-year (from 1990/91 to 1999/00) average annual temperatures, radiation, relative humidity, and wind speed to estimate the evapo-transpiration using the Penman-Montieth method which was then multiplied by the crop coefficient to get the crop evapo-transpiration. The estimated evapo-transpiration and the measured precipitation and runoff data were interpolated from point stations into the GIS grid. The recharge grid was then estimated by subtracting the evapo-transpiration and runoff grids from the precipitation grid. Finally, the SMA converted the recharge grid into a GIS contour map with an embedded table of attributes that shows the recharge estimate. The 10-year annual average estimated volumes for precipitation, evapotranspiration, runoff, and recharge were 2508, 1607, 78, and 679 MCM/ Yr, respectively, and the resulting estimated yield of the WSM was 679 MCM/Yr.