Evaluation of Water Budget for the Western Aquifer Basin in the West Bank, Palestine

This paper provides an update for the water budget for the Western Aquifer Basin (WAB) in the West Bank. The WAB is a shared inter-boundary groundwater basin between the West Bank (in Palestine) and Israel. Two thirds of the Palestinians in the West Bank (1.5 million capita) are living within the upstream portion of the WAB, where 75 percent of its geologic aquifer outcrops (recharge area) are located. We used a spatial modeling approach to create 10-meter cell-size grids showing the spatial distribution of precipitation, crop evapotranspiration (ETc), and runoff based on the 10-year (2001-2010) average available records of hydrometeorological data. We used the general water budget equation to estimate rates and volumes of groundwater recharge by subtracting the spatial grids of ETc, runoff, and an assumed change in storage from precipitation grid. Change in storage, which includes minor losses by initial abstraction, subsurface flow, depression storage, soil’s field capacity, and errors of measurement and estimation, was assumed at a lumped sum value of 5 percent of total precipitation. GIS geo-processing tools were used to clip the spatial grids of various water budget components for the WAB’s aquifer outcrops and for the West Bank portion of the WAB. The 10-year average groundwater recharge for the entire WAB (both Israel and West Bank portions) was estimated at 350 MCM/yr (million cubic meters per year). The 10-year average volumes of precipitation, ETc, runoff, and recharge were estimated for the West Bank portion of the WAB at 889 MCM/yr, 548 MCM/yr, 34 MCM/yr, and 263 MCM/yr, respectively, in addition to 44 MCM/yr of minor losses. Although the WAB’s West Bank portion receives an average recharge of 263 MCM/yr, the 2010 Palestinian water extraction was limited to a total of 29.45 MCM/yr for various water use purposes due to Israeli restrictions on Palestinian water use. The rest of WAB’s recharge is being fully utilized by Israel.