Updated Water Budget for the Western Aquifer Basin and Potential for Agricultural Development in the West Bank, Palestine

This paper provides an update for the water budget for the Western Aquifer Basin (WAB) and highlights the potential for agricultural development in the West Bank. The Tulkarem and Qalqiliya governorates are used as a case study for agricultural development because of their dominance of irrigated agriculture. The WAB is a shared inter-boundary ground-water 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 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 hydro-meteorological 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 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. In 2010, a total of 24.6 MCM/yr was extracted from 138 wells tapping the WAB’s aquifers for various water use purposes in the Tulkarem and Qalqiliya governorates. Of which, 17.1 MCM/yr was consumed by irrigated agriculture from 119 agricultural wells and the remaining 7.5 MCM/yr was used for domestic purposes from the other 19 wells. Although there are 233,000 dunums of cultivated lands in the Tulkarem and Qalqiliya governorates, only 31,000 dunums (13 percent) are currently irrigated, due to restrictions on the Palestinian water use imposed by Israel. The 10-year average groundwater recharge for WAB’s aquifers in the Tulkarem and Qalqiliya governorates was estimated at 81 MCM/yr. Assuming no Israeli restrictions on the Palestinian water use in those governorates, an extra 56 MCM/yr more aquifer recharge than current water use would potentially be enough to increase the current irrigated lands and significantly enhance the Palestinian economy. Keywords: Water Budget, Watershed, Aquifer, GIS, Agriculture.