Potential use of the deep aquifers in the Negev Desert, Israel — A conceptual model

Abstract

The deep aquifers (Jurassic-Paleozoic, 1–5 km deep) underlying the Negev Desert, Israel, contain brackish to saline water (800–120,000 ppm Cl −) and have been penetrated by only 47 wildcat oil drillings. The objective of this study was to evaluate the water potential of these aquifers for irrigation and for industrial consumption as well as their potential for serving as host rocks for hazardous wastes. We developed a special methodology for constructing a conceptual model for the thick sequence of layers in which these aquifers are found. It seems that, although these aquifers have different lithologies, they may be hydraulically connected. Statistics of the distribution of the aquifer system's parameters of state and analysis of their variance are used to aggregate individual formations into a few large hydrologic units. We employed regression analysis to supplement missing data and to evaluate estimation errors. Based on this methodology, a model consisting of three aquifers was defined. The consistency of the conclusions of the model is confirmed by our studies of pressure, permeability, salinity, temperature, and isotopic distribution. Wherever data were scarce, we estimated hydraulic parameters by linear regression. According to our study, the lower aquifer in the northern Negev contains only brines and is hydrologically separated from the two aquifers above it. The lower aquifer could, therefore, be considered as a possible site for toxic waste disposal or, at suitable locations, for hydrocarbon exploration. Hydrological continuity probably exists between the upper and middle aquifers in the eastern and central Negev, where brackish water is found in both aquifers. The methodology used here is suitable for constructing a conceptual model of any complex geohydrologic system in an area with scarce data.