Identifying watershed-scale groundwater flow barriers: The Yoqne'am Fault in Israel

Geological faults may serve either as groundwater conduits or barriers, depending on their hydraulic properties. Determining fault characteristics is therefore important when deciding inputs for numerical models developed for watershed-scale groundwater studies. Cutting-edge methods for determining fault characteristics have been widely applied for oil and gas reservoir characterization purposes, whereas water-resource studies simply use a priori values. This study evaluates the hydraulic properties of the Yoqne'am Fault (YF) in northern Israel, which impacts groundwater flow within the Judea Group Aquifer (JGA). The YF has a vertical throw of several hundred to one thousand meters accompanied by pronounced lateral throw. Detailed examination of hydrological and geochemical data from nearby wells, structural maps and numerical modeling results, suggests that the YF acts as a semi-impermeable feature with a hydraulic conductivity of less than 4 × 10e^-2 m/d. The YF hydraulic conductivity is four orders of magnitude below that of the surrounding Judea Group rocks, and only a limited volume of water can leak through the fault. For that reason, it is concluded that the YF acts as a boundary between two large groundwater basins.