RIVER-LIKE FLOW PATTERNS OF GROUNDWATER IN THE JUDEAN DESERT, ISRAEL

The Judea Group is an 800 m thick Cretaceous carbonate unit. The Judean Mountain ridge is a monocline, consisting of northeast plunging synclines and anticlines. The Judean Group Aquifer beneath the Judean Desert is characterized by a steep hydraulic head gradient, from 400 m above sea level near Jerusalem-Hebron to -400 m at the Dead Sea, 30 km apart. A thin aquitard vertically divides the aquifer into an upper and lower division. The aquifer annual yield of 10⁸ m³ fresh groundwater discharges through the Tsukim, Kane and Samar springs, located at the northwestern edge of the Dead Sea. We attempt to understand the groundwater flow direction, which is diverted from the simple eastward flow, parallel to the hydraulic gradient, to a northeastern one. We argue that only a 3-D modeling analysis may demonstrate groundwater flow field, because the geological structure plays a major role in controlling the flow regime. Better understanding of the groundwater flow field would benefit both, Israeli and Palestinian water supply.

A conceptual model has been constructed using a structural digital map in conjunction with other geological and hydrological data. The model demonstrates a plausible division of the area into three groundwater sub-basins, each discharging towards a separate spring. Mass-balance calculations at each of the sub-basins indicate a strong linkage between the recharge and discharge volumes. The flow patterns at the upper and the lower aquifers differ due to the varied thickness of the saturated zone. In the upper aquifer, the water table is not much higher than the aquifer base, therefore groundwater flows along the syncline axes towards the northeast, exhibiting a subsurface “river-like” flow pattern. This behavior explains the distinct position of the springs. In the lower aquifer an eastward flow is possible due to a relatively high water table. This hypothesis has been verified using a steady 3-D groundwater flow model using the MODFLOW code on the GMS platform.