The hydrogeology of the Golan basalt aquifer, Israel

The Golan Heights, located in northeastern Israel, is a part of the Hauran volcanic province. Plio-Pleistocene basalt rocks, ascribed to the Bashan Group, cover its surface. The basalts serve as a regional aquifer that is exploited for local consumption. New deep wells provide better information about the aquifer thickness, hydraulic parameters, and water levels. The objectives of this research were to develop conceptual and numerical hydrogeology models for describing the flow field in the Golan basalt aquifer. In order to establish the aquifer base, a structural map of near base "Bashan Volcanics" was produced for the southern and central Golan, which was combined with a paleo-relief map of the northern Golan. The conceptual groundwater flow model defines all aquifer boundaries, its division into basins and sub-basins, its hydrological connection with deeper aquifers, and its water balance. The computerized MODFLOW model verified the conceptual flow model quantitatively, and the aquifer hydraulic properties were calculated and calibrated. The regional basalt aquifer extends only to the north and middle parts of the Golan: at the south, only perched horizons are found. The aquifer is divided into two basins according to the groundwater flow directions: toward the Kinneret-Hula, and toward the Yarmouk. The water divide in between lies east of the volcanic cones in the northern Golan, and curves westward to Nahal Daliyyot. The Kinneret-Hula basin is divided into two sub-basins by a pre-basaltic topographic ridge that serves as a hydraulic barrier. The Kinneret-Hula basin yields about 85 million m³/y of fresh water on the average. It is discharged through the large springs on the western slopes of the Golan, and seeps toward Biq'at Bet Zayda (into Lake Kinneret), the Hermon River, the Jordan River, and the Yehudiyya plateau perennial streams.