Terminal Lake levels fluctuate in time as a result of climate change and/or anthropogenic reasons. This phenomenon has recently occurred in some lakes around the world (e.g. Aral Sea in Uzbekistan, Lake Urmia in Iran, Chad Lake in Africa, Mono Lake in California, etc.), which serve as a discharge base of groundwater basins.
In this study, the effects of extreme fluctuations of the Dead Sea and Lake Lisan Levels on the flow field of the Eastern Mountain Aquifer (EMA) were examined by a numerical hydrogeological model and found to be significant. The model was first calibrated to the current condition and then simulated the paleo and future groundwater-flow-field within the EMA. The results show that currently, 90% of the EMA water discharges in springs located at the Dead Sea shore, at an elevation of ~-430 m below sea level (mbsl), with almost no discharge north of the Dead Sea. However, when Lake Lisan stretched over a larger area within the Jordan Valley, at elevations of -160 to -250 mbsl, as much as 35% of the EMA water discharged through paleo-springs at the central Jordan Valley, north of the Dead Sea.
The high levels of the Lake Lisan affected the groundwater flow pattern by two means: (1) The hydraulic gradient was different from the current one, thus the flow from the Samaria Mountains (north-west side of the basin) discharged in the close paleo-springs, in the central Jordan Valley; (2) The groundwater flow within deep sub-aquifers was blocked due to higher location of the fresh-saline waters interface. Furthermore, the modeling shows that as the Dead Sea level drops down to ~-550 m, as expected to occur in the next centuries, the current coastal springs will dry up and the groundwater will migrate and discharge close to the Dead Sea along delta-fans.