The Yarmouk basin, an essential transboundary water resource

The Yarmouk River is the primary tributary to the Jordan River and a strategic transboundary freshwater resource of Syria, Jordan, and Israel. In the past decades, the Yarmouk watershed has been extensively exploited by the riparian with the construction of dams including the Al-Wehda and Adassiyeh dams. The operation of the dams is guided by international water agreements between Jordan and Israel and Jordan and Syria and control the flux of the Yarmouk River. Repeated sampling over 16 years revealed variable flow paths towards certain wells over time as documented by variable REE-pattern and δ18O, δD and 87Sr/86Sr signatures of groundwater and lead to new insight with respect to sources of groundwater, their flow patterns and salinization in the Yarmouk basin. The conjoint interpretation of water table fluctuations indicate unexpected interactions of the river with the major groundwater resources of the entire region. 2D transient numerical simulations of coupled fluid flow and heat transport processes are used to investigate the impact of (i) a zone of hydraulic anisotropy and (ii) abstraction on hydraulic heads and temperature profiles in the shallow aquifers. The models support the geochemical indicated existence of a structural feature along the principle axis of the gorge, which hydraulically connects groundwaters in both flanks, while cross flow of groundwaters is prevented. That implies a subsurface anisotropic zone, which lets the gorge act as a complex conduit-barrier system where adjacent N-S and S-N flow-fields confluence and get drained towards the Jordan Rift.