Tawil Quaternary Aquifer System

The Wadi Sirhan Basin is situated in Jordan and Saudi Arabia and forms a central depression surrounded by basalt and sedimentary plateau areas in the north and south. The basin surface is covered by Paleogene and Quaternary deposits, which make up the upper part of the exploited aquifer system. In the subsurface, thick deposits of Cretaceous and Tawil- Sharawra Formations occur in the depression and along the boundaries of the aquifer system. They constitute the lower part of an aquifer system that is denoted as the Tawil-Quaternary Aquifer System in this Inventory.

This aquifer appears to have evolved as part of the groundwater system in the Sakaka- Azraq areas, with limited recharge entering the system in the form of Mediterranean-type rainwater. Groundwater flows from the basalt and limestone plateau areas towards the central depression where it follows the hydraulic gradient in a south-east/north-west direction.

Since exploitation of the aquifer system started in 1986, annual abstraction for irrigation purposes has risen from about 100 MCM in 1984 to almost 3,500 MCM in 2004. However, the lower part of the aquifer system appears to have potential for further exploitation as only a few of the approximately 100 wells tapping this part of the aquifer system show signs of significant drawdown.