Hydrogeology

Cross sections

Fran├žois Zwahlen, Raoul Gonzalez, Ahmed Haj Asaad

CROSS SECTIONS

C1

This hydrogeological cross-section is located in the upstream part of the the Orontes River, where it flows in the Beqaa valley between the Mount Lebanon and the Anti-Lebanon Mountains. The system of Yammmouneh fault is visible in the Mount Lebanon, where it probably forms a preferential flow path for recharging the major Cretaceous and Jurassic aquifers. The Ain ez Zarqa spring, which spurts out in the bed of the Orontes Rivers, is present on this cross-section. This resurgence ensues from probable fractures allowing the flow of water from the middle Cretaceous through the Neogene formation. The middle-Cretaceous is saturated under the Beqaa; the groundwater level is located at the edge of the Neogene era. Overflow springs can occur when the groundwater level rises above the edges of the plain. The recharge of the middle-Cretaceous and Jurassic aquifers comes mainly from the Anti-Lebanon Mountains. Most of the precipitation falling on the Mount Lebanon flow towards the Mediterranean.

C2

This cross-section begins at the southern limit of the Coastal Mountain and goes through the city of Homs. The Orontes flows between crumbly and volcanic Neogene formations. The major middle-Cretaceous aquifer is probably confined in its western part by the volcanic Neogene unit, contrary to its eastern part, where many wells have been drilled.

C3

This cross-section goes across the highest part of the Coastal Mountain and the Ghab valley. The Orontes River flows through a multitude of channels, of which only the main channel has been shown. Faults both sides of the quaternary deposit give rise to many resurgences, like the Naur Shathah (2.17) and the Nab Al Huwayz (2.15) springs. To the east, the piezometric level in the aquifer of the middle-Cretaceous is probably in equilibrium with the level of the shallow aquifer. Exchanges must occur between the two aquifers, causing some sub-recharge of the shallow aquifer by the deep aquifer of the middle-Cretaceous era in areas of high exploitation of the shallow aquifer.

C4

The important Eocene-Miocene aquifer can be observed on this cross-section. This aquifer supplies two springs : the Ayn al Baqq (2.24) spring close to the village of Ari and the Ayn Alzarqa spring near the steep-sided bed of the Orontes River. This spring remains remarkably stable over years, which remains to be explained.