Karst and hydrogeology of Lebanon

Karst is very well-developed in Lebanon in thick, exposed, fractured and folded Jurassic, Cretaceous, and Eocene carbonates, as well as in localized, coastal Miocene limestones. This karstification not only results from the predominant calcareous lithology, but is also caused by the high, northerly trending ranges of the country, which cause abundant precipitation, as heavy rain and thick snow, to fall on Mt. Lebanon, Jabal Barouk, Jabal Niha, and Mt. Hermon. Lesser amounts fall on the Anti-Lebanon, Beqa'a Valley and the coastal hills of the country. Some 80% of precipitation occurs from November through February. The karst water emerges from five first-magnitude springs (Ain ez Zarqa (11m3/sec), Ain Anjar (max. 10m3/sec), Nabaa Ouazzani (max. 6m3/sec), Nabaa Arbaain (max. 3m3/sec) and Nabaa Barouk (max. 3m3/sec), plus hundreds of second- and third-magnitude springs, and thousands of smaller springs. The large springs are all karstic and contribute to 13 perennial springs in the main Lebanese ranges, and 2 in the Anti-Lebanon. These include major rivers, such as the Nahr el Litani, Nahr el Assi (Orontes) and Nahr el Hasbani (upper Jordan River).