The Litani River (Arabic: نهر الليطاني, Nahr al-Līṭānī), the classical Leontes (Greek: Λέοντες, Léontes, lit. "Lions"), is an important water resource in southern Lebanon. The river rises in the fertile Beqaa Valley, west of Baalbek, and empties into the Merranean Sea north of Tyre. Exceeding 140 km in length, the Litani River is the longest river in Lebanon and provides an average annual flow estimated at 920 million cubic meters. The waters of the Litani both originate and flow entirely within the borders of Lebanon. It provides a major source for water supply, irrigation and hydroelectricity both within Southern Lebanon, and the country as a whole.
After heading south parallel to the Syrian border, the course of the river bends dramatically westward. Near this bend, the Litani comes within five km of the Hasbani River.
The portion of the river flowing west is called the Qasimiyeh. The Qasmieh-Ras-el-Aïn region, irrigated from the river's lower reaches from main irrigation canals, to south and north, is one of the largest irrigated areas in the nation, consisting of 32.64 km², shared among 1257 irrigating farmers, who concentrate on citrus crops and bananas (Raad 2004). For the entire stretch of the Qasimiyeh as it flows into the Merranean Sea, the Litani River remains nearly parallel to (and about 29 km (18 mi) north of) the Israeli-Lebanese border. 10 km north of Tyre, the river is crossed by the ancient Leontes Bridge. In June 1941, the mouth of the river was the site of an attack by British commandos and Australian troops on Vichy French forces that became known as the Battle of the Litani River.
Qaraoun, an artificial lake of 11 square km, was created by the Litani River Dam, 60 meters high and 1,350 meters in length, which was completed in 1959. A spillway of 6503 meters carries the water to the underground station where generators produce a maximum of 185 megawatts of electricity, the largest hydroelectric project in Lebanon. The dam was intended eventually to provide irrigation for 310 km² of farmland in South Lebanon and 80 km² in the Beqaa Valley. The office is at the southern (dam) end of the lake on the left side. The lakeside has a hotel and a number of restaurants specializing in fresh trout.
The Litani River Authority (LRA) was formed in 1954 to facilitate the integrated development of the Litani River Basin. Shortly after its formation, the LRA engaged in a massive hydroelectric development project that tapped the 850 meter head potential between Lake Qaraoun and the Merranean. This development has brought about major hydrological changes to the Litani River Basin, where the flows from its upper reaches above Lake Qaraoun, referred to as the Upper Litani Basin (ULB), are diverted through a system of tunnels, ponds and plants, to meet the Merranean several kilometers north of its original natural tailwater. These changes have resulted in the effective hydrological separation between the ULB and the Litani lower reaches.The advent of a protracted civil strife in the 1970s followed by a prolonged occupation in the 1980s that lasted into the 1990s, have plunged the country into disarray, freezing development and investment in infrastructure. The subsequent return to normal conditions has encouraged the LRA to initiate several major water diversion projects from the ULB worth hundreds of millions of US dollars.