Although the country is well watered and there are many rivers and streams, there are no navigable rivers, nor is any one river the sole source of irrigation water. Drainage patterns are determined by geological features and climate. Although rainfall is seasonal, most streams are perennial. Most rivers in Lebanon have their origins in springs, which are often quite large. These springs emerge from the permeable limestone strata cropping out at the 915- to 1,524-meter level in the Lebanon Mountains. In the Anti-Lebanon Mountains few springs emerge in this manner. Other springs emerge from alluvial soil and join to form rivers. Whatever their source, the rivers are fast moving, straight, and generally cascade down narrow mountain canyons to the sea.

The Biqa Valley is watered by two rivers that rise in the watershed near Baalbek: the Orontes flowing north (in Arabic it is called Nahr al Asi, the Rebel River, because this direction is unusual), and the Litani flowing south into the hill region of the southern Biqa Valley, where it makes an abrupt turn to the west and is thereafter called the Al Qasmiyah River. The Orontes continues to flow north into Syria and eventually reaches the Mediterranean in Turkey. Its waters, for much of its course, flow through a channel considerably lower than the surface of the ground. The Nahr Barada, which waters Damascus, has as its source a spring in the Anti-Lebanon Mountains.

Smaller springs and streams serve as tributaries to the principal rivers. Because the rivers and streams have such steep gradients and are so fast moving, they are erosive instead of depository in nature. This process is aided by the soft character of the limestone that composes much of the mountains, the steep slopes of the mountains, and the heavy rainstorms. The only permanent lake is Buhayrat al Qirawn, about ten kilometers east of Jazzin. There is one seasonal lake, fed by springs, on the eastern slopes of the Lebanon Mountains near Yammunah, about forty kilometers southeast of Tripoli.