another barren area known as the Homs Desert, which has a hard-packed dirt surface. Northeast of the Euphrates, which originates in the mountains of Turkey and flows diagonally across Syria into Iraq, is the fertile Jazira region. This region is watered by two tributaries to the Euphrates, the Balikh and the Khabur. The area underwent irrigation improvements during the 1960s and 1970s, and it provides substantial cereal and cotton crops. Oil and natural gas discoveries in the extreme northeastern portion of the Jazira have significantly enhanced the region's economic potential. Water The country's waterways are of vital importance to its agricultural development. The longest and most important river is the Euphrates, which represents more than 80 percent of Syria's water resources. Its main left-bank tributaries, the Balikh and the Khabur, are small perennial rivers that both rise in the Syro-Turkish border region. The right-bank tributaries of the Euphrates are mostly small seasonal streams called wadis. In 1973, Syria completed construction of the Tabqa Dam on the Euphrates River upstream from the town of Raqqa. The dam created a reservoir named Lake Assad (Buhayrat al Assad), a body of water about 80 kilometers long and averaging eight kilometers in width. Throughout the arid plateau region east of Damascus, oases, streams, and a few interior rivers that empty into swamps and small lakes provide water for local irrigation. Most important of these is the Barada, a river that rises in the Anti-Lebanon Mountains and disappears into the desert. The Barada creates the Al Ghutah Oasis, site of Damascus. This verdant area, some 370 square kilometers, has enabled Damascus to prosper since ancient times. In the mid-1980s, the size of Al Ghutah was gradually being eroded as suburban housing and light industry from Damascus encroached on the oasis. Areas in the Jazira have been brought under cultivation with the waters of the Khabur River (Nahr al Khabur). The Sinn, a minor river which marks the borders between Tartus Governorate and Latakia Governorate, is used to irrigate the area west of the Jabal an Nusayriyah, about 32 kilometers southwest of the port of Latakia. In the south the springs that feed the upper Yarmouk River are diverted for irrigation of the Hawran. Underground water reservoirs that are mainly natural springs are tapped for both irrigation and drinking. The richest in underground water resources is the Al Ghab region, which contains about 19 major springs