State of the Environment Report - 1980: The Kingdom of Saudi Arabia

Saudi Arabia has an area of about 2.4 million sq. km . Structurally the country may be likened to a tilted block whose highest corner is in the south-west. On the west the highlands rise abruptly from the narrow coastal plain of the Red Sea, the Tihama with an average width of 50km., and drop north-eastwards in a series of steep steps to the sand and gravel plains of the interior. North of Mecca these highlands are broken into separate massifs but to the south they form a continuous range, the Asir Mountains 2400-2700 m. high, extending into Yemen. Inland a rugged, curved ridge, the Jabal Tuwayq and Najid highlands, rise some 300m. above the surrounding plains and are flanked on either side by a narrow belt of dune sands, the Nafud to the west, and it is covered with dunes with a few watering places and the Dahana which provides fairly good grazing during the winter seasons to the east. These connect the vast sand waste of the Rub'al Khali or the Empty Quarter basin which covers about 650,000 km 2 in the south-east to the much smaller Nafud Desert in the north. These sand deserts consist mainly of linear dunes, 90 - 150m. high, aligned N.E. to S.W. North of the Nafud, stony, desert pavements extend into Syria and Iraq. A vast network of dry river valleys (wadis), relices of a better climate, drain north-east and provide on important source of underground water. Surface water is found only in the highlands where storms may cause devastating local flooding. (2) Another mostly barren plateau lies between the Dahana and the eastern coast. Finally on the Gulf coast are the lowlands of El-Hasa and Sikaka where water is found near the surface. In this coastal area some of the richest oil fields in the world are located.