Hydrology and ground water potential of the Tihama-Yemen Arab Republic

Abstract

Tihama is Yemen's coastal strip of land bordering the Red Sea. It occupies an area of about 20,000 km² and represents the country's most promising agronomic resource. With a total median annual volume of about 1,000 MCM (million cubic meters), surface water enters the Tihama plain through seven major wadis that drain the mountainous catchments to the east. The Tihama's Quaternary section constitutes the region's only known ground water aquifer. It consists of a thick sequence of alluvial sediments. Ground water occurs under water table conditions, and is annually replenished primarily by seepage of surface runoff. Using the technique of flow net analysis, it was found that annual natural ground water discharge through the Tihama aquifer to the Red Sea amounts to about 300 MCM. A confirmation of this magnitude of discharge was possible by computing two water balances at two of the major wadis. Results of the discharge computations can be applied in the planning of future salvage of this non-beneficial loss. Given that the current system of surface and ground water irrigation in the Tihama supports an area of about 150,000 hectares, a recovery of as little as 50 percent of this loss can increase the irrigated area by an additional 15,000 hectares.