Abstract
Wadi Al-Yammaniyah constitutes one of the important sources of supply of groundwater to the Holy City of Makkah, in Saudi Arabia. The wadi has a drainage area of about 620 sq km. Quaternary alluvium, ranging in thickness from a few to 100 meters underlain by Precambrian rocks of metamorphic and igneous origin, constitutes an important source of groundwater in Wadi Al-Yammaniyah. The hydraulic properties, quality of water, and estimated change in storage in waterbearing rocks in the area were assessed. The results of eight pumping tests carried out in hand-dug, large-diameter wells, indicate that the hydraulic conductivity of the alluvial aquifer ranges from 0.000056 to 0.00185 cm/sec and its storativity varies from 0.0823 to 0.117. The aquifer is replenished by sporadic but intensive rainfall of short duration. The present withdrawal is only about 10% of the annual recharge which is estimated at 52,000,000 cu m. The wadi groundwater resource, when properly exploited, could be used for further development of the area as well as to meet the increasing demand for water for the Holy City of Makkah. (Moore-IVI)