Hydrogeology and Water Quality of Umm Alradhma Aquifer, Eastern Saudi Arabia

Umm Alradhma limestone aquifer represents the most important aquifers in Saudi Arabia. This aquifer is the largest groundwater reservoir in the Arabian Peninsula. It has high potential of groundwater with average saturated thickness of Umm Alradhma 270 m. the average transmissivity, hydraulic conductivity and effective porosity of Umm Alradhma limestone aquifer are 5800 m2/day, 33 m3/day and 30% respectively. The groundwater of the Umm Alradhma limestone aquifer exists under confined condition in the study area. The productivity of the wells reached 704000 m3/day and provided Riyadh City about 300,000 m3/day. The hydrochemical analyses of 52 groundwater samples representing Umm Alradhma limestone aquifer reveal that the groundwater origin is meteoric. The presence of marine salts in groundwater is attributed to the effective leaching and dissolution processes through the flow path within the aquifer materials (limestone, dolomitic limestone and dolomite). The groundwater salinity of the Umm Alradhma limestone aquifer in the study area ranges between 1195-1429 ppm. This suggests that groundwater of Umm Alradhma limestone aquifer is acceptable for domestic, industrial and agricultural purposes. Keywords: Umm Alradhma aquifer, Hydrogeology, Water Quality