Hydrogeology of the Saq Aquifer Northwest of Tabuk, Northern Saudi Arabia

Abstract

Groundwater resources are precious commodity in general and for arid regions in particular. Their exploration, exploitation, protection and management play significant role in societal activities. In the Kingdom of Saudi Arabia, extensive aquifers are available in the Arabian Shelf. The Saq aquifer is one of the most important aquifers in the northwestern part of Saudi Arabia. It is made up of a Cambro-Ordovician sandstone formation, which extends over 1200 km in Saudi Arabia and northwards in Jordan. Groundwater occurs under unconfined conditions in the southwestern part and changes to confined conditions northward. The study area is located at about 50 km northwest of Tabuk, where many agricultural projects have been established depending on groundwater of the Saq aquifer for irrigation. The present study deals essentially with the hydrogeology of the Saq aquifer and the impact of extensive pumping on both groundwater levels and groundwater quality. Pumping and recovery tests were carried out in order to estimate the aquifer parameters. A total number of 192 groundwater samples were collected during the period 2000-2004 for quality investigation. Results of analysis of pumping test data showed that the average transmissivity and storativity are 1572 m 2 /day and 2.86 × 10 -4 , respectively. Values of average TDS of groundwater range between 540 and 670 mg/l, which indicate that it can be used safely for irrigation. The TDS values showed general decrease towards the northeastern part of the study area, in the direction of flow. Extensive pumping from 260 deep wells with an average discharge rate of 0.015 m³/sec has resulted in continuous groundwater level drop since 1999 with an average rate ranges between 2.3 − 10.5 m/year. Additionally, the effects of pumping on the water quality for the period 2000-2004 were studied