Exploration of potential groundwater resources at Thuwal area, north of Jeddah, Saudi Arabia, using remote sensing data analysis and geophysical survey

The study uses the applications of remote sensing in analyzing the main topographic features of the study area. The digital elevation model derived from the Shuttle Radar Topography Mission (SRTM) satellite is used to devise spillway torrents and their tributaries of the different drainage basins in the study area. The digital rainfall data recorded by the Tropical Rainfall Measuring Mission (TRMM) climate research satellite is used to determine places with the highest rainfall within the different drainage basins in the area. Other satellite data (e.g. Landsat-8) are used in identifying and studying the various geological structures in the study area, which intersect the spillway torrents. Such areas may allow seizure of large quantities of water as potential, close to the surface, groundwater (Quaternary) aquifer. Areas of potential hydrological traps have been identified and marked for further geophysical (geoelectrical) surveys. The geophysical studies helped in identifying the shallow geological structures and the thickness of the subsurface sediments. It also assists in determining the size of the groundwater aquifer and the water quality within these aquifers. The study showed a decline of freshwater aquifer in Quaternary sediments. The Tertiary groundwater aquifer is the most prevalent, where this appears normal saline aquifer. All the aquifers within the study area are being recharged from Quaternary sediments by rainwater. The cumulative annual precipitation rate increases in the South-East of the study area, specifically over Wadi Khulais and significantly drops to lower rainfall rates in the rest of the region. Running water permeates the Quaternary sediments, which in turn infiltrates and recharges the Tertiary aquifer. The salinity of the latter depends mostly on the nature of its constituent rocky material.