ASSESSMENT OF RISING GROUNDWATER LEVELS IN THE COASTAL ZONE OF AL QUNFUDAH AREA, SOUTHWEST SAUDI ARABIA

An integrated (remote sensing, hydrology, geochemistry, Geographic Information Systems (GIS), and field investigations) approach was adopted to identify areas witnessing a rise in groundwater to near-surface levels in Al Qunfudah area, southwest Saudi Arabia. The areal extent of this phenomena, and the factor(s) causing the observed rise in groundwater are not fully understood. Potential factors include: increased precipitation over the recent years, urbanization and associated releases of municipal sewage in the alluvial aquifers, and infiltration from impounded water in reservoirs upstream of dam locations. A fourfold approach was applied: (1) a digital database (GIS) was generated to host relevant geologic, hydrogeologic, topographic, land use, climatic, and remote sensing datasets. (2) We then identified criteria by which the occurrences of near-surface groundwater could be located from satellite-based observations and applied these criteria to identify similar occurrences of near-surface groundwater across Al Qunfudah area. (3) Developed a conceptual model to map the distribution of near-surface groundwater occurrences; (4) the distribution of the field-verified distribution of shallow groundwater was correlated with relevant geologic and hydrogeologic data in search of causal effects. The following criteria were identified over the test site (Al Qunfudah city); 1) NDVI values are high (> 0.19) over areas witnessing a rise in groundwater to near-surface levels compared to their surroundings; 2) brightness temperatures over areas witnessing a rise in groundwater levels are 3 to 6°F cooler than those for their surroundings; and 3) temporal mean radar backscattering coefficient over areas witnessing rise in groundwater levels are high ( > 0.09 dB) compared to those measured over the surroundings.