REMOTE SENSING OF GROUNDWATER UPWELLINGS OFF THE NORTHEASTERN COAST OF OMAN BY LANDSAT THERMAL DATA

Groundwater upwellings in the coastal waters of Oman have been widely reported from in-situ measurements. These upwellings have traditionally been related to small offshore fresh water springs related to groundwater outflow, and recently to groundwater movement along lineaments. Considering the value of fresh water resources in this arid country, understanding of groundwater dynamics is of paramount importance. Here, we report on the detection of relatively large offshore upwellings using thermal satellite data. With the help of Landsat TM thermal data (Band 6), we observed two linear upwellings off the northeastern coast of Oman, approximately 20 km East of the town of Qurayyat. Both upwellings are approximately 1-2 degrees C warmer than surrounding waters. A large upwelling is N-S oriented, approximately 68 km in length, and 5.5 km in width. A smaller upwelling has NE-SW orientation and is roughly 18 km in length. The latter intersects the larger upwelling at its midpoint, generating a relatively warmer, circular upwelling center located at 59.199 E longitude and 23.261 N latitude. At the present time, there is very little information on the depth at which the upwellings originate. However, we believe that they are not related to the periodic monsoon-induced upwellings observed off the coast of Oman. Their linear shapes and massive size, in addition to the lack of marine isopycnals, suggest that they may be related to offshore fresh water springs along fractures. These springs are a result of groundwater movement along fracture zones that affect the carbonates and other recent sediments of the Arabian Platform. We correlated the orientation of the upwellings with the strike of Tertiary and Quaternary faults mapped both in the field and on satellite imagery. Therefore, we suggest that thermal monitoring of these fault-related offshore springs from well-calibrated ASTER or MODIS sensors on board the spacecraft TERRA would be a valuable tool in the understanding of the extent, direction, and periodicity of groundwater exits along several major fault systems beneath the coast of Oman. Knowledge of these locations would allow the exploitation of the groundwater by drilling along the inland extensions of the fracture zones, before the valuable resource is lost to the sea.