Detection of Low Salinity Groundwater Seeping into the Eastern Laizhou Bay (China) with the Aid of Landsat Thermal Data

Low-salinity groundwater storages beneath the sea bottom and submarine groundwater discharges (SGD) are of great importance in environmental management and the use of coastal water resources. A preliminary hydromorpho-geologic analysis allows for considering the presence of low-salinity groundwater in the offshore of the Laizhou Bay (Southern Bohai Sea, China). In order to detect the potential SGD, the analysis of the Sea Surface Temperature (SST) anomalies was carried out using Landsat thermal images acquired in the seasons characterised by the largest difference in temperature between seawater and groundwater. At the nearshore scale, patchy cold water anomalies occur approximately in the same positions along the intertidal zone of the Southern bay, where the unconfined aquifer discharges, independently of tide conditions. At the embayment scale, cold water anomalies spread out in the Eastern Laizhou Bay where the confined aquifer is likely exposed. Salinity and temperature measured in surficial waters of the eastern Laizhou Bay support the hypothesis of SGD, which can be derived from remote sensing images; the occurrence of macroalgal blooms might also be the consequence of the SGD-enhanced nutrient supply. This work pointed out the need of future oceanographic and groundwater flow modeling along with long-term monitoring of processes associated with the suspected SGD. The outcomes of this preliminary study will be of great help to direct effective in-situ investigations aimed at quantifying the volumes of SGD and to simulate coupled groundwater/ surface-water flow.