Investigation and assessment of submarine groundwater discharge of Ping-Tung nearshore area in Southwestern Taiwan. (Special Issue: Sustainable water and land management in tidal areas.)

摘要

Submarine groundwater discharge (SGD) is a potential pathway for nutrients and anthropogenic pollutants that flow from the land into the coastal ocean, and probably influences the aquatic ecosystem in tidal areas. This paper focused on surveying possible groundwater locations around the coastal area. The possible location, pathway and discharge of SGD in the Ping-Tung Shelf of southwestern Taiwan were described by oceanographic measurements. During the field surveys of the study area, onboard surface to bottom CTD (conductivity, temperature, depth) profiling, ADCP (Acoustic Doppler Current Profiler) measurements, and fluorescence profiling were carried out at 25 different stations. The collected hydrographic data were used to identify a suspected SGD site in the central part of the study area, where a local drop of salinity by up to 0.06 psu has been observed in the lowermost 0.2~1.5 m of the water column. Thanks to explicit evidence for a possible pathway and locations, seepage meters were deployed on the sea bed to measure the SGD rate at about 6.0 ml h-1 m-2 in the dry season. Based on the surveyed data, the likely locations of the SGD sources in the study area were specified, all of which were restricted to the inner shelf at a depth less than 8 m.