Seminar

The South China Sea is a marginal sea of the Western Pacific Ocean with a broad continental shelf exposed since the Last Glacial Maximum. Five enormous subaqueous deltas were developed in the then river deltaic estuaries and adjacent continental shelves of the South China Sea. Pearl River is the second largest river in China in terms of water discharge, and the accompanying subaqueous paleo delta extends to the slope at the northern margin of the South China Sea with an offshore distance of 200 km. A total of 31 offshore boreholes with high-resolution porewater geochemistry profiles have been obtained in this area. These boreholes have led to an identification of a large and unexpected offshore freshened groundwater (OFG) bodies with a static volume up to 546.4±73.9 km³, with the freshwater (< 1 PSU) extending as far as 55 km offshore. The distribution of the OFG is closely related to the morphology of the subaqueous paleo-delta of the Pearl River, where the buried paleochannel system is widely distributed. An integrated analysis of stable isotopic compositions and water quality indices reveals the meteoric origins of such freshened groundwater and its significance as potential potable water or raw water source for desalination. Hotspots of offshore freshened groundwater in large-river deltaic estuaries and adjacent continental shelves, likely a global phenomenon, have a great potential for exploitable water resources in highly urbanized coastal areas suffering from freshwater shortage.

Additional information: Mr. Chong SHENG, chongsh@connect.hku.hk