RECENT SYNCHRONOUS SPATIOTEMPORAL CHANGES IN WATER AND SEDIMENT DISCHARGES OF THE PEARL RIVER DELTA

The water and sediment movement in the Pearl River Delta is rather complicated. The simultaneous distribution of water and sediment in the estuary is essential for study of water and sediment budget.Synchronous hydrological observation was carried out by the authors at 16 stations for 4 voyages in the Pearl River Delta in December 2016(dry season) and July 2017(flood season). Our results show that the Xijiang River is the major source of both water and sediment of the Pearl River Delta.There are three channels flowing through the Modao estuary (26% in dry season, 33% in flood season), the Hu estuary (20% in dry season, 18% in flood season), and the Hongqili estuary (16% in dry season, 21% in dry season) respectively into the ocean.The total flow charge of the three estuaries reaches 69% in flood season and 65% in dry season.There are two major channels for sediment transportation: the Modao estuary (34% in dry season, 43% in wet season), and the Hongqili estuary (16% in dry season, 26% in wet season). The total sediment discharge of the three estuaries occupies 50% in flood season and 69% in dry season respectively.The seasonal difference in flow and sediment charge is rather significant in a decreasing order of the Beijiang, Xijiang and Dongjiang, and decreases from the middle of estuary to the sides.Seasonal variation in sediment concentration is similar to the sediment transport rate.Sediment concentration is tide dependant. It is higher in spring tide, but lower in neap tide.