当代珠江三角洲网河同步水沙时空变化特征

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

珠江三角洲网河水沙形式复杂,河口的同步水沙分配特征对研究河口水沙输运以及泄洪排放路径的理解至关重要。分别于2016年12月枯季大小潮与2017年7月洪季大小潮,通过4个航次对珠江三角洲16个站位进行了同步水文观测。观测结果显示,洪枯季西江都为珠江三角洲水沙的主要来源,网河区流量输送存在3条通道,最终经由磨刀门(枯季26%,洪季33%)、洪奇沥(枯季18%,洪季20%)、虎门(枯季20%,洪季16%)三口门入海,三口门枯季总流量占八大口门的64%,洪季占69%。泥沙输运存在2条主要通道,最终经由磨刀门(枯季34%,洪季43%)与洪奇沥(枯季16%,洪季26%)入海,两口门枯、洪季泥沙量约占八大口门的50%、69%。16站位流量与输沙率季节性差异显著,网河区流量季节性差异北江大于西江大于东江,八大口门季节性差异由中间口门向两侧口门递减;网河区输沙率季节性差异西江大于东江大于北江,八大口门季节性差异也由中间口门向两侧口门递减,含沙量的季节变化与输沙率相似,受潮流作用影响,洪枯季大潮含沙量一般大于小潮含沙量。

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.