珠江三角洲近期水沙分配的变化及其影响与对策

近20多年，珠江三角洲西江与北江的水沙分配发生了重大变化，相当于增多了一条北江的水量和沙量向东输送，导致珠江三角洲腹心地区洪峰水位异常壅高，河道由淤转冲，口门水域面积缩小，滩涂面积扩展，伶仃洋尤其是西岸的淤积加速，对港口和航道有较大影响。

THE RECENT CHANGE OF DISTRIBUTIVE RATIOS OF RUNOFF AND STREAM LOAD AND ITS IMPACTS AND COUNTERMEASURES IN ZHUJIANG RIVER DELTA

During the recent twenty years owing to quarrying sand resource from river and deeply scouring of channels, the raio of runoff increased from 14.2% to 23.0% and the raio of stream load increased from 10% to 20% for North River. As a result, the water level of rivers tends to rising secularly with a rate of 4.7-7.9 mm/a.In local sections of river, the flood water level rose abnormally from once 20-50 years to 100-200 years. The acceler- ation of accumulational process in estuary resulted in the reduction of sea area. The annual accumulation rate in estuaries is 2.0-3.4 cm/a. The increase rate of area of mudflat is about 500 hm^2/a in average. The estuaries extended 11-13 km. In general, the natural depositional rate is 2-5 cm/a in harbours and channels. However, the accumulated return rate after sweeping is 30-60 cm/a which is larger by one class in quantity than that of natural deposition. For example, in Zhongshan harbour and Jiuzhou harbour, the sweeping amount was accumulated return only by half year or one and half year. To heighten the protection standard of embankments,reasonably dredging estuaries and to constructe the water gate of Sixianjiao are the basic countermeasures of administration in Zhujiang River Delta.