珠江三角洲治水方针的实施和发展

On the Flood Control Measures in Zhujiang Delta

珠江三角洲网河区治水方针从联围筑闸、以防为主,到合理导治、以泄为主,再到近期以清障为主。联围筑闸,利多弊少。洪水位长期呈上升趋势,但堤围的标准偏低。十余年来,口门的水沙分配发生了很大变化,口门整治必须合理围垦和适当疏浚。三角洲腹心地区洪峰水位异常壅高,主要是由于北江的分流比增大。近期有必要清除河障,疏浚主干河道,但是长远之计是兴建思贤和南华水闸,调控西江、北江的流量,确保防洪安全。

To prevent flood is the most important mission of harness of rivers in Zhujiang Delta. The basic guiding of harness is to take account of the upper, middle and lower reaches of rivers, to give priority to prevention, combining reservoirs with embankments, to give consideration to storing water and discharging flood, and to give first place to flood discharge. Joining dykes and constructing sluices is the basic countermeasure of preventing flood in the braided river area of the delta. However, the protection standards of embankments are now on the low side in common. About 23.3 % of length of the embankments protecting land of above 0.67 × 10^4 hm^2 did not reach the design standard. Reasonably dredging and smoothly discharging flood are the basic countermeasures of estuary administration in the delta. However because the rivermouth is extending towards the sea resulting in accumulation of outlet reaches and development of shallows, so that the discharging of flood gradually becomes unfavorable. Therefore it is important to carry out the programme of dredging the estuary. Although the reappearing periods of the floods in 1994 and 1998 were only once 20 -- 50 years but the flood peak levels had reached once 100--200 years in the central part of the delta. During the recent twenty years,a large number of sand resources in the channels of the North River were excavated, the river bed was dropped, so that the distributive ratio of discharge of the North River increased from 14 % before 1992 to 22 % --25.4 % during 1993--1997. This is the main cause of the abnormally rising of flood water level in some channels. It is necessary to remove obstacles in the waterways and to dredge the main channels in the near future, but from a long-term point of view, the water gates of Sixianjiao and Nanhua should be constructed to regulate the runoff from West River and North River, and so the flood discharge safety can be ensured.