南水北调对长江口粗颗粒悬沙来量的影响

探索了长江南水北调占总径流量10%情况下对长江粗颗粒悬沙(≥0.05mm)入海数量变化的可能影响。研究表明:南水北调对入海细颗粒泥沙的影响主要为南沙北调,但数量较小,在1%左右,而对粗颗粒悬沙的影响主要表现在入海流量减少导致的水体挟沙能力的降低。通过建立大通站典型枯水年(1978),平水年(1987)及洪水年(1983)月平均流量与月平均床沙质输沙率相关曲线,估算出各典型年在典型流量23000m3/s,30000m3/s与40000m3/s水平下调水流量3000m3/s时导致的入海床沙质输沙率的变化。结果表明,输沙率的相对变化在-39%至-24%之间,且在较高的流量水平下,输沙率相对变化较小,但绝对变化增大,经大通入海的床沙质数量每年约减少2350～4700万t.

Effect of the South to North Water Diversion on the Coarse Grained Sediment Discharge into the Yangtze River Estuary

Bcause of the sharp spatial difference in water resource distribution, the present serious water shortage problem and the future increasing demands for water resource in the North China, the large-scale south-to-north water diversion will become an inevitable trend.this paper studies the effect of such engineering works on the coarse-grained sediment output into the Yangtze River Estuary under the background that about 10% of the total Yangtze River runoff discharge were diverted to the other drainage basins in the North China.The study indicates that under the typical hydrological years, for examples, 1978, 1978, 1983 representing dry year, ordinary year and flood year, respectively,a reduction of about 3 000m³/s runoff discharge to the sea from the typical discharge level 23 000m³/s, 30000m³/s and 40 000m³/s would result in a decrease of sediment discharge(>0.05mm in grain-size) ranging from-39% to-24% of the total sedunent output, corresponding to 2350×10⁴-4700×10⁴ tons in the sediment amount.The relationship between the monthly mean runoff discharge and coarse-grained sediment discharge shows that under the higher runoff discharge, the percent of decrease is smaller, but the absolute decrease in sediment amount become greater.Such a reduction of coarse-grained sediment discharge into the estuary is expected to exert significant effect on the estuarine and coastal sediment dynamics and morphodynamics in the coming 21st century.