西江输沙量特性变化及趋势分析

Processes of sediment transport in the Xijiang River

在分析西江近60年输沙量特性变化的基础上,根据库区泥沙淤积及控制站水沙实测资料,运用Brune拦沙率方法,估算干支流梯级水库拦沙量,提出西江水库群拦沙率修正式,并预测在建和拟建水库运行后西江输沙量变化趋势。西江干流梧州站泥沙组成发生显著变化,红水河迁江站来沙所占比例由1990年以前的71. 37%,减小为2003-2016年的12. 57%。1992-2002年干支流水库群年平均拦沙量约为5 979. 3万t/a,拦沙率约为69. 58%;2003-2016年水库群年平均拦沙约为4 577. 2万t/a,拦沙率为77. 11%。大藤峡及柳江拟建大型水库运行后,梧州站沙量将降至约907万t/a,仅为1956-1991年沙量的12. 4%。

Based on runoff and sediment variations in the mainstream and tributaries of the Xijiang River at main hydrological and sediment observation stations in the past 60 years,the sediment trapping efficiency of the reservoirs had been estimated. A modified trapping efficiency formula was proposed based on the trapping efficiency curves obtained by Brune,and was used to study the influence of cascade reservoirs on sediment transport. The results showed that the sediment composition of the Wuzhou Station at the main stream of the Xijiang River,has changed significantly. The proportion of income sediment in the Hongshui River decreased from 71. 37% before 1990 to 12. 57% during 2003-2016. About 59. 79 million ton( Mt) of sediment was trapped annually by large reservoirs in 1991-2005,and the sediment trapping efficiency of the reservoirs was about 69. 58%. During 2003-2016,about 45. 77 Mt of sediment was trapped annually by large reservoirs and the sediment trapping efficiency was 77. 11%. After the operation of the Datengxia reservoir and the large reservoir proposed in the Liujiang River in the near future,the sediment discharge at Wuzhou Station would most likely be decreased to 0. 907 Mt/a,which is only 12. 4% of the amount observed during 1956-1991.