人类活动和降水变化对嘉陵江流域侵蚀产沙的影响

基于大量实测资料,用经验统计方法研究了人类活动和降水变化对嘉陵江流域侵蚀产沙的影响。结果表明,水利水保措施和20世纪80年代以来的降水减少,共同导致了嘉陵江流域产沙量的减少。分基准期(1956~1982)和措施期(1983~2000)分别建立嘉陵江江流域产沙量与年降水的指数方程,运用这些方程对于降水变化与水利水保导致的产沙量变化进行定量区分,得到了措施期中降水量减小所导致的减沙量、水利水保措施导致的减沙量、总减沙量以及降水减少和水利水保措施各自占总减沙量的百分比。水保减沙效益随降水量的增大而减小。当降水量超过某一临界值,还可能出现负效应。研究表明,水利水保减沙量随年降水量而增大,在年降水量为970mm时达到最大值,然后减小;当年降水量为1180mm时,水利水保减沙量变为0。

Effect of Human Activities and Precipitation on Sediment Yield of the Jialingjiang River

Based on hydrometric and meteorological dada, effect of human activities and precipitation on sediment yield of the Jialingjiang River basin has been evaluated by using empirical statistical approach. The results show that soil-water conservation measures and hydraulic engineering works have resulted in significant reduction of sediment yield in the Jialingjiang River basin since the 1980s. A "base-line" (1956-1982) and a "monitoring" (1983-2000) periods have been identified, and regression equations between annual sediment yield in the Jialingjinag River basin and area-averaged annual precipitation is established, separately. Based on the two equations, the sediment reduction induced by the decrease in precipitation and by soil-water conservation measures and hydraulic engineering works was differentiated. As a result, the sediment reduction by the decrease in annual precipitation in the "monitoring" period, the sediment reduction by soil-water conservation measures and hydraulic engineering works, and their percentages of the total sediment reduction have been estimated. This study indicates that the sediment reduction by soil-water conservation measures and hydraulic engineering works (ΔQ_s) depends on annual precipitation (P), the former decreasing with the latter. When annual precipitation exceeded some threshold, negative ΔQ_s would occur. The ΔQ_sincreased with P, and when P=970 mm, ΔQ_sbecame the maximum,and then ΔQ_sdecreased to 0 when P=1180 mm.