嘉陵江流域输沙量演变规律分析

Variation of Sediment Discharge in the Jialingjiang River Basin

嘉陵江流域水土流失严重,是长江流域重点产沙区之一,研究流域输沙量演变规律及其影响因素,对揭示其水土流失规律及人类活动水文效应具有重要意义。基于嘉陵江北碚站月及年输沙量,分析了流域输沙量演变规律及流域内人类活动对输沙量的影响。结果表明:年输沙量总体呈降低趋势,1980s—1990s年输沙量波动程度相对较大;流域年输沙量在1992年发生突变,突变年份后年径流量有所增加,年输沙量明显减少,突变年份后年输沙量波动程度加剧;年内输沙量主要集中在汛期(7—9月),占全年72%以上,总体变化呈单峰型;根据北碚站1956—2008年降雨—输沙双累积曲线,流域输沙量相对降雨量在1984年发生突变,降水和人类活动在突变年份前后对输沙量衰减的影响分别为25%和75%,人类活动的影响占据了主导地位。

Severe soil erosion in the Jialing River Basin contributes to large amount of sediment yields in the upper reaches of the Yangtze River. Analysis on variation of sediment discharge is helpful to understand the mechanism of soil erosion and impacts of human activities. This paper applied the Mann--Kendall test and double mass curve methods to detect the variation of annual and monthly sediment flux at Beibei station in the Jialing River. The results indicated that a general decline in sediment discharge was detected, and the changing point at 1992 was found. Furthermore, the streamflow showed slight increasing trend, while the sediment flux reduced significantly at 95% confidence level. Sediment yield mainly occurred during the flood season from July to September, accounting for more than 72% of the annual amount. Double curve analysis between sediment flux and precipitation showed two stages for the whole study period Ⅰ （1956--1984） and Ⅱ （1985--2008）. Soil and water conservation is responsible for the notable reduction in sediment flux, accounting for about 75%.