横断山区典型流域次降水事件水沙特征分析OA北大核心CSTPCD

[Background]The dry-hot valleys in the Hengduan Mountain Region has the unique characteristics of high temperature,low humidity and sparse vegetation,resulting in severe soil erosion,which was mainly contributed by several rainstorms.Currently studies on dynamics in runoff and sediment in the watersheds in the dry-valley region,especially on the rainfall event scale,are large lacking,bringing difficulties for analyzing the impacts of changes in rainfall and underlying surfaces on changes in runoff and sediment,assessing the relative contributions of different influencing factors and guiding the future practical works on soil and water conservation.[Methods]Based on the measured runoff and sediment data from 1966 to 2018 in the Xiaohuangguayuan hydrometric station in the Longchuanjiang watershed,a first-order tributary of the Jinsha River,two periods have been distinguished based on the temporal changes in annual runoff and sediment using the Mann-Kendall method:The baseline period(1966-2008)and the response period(2009-2018).For both periods,the average annual runoff and sediment under the same rainfall grade,and the same area proportion grades for torrential rainfall(the percentage of area covered by the torrential rainfall(＞50 mm in the rainfall)to the area covered by the rainfall event)were analyzed and compared.The annual runoff and sediment for some similar rainfall events across the two periods were also analyzed to detect the variations between the two periods.[Results]1)Substantial decreases of both runoff and sediment in the Xiaohuangguayuan hydrometric station have been found from the baseline period to the response period with the mutation year of 2008.2)For the rainfall events with same rainfall grade,the average runoff and sediment in the response period were about 48.72％and 29.06％of the baseline period,respectively;for the rainfall events with the same area proportion grade of torrential rainfall,the average runoff and sediment in the response period were about 48.77％and 28.97％of the baseline period.3)For the similar rainfall events,the average runoff and sediment in the response period were about 74.16％and 33.12％of the baseline period.4)The comparisons of both runoff and sediment between the two periods all indicated that the changes in underlying surface that dominant by the implication of the soil and water conservation measures were probably the primary reasons for changes in runoff and sediment since the rainfall amount,the covering area of torrential rainfall and the rainfall characteristics of the rainfall events that used for comparison between the two periods were similar.[Conclusions]This study highlights the contribution of soil and water conservation on changes in characteristics in runoff and sediment in the Longchuanjiang watershed,which may provide guidance for optimal deployment and management of soil and water conservation measures.