基流作为河川径流的重要组成部分，对维系河流生态系统稳定起着关键作用。以淮河中上游流域为例，采用Chapman Maxwell、Lyne Hollick和Boughton Chapman三种数字滤波法对淮河干流和支流沙颍河不同闸坝调控的7个站点2001-2015年日径流序列进行基流分割；采用Mann Kendall趋势分析检测基流量在年际、汛期和非汛期多种时间尺度下的变化，对比分析闸坝调控的影响特征。结果表明：（1）Chapman Maxwell数字滤波法对基流过程分割更合理，沙颍河水系站点的基流系数在0.23～0.46之间，淮河干流站点系数在0.36～0.50之间，沙颍河水系站点基流系数均小于淮河干流站点；（2）沙颍河和淮河干流的站点基流量均呈现出减少的趋势，其中沙颍河的基流量减幅明显高于淮河干流；沙颍河槐店、阜阳闸和淮河干流王家坝的年平均基流量，以及沙颍河白龟山、槐店和阜阳闸的汛期基流量减少趋势显著；（3）闸坝拦蓄导致下游的径流和基流量均呈现减少的趋势，沙颖河站点影响较严重，特别是在汛期8月减少趋势具有统计显著性；淮河干流站点受闸坝调控较弱，减少并不显著。研究可为认识淮河中上游流域的水循环特征及其转化关系提供技术支撑，也可为流域地下水资源可持续利用、人类活动影响评估等提供依据。

As the most important part of runoff,base flow plays a key role in maintaining the river ecosystem stability.In this study,three digital filtering methods (Chapman Maxwell,Lyne Hollick,and Boughton Chapman) were adopted to divide the baseflow series.The daily observed runoff series were obtained from 2001 to 2015 at seven stations in the Huai River and Shaying tributary.Temporal and spatial variations of base flow were further explored at inter annual and seasonal scales using the Mann Kendall trend analysis method and regional impacts of dam regulations were also identified.Results showed that:(1) the Chapman Maxwell digital filtering method was more reasonable for the division of the baseflow process.The baseflow indices of Shaying River were between 0.23 to 0.46,much less than those of the Huai mainstream which were between 0.36 to 0.50;(2) The inter annual base flows in the entire Huai River Basin decreased gradually,particularly those at the Huaidian and Fuyang stations in Shaying river and Wangjiaba station in Huai river,which showed statistically significant decreasing trend.The baseflow series in the flood season at Baiguishan,Huaidian and Fuyang stations in the Shaying River also showed significant decreasing trend.(3) The regulations of dam and sluice decreased the downstream runoff and baseflow,and the regulation effects in the Shaying River were more serious,especially in the flood season (i.e.,August).The mainstream of the Huaihe River was weakly regulated by the dam,and the reduction was not significant.The study is expected to provide technical support for understanding the characteristics of water cycle and its transformation relationship in the upper and middle reaches of the Huai River Basin,and also provide a basis for sustainable utilization of groundwater resources and impact assessment of human activities.

“十三五”国家重点研发计划( 2016YFC0400902) ; 国家自然科学基金( 41671024)