为解决河流生态基流保障目标制定缺乏参考标准这一问题，提出一种分区分类的河流生态基流占比（即生态基流占多年平均天然径流的百分比）阈值确定方法。同时，选择我国10个水资源一级区439个水文监测断面，通过对断面1956—2018年天然与实测流量资料的分析，综合考虑断面径流大小、年内变化是否剧烈、是否受控制性水利工程调控等，提出我国河流分区分类的生态基流占比阈值，包括上限值、下限值和推荐值。结果表明：无控制性水利工程调控时，断面生态基流占比随其集水面积增加呈上升趋势，而全国小、中、大型断面生态基流占比的分区平均推荐值在枯水期分别为4.4%、6.6%和9.2%，非枯水期分别为9.4%、11.6%和16.2%；在有控制性水利工程调控时，断面在枯水期的平均推荐值为12%，而在非枯水期为17%。成果较好反映了全国河流生态基流的时空差异，可为生态基流保障目标的分区域、分类型、分时段制定提供支撑。

The ecological base flow is very important for coordinating the ecological protection and development of rivers.However,the threshold system that can effectively guide the determination of China′s ecological base flow is still lacking.In previous studies,it is generally required that the proportion of river ecological base flow to its multi-year average natural flow (referred to as “ecological base flow proportion”) should not be less than 10%.Considering the different hydrological and ecological conditions in different regions of China,it is difficult to effectively meet the macromanagement needs of China′s ecological flow by adopting a unified threshold standard. Through the analysis of natural and measured hydrological data of 439 sections,a threshold system is proposed for the ecological base flow proportion of rivers distributed in 10 Class I water resources zones and different catchment areas of China (excluding Hong Kong,Macao and Taiwan).The proportion thresholds of ecological base flow are composed of the upper limit,lower limit and recommended values. The results show that:When there is no controlled engineering control,the ecological base flow proportion shows an upward trend with the increase of catchment area.The average recommended values in small,medium and large sections are 4.4%,6.6% and 9.2% respectively in dry season and,9.4%,11.6% and 16.2% respectively in wet season.In terms of large sections with a catchment area of more than 10,000 km2,the recommended value in the dry season in the water resources zones is 9.2% on average.Among them,the highest in the Yellow River,southwestern rivers and northwestern rivers regions,reaching 16%,while the lowest is only 1% ~ 3% in Songliao and Huaihe regions.the average recommended value in the dry season in the water resources zones is 15% under the regulation of water conservancy projects. The proposed threshold values can provide support for the determination of ecological base flow considering different regions,section types,and periods.