密云水库白河流域基流演变特征

基流是水文过程的一个重要组成部分，选择科学合理的基流分割方法，研究明确影响基流变化的驱动因素，对于保证河湖的生态水量至关重要。以北京密云水库的白河流域为例，根据白河流域张家坟水文站1967—2012年的实测径流数据和相关气象数据，对比分析了局部最小值法、单参数数字滤波法和递归数字滤波法三种方法的基流分割结果，并从气候变化和人类活动两方面分析影响基流变化的驱动因素。结果表明，相比局部最小值法和单参数数字滤波法，递归数字滤波法在白河流域有着更好的应用稳定性；在密云水库白河流域，基流对河川径流有着相当高的贡献比例(BFI>0.65);1967—2012年白河流域年基流量存在极显著的减少趋势(P<0.01),而年基流指数值基本保持不变。白河流域基流序列分别在1980年和1999年发生了突变，其中1999年的突变主要受到降雨过程(气候变化)的影响，而1980年的突变点主要受到其他因素(如人类活动)的影响。

Change characteristics of baseflow in Bai River Basin of Miyun Reservoir based on comparison of separation methods

Baseflow is the portion of streamflow that comes from groundwater storage and other delayed sources, and is an integral part of the hydrological process. It is crucial to ensure the ecological water volume of rivers or lakes by choosing a scientific and reasonable baseflow separation method and identifying the driving factors that affect the change of baseflow. Therefore, the original achievement and objective of this study were to further contribute to the literature to fill the gap in the knowledge of how to analyse the impacts of climate change and human activities on baseflow more reasonably and comprehensively. The Bai River Basin of Miyun Reservoir was selected as a case study in this paper. The comparison and selection of methods were discussed, and the evolution characteristics of baseflow and its influencing factors were analyzed. Finally, the corresponding management guidance was given. The baseflow separation results of local minimum method, single parameter digital filter method and recursive digital filter were compared based on the measured streamflow data and related meteorological data from the Zhangjiafen Hydrological Station in the Bai River Basin from 1967 to 2012. Driving factors that affect baseflow changes were also identified from two aspects of climate change and human activities. The results showed the recursive digital filter method had better application stability in the Bai River Basin compared to other methods. The baseflow had a relatively high contribution rate to the river streamflow (BFI >0.65) in the Bai River Basin of Miyun Reservoir. The amount of annual baseflow of the Bai River Basin had a very significant decreasing trend (P<0.01) from 1967 to 2012, while the annual baseflow index remained unchange. The baseflow sequence of the Bai River Basin had abrupt changes in 1980 and 1999, respectively. The abrupt change of the baseflow sequence in 1999 was mainly affected by the precipitation (climate change). The abrupt change in 1980 was not dominated by precipitation, but mainly affected by other factors, such as human activities. Therefore, in the future, it is necessary to rationally conserve the source of baseflow, and deepen the understanding and research on the rule of streamflow evolution, especially the impact of climate change and human activities on water resources. It will be of great significance to the safety of water supply in Beijing and the optimal allocation and management of regional water resources. This study enhances our understanding of the relative roles of climate variations and human activities on baseflow.