无定河流域基流变化特征及其对降水的响应

基流是干旱区河流水资源的重要组成部分，在维持河川径流和维护流域生态安全等方面具有重要作用。探究无定河流域基流变化特征及其对降水的响应，对优化黄土高原水资源配置意义重大。基于无定河流域1960—2019年逐日降水量、径流量数据，利用数字滤波法、小波变换、双累积曲线及弹性系数法等，分析了降水量与基流深年际和年内变化特征，探讨了降水量与基流深的时频域关系及基流对降水的时滞效应，并明确了降水—基流关系的变化方向。结果表明：无定河流域年基流深和年基流指数分别呈极显著下降趋势(p<0.001)和不显著增大趋势(p<0.1),多年平均值分别为23.83 mm和0.67。基流深和基流指数值在春秋两季较大，夏冬两季较小；夏秋季降水对基流的控制能力在高能量和低能量区均明显强于春冬季；基流对降水的年均时滞时长为3.2天，月均(5—10月)时滞时长均在7天内。在过去60年间，流域基流储量增加7倍以上；降水量与基流深的关系发生2次变化，变化点分别为1971年和2000年；2000年后基流对降水的敏感性减弱，二者关系变化的方向更加稳定。研究结果以期为黄河中游地区水资源可持续开发利用提供理论支撑。

Variation Characteristics of Baseflow and Its Responses to Precipitation in Wuding River Basin

Baseflow is an essential part of river water resources in arid areas, which play an important role in maintaining streamflow and ecological security in the basin. Investigation on the change characteristics of baseflow and its responses to precipitation in Wuding River Basin is of great significance for optimizing the allocation of water resources on the Loess Plateau. Based on daily precipitation and runoff data of Wuding River Basin from 1960 to 2019, and combined with digital filtering method, wavelet transform, double cumulative curve and elastic coefficient method, the study analyzed inter-annual and intra-annual variation characteristics of precipitation and baseflow depth, discussed the time-frequency relationship between precipitation and baseflow depth as well as the time lag effect of baseflow on precipitation, and clarified the change direction of precipitation-baseflow relationship. The result showed that annual baseflow depth displayed a highly significant downward trend (p<0.001), and annual baseflow index showed a non-significant upward trend (p<0.1), with perennial average values of 23.83 mm and 0.67, respectively. The values of baseflow depth and baseflow index were higher in spring and autumn, and lower in summer and winter. The control ability of precipitation on baseflow in summer and autumn was stronger in both high and low energy regions than that in spring and winter. The average annual lag time of baseflow to precipitation was 3.2 d, and the average monthly (May-October) lag time was less than 7 d. In the past 60 years, baseflow reserves in the watershed increased by more than 7 times. The relationship between precipitation and baseflow depth changed twice, the change points were 1971 and 2000, respectively. The sensitivity of baseflow to precipitation weakened gradually after 2000, and their relationship evolution became more stable. The results would provide theoretical support for sustainable development and utilization of water resources in the middle reaches of the Yellow River.