Cheng Qingping, Zhong Fanglei, Wang Ping
School of Geography and Ecotourism, Southwest Forestry University, Kunming, Yunnan 650224, China; Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
School of Economics, Lanzhou University, Lanzhou 730000, China.
Sci Total Environ. 2021 Jun 10;772:145013. doi: 10.1016/j.scitotenv.2021.145013. Epub 2021 Feb 2.
Baseflow is a component of streamflow derived from shallow and deep subsurface flows that is concurrently controlled by multiple factors. Rational estimation of baseflow is critical for understanding its spatiotemporal dynamics and influencing factors within a river basin. To address this, different filtering parameters were applied to separate the baseflow of the Heihe River Basin (HRB) in Northwest China using digital filtering methods. Moreover, using bivariate and multivariate wavelet coherences, multivariate relationships between baseflow and meteorological factors/large-scale circulation indices were identified for several factors, which explained most of the variations. Results showed annual average baseflow was 10.3-91.1 mm and that the baseflow index (BFI) varied between 0.50 and 0.72 (average: 0.62). This indicates that 62% of long-term streamflow likely originates from groundwater discharge and other delayed sources. Positive/negative Spearman correlation coefficients between baseflow and extreme climate indices were more significant at upstream (Yingluoxia, Liyuanbao-and Wafangcheng) stations in comparison with midstream (Suyukou, Shunhua) and downstream (Yangyangchi) stations. Correlation for the BFI was relatively weaker than for baseflow. Furthermore, bivariate wavelet coherences revealed that precipitation (six stations) and the Atlantic Multidecadal Oscillation (four stations) were the individual factors that best explained baseflow variations. Multiple wavelet coherence demonstrated that all meteorological factors/large-scale circulation indices had the highest percentage of the numbers of power significant at the 95% significance level that could best explain baseflow variations. However, the average power of wavelet coherence was not increased. Differences likely attributable to consideration of additional variables were diminished by collinearity effects among factors. Furthermore, baseflow at the midstream Zhengyxia and downstream Yangyangchi stations had significant positive and negative correlation with population and effective irrigation area, respectively. The findings indicate that development of regional hydrometeorological models should primarily consider the impact of climate change in the upstream HRB, whereas the effects of both climate change and human activities should be considered in the midstream and downstream HRB.
基流是源自浅层和深层地下水流的河川径流组成部分，同时受多种因素控制。合理估算基流对于理解流域内基流的时空动态及其影响因素至关重要。为解决这一问题，采用数字滤波方法，应用不同的滤波参数来分离中国西北黑河流域（HRB）的基流。此外，利用双变量和多变量小波相干分析，确定了基流与多个气象因子/大尺度环流指数之间的多变量关系，这些关系解释了大部分变化情况。结果表明，年平均基流为10.3 - 91.1毫米，基流指数（BFI）在0.50至0.72之间变化（平均为0.62）。这表明长期河川径流的62%可能源自地下水排放和其他延迟水源。与中游（苏峪口、顺化）和下游（盐池）站点相比，基流与极端气候指数之间的正/负斯皮尔曼相关系数在上游（莺落峡、梨园堡和瓦房城）站点更为显著。BFI的相关性相对基流较弱。此外，双变量小波相干分析表明，降水（6个站点）和大西洋多年代际振荡（4个站点）是最能解释基流变化的单个因素。多变量小波相干分析表明，所有气象因子/大尺度环流指数在95%显著性水平下具有最高比例的显著功率数，最能解释基流变化。然而，小波相干的平均功率并未增加。由于因素间的共线性效应，考虑额外变量可能导致的差异减小。此外，中游正义峡和下游盐池站点的基流分别与人口和有效灌溉面积存在显著的正相关和负相关。研究结果表明，区域水文气象模型的开发应主要考虑上游黑河流域气候变化的影响，而中游和下游黑河流域则应同时考虑气候变化和人类活动的影响。
