渭河径流年内分配变化特征及其影响因子贡献率分解

研究渭河径流年内分配变化特征及其影响因子,有助于在区域视角下进一步掌握全球变暖与人类活动不断加剧背景下的水文响应。本文基于1960-2005年实测径流、面降雨以及潜在蒸发量的月序列数据,采用集中度与不均匀系数两个指标分析渭河径流年内分配特征的时空变化规律。运用Mann-Kendall法求算了渭河流域径流集中度与不均匀系数的变化趋势,采用启发式分割法诊断径流年内分配特征值的变异点,并运用累积量斜率变化率比较法定量计算气候变化与人类活动对径流年内分配特征变化的贡献率。结果表明:①渭河实测径流年内分配特征值的年变化过程呈现上升趋势,其中张家山站呈现显著上升趋势,该流域旱涝风险有所增加;②林家村与张家山站的实测径流年内分配特征值均存在1973年这一变异点,而华县站无变异点存在;③气候变化与人类活动影响对林家村站径流年内分配集中度与不均匀系数的贡献率分别为27.15%,72.85% 和12.10%,87.90%,而对张家山站的贡献率分别为39.11%,60.89%和33.73%,66.27%。人类活动是渭河实测径流年内分配特征变化的主要驱动力。

Change in runoff seasonal distribution and the decomposition of contribution rate of impacting factors in the Wei River

Investigating the change characteristics of seasonal runoff distribution and analyzing the contribution of the impacting factors will help to further understand the hydrological responses of river runoff to global warming and the increasingly intensified human activities in the Wei River Basin. In this study, concentration ratio and unevenness coefficient indices were employed to analyze the spatiotemporal trend of seasonal runoff distribution of the Wei River based on the runoff, precipitation, and potential evaporation monthly time series data in 1960-2005. The Mann-Kendall method was used to analyze the trend of the concentration ratio and unevenness coefficient at the Linjiacun, Zhangjiashan, and Huaxian Stations; the heuristic segmentation method was used to detect the change points of the runoff distribution characteristic values; and the slope change ratio comparison method was employed to quantitatively compute the contribution of climate change and human activities to the change in runoff seasonal distribution characteristic values. The results indicate that: (1) characteristic values of the observed season runoff distribution (concentration ratio and unevenness coefficient) of the Wei River show an upward trend and at the Zhangjiashan Hydrological Station these values show a remarkably increasing tendency, which is significant at the 99% levels. The risk of drought and flood has increased in this basin as a result of this change; (2) the characteristic values of the observed runoff seasonal distribution at the Linjiacun and Zhangjiashan Stations have a change point in 1973, while those at the Huaxian Station has no change point. The possible reason for this difference is that the Huaxian Station receives runoff from nearly the whole river basin where the effect of human activities, for example, construction of reservoirs and water diversion works, is limited. Part of the water diverted at the upper and middle reaches returns to the lower reach of the Wei River; (3) the contribution of climate change and human activities to the change in runoff concentration ratio and unevenness coefficient at the Linjiacun Station is 27.15%, 72.85% and 12.1%, 87.9%, respectively and that at the Zhangjiashan Station is 39.11, 60.89% and 4.62%, 95.38%, respectively. The main driving factor of the change in runoff seasonal distribution of the Wei River is human activities, but climate change has also played an important role. Since the Wei River Basin is a typical arid and semi-arid region, the findings of this research can be an useful reference for other similar areas of the world.