关键词: 径流年内分配, 集中度, 不均匀系数, 启发式分割法, 累积量斜率变化率比较法, 渭河

Abstract:

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.

Key words: runoff seasonal distribution, concentration ratio, unevenness coefficient, heuristic segmentation method, slope change ratio comparison, the Wei River