大通河上游径流演变及驱动因素定量分析

近60年来,位于青藏高原东北边缘祁连山区的大通河上游气温、降水和潜在蒸散发均显著增加,同时在冰川消融50%、冻土退化、源头797km2沼泽退化等多重因素影响下,年径流深以6.0mm/(10a)趋势增长;基流分割表明,径流突变以来基流总量和占比均增加,8月基流量由谷值转变为峰值,汛后和枯水期基流显著增加;采用基于Budyko假设的气候弹性系数法对径流增量进行驱动因素定量分析,径流突变之后相对于基准期而言,年径流深变化+33.6mm,其中降水影响+18.3mm,潜在蒸散发变化影响-3.0mm,冰川融化对径流增量的影响至多为+10.0mm,剩余项+8.3mm为冻土退化和误差项的综合影响。由于各要素影响机制、持续时间各不相同,未来水文情势尚不明朗。

Quantitative analysis of runoff evolution and driving factors in the upper reaches of Datong River

In the past 60 years, temperature, precipitation, and potential evapotranspirat ion in the upper reaches of Datong River, which is located in the Qilian Mountain area, the northw est edge of Qinghai-Tibetan Plateau, have increased significantly, with the synthetic effect of 50% glacial ablation, permafrost degradation, and 797 km2 marsh degradation in the source area, annual runoff depth increased with a trend of 6.0 mm/(10 a); the base flow segmentation indicates that the total baseflow and its prportion have both increased since the runoff abrupt change,The base flow in August changed from the valley value between July and September to the peak;a quantitative analysis of the driving factors of the increase in runoff is carried out by the climate elasticity method based on the Budyko assumption. Compared with the base period,the annual runoff depth changes by +33.6mm after the sudden change of runoff, and the increase in precipitation affects +18.3mm. The effect of evapotranspiration change is-3.0 mm, the effect of glacier melting on runoff increment is at most +10.0 mm, and the remaining term +8.3mm is the combined effect of frozen soil degradation and error terms. Due to the different influence mechanism and duration of each element, the future hy drological situation is still unclear.