长江上游径流持续偏枯地区贡献度及成因研究

Spatial Contribution and Cause Analysis for Runoff Decreasing in the Upstream of Yangtze River

摘要: 20世纪90年代以来，长江上游来水持续偏枯，影响到长江上游水库群综合利用效益的发挥以及长江流域水资源的合理配置。本研究将长江上游分为金沙江、岷沱江、嘉陵江、乌江、长上干区间五个水系分区分别进行年径流量偏枯程度统计，分析不同分区对长江上游年径流量偏枯的贡献度，并从降雨变化和人类活动两方面对径流偏枯进行了成因分析。结果表明：(1) 1991~2015长江上游径流量偏枯贡献最大的是嘉陵江水系和长江上游干流；(2) 偏枯的主要原因是降水量偏少，其次是流域耗水量增加、上游水库拦蓄与水库库面蒸发增损。

Abstract: The upper reaches of the Yangtze River has continued to be dry years since 1990s, which will affect the comprehensive benefits of reservoirs and water resources allocation in the Yangtze River basin. In this study, the upper reaches of the Yangtze River were divided into five watersheds, i.e., Jinsha River, Mintuo River, Jialing River, Wu River and the mainstream watershed from Yibin to Yichang cities. The contribution rate of different watershed to the runoff in the upstream of the Yangtze River was analyzed. Two aspects including rainfall and human activities that may induce the runoff decreasing were discussed. The results show that: (1) Jialing River and the mainstream watersheds are the two major contributors to the runoff decreasing for the whole upper Yangtze River during the period of 1991-2015; (2) the main reason for the dryness of the upper reaches of Yangtze River is precipitation reduction, follow by the increase of water consumption, water storage loss and evaporation augment by the reservoirs.