Abstract:

The changing environment alters river water quantity. Scientifically clarifying the change trend of water quantity is fundamental for water resources management in river basins. This paper focuses on 23 rivers for water allocation in the Yangtze River Basin. Utilizing measured runoff data, we analyzed the annual and monthly flow trends of major rivers and the change trends of outbound flow across different provinces within the basin. Results indicate that since 2012, the annual water volume of rivers for water allocation in the Yangtze River Basin has remained stable with an upward trend in 2020, followed by a significant shift from wet period to moderately dry period. The monthly runoff of each river exhibited an obvious unimodal pattern, yet the annual water volume gradually concentrated towards non-flood season. The outbound water volume across provinces in the basin showed multiple alternations between dry and wet seasons, generally presenting a fluctuating upward trend that peaked in 2020. After that, the outbound water volume across provinces continuously declined to the present state. The annual overall compliance rate of Guizhou and Hunan showed a downward trend, while Hubei followed behind.

Key words: water allocation, least square linear regression, runoff, outbound water volume, annual overall compliance rate