4.4 Value of the comprehensive evaluation function
The value of the connectivity comprehensive connectivity function increases with time gradually and is basically above 1.0 after 1990 in the main stream reaches of the Jingjiang River, which indicates an overall improvement in channel connectivity (Fig. 8). The comprehensive connectivity function value of the Shashi - Jianli reach is the largest, and its connectivity is the best; the value of the Zhicheng - Shashi reach is the smallest, and its connectivity is the worst. The variation in channel connectivity can be divided into two processes, and the functional value of connectivity fluctuated from 0.87 in 1956-1987 to 1.0 in 1988-2015. In addition, the range of the connectivity function values in the Jianli-Luoshan reach is large, which may be affected by the regulation and storage of the Dongting Lake.