6 Conclusion
The comprehensive function value of the channel connectivity increases gradually with time, so the channel connectivity increases from 1955 to 2015 in the Jingjiang River. The average values of —Shashi-Jianli reach, Jianli-Luoshan reach and Zhicheng-Shashi reach are 0.97, 0.99 and 1.00, respectively.
In the Zhicheng-Shashi reach, the comprehensive function value of the channel connectivity decreased from 1967 to 1972, with a range of 0.72-0.85, which may be caused by river straightening. Then, the value increased due to the impoundment of the Gezhouba Dam after 1980. However, the values were basically greater than 1.0 since 2003, which shows that reservoir construction will improve downstream channel connectivity.
In the Shashi-Jianli reach, the comprehensive function value of the channel connectivity fluctuates across 0.85 from 1965 to 1972, and the range of the value was 0.9-1.0 from 1972 to 2002. After the impoundment of the TGD in 2003, the value continued to increase with good channel connectivity.
In the Jianli-Luoshan reach, the change in channel connectivity can be divided into two processes: the comprehensive functional value of the channel connectivity fluctuated across 0.87 from 1956 to 1987; then, the value increased and ranged from 0.9 to 1.1 after 1988. In addition, the construction of the TGD has little effect on the channel connectivity of the Jianli-Luoshan reach because the influence of reservoir regulation is reduced by the upper reaches.
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Data Availability Statement : Research data are not shared