Eco-hydrological impacts of Three Gorges Reservoir's operation on three outfalls of Chingjiang River

Abstract

Based on the measured daily flow prototype sequence of five hydrologic stations in the three outfalls of Chingjiang River from 1990 to 2014, its hydrological characteristics and its changing trend was analyzed by using the Mann-Kendall statistical test and the cumulative anomaly method, while the effect of the operation of the Three Gorges on the variation of the 33 indexes of ecological hydrology was also analyzed by the index system of ecological hydrology and range of variability approach. The results showed an obvious decreasing trend in annual mean discharge with the confidence degree of 95% with a decrease rate of 19% during 1990-2014. The jump point appeared in 2003, with the annual mean discharge being 1981.1 m3·s-1 before 2003 but 1603.25 m3·s-1 after. There was an obvious increase in monthly mean discharge from January to April (the degree of deviation was 1.58, 1.86, 0.83 and 0.62 respectively), an obvious increase in the late May and the early June, a slight decrease in July and August (the degree of deviation was -0.12 and -0.10 respectively), and a significant decrease in October (the degree of deviation was -0.40). There was a great change in annual minimum flows while a slight change in most of the annual maximum flows and a moderate decrease in 1-day and 3-day maximum flow. It also had a great change in duration and frequency of the low-flow pulse and slight change in high-flow pulse.