ABSTRACT
Water temperature, a crucial environmental factor, has a direct impact on the ecological and biogeochemical processes in rivers. The water temperature regime in the middle reach of Yangtze River has been altered by intensified human activities, particularly the dam construction. In this study, the optimal moment-POME-copula framework is developed from a probabilistic perspective to examine the joint dependence structures of air-water temperature and discharge-water temperature in the middle reach of the Yangtze River. To assess the effect of TGR on water temperature, we compare the joint dependence in the pre-TGR (1983-2002) period with the post-TGR (2003-2014) period. The results show that dependence structures of air-water temperature and discharge-water temperature in the middle reach of Yangtze River have changed in different extent, which is mainly attributed to the impoundment of the TGR. In addition, it is found that marginal distributions of each hydrological variable derived from the POME-based method can well capture respective distribution patterns in contrast to traditional distributions. Thus the results of dependence structures appear to be more accurate based on well-fitted margins. We hope this study could provide a scientific reference for ecological operation of TGR facing biological conservation.
