长江枯季入海流量变化的历史与趋势研究

This scientific project explores the changes in water discharge from the Changjiang River (Yanggtze) into the sea during dry season, with a focus on the causes for such changes, the processes, the historical development as well as its future trend, which will provide with scientific basis for the future operation of large-scaled hydro-engineering projects and the water resource planning for the Changjiang River drainage basin. The study indicates that, as a result of human impacts, the water discharge from the Changjiang River into the sea had already shown a large and episodic decrease during dry season, although both the long-term monthly mean and yearly mean discharge from the Changjiang River into the sea has not yet shown any significant trend since the 1950s. The hydrological evidence show that the hydrometric records at Datong Station，which is more than 600 km upstream from the river mouth, could no longer be used to represent the water discharge from the Changjiang River into the sea during dry season due to the anthropogenic hydrological processes in this area. Until 2000, the water-extraction hydro-engineering projects downstream Datong (the tidal limit) has amounted to 64 in number. The total capacity of pumps and sluices had reached to 7000 m3/s, equivalent to a daily mean capacity of 4600 m3/s and equall to the historical minimum discharge recorded at Datong. It is expected that the water discharge will fluctuated greatly in future in response to yearly and seasonal climate changes and demands for water resource. The anthropogenic hydrological processes in the middle and lower Changjiang are already strong enough to produce a profound effect on the freshwater discharge from the Changjiang River into the sea during dry season, and therefore remarkally infuence the freshwater resource in the Changjiang River delta and the entire ecosystem around the Changjiang River estuary.

长江枯季入海流量的变化问题是人类活动对我国环境变化影响研究领域的一个重要课题。在未来长江流域内部水资源需求迅速增长，黄河、淮河、海河流域水资源极度短缺及未来大规模南水北调背景下，研究长江枯季入海流量的变化更显得十分迫切与重要。本项目在着重研究自然过程的基础上，探索人类活动对近百年来长江入海流量变化的影响、主要过程及其机制；并结合21世纪全球变化、长江流域人类活动发展趋势与跨流域调水，探索未来几十年长江枯季入海流量的变化趋势与幅度。