The reservoir group focusing on the Three Georges reservoir has been established in the upper Yangtze River, with a total regulation capacity of 51.5 billion m3. The reservoir group dispatch plays an important role in regulating the runoff. Economic activity in the Yangtze River estuary poses high requirements for water resources security. The water quality of main water supply reservoirs is influenced by the saltwater intrusion. The upstream reservoir group dispatch can enhance sea inlet runoff and mitigate saltwater intrusion hazard. In order to clarify the upstream reservoir group’s influence on the sea inlet water quantity in the Yangtze River estuary, the author designed three typical reservoir group dispatch scenarios to analyze flow rate change and different dispatch scenarios of Datong section. According to the findings, the upstream reservoir group dispatch is important to secure water quantity in the dry season. Through normal dispatch, the Three Georges reservoir can cut the days with a flow rate less than 100 million m3/s from 50.6 days to 8.8 days. In the special dry year, the sole emergency water supplement by the Yangtze River reservoir to the estuary will exert influence on the reservoir power generation. The joint operation of upstream reservoir group can basically eliminate such influence.

Ecological water replenishment is the part of ecological flow deducting the remaining local existing water that needs to be recharged by other water sources. It has become the basic basis for water resources development and utilization and water affairs coordination. Ecological flow is a complex concept with numerous calculation methods and obvious regional differences. In view of the characteristics of the Mintuo River Basin, especially the problem that the extensive economic development exceeds the environmental carrying capacity of the river, considering the lack of natural rainfall, this paper recommends a one-dimensional water quality simulation method that maintains environmental capacity. Taking Jingyan County as a representative, a case study was carried out. The river was divided into several sections according to the water function zoning, and the water quality of each section was simulated to determine the section and the total river water replenishment, and through compared with the traditional calculation method of water conservancy planning, the rationality and benefit of the period are analyzed.