Climate change and human activity result in the variations in river discharge and sea level rise, both of which are very important for setting the boundary conditions of a numerical model.Thus, to obtain proper boundary conditions, this study presents projected variations in the amounts of Changjiang river discharge and sea level rise caused by climate change and human activity in 2030, 2050, and 2100. Considering the Three Gorges Dam closure in 2003 and utilizing the historical river discharge data at Datong Station from 1865 to 2002, the river discharge variations resulting from the extrapolation of historic data and climate models are almost identical. The mean river discharge in January and February will reach 12\,348, 12\,683, and 13\,522 m$^{3}\cdot$s$^{-1}$ in 2030, 2050, and 2100, respectively, due to climate change. In the past 20 years, the rate of absolute sea level rise was approximately 2.5\;mm$\cdot$a$^{-1}$ in the Changjiang River Estuary. In accordance with the observed tidal data that based on the sea level change over time analysis-based forecasting model, the absolute sea level rise will be 49.1, 148.1, and 395.6 mm in 2030, 2050, and 2100, respectively, compared to the 2012 levels. The saltwater intrusion simulation numerical model for the Changjiang River Estuary must consider the impacts of the Three Gorges Reservoir and South-to-North Water Diversion on the river discharge. The earth crust and land subsidence should also be considered for an accurate determination of the relative sea level rise. These values are presented in this paper for each prediction period