In order to supply water during severe saltwater intrusions in the Yangtze Estuary, the Chenhang Reservoir sometimes took brackish water. The chlorinity in the reservoir was measured during November 27 in 2009 to March 12 in 2010. Combined with the river discharge, water level, wind stress, chlorinity at the upstream station and its inlet，the saltwater intrusion in the estuary, the way of water intake operation, and temporal/spatial variations of the chlorinity in the reservoir were analyzed. The simulated results showed that, the upstream was tended to be present around its eastern coastline under westward wind. Before the brackish water reached the reservoir, the amount of the water intake was increased to make it to high water level. At the beginning of a saltwater intrusion, the reservoir took the brackish water to keep its higher water level. In the later of the saltwater intrusion, some freshwater was taken from the Baogang Reservoir and the amount depended on the intensity of saltwater intrusion. Furthermore, the water intake from the Yangtze River must be paused when the chlorinity at the supply outlet in the reservoir was close to 250 mg/L. The measured data indicated that the chlorinity of the reservoir was increased when the brackish water in-taking was conducted and experienced a spatial variation under different wind stresses. The water intake operation of the Chenhang Reservoir was dependent on the chlorinity inside/outside it. In addition, its water level, the chlorinity in its upstream as well as the wind stress should also be taken into account. This study can bring experience to the reservoirs built in estuaries for better operation.