Response of Salinity Intrusion to the Fictitious Blockade of the North Branch in the Yangtze Estuary, China

The Yangtze Estuary plays an important role in the economic development in the Yangtze River Basin, China. Shanghai is a megalopolis, and more than 70% of its water is supplied from the Yangtze Estuary. Salinity intrusion has become the most restrictive factor for water supply in nature, while the North Branch is the most serious branch compared to others where the salt water in water sources mainly comes from. If the North Branch is properly blocked, construction of tidal gate for example, may alleviate the salinity intrusion. In this chapter, a numerical model is established to study the fresh water distribution characteristic and the impact of the salinity intrusion on the water sources after the North Branch is fictitious blocked. The study shows that salinity intrusion in the Yangtze Estuary is the most serious in January, during which the safety of water sources is likely to be threatened by salt water. The salinity would be greatly reduced in the water sources intake with the North Branch blocked. The salinity of the water intake in the Dongfengxisha Reservoir and Chenhang Reservoir would be close to 0 in any condition while the Qingcaosha Reservoir is still threatened by salt water when continuous northerly wind happens. This study could provide a reference for the discovery of measures for the water source safety in the Yangtze Estuary.