The Yangtze Estuary is the lower, tide-affected part of the Yangtze (or Changjiang)—the longest river in Asia and the third longest in the world. The estuary occupies 430 miles (700 km) of the river’s 3,900-mile (6,300-km) length. Near its mouth, it splits into three smaller rivers and numerous streams that run through a delta. Here, silt deposition continually creates new land, which is used for agriculture.
The estuary carries an average of 7.9 million gallons (30 million liters) of water per second into the East China Sea; its average depth is 23 ft (7 m), and the average tidal range at its mouth is 9 ft (2.7 m). It supports large numbers of fish and birds, although fish stocks have declined over the past 20 years due to overfishing and pollution. The estuary’s waters may be fresh, brackish, or salty, depending on the season.
In winter, salt water intrudes a significant distance upstream, making the water unfit for drinking and irrigation. Recently, this intrusion has occurred more frequently due to reduced river flow—a reduction that is likely to be exacerbated by the Three Gorges Dam project farther upstream. Reduced flows may worsen the acute water shortage in the city of Shanghai on the estuary’s southern shore, as well as affect the dispersion and dilution of pollutants around the estuary. Silt deposition in the delta is also likely to fall, reducing the rate of new land creation.