Three Gorges Dam water flow increase helps spawning

An experiment to increase water flow from the Three Gorges Dam has helped fish to spawn and softened the negative impact of hydro plants on the ecosystem.

The experiment has been carried out by the Three Gorges Dam and Yangtze River Water Resources Commission to boost water flow since 2011.

The dam released water three times from April to June each year.

Zhao Yimin, head of the Yangtze River Fishery Resources Committee, said the move is aimed at restoring aquatic conditions downstream from the dam during the spawning period of four major types of Chinese fish.

The committee found more fish spawning after the water discharge.

According to research data from the Yangtze River Fisheries Research Institute under the Chinese Academy of Fishery Sciences, the quantity of fry from the four major types of fish in the lower reaches of the Three Gorges Dam has fallen dramatically since the reservoir began to store water.

The average number of fry passing the monitoring section each year on the Yangtze from 1997 to 2002 was 2.5 billion.

However, the quantity fell to 406 million, 339 million, 105 million and 231 million, respectively, from 2003 to 2007.

Research by the institute showed that changes in water flow and water temperature were behind the dramatic drop in the number of fish.

While spawning of the four types of fish requires a temperature of above 18 C, water flow is also needed to stimulate the spawning and to keep the spawn floating downstream and incubating at the same time.

The institute's report suggested the water level of the Three Gorges reservoir should be at least 157 meters so there would be sufficient water for spawning.

The dam needs to take the initiative to carry out the program, Zhao said.