Authorities from East China's Jiangxi province said the dam-building project in Poyang Lake will have little impact on the environment and a variety of species of fishes and migrating birds.

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"We have carried out a thorough assessment to analyze and minimize possible damage to the ecosystem, such as the wetland, the migrating birds, fishes and the water quality," Sun Xiaoshan, director of the Jiangxi provincial water resources bureau and also a deputy to the National People's Congress, told China Daily at the sidelines of the annual NPC session on Monday.

The project has received preliminary approval from the Ministry of Water Resources, Sun said. The dam, consisting of sluice gates, will only control the water level in the lake and may relieve severe droughts like those in recent years, he added.

Generally, lake water flow into the upstream Yangtze River in dry seasons. During rainy seasons Poyang is replenished with floods from the river.

The project can divert floodwater for the Three Gorges Dam during flooding seasons, reserve water needed for the coming dry seasons, and discharge the rest, according to Sun.

The water level of Poyang Lake, which connects to the Yangtze River, remained low from 2001 to 2010, compared with a decade ago, according to Jiangxi Poyang Lake hydrologic bureau.

Wang Shigang, deputy director of Jiangxi Poyang Lake hydrologic bureau, said the water level recorded at the Xingzi hydrometric station on Jan 6 was less than 8 meters, more than 1 meter lower than the average level in the past six decades.

"If we had contained part of the floodwater in the previous flooding season, the drought wouldn't have been so severe this year," Sun said, sighing.

The proposed dam will be built across the narrowest part of the channel linking Poyang and Yangtze, which measures a width of 2.8 kilometers.

Besides relieving the drought, the project also takes into consideration possible environmental impacts.

Thanks to annual natural changes to its water levels, the lake and its coastal areas form one of the most important wetland in the world, providing a unique and critical habitat for a variety of water birds.

About 98 percent of the world's Siberian cranes depend on the lake for survival every winter, according to the International Crane Foundation. It is also home to more than 120 species of fishes and 300 species of birds.

"To maintain the wetland, the water level of the dam will be strictly controlled. We will also increase the sluice gate width from the original planned 30 meters to 60 meters, to provide as wide a channel as possible for fish traveling through," Sun said.

Yao Mugen, deputy governor of Jiangxi province and also an NPC deputy, concurred, and said environmental protection is a top priority in the project.

Ecologists and scientists have been evaluating the impacts. Although local authorities have made great efforts to prove that the project will be friendly to the environment, many environmentalists believe that the government has been trying to downplay the impact of the proposed project.

Fifteen academics jointly wrote to Premier Wen Jiabao in September 2009 to express their concerns about possible damage to the ecosystem of Poyang Lake by the dam.