Some of China's leading scientists have won their case for a review of a controversial dam proposed for the country's largest freshwater lake.

Officials of the Jiangxi provincial government have conceded that the planned dam and hydropower project might harm the wildlife and environment of Poyang Lake.

They have dropped the hydrostation in favor of a simple sluice gate, which, they say, would prevent water from the diminishing lake flowing into the Yangtze River.

However, opponents fear even this plan could seriously damage the lake's fragile ecosystem.

The provincial government had proposed the dam as part of its State Council-sanctioned Poyang Lake eco-economic zone and wants to start construction this year.

But 15 academicians and experts from the Chinese Academy of Sciences asked the State Council to suspend the project pending a more detailed environmental impact assessment.

In response to the concerns, the provincial government invited environmental experts, including objectors, to study the impact of the dam on the environment.

The objections focus on three main concerns:

-- that the dam would cause water shortages in cities on the lower reaches of the Yangtze River;

-- it would reduce water circulation and lower the lake's water quality;

-- it would change the ecosystem, which would threaten the habitats of diverse rare fish and birds.

The new assessment of the impact of the dam comprises six projects. All started in January and are expected to be completed in June.

Academician Cao Wenxuan, an expert in aquatic organisms, is heading a research project into the impact of the dam on aquatic creatures.

Cao said he was at first totally against the dam, fearing it would have a negative impact on wildlife, including the almost extinct baiji, or white-flag dolphin, a native of the Yangtze River, the finless porpoise and many other rare species.

Cao said the Jiangxi government had made concessions by scrapping the power station in favor of the sluice to maintain the water level during the dry season.

"But the sluice as well will bring problems. For example, the water gate would narrow the mouth of the lake to the Yangtze River to two thirds the original size, which would accelerate water flows and hinder some fishes' breeding migrations," said Cao.

Fellow academician Liu Xingtu, who is heading research of the impact on wetlands and migrant birds, said he wanted to be responsible to the state and the eco-environment of the Yangtze River.

Liu said he would present both the anticipated benefits and harms of the dam, without regard to how they influence the final project.

However, Zhu Laiyou, director of the general office of the dam construction project, said receding water levels meant some of the lake's wetlands were no longer "wet" and wildlife habitats were threatened.

Zhu said the dam would help stabilize water levels during the dry season, prevent water from being lost to the Yangtze River and solve a long-standing water shortage problem.

The Jiangxi government had invited the research team, including academicians who opposed the project, to study and analyze possible impacts the dam would have on the environment, and to propose solutions.

Cao said he hoped to provide some useful suggestions to the decision makers to build a more environmentally sound dam after his research.

Poyang Lake covers 3,583 square km with an average water depth of 8.4 meters. It is fed by five rivers in Jiangxi and empties into the lower reaches of the Yangtze, China's longest river.

According to the eco-economic zone plan, development will be "forbidden" in the 5,181-square-meter core region, and "strictly controlled" in the 3,700-square-km belt along the lake. Environmental protection will be crucial in these areas in order to protect the environment.

The rest of the 51,200-square-km zone, home to 20 million people in 38 cities and counties, including the provincial capital, Nanchang, will be "intensively explored" by eco-friendly industries.

The lake has been threatened by receding water levels since 2003 due to a number of factors, including climate change, decreased flows from upstream rivers, and the start of water storage at the Three Gorges Dam.

Some experts argue more research is needed into claims that the volume of water flowing out of Poyang Lake into the Yangtze River increased as the Three Gorges Dam reduced water levels along the river.

The lake in 2007 shrank to 56 square km from the maximum 4,500 square km in 1998 due to a severe drought.

Not only did the quantity of water decrease, but its quality as well.

Over-exploitation and pollution have harmed fish stocks in the lake, damaging the area's fishing industry and the livelihoods of about 100,000 fishermen. Since 2002, a seasonal fishing ban has been enforced to protect fish stocks.

The lake is home to at least 140 fish varieties and is a winter habitat for many waterfowl species.

In April 2010, experts from five international organizations -- the Ramsar Convention on Wetlands (Ramsar), the Worldwide Fund for Nature(WWF), the International Union for the Conservation of Nature and Natural Resources (IUCN), the International Water Management Institute (IWMI) and The International Crane Foundation (ICF) -- visited Poyang Lake at the invitation of the Jiangxi government.

They examined the environment around the lake during the five-day visit.

Sun Xiaoshan, director of Jiangxi Provincial Water Bureau, said all experts who were at first against the dam project, had basically approved the province's revised plan of the "water gate."

Sun said the experts would report to their own organizations the results of their studies and provide international experience of successful water management schemes to the project.