In areas where rain is scarce it is common to see people storing water to get them through dry seasons.

Using the same principle, officials want to dam a major lake in Jiangxi province that has shrunk noticeably but their plan has run into opposition.

Little egrets are a common sight on Poyang Lake's wetland areas in mid-February. [China Daily]?

Their proposal to dam Poyang Lake took a major step forward this month when it won the backing of the Hydroelectricity Planning Institute.

Since 2008, the eastern Chinese province has strongly lobbied leaders in Beijing, lauding the project as a way to tackle drought as well as adjustments to the water flow caused by the massive Three Gorges Dam upstream.

But critics of the 10 billion yuan ($1.58 billion) plan say authorities have played down the potentially disastrous ecological impact that a dam might bring to China's largest freshwater lake. It is also a crucial winter habitat for endangered migrating birds protected under international conventions.

Environmentalists have also cast doubt on the independence of crucial ecological assessments.

The province's proposal, which features a 3-kilometer-wide dam with sluice gates across the narrowest part of a channel linking Poyang Lake and the Yangtze River, was put to the Hydroelectricity Planning Institute on Feb 12.

After two days of discussions, the institute, which is affiliated to the Ministry of Water Resources, offered its support, China News Service reported.

The verdict takes the project into the final stages of the decision-making process, the report said, yet to get full central-government approval it still needs to clear the State Council and the National Development and Reform Commission, the country's economic planner.

Important habitat

Poyang Lake is fed by five rivers and is connected to the lower reaches of the Yangtze. Its water flows into the Yangtze during dry seasons (September to March) and is replenished by flooding during rainy seasons (May and June).

The annual change in the lake's water level has helped maintain one of the most important wetlands in the world, home to more than 120 species of fish and 300 varieties of bird.

Yet, the water has been continuously low over the past year. A prolonged drought the worst in 60 years saw the lake dwindle to less than 200 square kilometers in January, down from a peak of 4,900 sq km.

A fishing boat on the dry bed of Poyang Lake during the severe drought in May. The dam project is intended to prevent further damage to the lake. [Xinhua]?

The drinking water supplies of people living nearby and their livestock have been threatened, while fishing resources are dwindling, making life difficult for both fishermen and water birds.

Figures from Jiangxi's hydrological bureau show Poyang Lake received 30 percent less rain than usual last year. Yet, experts say the lack of precipitation is not the only reason for the frequently low levels.

In addition to changing climate patterns on middle and lower reaches of the Yangtze, water storage at Three Gorges Dam and increased water consumption by surrounding communities are also contributing factors, said Wang Shengrui at the China Research Academy of Environmental Sciences.

Citing official statistics covering 1952 to 2010, he said extremely low water levels (shallower than 8 meters) were reported seven times six times after 2003, when Three Gorges Dam began to store water for electricity generation.

"The seasonal decline of the water level each winter also starts earlier and lasts longer," said Wang, who previously worked on a water pollution study for Poyang Lake.

Pollution concern

Such concerns appear to give Jiangxi officials a legitimate reason to push the dam proposal with urgency.

The website of the provincial water conservation bureau has a detailed record of how often its staff members have traveled to Beijing to lobby the central government. Over the last 12 months, top officials have regularly visited the ministries of water conservation, environmental protection and forestry, as well as the National Development and Reform Commission and other departments, to "plead with them to speed up the review of the Poyang project".

However, provincial authorities have mentioned little about the irreversible environmental impact the dam could have.

Environmental expert Wang warns that the water quality in Poyang Lake's peripheral areas is likely to deteriorate because the sluice gates will slow down if not completely cut off the winter water flow that dilutes and flushes out pollutants.

"A dam will definitely change the natural hydrological process," he said, "The pollutants will be kept in the lake if the water flow is cut off."

Poyang Lake has so far escaped major industrial pollution, due largely to the relative slow economic development in Jiangxi. It is also one of only two sizeable lakes in the middle and lower reaches of the Yangtze that still retain a natural connection to the huge river.

Its natural ecosystem clear but shallow water, aquatic resources and scattered wetlands sustain a large population of water birds, with about 98 percent of the world's endangered Siberian cranes depending on its marshes for survival each winter, according to the International Crane Foundation.

A dam would destroy the lake's natural state, critics say, although water authorities insisted that the province will store supplies only in dry seasons and will ensure the water remains clear.

With more water available for agricultural and industrial use, however, Wang predicted that more factories will likely be built, bringing new sources of pollution, especially as Jiangxi authorities are desperate to boost the local economy.

Meanwhile, a more direct result of the project will be the flooding of the Siberian crane's winter habitat, said Chen Kelin, director of Wetlands International China.

In 1992, about 5 percent of the lake's wetland was listed as being of international importance under the Ramsar Convention, an intergovernmental treaty on conservation and the use of wetlands.

"China actually has an international obligation to protect the status of Poyang Lake, which Jiangxi officials seldom mention in their pursuit of the project," Chen said.

Assess the impact

Wang and Chen are not the only ones worried about the dam's negative environmental impact.

In September 2009, 15 top academicians signed a joint letter to Premier Wen Jiabao expressing their concerns about the plan, which was included in a blueprint for the Poyang Eco-economic Development Zone.

The central government approved the blueprint three months later, but the dam was ruled out. Instead, the province was asked to prepare scientific assessments on the potential impact.

Jiangxi invited a collection of academics, including some of those who opposed the plan, to look into key aspects, such as how the dam would affect the water quality, wetlands and migrating birds. The studies funded entirely by the provincial government to the tune of 10 million yuan were intended to provide scientific recommendations on whether the dam project should go ahead.

Several people who reviewed the studies told China Daily on condition of anonymity that they had concerns about the independence and transparency of the reports. One researcher even said he had been pressured by Jiangxi officials to highlight the benefits of the dam and to draw the conclusion that the project will "do more good than harm".

All six studies were completed in 2010, but the Jiangxi government did not make the complete reports public. Requests by several conservation groups to see the studies were turned down.

The province also organized another environmental assessment for the Poyang Lake Development Plan, of which the dam is a major part, to be carried out by the Yangtze Water Resources Protection Institute, which is affiliated with Ministry of Water Resources, and the Jiangxi Environmental Protection Institute.

The joint report concluded that the plan "will have both positive and negative effects on the ecology and environment, but there will be more good than harm". It said the negative impact will be on migrating birds, aquatic animals and water quality, but added that this could be prevented by certain measures.

Authorities solicited public opinion on the assessment between Sept 27 and Oct 7, a period that included the weeklong National Day break, and won approval from the Ministry of Environmental Protection in January, Jiangxi Morning Post reported.

However, Bai Chenshou, a senior official at the ministry, said a separate environmental impact assessment for the dam itself is still needed, and vowed that the ministry will be tough when reviewing the project due to the international wetlands treaty.

Another ministry official, who did not want to be identified discussing the project, told China Daily that Jiangxi is obviously pushing hard for the dam.

"We actually don't approve environmental assessments for development plans. Instead we give feedback," he said. "For Poyang Lake, we made it clear that the dam will have significant negative effects, and a separate evaluation is definitely necessary."

Even so, the future of Poyang Lake looks far from clear.

Environmentalists say the efforts of Jiangxi are just another example of how local governments relentlessly push projects that involve damming rivers and lakes for economic gain.

"It's still all about GDP and temporary economic growth," said a wetlands expert for an international environmental group who did not want to be identified. "The officials who make accomplishments (in getting approval and building dams) will soon get promotion, before the ecological woes start taking shape.

"With the dam, I'm really worried that Poyang will turn into another dead lake," he said.