BEIJING -- China should clamp down on rampant illegal sand mining in its largest freshwater lake to protect the local ecology, said a legislator on Thursday.

"Excessive illegal sand mining in the Poyang Lake area has posed a grave threat to the safety of river channels and dikes, and flood prevention, and might bring calamity to the ecological environments in the water area," said Fu Qionghua, a deputy of the 12th National People's Congress, China's legislature.

Poyang Lake is located in east China's Jiangxi province. With a water body of 2,805 square km, it supplies 145 billion cubic meters of water annually to the Yangtze River. This equates to 15.6 percent of the total runoff of the Yangtze, the country's longest river.

Poyang Lake, known as paradise for migrant birds, is Asia's largest winter destination for migrant birds. About 95 percent of the world's white cranes, 50 percent of its white-napped cranes and 60 percent of its swan geese spend the colder months here every year.

The five branch rivers directing toward the lake cover drainage areas that total 97.2 percent of the province.

"The lake water, in amount and quality, carries a big weight in safeguarding the ecological safety of the medium and lower reaches of the Yangtze River," said Fu, vice president of the Jiangxi Provincial Institute of Water Sciences.

In 2000, the Chinese government banned sand mining in the Yangtze River. Many illegal sand mining businesses subsequently set their eyes on Poyang Lake and its branch rivers. Local residents say that the noise and activity of the operators' vessels has made it hard to sleep in some towns.

Extravagant profits are undoubtedly the root cause of the illegal mining, Fu noted.

Sand, a necessity to build houses, is priced at 20 yuan ($3.2) to 50 yuan per ton around Poyang Lake. When it is shipped to Shanghai, the country's economic powerhouse to the east of Jiangxi, however, the sand can sell for as much as 200 yuan per ton. Because of the huge profits, miners have gone after the "heroin in the water," as it is popularly known among local people around Poyang Lake.

"In response to the booming real estate market, China will raise increasingly bigger demands on sand. Mining sand has become a 'short cut' for many to get rich rapidly," according to Fu.

While bringing sudden and huge profits for some, the unchecked sand mining has posed damage to the safety of dikes, bridges and local ecological environments. It has even threatened the integrity, wild fishery resources and migrant bird food chain of the Poyang Lake wetlands, officials say.

According to a local resident surnamed Ye from Wucheng Town, Yongxiu county, a big sand mining vessel can suck up sand and leave a hollow of 60 meters wide in a river bed in one operation.

To protect Poyang Lake, sometimes known as "China's last lake of clear water," Jiangxi has made extensive efforts to combat illegal sand mining.

On July 1 last year, the municipal government of Jiujiang launched a crackdown on the practice in the lake and branch rivers. It punished 51 offenders and detained 200 vessels. Some 53 percent of the Poyang Lake water area falls within Jiujiang.

However, municipal water police chief Bao Daxin admits Poyang Lake is too large to manage well. It remains hard to put an end to illegal sand mining.

The government must resolve the current problems and eliminate the root causes, officials say.

Combating the building of illegal vessel is believed to be an effective, drastic measure.

On February 3, the municipal government of Nanchang, which borders the lake on its western bank, dismantled 92 illegal sand mining vessels, the largest scale crackdown in recent years.

Fu proposed that the government work out a regulation on watercourse sand mining management as soon as possible to straighten out the system of administration.