In the town of Balkhash, 500 kilometres (310 miles) west of the Chinese border on the shores of the lake, environmental damage is already evident.

Next year will be the 70th anniversary of the town and the metallurgical complex that provides a living for its 80,000 inhabitants.

But the vast factory is a mixed blessing, with its 10 smoking chimneys wrapping the Soviet-built industrial city in a thick black veil that is visible from kilometers miles around.

The factory's waste is buried within 300 meters (1,000 feet) of the shore of Lake Balkhash, allowing it to seep down and pollute the water.

"At least 25,000 tonnes of heavy metals find their way into the lake each year," notes Professor Malik Burlibayev, who is directing a European Union project to safeguard the lake.

In addition to this, the principal source of pollution, Chinese and Kazakh industrial and agricultural waste contaminates the main source of Balkhash's water, the Ili river.

"Ten years ago I could catch a hundred small fish a day. Today, I don't catch more than 10", says Nadya Tsetsova, 58, sitting with her fishing rod near a vast brown pool that is slowly spreading across the lake's blue waters.

To oversee the 5,500 square kilometers (2,100 square miles) of the northern bank of Balkhash the Kazakh environment ministry has only one inspector.

Using the car he bought with his own money to do the job, Zhomart Zhakenov attempts to monitor some 450 farms and 10 factories.

"It's quite simply impossible", he said.

But the lake faces a bigger threat: the encroachment of the desert that has already caused the Aral Sea, west of here, to shrink and split into smaller lakes, and has destroyed the livelihoods of whole communities.

The 3.3 million Kazakhs who live on the banks of Balkhash are all too familiar with images of the boats that lie rusting in the desert that was the Aral Sea, before cotton farming drained away its water.

Now, scientists warn that the lake is also under threat from desertification -- the slow advance of sands which gradually push back the shore and choke the vegetation.

"Between 1974 and 2002, at certain places the lake retreated by two kilometers (1.25 miles) and since 2002 its level has dropped by 36 centimetres (14 inches)", said Professor Burlibayev, using satellite photographs to demonstrate his point.

The retreat of the water, he explains, is not due to natural phenomena, but excessive use of water from the River Ili, whose source is in western China's Xinjiang province.

The Chinese authorities, who want to develop the area by moving in millions of settlers, each year pump a little more water from the Ili and its tributaries in order to extend arable areas and supply the Chinese oil city of Karamai.

According to Professor Burlibayev, Beijing also wants to dig 13 water storage facilities using water from the river, something he says would be a death sentence for the lake.

"Nobody knows exactly how much water the Chinese use. If this continues, a few years from now Balkhash will be divided into several small lakes," said Kuanysh Isbekov, an official with the regional branch of Kazakhstan's agriculture ministry.

But Kazakhstan is well aware of the degradation of this lake that is 17,000 square kilometers (6,500 square miles) in area and 650 kilometers (400 miles) long, the eastern third of it, for unknown reasons, salty.

For one thing, the waters of the Ili supplies Kazakhstan's economic capital Almaty, and the surrounding area.

To avoid a repeat of the ecological, economic and social tragedy suffered by the Aral Sea, the European Union has proposed a treaty to control the management of water and pollution, to be signed by the countries of the Ili basin: China, Kazakhstan and Kyrgyzstan.

"It is a question of reconciling the economic and the ecological, of introducing principles of sustainable development here", said Adriaan van der Meer, the head of the European Commission's delegation in Kazakhstan.

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