Such diversions are expensive and damage the environment, the report said.

“Whether diverting surface water or digging ever-deeper for groundwater, the underlying solution proposed is like trying to quench thirst by drinking poison,” the report said.

It didn’t say why the compilers had requested anonymity, although the Olympics are a hugely sensitive issue and authorities have responded harshly at times to perceived critics of the games.

Explosive growth combined with a persistent drought for over two decades have drawn down Beijing’s water table, meaning the city of 17 million people is fast running out of water.

Beijing has drained surrounding regions in recent years to supply its growing water needs, depriving poor farmers of water and encouraging wasteful consumption, the report said.

Workers have also dug a canal south of Beijing that is bringing water to the capital for the Olympics, an accelerated part of a major water transfer project that in two years will start delivering water to the parched north from China’s longest river, the Yangtze.

Authorities say they know they have a problem. Beijing says it has spent around US$3 billion since it won the Olympic bid in 2001 to build wastewater treatment plants, move polluting and water-intensive industries out of the city, and cut down on pesticide and water use by farms.

However, Probe International said that even with the ambitious Yangtze transfer scheme, Beijing will still have to rely on groundwater that is currently being pumped out faster than it is being replenished. It said groundwater makes up more than two-thirds of Beijing’s water supply.

The city’s two main reservoirs are also holding less than 10 percent of their original capacity, it said.

The report said the government needs to curb water demand by using economic and legal measures such as increasing the price of water and having a water industry regulator. Some state water companies act as their own regulator, it said.

Beijing has one of the world’s lowest per person available water resources, at one-thirtieth of the world average.

The city has constructed water-guzzling golf courses since the 1980s, and projects across the city including landscaped gardens and artificial lakes for the Olympics.

Nearly all Olympic venues and the Olympic Village will use treated wastewater for heating systems and toilets. Recycled wastewater also will irrigate the Olympic Park, which will include a wooded area and an artificial lake.

But the rowing venue, built on the dried-out Chaobai river bed in Beijing’s Shunyi district, will use precious reservoir water. An eight-mile (13-kilometer) underground tunnel will divert water from the Wenyu River to keep the landscape green.