SINGAPORE — The Chinese government has made a huge effort to improve air quality and beautify Beijing for the Olympics. But it cannot apply a short-term "fix" to another problem that visitors to the Games will not see — the steady depletion of underground water supplies in northern China, where the capital is located.

A study published in June by Probe International, a Canadian environmental research group, found that over two-thirds of Beijing's water is being pumped from beneath the ground to compensate for dwindling surface water from reservoirs and rivers that once supplied the city. It warned that the underground saturation level, known as the water table, is dropping because water is being pumped out faster than it can be replenished, and that plans for long distance water diversion will aggravate the impending crisis unless water is used much more efficiently.

Two years ago, the Bureau of Hydrology and Water Resources in Hebei Province, a major source of water for both Beijing and Tianjing, issued a similarly stark warning. It said that only severe over-exploitation of underground water was making up for the shortfall between water from rain and rivers, and rapidly rising demand from urban residents, industries and agriculture.