China may have 2.8 trillion cubic meters of freshwater reserves, sixth in the world, but because of the country's population of 1.3 billion its per capita water availability is only one-fourth of the world average, according to the Ministry of Water Resources.

This means China's water sources are limited and may not be able to support its fast economic growth over an extended period, says Pang Zhonghe, a scientist with the Institute of Geology and Geophysics, affiliated to the Chinese Academy of Sciences.

The demand for better quality and higher volumes of water increases as the country's industries prosper and people's quest for better life intensifies. Besides, the fast pace of urbanization and industrialization, especially the increase in high-energy consuming and high-polluting industries, are contaminating water sources and threatening people's health.

In fact, shortage of water is becoming one of the biggest obstacles for sustainable economic development, Pang says.

The scene is equally stark on the other side of the spectrum. Floods and torrential rain have become more frequent in recent years. They are not only claiming lives and destroying property, but also causing precious water to flow into the seas unused.

Though many people attribute extreme weather to climate change, only a few have noticed its effect on water sources. Generally, a change of 1 to 2 degrees in temperature has little or no effect on the human body. But this small change can wreak havoc on the hydrological cycle, triggering floods or causing droughts.

In China, water problems are three-pronged: frequent disastrous floods, overall lack of water and declining water quality.

A third of China's water reserves is below the ground surface, which is vital for the nation's water supply. The country gets about 70 percent of its drinking and 40 percent of its irrigation water from the underground water table. But groundwater is being overdrawn across the country, especially in North China, Pang says.

Special attention should be paid to North China, where groundwater is depleting fast. The underground water tables in some northern areas have not been replenished in decades or even centuries. As a result, wells have to be dug deeper to find water, which may have been accumulated hundreds of years ago.

Pang and his team have visited many areas in North China and tested groundwater samples for age. To their surprise, they found that some of the water samples were thousands of years old, and may have accumulated in prehistoric times.