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Let's water our way to future

By He Bolin (China Daily)
Updated: 2010-12-09 08:01

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.

Therefore, the need is to devise the most efficient way of using groundwater, or freshwater from any source, both for industries and agriculture. The older the groundwater, the more frugal should be its use.

The first step, no doubt, should be to save water. Since North China is the main producer of farm products such as wheat, corn, millet, potatoes and various types of fruits and vegetables, minimizing the use of water for irrigation will be of greatest help, Pang says, especially because huge volumes of water is wasted in irrigation.

Irrigation accounts for about 90 percent of the water used in agriculture in areas from Northeast to Northwest China, and a great percentage of that water is wasted. An example should prove the point.

When the Xinjiang Uygur autonomous region was under the grip of drought a few years ago, the authorities limited the use of water to 350 cubic meters per mu (0.07 hectare) for irrigation without harming agricultural production. But during normal times, the same farmers use 1,000-1,500 cubic meters of water to irrigate 1 mu of land.

Water-saving mechanism brings Zhangye city in Gansu province to mind. The Zhangye local government instituted a coupon system for farmers to draw water for irrigation and told them that they would be paid in cash for every coupon they returned, Pang says. A farmer can draw 50 cu m of water for one coupon. So the onus of saving water fell squarely on farmers. This arrangement has seen farmers saving about 50 cu m of water for every mu. The government should seriously consider introducing this measure to all areas facing water shortage.

Another problem groundwater faces is contamination because of seepage of pollutants discharged by industries. This is threatening people's health in many areas. Stricter measures have to be taken to compel industries, especially high-polluting industries such as petrochemicals, to treat wastewater and other effluents before discharging them.

Geological funnels with sedimentation of ground surface and depleting underground water tables are expanding in Hebei province, with Cangzhou at the center, because of overdrawing of groundwater. In fact, the underground water table in Cangzhou is now more than 100 meters below the ground level, Pang says.

Since saving water alone cannot solve all the problems, efforts should be made to increase funds to strengthen water resources management. After the government spent about 10.7 billion yuan ($1.61 billion) to stop degradation of the ecosystem and desertification in the Tarim Basin, the situation has improved and the groundwater level has started rising.

Perhaps our ancestors paid more attention to proper use and preservation of water. They have left us the karez water system, known as kan'er'jing in Chinese, in Turpan, Xinjiang, and the Dujiangyan irrigation system near Chengdu in Sichuan province as examples of their intelligence and ingenuity.

The karez system teaches us how to conserve and channel water in dry areas and the Dujiangyan system tells us how to harness water of flooded rivers. Given that global warming is turning more areas dry as well as causing more floods, the karez and Dujiangyang systems can be good examples for us to follow, Pang says.