WATER-SAVING AGRICULTURE: Sprinklers are used to water the fields in Baita Village, Zhangjiakou, Hebei Province. Sprinklers use 70 percent less water than traditional surface irrigation (GONG ZHIHONG)

A report released by the China Geological Survey in 2008 showed that the direct economic losses from land subsidence in the North China Plain amounted to 40.4 billion yuan ($6.2 billion) as of the end of 2007, while the indirect economic loss to the area was 292.4 billion yuan ($43.4 billion).

The North China Plain, with megacities such as Beijing and Tianjin, has traditionally been China's cultural, political and economic center. Currently, it is home to one fifth of China's population and arable land.

In spring, the major crop growing season, the weather in this area tends to be dry. "Over the past two decades, precipitation in north China has decreased by 10-15 percent," Shi said.

Natural rainfall on the plain is not sufficient to sustain the population increase and industrial and agricultural development. Too much groundwater has been extracted.

Wu Ai'min, an official with the China Geological Environmental Monitoring Institute, said that groundwater supplies between 75 percent and 80 percent of the water consumed in the North China Plain.

Groundwater used to be within the reach of a biandan, a 2 to 3-meter shoulder pole used for carrying water. Farmers once ladled water from wells with a bucket hooked to one end of the biandan. Now, they have to drill dozens or even hundreds of meters to reach groundwater.

Shen Yanjun, a researcher in the Key Laboratory of Agricultural Water Resources at the Chinese Academy of Sciences (CAS), found that the average annual precipitation on the North China Plain is about 500 mm, whereas agriculture in the area consumed the equivalent of 870 mm of precipitation each year, and the shortfall, which amounts to 370 mm of precipitation, is made up by groundwater.

Wu said that it would take the natural water cycle more than 10,000 years to replenish the 100 billion cubic meters of groundwater that has been overexploited, to date, in the North China Plain.

"Moreover, the over 1,600 reservoirs built in the upper reaches of rivers flowing across the North China Plain will increase water evaporation and reduce natural underground water replenishment in the lower reaches of these waterways," Shi said.

Water-saving agriculture

In terms of replenishing the overused groundwater, Jia Shaofeng, a researcher with the Institute of Geographic Science and Natural Resources Research of the CAS, pinned a lot of hope on China's ambitious South-to-North Water Transfer Project.

He told the Guangdong-based Time Weekly magazine that in recent years, water consumption in north China has declined and the water transferred from the south will make it unnecessary to overexploit groundwater in the north, so aquifers will gradually be replenished.

But, Fei Yuhong, a researcher with the Institute of Hydrogeology and Environmental Geology, was skeptical of Jia's point.

Fei believes that although the water transfer project may supply drinking water to cities, it will not meet agricultural demand for water, and hence will not significantly rectify the damage from overexploitation.

"Because the North China Plain is so big, transferred water will only be available to farmers close to the transfer routes; even so, the water price will be too high for farmers," Fei said.

Fei believes that a better way to tackle land subsidence is to plant drought resistant crops and use more efficient irrigation methods such as dripping and sprinkling.

Efficient irrigation methods such as dripping and sprinkling were promoted in Zhangbei County after the Angulizhuo Lake dried up in 2004. The county used national subsidies for water conservation projects to promote water-saving agriculture.

As of the end of 2010, efficient irrigation methods had been used in 63.7 percent of the total irrigated land in Zhangbei County, said the county government. The new irrigation methods consume 30-50 percent less water than traditional methods.

To limit groundwater extraction, the county government now requires those who dig wells to have a permit. In addition, the county has also converted 61,000 hectares of arable land to forest. Similar efforts have been reported in Zhangbei's neighboring counties, such as Shangyi, Kangbao and Guyuan counties.

Zhangbei County is also piloting innovative water-saving reform in its Mantouying Township. Tiered water prices have been introduced and groundwater consumption is inferred from the electricity used to pump water. The reform is expected to be implemented countywide in 2013, reported hebei.com.cn, a local news portal.

In September 2010, after heavy rain, some water in fact returned to Angulizhuo Lake, for the first time in six years. Staff members at the local hydrological department found that water covered an area of 1,212 hectares, about one fifth of the lake's previous area, and the maximum depth of water was about 50 to 100 cm.

Local hydrological experts believed that the improvement of the ecological environment in the county and its neighboring areas will eventually help the lake retain water and once again become a place of outstanding natural beauty.