The groundwater situation in many parts of China is deteriorating due to excessive exploitation and increasing pollution, a senior hydrogeologist warned yesterday.

More than 79 billion cubic metres of fresh groundwater are tapped annually in northern China, accounting for 51.5 per cent of the total exploitable groundwater resources, Zhang Zonghu, an academician of the Chinese Academy of Engineering, said at the 34th Congress of the International Association of Hydrogeologists (IAH).

At the same time, 26.7 billion cubic metres of groundwater is tapped in the south each year, accounting for only 13.2 per cent of the exploitable reserves, he said.

Based on developments in the past decade, the groundwater situation will remain stable in the south, where rainfall is ample, but will become worse in the north, Zhang said.

As a result, many places have suffered from environmental damage such as ground settling and depression, salt-water intrusion in some coastal regions, and desertification in the hinterland, Zhang said.

To reverse the situation, China has brought the study of groundwater into its national economic development plan, the researcher noted.

Groundwater in most parts of the Pearl and Yangtze river deltas has been contaminated, said Yin Yueping, a researcher with the China Geological Survey (CGS) under the Ministry of Land and Resources (MLR).

Yin, director of the CGS Hydrogeology and Environmental Geology Department, said China's groundwater management model is inadequate, with a poor supervision system and outdated decontamination methods.

"The nation's groundwater management has lagged behind the world for years," he said.

Groundwater is any water found below the land surface. It exists almost everywhere underground, for example in the space between particles of rock and soil or in crevices and cracks in rock.

More than 240 scientists from 56 countries attended the five-day event, which "is an important forum for Chinese researchers to learn groundwater management from other countries," said Yin, who is also the secretary-general of the organizing committee.

Co-sponsored by the MLR and the IAH, the congress will promote the survey, assessment, utilization, protection and management of groundwater in China, and its role in sustainable social economic development, Yin said.