A Shenzhen factory has sealed two wells it had dug without official approval and called for other well owners to follow suit, amid reports of falling groundwater levels and seawater intrusion underneath the city.

Shenzhen Zhujiang Junan Cement Products Co. Ltd. filled the 30-meter-deep wells with bricks Sunday after officials said they would crack down on private wells within the special economic zone by the end of the year.

This followed reports by the Shenzhen Special Zone Daily, which said the city was being threatened by major seawater intrusion unless urgent measures were taken to curb excessive groundwater use.

Officials with the Shenzhen Municipal Bureau of Water Resources confirmed that the city was witnessing falling levels of groundwater, which meant it might become contaminated with the seawater coming in to replace it.

Excessive use blamed

"The excessive use of groundwater since the 1980s has lowered the underground water level," Zhao Bingbing, an official with the bureau, said.

Experts say too much groundwater has been used up in Shenzhen, as tap water was not widely used until the 1980s when the city witnessed urban expansion, and the city is suffering a chronic water shortage.

According to Zhao, the city's water authority conducted a survey early last year and found that seawater had already intruded into some coastal areas in the city.

The groundwater in Honey Lake, Overseas Chinese Town and other places along Shennan Thoroughfare has been found to contain excessive seawater, according to the survey.

"Seawater has intruded northward beneath the thoroughfare, and it is expected to come over to the city's center," Zhao was quoted as saying.

Shenzhen has a coastline of more than 230 kilometers, which is likely to see further intrusion by seawater if no prompt measures are taken to curb excessive groundwater consumption, according to Zhao.

"Residents are being suggested not to use groundwater in the southern part of Shennan Thoroughfare since it has been invaded too much by seawater," Zhao was quoted as saying.

The groundwater there is found to contain chloroquine at 4,000 milligrams per liter, much higher than the average standard for drinking water.

The newspaper said more than 20 people suffered diarrhea and stomach problems earlier this year after drinking water taken from a well.

Seawater intrusion could also destroy geological structures by lowering ground surface levels, Zhao said.

At present, the city still has more than 1,000 private wells in operation, which must be soon filled up, according to Zhao, who also called for the ban on groundwater exploitation and the establishment of a monitoring system along the coastline to detect problems.

Editor: Yan