In response to discoveries of radiation-tainted water following the nuclear plant explosion in Japan, Shanghai water authorities said the city has plans to draw water during emergencies from more than 50 deep wells by 2015.

Speaking on World Water Day, Meng Mingqun, director of Shanghai Water Supply Administration, said the city will drill the wells beneath large residential areas and universities, thus ensuring residents can get safe drinking water during disasters.

The city now has 10 deep wells.

"Some abandoned wells, which are scattered in suburbs, may also be reused, depending on their locations and the quality of the water they contain," Meng said on Tuesday.

In the past few years, 123 small water projects and 111 wells have been shut down as the city turns to larger and safer sources of water, according to the Shanghai Water Authority. The old wells and treatment plants used to be the water sources for Shanghai's seven suburbs, including the Chongming county, Qingpu and Fengxian districts.

"The risk report on Shanghai's water resourcespointed out that many of our suburbs' small water works draw from inland surface water, which is easy to pollute and hard to control once it is polluted," said Zhang Jiayi, director of the Shanghai Water Authority.

"That's why the local government plans to spend more than 1.1 billion yuan ($167.79 million) in building larger water sources and purification plants in five years, as well as switching to much safer water sources such as the Qingcaosha reservoir."

Meng said water sources that lie near residential areas are more likely to be used in emergencies.

"We would only select the well-equipped sites," he said. "We want to make sure things run smoothly if something like Japan's earthquake really happened here. They (emergency water sources) will be used as backups when unpredictable factors cause the existing water supply to be cut off."

Last year, 10 wells were drilled at Fudan University, Tongji University, Shanghai University, Shanghai Ocean University and four other universities in the city. They were each about 240 meters deep.

"The university is responsible for the daily maintenance of a well and must take water samples to see if it is polluted or not," said Guo Bin, a staff member responsible for well maintenance at Shanghai Ocean University.

But Guo said the university cannot use water from the well without first receiving permission from both the municipal government and the Shanghai Water Authority.

"That rule was adopted because Shanghai, a low-lying city, is likely to subside into the ground or sustain other damage if too much underground water is taken," said Chen Zhenlou, a professor from the College of Resources and Environmental Science of East China Normal University.