The British Geological Survey and the Environment Agency have published the results of a large-scale study into the risk of drinking water being contaminated by fracking operations. Researchers have mapped the areas where shale formations coincide with major aquifers in England and Wales, marking water sources that could be affected by potential methane leaks around oil and gas wells.

The study reveals that almost half of the key natural sources of water are located above shale plays where oil and gas could be extracted, BBC News reported. One of the areas where shale rocks and major aquifers coincide is the Bowland Shale in northern England, which is situated under six of the most important water sources in the area. However, researchers also note that 92% of the shale is more than 800 meters below the water reserves, while the Weald Basin in southern England lies at least 650 meters below major aquifers.

According to industry experts, contamination of these aquifers is practically impossible. In fact, industry representatives explained that drilling for shale gas and oil is safe for water reserves, as wells are sealed with steel and concrete, meaning that leaks into aquifers are highly unlikely. But environmentalists are unconvinced, as they claim that risk of drinking water contamination is inherent to the fracking process.

Dr. John Bloomfield of the British Geological Survey commented that results from the research could be used as a basis for further risk evaluation and as a guide for regulators, the BBC said.