Below that layer lies an underground reservoir of water, which also needs protection.

The most important type of gas storage is in underground reservoirs.

In the 1920s it was used as an underground reservoir by the water authorities.

A particular concern expressed was that the underground reservoir might trigger earthquakes.

It is said that this vast underground reservoir could supply fresh drinking water to the world for 200 years.

The gas is injected back into the huge underground reservoirs, helping to push out the remaining oil.

The principal goal: to protect a vast underground reservoir of pure drinking water.

Each strongpoint had an underground reservoir filled with crude oil.

The fountain uses a classic water management solution with an underground reservoir.

Gas more recently was stored in large underground reservoirs such as salt caverns.