Subsidence
Gas is located in a layer of rock at a depth of 3 kilometres. As the gas is extracted, the rock layer shrinks. All soil layers above this rock layer sink down. By 2070, the ground in the area where gas has been extracted is expected to have sunk by approximately 54 centimetres.
When the ground subsides, the bottom of watercourses in that area also sink. If such an area is connected to water from an area where the ground is not sinking, the ditches and canals will fill up until the water is at the same level everywhere.
Consequences
As the water rises in an increasingly low-lying area, the soil becomes wetter and wetter. At that point, agriculture can no longer make good use of the soil.
Bridges are sinking. Boats have less and less space to sail underneath them. Our dykes and flood embankments are sinking too and water has more opportunity to flow in.
What are we doing about the consequences?
First, we investigate whether subsidence is the cause of the problems in an area. If it is, we investigate whether the water level can be lowered. We also look at how this can be achieved. If we can lower the water level, we have to record it again in a new Water Level Regulation Plan. This is not something we do just like that. We discuss it with the local community. There are also formal procedures to ensure that all interests are taken into account before a final new Water Level Regulation Plan is adopted. The aim of new water level regulation plans is to restore the difference in height between the ground and the water.
The water authority uses pumping stations to maintain the water at the agreed level. As a result of subsidence, a large number of additional pumping stations had to be built.