Pumps, weirs, and locks

A pumping station is a pump that can move water from a low to a high level and pump water into and out of an area. With pumping stations, we can keep the water at the agreed level. We use four types pumping stations: the catchwater pumping station, the subcatchment pumping station, the polder pumping station, and the sewage pumping station.

Catchwater pumping station

A catchwater pumping station pumps excess water into a catchwater. A catchwater is a system of lakes or canals in which we store water temporarily. We also use a catchwater to drain water. De Waterwolf in Lauwerszijl/Electra is an example of a catchwater pumping station. In 1920, De Waterwolf began its important task in the Reitdiep: draining water from a large part of the province of Groningen and the Kop van Drenthe. De Waterwolf was unique for its time and is a beautiful piece of industrial heritage. Today, the pumping station is still in operation. In fact, the pumping station is indispensable in draining excess water into the Wadden Sea.

Subcatchment pumping station

A subcatchment pumping station is a special catchwater pumping station that we use in areas where the ground is subsiding. The ground in north Groningen is subsiding due to gas extraction. If the water level remains the same and the ground subsides, the water level will rise in relative terms. To deal with the negative effects of subsidence, Noorderzijlvest lowers the water level. The Abelstock pumping station is an example of a subcatchment pumping station. It is in the Hoornsevaart between Mensingeweer and Wehe-den-Hoor. This pumping station is in the second subcatchment of the Electra catchwater.

Polder pumping station

A polder pumping station pumps excess water in the polder to a catchwater. We have approximately 140 polder pumping stations in our region. One example is the Leutingewolde polder pumping station. Here, we measure the water level of lake Leekstermeer. The lake also collects excess water during wet periods. That is why the lake must be able to cope with higher water levels. Here, we regulate this with a polder pumping station.

Sewage pumping station

A sewage pumping station pumps used water from homes and businesses through the sewer system to the treatment plant. One example is the Groningen sewage pumping station on Damsterdiep, which is a listed building. It pumps all the used water from the city of Groningen through an eight-kilometre-long pipe to the sewage treatment plant in Garmerwolde. The immense pumps in the pumping station produce the pressure and push the water to the treatment plant, as it were.

Locks are built between two watercourses that have different water levels. On one side of a lock, the water is higher or lower than on the other side. We can open a lock to allow water to flow through. There are eight types of locks:

Navigation lock

The navigation lock the best-known type of lock. The lock takes a boat from one water level to another. This is how it works:
A navigation lock has two doors. One door opens and the boat enters the lock. The door then closes.
We raise or lower the water in the lock chamber. This depends on the water level on the other side of the lock. Finally, the second door opens and the boat continues on its way.

Tidal barrier

We use a tidal barrier to keep water out. When the water level is normal, the lock is open. When the water level is extremely high or low, we close the tidal barrier. The Oosterschelde barrier in Zeeland is an example.

Drainage sluice

Drainage sluices can be found in flood embankments, dykes, and dunes. We use these sluices to drain excess water from the land into a catchwater, canal, river, or sea. The Clevering locks in lake Lauwersmeer are an example.

Relief sluice

We only open the relief sluice after a flood. When we open the sluice, water from a polder can flow into a canal, river, or sea.

Inlet sluice

We use the inlet sluice for two things. We open the sluice so that freshwater flows into city canals or agricultural areas, for example.
We open the sluice when it is very dry. For example, if we open the sluice in the Gaarkeuken, water from lake IJsselmeer flows into the ditches and canals of our region.

Tidal sluice

Tidal sluices are found in seaports. The sluice ensures that the channel between the sea and the port does not silt up with mud. Behind the sluice is a large bowl-shaped hole. At high tide, we allow water to flow into this bowl. When the water is at its highest, we close the sluice. At low tide, we open the sluice and the water flows out of the bowl back into the sea. The water carries the mud in the channel with it.

Inundation sluice

Inundation is a fancy word for 'flooding'. This lock allows us to flood a piece of land. In the past, the inundation lock was used by the army for defence. They ensured that the water was too low to sail on and too high to walk or drive through. Now we use the lock to allow water to flow into reservoirs. Or to flood agricultural land.

Dock lock

A dock lock can be found in harbours. This lock ensures that there is water in the harbour at low tide. This means the boats are always in the water. Is it high tide and the water level is high? Then we close the lock. This keeps the water in the harbour at low tide.

A weir is a valve in a ditch or canal. Behind it, the water remains in place to keep the water at the agreed level. A weir be fixed or movable.

• A fixed weir always produces the same water level.
• With a movable weir, we use a valve to produce different water levels. The water level is lower in winter: we open the valve to drain excess rainwater. This prevents flooding. The water level is higher in summer: we close the weir to retain water for agriculture and nature during dry periods.