Balancing lakes

There are periods when a lot of precipitation falls in a short period of time. Sometimes there is so much that there is a risk of flooding. The water authority discharges excess water to the sea. When water levels are high, this is not always possible immediately. In that case, we temporarily store the water in areas that have been specially designed for this purpose. We then slowly drain the water to the sea. This way, we keep our feet dry.
 

Balancing lakes in our region

We drain excess water into the sea. If we don't, we will have to deal with flooding. Sometimes the sea level is higher than the water level in the rivers, canals, streams, creeks, and small canals behind the coastline. In such situations, we cannot drain any additional water. After all, water flows from high to low. The climate is changing and the chance of heavy rainfall in a short period of time is increasing. That is why we are creating areas where we can store water temporarily before draining it. This ensures that we keep our feet dry. We  now have a number of such storage facilities in our region .

Balancing lake De Onlanden

In 1998, heavy rainfall caused flooding in the northern Netherlands. We didn't want that to happen again. That's why, between 2000 and 2014, we developed an area where we can store water: De Onlanden. It is located between Groningen, Eelde, and lake Leekstermeer and covers 1,700 hectares. 
The De Onlanden balancing lake can store up to 7.5 million cubic metres of water. The greater the flooding, the larger the area where we store water and the more water it can hold. 

The construction of this balancing lake was completed in 2014. It has developed into a beautiful nature reserve with lots of water, plants, and animals. There is also space for agriculture and recreation. 

Expansion of De Onlanden balancing lake

This balancing lake is currently unable to store enough water to ensure that our residents can continue to live safely with water in our region in the future. Therefore, at the end of 2018, the Board of Directors of Noorderzijlvest decided to improve the balancing lake. More specifically, this means: 

  • In the future, the balancing lake will be able to handle a maximum water level of 15 centimetres above Amsterdam Ordnance Datum (NAP). Currently, the balancing lake can handle a maximum water level of 20 centimetres below NAP. A difference of 35 centimetres.
  • This means that it must be possible to store more water in the area in extreme situations: an additional 5 million cubic metres (in addition to the 7.5 million cubic metres that is already possible). With this plan, the water authority will be able to raise the water level further than is currently possible on an occasional basis.
  • We are building automated weirs: the balancing lake will start working as soon as conditions require it.
  • We need to raise existing flood embankments around the area in some places.
  • A new flood defence is being built between De Onlanden and lake Leekstermeer. 

These additional measures have consequences for the use and layout of an area beyond the boundaries of De Onlanden. That is why we are going through the process of improving the function of the balancing lake with our partners, the Drenthe provincial executive, the local councils of Tynaarlo and Noordenveld, Staatsbosbeheer (Dutch Forestry Commission), and Natuurmonumenten (Dutch Society for Nature Conservation).

A balancing lake in the Southern Westerkwartier

The province of Groningen and the water authority are jointly responsible for the overall development of a large area in the Zuidelijk Westerkwartier. A special area committee is working with many other parties to carry out all the work. In this area, nature development and the construction of balancing lakes go hand in hand. Passers-by on the A7 between Drachten and Groningen can clearly see the progress of the work. 

A balancing lake is one of the aspects we are implementing in the Zuidelijk Westerkwartier. It involves:

  • Designing a balancing lake and nature area in "De Drie Polders" with a capacity of 1.3 million cubic metres of water.
  • Designing a balancing lake and nature area within the "De Dijken-Bakkerom" polder with a capacity of 1.2 million cubic metres of water.

Want to know more?

The project in this vast area involves much more than just a balancing lake. You can find out everything about the project on a special website.

A balancing lake or water retention: what is the difference?

Now that dry periods are becoming more frequent, many people are wondering why we continue to discharge so much water into the sea instead of retaining it in the area. The answer is simple: we have to continue to discharge large amounts of water because otherwise we would no longer be able to live safely in our country. We sometimes have to discharge millions of litres (at once).
We store water to prevent flooding. We store water in low-lying areas. We store the water for a while and then slowly discharge it into the sea.
Of course, the water authority is aware of the need to retain water for longer. We do this to get through times of scarcity and to have enough water in every season.

In the projects we carry out, water storage and water retention often go hand in hand. However, different measures are needed to retain water for longer periods of time.