It has been high tide in the province for days. Where does all that excess water go? And can we expect these high water levels more often? We asked the Hoogheemraadschap Hollands Noorderkwartier, the manager of the water in (part of) North Holland.
The large amount of water has caused a so-called storm surge on the IJsselmeer. This means that the water level is exceptionally high.
First of all, what does the Hollands Noorderkwartier (HHNK) water board actually do?
“Every day we work to protect the country against water, against flooding and water shortages, for clean and healthy surface water and for safe waterways. We do this in North Holland above the North Sea Canal: Hollands Noorderkwartier.”
Has the highest point in the IJsselmeer already been reached?
“It seems that we have reached the highest point. This was approximately NAP +0.62m. This value differs per location, due to the tilt of the water.”
How high is the highest the IJsselmeer has ever been?
“This question is a bit difficult to answer, because it depends on the location in the IJsselmeer. Then you would have to look at an average level. Since 1976 this has been NAP +0.51m. We now (still) have the average values. not, but it is clear that it is now very exceptional.”
Where will all that excess water from the IJsselmeer go?
“The IJsselmeer water is drained (discharged, ed.) into the Wadden Sea, but with drainage you are dependent on the water level on the Wadden Sea. If the wind is northwest, then there are hardly any drainage options. In addition, you are also highly dependent on the tide to be able to flush.”
“The water level on the IJsselmeer has dropped by 25 to 30 cm due to the discharge, but it is now rising again due to the high river water discharges and limited drainage options in the coming days.”
It will become more difficult to drain water to the Wadden Sea in the coming days. This is due to the strong wind, but also because the spring tide is approaching again at sea. In addition, the peak that is currently in the rivers in the east of the country will soon all end up in the IJsselmeer.
Why does high water cause more problems in the east of the country (Overijssel, etc.) than in the ‘water provinces’ of North Holland and Zeeland?
“There they have to deal with high water levels in the rivers (high water wave). We don’t have that here. The IJsselmeer is the outflow for some of the rivers and rainwater. That now gives us the high water levels in the IJsselmeer.”
Is this exceptional or is there a good chance that this will occur annually?
“These circumstances occur approximately every 30 years. It is therefore exceptional, but given the developments in the climate, including more precipitation, it is expected that this will occur more often. This does not pose any problem for our dikes. They are designed to withstand a lot more severe conditions.”