“Water and Soil Directive” is the title of a letter that Secretary Mark Harpers and Secretary of State Hagen (Infrastructure and Water Management, VVD and CDA) sent to the House on Friday afternoon. It’s the new mantra for all things spatial design. Because we are increasingly reaching water-soil system limits, they write, partly because of climate change. The Netherlands should prepare for sea level rise and a more extreme precipitation pattern.
33 Structuring Options are discussed in 32 pages. From stopping dwellings in deep polders to careful processing of sand extraction. Water has to be given space, and the IJsselmeer district plays a major role in that.
Experts welcome the letter. “It’s a great text,” says Gualbert Oude Essink, geologist and groundwater expert at the Deltares Institute of Knowledge and the University of Utrecht. The long list shows that this is an integrated approach, with water and soil getting the attention they deserve. A lot is connected.” He believes that the government is making real decisions. “Take a salt. The goal is no longer to prevent this always and everywhere.”
“The message indicates a trend break,” says Harold van Weveren, flood risk management strategic advisor at Rijkswaterstaat. Two thousand years ago, water and soil also led us. When the waters came, the people retreated to the hills. For the past thousand years, we have been bending the earth and waters to our will. I live at the bottom of the Zuiderzee. We don’t have to live on hills again, but the landscape of water will change again.”
The 33 options aren’t entirely new. The same measures are included in different water programmes. “The transformation has already begun,” says van Weveren. In 2007, the Room for the River program began widening and deepening the floodplains and moving river dikes to prevent flooding. “This is a logical continuation.”
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Many of the selections made in the letter are related in one way or another to the IJsselmeer area. In times of drought, it should be possible to draw from it, and in case of overflow, water should be stored in it. Shaking sea waters right at the gates of Afsluitdijk.
More flexibility in the water level helps with all of this. Water managers will be allowed to fluctuate the summer level by fifty centimeters, at the moment it is still twenty centimeters. When dryness is expected, the water level can be set a little higher beforehand and it can be lower than now if it stays dry for a long time. For the winter, there is the option of allowing the water level to rise as the sea level rises up to thirty centimeters.
“It is necessary to allow the water to rise with sea level, because at higher sea level, draining into the Wadden Sea becomes more difficult,” says Van Wyveren. “Afsluitdijk is now being refurbished and will be fitted with larger vacuum capacity and pumps to better handle this. I do not expect that before 2050 it will be necessary to raise the bar.
“Thirty centimeters is too big,” says van Wyveren. The level is now deliberately kept lower in the winter than in the summer, because storms are more common in the winter months and this can be dangerous for the surrounding areas. “If you raise the water levels in the winter, you also have to raise the dams. These are far-reaching and expensive measures.”
“I don’t think we have to use the fifty centimeters of leeway very often in the summer,” says van Weveren. “A low water level does not have such serious consequences as a high water level in winter. Although I say it very carefully, because the IJsselmeer has many functions, not only for water supply, but also for shipping, recreation and nature.”
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Birds and freight
Before the 2018 Water Level Decree came into effect, when a twenty centimeter fluctuation became possible in the summer, the consequences of all these functions were examined and compensated if necessary. “For example, additional sheltered places have been created for birds. For shipping, it may be necessary to make canals deeper at lower water levels. Additional pumping stations may be needed to properly deliver water to remote areas. If large fluctuations become structural, we have to We go through all these jobs again.”
The water in the IJsselmeer is also very important for the upper half of the Netherlands to prevent salinization. “It is used extensively for cleaning, spraying crops, and keeping peat soils in order,” says Oude Essink of Deltares. “Lower Holland is salty. The bad thing about salt water is that a little bit can make a large amount of fresh water very salty. It’s best to rinse with pure water as much as possible, every milligram less salt helps. Such a higher level is really good for preventing the water from overflowing.” Salty from the Wadden Sea.”
It is no longer always necessary to prevent salinization
Gwalbert Old Ascend hydro
Oude Essink is optimistic that the message states that saltiness everywhere cannot always be stopped in the long term. “It enables smarter cleaning, for example,” he says. “Now the polders are surveyed in a general way. But if you do it in a limited number of ditches from which water is already extracted, where the need of the farmers is great, for example, you can give away the less used areas. And then, in general, there is a need to a smaller amount of rinsing water.
“The Netherlands should once again become a sponge out of a colander,” says van Wyveren, “this is how the letter sums it up.” “There are all kinds of big options aimed at this. The great thing is farmers and water boards have been working on this for a long time. It can be done very simply, by putting a slab in a hole. We are now moving towards a new equilibrium for the whole country.”
A version of this article also appeared in the November 28, 2022 newspaper
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