In the lowest polder in the Netherlands you can see why the water level can no longer be lowered

We are more than six meters below sea level, on the floor of a pumping station that keeps the deepest polder in the Netherlands dry. This is the Zuidplaspolder. The water managers took a remarkable decision this week about part of this area: although the peat soil sinks every year, the water level will no longer fall with this fall. “If we continue in the same way, we will have reached the end of the makeability of the Netherlands,” says Toon van der Klugt, who is the chief executive of the Schieland and Krimpenerwaard Water Board as dike warden.

The soil in part of the Zuidplaspolder has sunk so much that saline groundwater bubbles up and pollutes the ditches, which turn orange as a result, due to oxidizing iron. Cozy for football fans these days, but in no way undesirable. Van der Klugt: “In previous centuries, we always adjusted the water level to the subsidence, so that the same agriculture remained possible. But that process is finite. We are now saying in time: we can no longer lower the water level, keep that in mind.”

Government policy

The measure was adopted unanimously this week, so also with the approval of the representatives of the farmers, taken by the general board of the Rotterdam Water Board. “That is special,” says the dijkgraaf. “Everyone realizes that adjusting the water level is no longer possible. We have been urged to come to a good future perspective more quickly with the municipality and province.”

The decision is a rather ideal illustration of the usefulness and necessity of the policy announced by the cabinet last week, in which water and soil will from now on be ‘steering’ in the spatial planning of the country. “Confidence in the manufacturability of our landscape is great. But we are now increasingly coming up against the limits of the water and soil system,” wrote Minister Mark Harbers (Water Management, VVD) in a letter to parliament. “Soil subsidence and low water levels cause a lot of damage to building foundations and extra maintenance on roads and railways. Sufficient good drinking water is no longer a matter of course. The survival of plant and animal species is under pressure.”

Some of the measures favored by the government: no more building should be done in areas that are necessary for the storage and drainage of water, such as floodplains and the deepest parts of deep polders; and the Netherlands must strive for a higher groundwater level, because that provides sufficient water if it has not rained for a while, slows down the subsidence of peat soils and reduces greenhouse gas emissions.

In a part of the Zuidplaspolder, which was drained almost two hundred years ago, between Rotterdam, Zoetermeer and Gouda, it can be seen that such policy intentions are not a thing of the future, but are already a dire necessity. This is the first area known to have reached the ‘breaking point’. The Restveen, a part of the polder between Moordrecht and Nieuwerkerk aan den IJssel of almost four hundred hectares, consists of peat that dries out further every year and actually burns and shrinks. As a result, the increasingly lighter soil is no longer able to withstand the upward pressure of the groundwater. The soil cracks open and poor-quality groundwater damages farmland, nature and inhabited living environments. This effect is also extra large here in the lowest part of the Netherlands. Elsewhere in the polder, too, the soil threatens to crack without measures. “You get stuck on all sides,” says Van der Klugt.

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In addition to the damage caused by poor quality water, there is also a risk of subsidence elsewhere. “There is a railway here. If it starts to sag, you’re talking about millions of dollars in damage. The NS has already warned about this.” Other users such as homeowners could also get involved. The usefulness of stopping the downward lowering of the water level was already known twenty years ago, when the province of South Holland had plans to turn the Restveen into a piece of ‘wet nature’ and thus counteract subsidence. However, the plans fell through when the government suddenly turned off the money tap. In the following years, the level was not lowered ‘for the time being’. From now on it is finally clear that a lowering of the level will not happen again. Van der Klugt: “The benefits no longer outweigh the costs. The time of porridge and keeping wet is over. The current water level is the starting point for everyone.”

Alternatives

The consequences of the decision will mainly be felt by a limited number of farmers and a few horse owners. Grazing cattle and harvesting grass, now also one tour de force in the fairly wet area, will be less and less possible. “Farmers understand that. But this decision is also a signal to the province and the municipality to discuss alternatives with users.” In the next ten or twenty years you could still drive lighter machines across the farmland, and later grow other crops or build solar parks. For example. Or still construct wet nature. “That could be.” Will the rest of the Netherlands follow suit? “We do not know that. Every area is different. We do it wisely.”

A version of this article also appeared in the December 3, 2022 newspaper