Milling Water to the Sea

By Eilene Lyon

We recently took a trip to the Netherlands and Norway, so expect a few posts on sights, scenes, and travel. But first, I want to share a bit about the Dutch genius for engineering water.

It’s no secret that much of the Netherlands is below sea level. Since more and more land around the globe will be dealing with risings seas, there might be a boon for Dutch engineers soon!

One evening, on the barge that provided our nightly lodging as we biked around Holland (a “state” or “province” of the Netherlands), we watched a video about early dikes and polders, which went on to show the construction of one of the massive, mobile sea walls that protect the country from storm surges. Built in the 1980s, the technology for that time was astounding to me.

Oosterscheldedam (Wikimedia commons)

More interesting to me, as a tourist anyway, was the traditional system of dikes, canals and windmills (a system that began as early as 1000 CE). As our guide, Niko, explained to us, there is no “Nature” in the Netherlands. Every landscape in the country has been transformed by human occupation. Despite that, they have done a lot of work to create habitat for wildlife and we saw many birds, especially, that have benefited.

Cattle and sheep are used to maintain parkland and “nature” preserves

In the latter part of our tour, we stopped at Kinderdijk, which has many windmills, but these have been situated here primarily for show and the place was overrun with people bussed from nearby cruise ships. On our first full day of biking, though, we got to see the “real deal.”

Our guide, Niko, at Kinderdijk

Where I live in the desert southwest, traditional windmills are used to draw water from deep aquifers for livestock and household use. The Dutch, however, are awash in water and need to pump it away and send it out to sea. It seemed that every farm and suburban home we saw had its very own encircling moat. Cities are criss-crossed by picturesque canals.

We had the good fortune to visit a polder (land surrounded by dikes) in Aarlanderveen that is still drained by a series of four windmills, originally constructed in the late 1700s to 1801. The last mill built is currently the oldest, because the other three were destroyed by fire and other events and had to be rebuilt. This fourth mill is the one we were able to tour, inside and out, as well as observe the miller at work, setting the whole thing in motion.

It’s important to understand that the land wasn’t originally below sea level as it is now. In the process of creating drainage canals to remove water from the peat, subsidence occurred (and continues to occur). Once drained, and sometimes with the peat removed, the soil remains too soft for crop production, thus all the polders are used for grazing sheep and cattle.

These diagrams from the Molenviergang Aarlanderveen website show how the windmills work in a series of steps to raise the drained polder water from the lowest point, 5.4 m (17.7 ft) below sea level, to the level of the river which takes the water out to sea.

The yellow section is the “Put” or lowest part of the polder, and drained by Mill No. 4. The rest of the polder is the darker green area and drained by the other three windmills. Gray routes are roads. The green route is a walking/cycling path.

The millers keep an eye on the water level in the canal, and when necessary, set the mill to work. The current miller is the son of the previous miller and grew up in the windmill itself. Water mills have enough space inside to serve as a house for the miller and his family. Grain and sawmills don’t have interior living space.

The long staff on the back of the mill is the brake, which keeps the vanes from turning. A large wheel allows the miller to turn the vanes in the proper direction to catch the wind. Each vane is latticed so the wind can pass through when the mill is not at work. The vanes are equipped with canvas sails to drive the mill when in operation.

The miller cranks this wheel to turn the hood (upper part) of the windmill into the wind.

The miller unfurls the canvas sail to catch the wind. Yes, he is wearing traditional wooden clogs!

Once in motion, the power of this enormous machine was evident. Getting hit by a vane must be equivalent to getting hit by a bus, with similar results, I would imagine. The rumbling “whoosh!” made by the canvas as the blade spun was mesmerizing and intimidating at the same time.

Three of the mills use a water wheel to lift the water, but the fourth mill uses an auger. I had never thought of putting an auger to use in moving water!

This photo shows the housing for the auger that moves the water uphill.

The auger at work.

Some of the machinery at work inside the mill.

A final interesting feature of the water system in this polder is shown in the middle of the diagram above – a siphon. Because the channels used by this polder cross another polder and one of its canals, and the owners of that polder didn’t want to carry Arlanderveen’s water, too, the Aarlanderveen polder water goes underneath theirs through the siphon. Another engineering marvel!

We also learned about the secret communication of the windmill vanes. You can tell a working windmill from one that is for show, because a working windmills’ vanes will be horizontal and vertical. They can’t be left that way for long periods, or the horizontal vanes will begin to sag, so non-working mill vanes will be in an “X” position.

The vanes can be positioned to transmit messages of deaths and births over distances from mill to mill. They were also used this way to warn people of Nazi raids during WWII.

The windmills have several entrances, so the interior can always be accessed regardless of which way the hood (mobile upper part of the mill) is positioned. The children may go out one door on their way to school and walk in a different door when they come home!

As we prepare to leave the polder, I catch this scene of the windmill in motion and the model down below, which is fully functioning as well.

Sources:

https://en.wikipedia.org/wiki/Flood_control_in_the_Netherlands#Modern_developments

https://en.wikipedia.org/wiki/Oosterscheldekering

https://www.npr.org/templates/story/story.php?storyId=4847805