Science Tourist: Water Engineering Part 1 – Cruquius Museum and Amsterdam Ordnance Datum

I spent most of my childhood on the bottom of a lake. If you’ve ever flown to The Netherlands’ Schiphol Airport, you’ve been there, too. Luckily for us, the Haarlemmermeer (Haarlem Lake) was drained in the 1850s.

Where there is now a large international airport, several towns, farms and business parks, was once a 170 square kilometre lake. And where there was once one lake, there used to be multiple smaller ones. in the sixteenth century, Haarlem lake was smaller than 30 square kilometres. Flooding, erosion, and the harvesting of peat caused the small lake to merge with three other lakes in the area. The lake kept growing and growing. This hungry habit of lakes to eat away at the surrounding land was called “waterwolf”. It started becoming a nuisance, as the lake encroached further toward the surrounding cities. When it edged closer and closer toward Amsterdam, plans were made to dry the lake.

One of the first to advocate for the drying of the lake, in the 17th century, was an engineer called Leeghwater, for “laag water” (“low water”). That wasn’t his birth name, but like modern day DJs he changed his name to reflect his career. Leeghwater was responsible for reclaiming the first land from a lake in the Netherlands, so he know what he was talking about. In the 18th century, another engineer, Kruik, also recommended reclaiming the Haarlem Lake.

It wasn’t until about a century after that that the engineering works to dry the lake were finally put in place. Three very large steam engines were built at different points around the lake. One was named after Leeghwater, and one of the other ones was named after Kruik’s Latin name of Cruquius. Within three years, between 1849 and 1852, the machines had emptied the entire lake. After that, two of the engines kept running to continue pumping water out, but the Cruquius engine retired and is now a museum.

I have no photos of my visits here, because I was very small. There are some pictures in existence of a school trip with my grade 1 class, but nothing in which you can actually see the museum. Luckily Wikipedia has one on which you can see the size of the pumping station and the depth of the former lake. The hill is the edge and bottom of the lake.

Inside the museum you can see how the steam pumps work, and learn how the lake was dried. There’s an animation here that shows how it’s done. The steam engine in the Cruquius pump was one of the largest ever built, and the structure is internationally recognised by the American Society of Mechanical Engineers.

The museum also houses a general exhibit about the water level in Holland. I remember seeing this as a kid and being shocked by how much of the country would be under water if there were no dikes and pumps to keep the water out.

The municipality on the area of the former lake still carries the name of the lake: Haarlemmermeer. It’s about 5 meters below sea level (consider that when you next land at Schiphol Airport!), and right in the middle of the part of the country that would flood without the ingenuity of engineering.

In the official calculations of what’s considered “below sea level” in the Netherlands, the comparison is not with sea level itself, but with a standard measurement in the city of Amsterdam. The official point is marked in brass on a pole underneath Dam Square, but there is another marker at city hall, where you can walk down and look at it.

This Amsterdam Ordnance Datum is used as a standard throughout the Netherlands to keep measurements of water levels consistent. In a country that would be half under water if it weren’t for flood maintenance, this is not an entirely trivial matter!

Next week: a completely different feat of water engineering.

Credits: all images from Wikimedia commons. Museum: cc-by-sa credit Caspar. Flood map: public domain. NAP in Amsterdam City Hall: cc-by-sa M.M.Minderhoud.