Crystal clear canals

By Jelle Voort

How the slowing down of the tourism industry has affected the water quality in Amsterdam’s oldest waterways

“When I read about the water of canals in Venice clarifying on Twitter, I wondered what the quality in Amsterdam would be like,” says Maarten Ouboter, a hydrologist at Waternet in Amsterdam. “So, we started doing some transparency measurements. In some extreme cases the water in the canals turned out to be twice as transparent in comparison to the historical data we compared it to.”

Before there were garbage trucks, the canals in the Dutch capital were used as a dump. There also wasn’t a proper sewage system in the city, so households would just dump their wastewater in the canals. Ever since the city’s households were connected to the sewage system in 1987, the quality in the canals started improving.

“After this connection they moved the purification pumping station from the Amstel to the Westelijk Havengebied. This meant that after 2006 there wasn’t any purified wastewater flowing to the river. This led to the growth of aquatic plants in the Amstel. But we also noticed that these aquatic plants were much more present in places where there wasn’t as much boating traffic. We had the impression that the actual ecological improvement lingers on the clusters where there are much more boating movements”, Ouboter explains.

It’s now been over two months since the tourism sector has come to a halt due to the corona restrictions in Amsterdam. This led to less boat traffic in the canals; the sightseeing cruises have stopped sailing and for a while the canals were also closed off to private recreation. Therefore, the transparency in the canals has improved significantly, which leads to more sunlight penetrating through the water. “This is the mechanism we had hoped for,” Says Ouboter.  “When we noticed that the transparency of the water improved, we knew the light would have the chance to get into the water more. If that light hits the sediment it could lead to the germination of seeds and the growth of aquatic plants in the canals. This could then have a snowball effect on the quality of the water since these water plants collect silt. If you look at the water in the Transvaalkade, where there are a lot of water plants since there is almost no boating traffic, you can see that the water is almost crystal clear. That could arise in the canals as well. It is possible to have more clear canals with water plants in them, look at Delft and Leiden for example. The boating traffic there is less intensive.”

The clearing up of the canals, in a relatively short period of time, also raises political questions. The tourism sector in Amsterdam has grown exponentially over the last decade. This sudden stop might create an opportunity to change the way we use the canals. “You could think of creating several zones where you cannot sail. This provides an environment for these water plants to grow. In a way there already are several zones where boating traffic is prohibited. There are a couple of really low bridges near the Ringvaart which you can’t pass because they are simply too low. The same goes for the Keizersgracht because there are low bridges near the Utrechtsestraat where big tourist boats cannot pass through. These are exactly the spots where these water plants are now appearing. I would say, keep these bridges the way they are, keep them low. But unfortunately, there are a lot of lobbyists that want to raise these bridges. Then you would have one-way traffic in the Keizersgracht and one-way traffic in the Prinsengracht, which would generate a lot more income for the city’s tourism sector.”

Perhaps this standstill of the city is a moment of realization; in a short amount of time the water quality in the city has improved substantially. This shows the great possibilities we have when it comes to water management and water purification. But on the other hand, the tourism sector can’t wait to start the motors of their boats again, to show people from all around the world the romance the city’s canals have to offer. This leads us to a two-way split; will Amsterdam go for the money or will we realize that water is a scarce commodity and good water quality will benefit us all?