Information for swimmers

12 August 2016

Water has always played a central role at Marineterrein Amsterdam: as a shipyard for the Admiralty of Amsterdam and later as a logistical centre for the Royal Netherlands Navy. As in the rest of the city, the water was not only used for transport but also for the discharge or dumping of waste. We are still seeing the consequences of this. However, there is some good news: the quality of Amsterdam’s water is improving every year.

Swimming at your own risk

Waternet has been monitoring the water quality since spring 2016. The inner harbor will still not be an official swimming location in the coming years due to strict regulations and fluctuations in the water quality. Swimming here is permitted, but at your own risk. Students of the University of Amsterdam have investigated the water quality, the bottom conditions, and the ecology of the water, so that you can make a well-considered choice before going into the water for a swim.

How clean is the water?

The water quality in the Amsterdam canals is usually good. Sometimes, however, after long periods of rain and downpours, the sewers can get so full that sewage water flows into the canals. This results in bacteria getting into the water. In warm weather, the bacteria also reproduce quickly. Swimmers who swallow some of that water can suffer from abdominal pain, vomiting, or diarrhea. Children and older people are at a greater risk of getting ill.

What is on the bottom?

The bottom has become contaminated with heavy metals and oil remnants over the centuries. If the bottom is stirred up, these substances can become mixed with the water. This is unlikely to happen as a result of someone swimming, as the bottom of the canal is at a depth of 3 to 4 metres, but it can happen as a result of lots of ships passing through. In the future, the bottom could be covered with a clean layer of sand, so that the contaminated sediment doesn’t get mixed into the water as easily.

What life is there in the water?

Marineterrein has been closed off for many years, including for biologists and ecologists. As a result, we know little about the nature on land and in the water. What we do know is that the high stone walls offer little opportunity for water plants and fish to make their homes in. It is beneficial to create alternative habitats in the inner harbour, as a good ecosystem is the best way to promote clear, clean water.

Underwater gardens

In order to improve water quality, the students have created underwater gardens: floating baskets with a variety of water plants such as hornwort, yellow water-lily, and charales. These plants oxygenate the water and combat the growth of blue-green algae. Young fish also find shelter and protection between the plants. This improves the water quality in a natural way.

Publisher’s imprint

Students of the Tesla minor (University of Amsterdam) are performing the research on the instructions of Bureau Marineterrein Amsterdam and in cooperation with Waternet. The study will be concluded and published in the summer of 2016.