Swimming Safely in Copenhagen’s Harbour Basin: Lessons from UrbanM2O

In Copenhagen, you can officially swim in the harbour basin — a refreshing experience and a great example of smart urban water management.

While in Münster, many people cool off in the canal during summer, it’s not officially allowed. The canal is primarily used for shipping and isn’t designated as bathing water. Copenhagen takes a different approach. During the UrbanM2O project kick-off meeting, participants learned that the harbour basin is designated as bathing water (mostly), even though it also receives combined sewer discharges.

The city has implemented a simple yet effective system: LED displays at swimming areas indicate how many days have passed since the last combined sewer overflow event (maximum 3 days). This allows swimmers to gauge the potential bacterial load in the water. Beyond safety, this system also raises public awareness about wastewater management — an issue many people are unaware of, despite its importance during heavy rainfall events.

All monitoring points are also publicly accessible online, providing transparency and empowering citizens to make informed choices about bathing water quality. UrbanM2O highlights this as an inspiring example that could be implemented elsewhere, including Germany. With most overflows already monitored and others expected to be retrofitted (thanks in part to the KARL project), the hope is that cities like Münster could one day allow official swimming in their harbour basins.

Copenhagen’s approach demonstrates how urban water management can combine public health, recreation, and transparency in a practical, user-friendly way — a model for cities across Europe.