Blue Flag beaches may have poor water quality

Denmark’s Blue Flag beaches do not guarantee clean water in real time, warns Sune Rønne Møller, a consultant at the Danish Outdoor Council, according to a report by DR.

Heavy rainfall and cloudbursts can cause sewage overflows, increasing the risk of harmful bacteria such as E. coli and enterococci in the water. Even if a beach flies the Blue Flag, the water may be contaminated in the days following such events.

“If you’re at a Blue Flag beach—or any beach—right after a cloudburst, it’s a good idea to check the latest water quality analysis before swimming, especially in areas prone to sewage overflow,” Møller said.

The Blue Flag certification requires at least ten water samples per season, typically spanning 3–3.5 months, but results take days to process. Denmark has 144 Blue Flag beaches this year, all of which must display current water quality data on information boards.

Under EU bathing water directives, all Danish beaches with regular swimming activity must be monitored, with at least four samples taken per season. If tests show poor quality, swimming is discouraged, and signs must be posted.

Climate change is expected to increase the frequency of cloudbursts, with projections suggesting a 50% rise in such events annually in a world 3°C warmer, according to Mark Payn, scientific leader of DMI’s Climate Atlas. Denmark has improved its sewage systems to handle extreme weather, but risks remain.

Water quality analyses are available on municipal websites.