On July 29, 2026, a warning, negative swimming advisory, or swimming ban was in effect at 162 Dutch swimming locations. This represents over 17% of the 945 locations on the current map of Zwemwater.nl. Warm weather and drought can degrade water quality, but also pose safety risks due to low water levels.
More than one in six locations has a measure
A count of the current map from Zwemwater.nl on July 29 yields the following picture:
- 104 locations: risk of health complaints;
- 56 locations: swimming is discouraged;
- 2 locations: swimming is prohibited.
In addition, 781 locations had a 'good' status and two locations were investigated further. In total, this meant that 162 of the 945 locations were at a warning level. That is 17,1%; more than one in six official swimming locations.
The situation is a snapshot. Zwemwater.nl is updated daily, and measures can be implemented or withdrawn as soon as new measurement results are available.
A warning does not always mean closure.
The different statuses do not have the same meaning. With a warning, visitors may still swim, but there is an increased health or safety risk. Vulnerable groups, such as young children and the elderly, would be better off choosing a different location.
With a negative swimming advisory, swimming is discouraged for everyone. A swimming ban means that visitors are not allowed to enter the water. The reason for this can be a problem with water quality, but also an unsafe situation at or around the swimming location.
Heat and little current promote blue-green algae.
The warm and dry weather may explain some of the warnings. Blue-green algae grow particularly rapidly in nutrient-rich water with little current and a temperature between 20 and 30 degrees. They can form floating layers and cause skin irritation and gastrointestinal problems.
The Netherlands was upgraded to an actual water shortage on July 16. Due to the persistent drought, little rain fell, river flows were historically low, and water demand was high due to the warm summer. High water temperatures and limited flushing can put further pressure on surface water quality.
However, based solely on the map count, it is not possible to determine how many of the 162 measures were caused directly by blue-green algae, bacteria, drought, or a safety issue.
Low water levels also cause steep bottoms
In Gelderland, the drought led to a different risk. On July 24, the province warned of potentially excessively steep underwater beds at thirteen swimming locations.
Due to low groundwater and water levels, the waterline has shifted. As a result, the bottom may slope down sooner and faster than visitors are used to. This can cause children and less experienced swimmers, in particular, to unexpectedly end up in deep water. The locations include campsites and holiday parks, including Vakantiepark aan de Maas, Camping IJsselstrand, and Camping De Waay.
Additional communication for recreation businesses
For campsites, holiday parks, and day recreation locations with a swimming lake, up-to-date communication is important. A warning on Zwemwater.nl also requires information at the reception, on their own website, and at the entrance to the beach.
It must be clearly indicated whether this concerns blue-green algae, bacteriological contamination, a low water level, or another safety risk. Where possible, business owners can direct visitors to an alternative swimming pool, beach, or recreational program.
More information
Resources and more information:
- Zwemwater.nl: current swimming water map with warnings, negative swimming advisories, and swimming bans.
- Zwemwater.nl: explanation about safe swimming and swimming water statuses.
- RIVM: information about blue-green algae in swimming water.
- National Government: actual water shortage due to the persistent drought.
- Zwemwater.nl: Warning for steep underwater bottoms in Gelderland.