Water quality warnings at official outdoor swimming locations across the Netherlands have more than doubled over the past month. An analysis of official monitoring data shows that 104 designated swimming spots currently carry health warnings, up from 46 at the end of June.
Local water boards routinely test hundreds of official bathing sites throughout the country to ensure conditions remain safe for the public. Of the approximately 950 registered swimming locations in the Netherlands, 781 are currently cleared as safe for swimming.
Risks from algae and sewer overflows
Warm temperatures and calm conditions allow blue-green algae to thrive in stagnant water. Swimming in affected spots can cause skin irritation, stomach cramps, nausea, and flu-like symptoms due to toxins released by the algae.
High temperatures also encourage the rapid growth of bacteria such as E. coli and intestinal enterococci. These bacteria increase the risk of gastrointestinal, ear, and eye infections for swimmers.
Summer rainstorms present an additional hazard for local water quality when heavy downpours overwhelm municipal drainage systems.
Regional water authority Waterschap Amstel, Gooi en Vecht occasionally issues broad advisories because flooded sewers discharge untreated water into canals and rivers, which typically takes a few days to clear.
Checking water conditions before swimming
Water managers and provincial authorities test official bathing zones at least once a month during the summer. If a site fails to meet safety standards, officials increase testing to once every two weeks.
Residents planning to cool off in local waterways can check real-time water quality assessments through the official Zwemwater app or website. Monitoring at designated sites across the country will continue through October 1.
