Pesticides in Swiss water: new WWF maps reveal where contamination has been detected

WWF Switzerland has launched an online platform showing pesticide contamination in the country’s waterways and groundwater. Unveiled on Tuesday, 20 October, it brings together measurements from 2019 to 2024 in four interactive maps. Users can explore which rivers, streams and groundwater bodies are affected, which substances have been detected and how their concentrations changed over that period. It makes an environmental problem that is usually invisible in clear water more tangible.

The environmental organisation has coupled the launch with political criticism, accusing the federal authorities of insufficient transparency and criticising a weakening of protection rules. The maps aim to make information that was previously difficult for the public to navigate more accessible. Their immediate value is in putting measurements on a map and making contamination by individual substances easier to understand.

Four maps for a closer look

Two maps cover surface water and two focus on groundwater. The distinction matters: conditions in a stream or river differ from those in water beneath our feet. Rivers and streams can respond quickly to pollutants entering the water and to rainfall, whereas groundwater often moves more slowly. Contamination below ground can therefore persist for a long time.

The platform offers both an overview of pesticide contamination and searches for around 60 individual substances, including glyphosate and 1,2,4-triazole. Alongside the affected areas, users can examine the substances recorded, their risk classifications and changes in their concentrations between 2019 and 2024.

WWF requested the data from the Federal Office for the Environment, Switzerland’s federal environmental authority, and brought it together in a single tool. Eva Goldmann, an agriculture specialist at WWF Switzerland, describes the aim as combining the information in an accessible format. For interested residents, it offers a way to move beyond an abstract debate about pesticides and see what has actually been measured in a particular waterway.

A detection is not a verdict on tap water

Groundwater quality is particularly important in Switzerland. Groundwater and spring water are central pillars of the drinking water supply. Protecting them is therefore not only a matter of safeguarding nature: it also concerns infrastructure on which households and businesses depend every day.

Nevertheless, a map of contamination in waterways and groundwater should not be confused with an assessment of the water coming out of a kitchen tap. A measurement taken in a stream or at a groundwater monitoring point does not, by itself, establish the quality of locally supplied drinking water. That also depends on the water intake being used, any treatment and the checks carried out by the water supplier.

The details matter when interpreting a pesticide detection, too. Which substance was found, at what concentration and when? Detecting a substance, exceeding a legal limit and identifying a health risk are not the same thing. Being able to examine individual substances and their concentrations over time is therefore more useful than simply dividing areas into contaminated and uncontaminated zones.

Why past contamination can linger

WWF also wants the platform to draw attention to the persistence of the problem. Goldmann points to chlorothalonil as an example of pesticide contamination that can remain detectable years after a ban. Prohibiting a substance ends its permitted use, but does not automatically remove residues already present in soil and water.

Breakdown products can also play a role. When an active substance changes in the environment, that does not necessarily mean all the substances resulting from that process disappear immediately. Water protection is therefore not only about current pesticide use. Understanding how contamination from earlier use develops over longer periods is equally important.

Another substance searchable on the platform is 1,2,4-triazole. It attracted greater attention after contamination was discovered in Lake Geneva in summer 2025. Here, the maps’ time limit is important: the displayed series ends in 2024. It can show earlier measurements, but the discovery in summer 2025 falls outside the period covered.

Greater insight, not a real-time picture

The platform is primarily a tool for understanding documented contamination. It does not provide a real-time picture of Switzerland’s waterways and groundwater in October 2026. Anyone assessing changes needs to consider both when and where measurements were taken. Nor can a single finding automatically be treated as representative of an entire waterway or every groundwater body in a region.

For the wider debate, the maps provide a concrete starting point. Where does contamination persist, where is it changing, and which substances warrant particular attention? Residents can explore those questions through recorded measurements rather than relying solely on broad descriptions of the problem. The distinction between a historical record and current conditions remains essential when interpreting what the maps show.

WWF’s criticism of transparency and protection rules now comes with a publicly accessible body of data. Whether that leads to political changes remains open. For now, the platform makes clearer why protecting water is a long-term task — even when, at first glance, it looks clean.