Elevated concentrations of Dimethenamide in the Rhine near Bad Godesberg

On 23 May, the Landesamt für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen (LANUV) reported elevated concentrations of the plant protection products Dimethenamide and Metolachlor in the Rhine near Bad Godesberg. Since 17 May 2024, these elevated values have been observed at Rhine kilometre 647.5 on the left bank. No abnormalities were initially found on the right bank, at Bad Honnef (Rhine-kilometre 640).  

The observations were transmitted through the International Warning and Alarm system of the ICPR as information and search reports. Traces of both substances were also found in Worms, Rhineland-Palatinate.   A previous report (number 4) reported that markedly elevated concentrations have since been measured on both banks near Bad Honnef and Bad Godesberg. The values rose to 0.43 μg/L for Dimethenamide and 0.14 μg/L for Metolachlor in Bad Godesberg, and 0.22 μg/L for Dimethenamide and 0.11 μg/L for Metolachlor in Bad Honnef.

In its most recent report, LANUV reports that pollution waves have arrived unabated in Kleve-Bimmen and Lobith, indicating that the pollution has moved downstream and is now affecting these areas as well.

These increased concentrations of Dimethenamide and Metolachlor represent a worrying development for the water quality of the Rhine. RIWA-Rijn is closely monitoring this situation and working with relevant agencies to assess the impact and take appropriate measures to safeguard water quality. It is essential to identify and address the sources of this contamination to prevent recurrence and protect the Rhine as a source of our drinking water.