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News Centre > Thursday 04 May 2023

Guernsey Water encourages islanders to stop, or reduce, their use of pesticides

WQ testing

Guernsey Water is once again encouraging islanders to do everything they can to avoid using pesticides to control plants and insects.

Although rigorous testing confirms drinking water has been protected and continues to be of excellent quality, traces of herbicides and insecticides are regularly detected in raw water samples. In the first three months of 2023, 58 pesticide detections were identified in the island's streams excluding glyphosate, this included the detection of one pesticide that had not been detected in 17 years.

These chemicals are believed to have been released into the environment through both commercial and domestic use in gardens. Use on driveways, paved areas and near to streams presents a particular problem, as applications can quickly wash away into watercourses when it rains.

Guernsey Water is asking islanders to avoid using pesticides wherever possible, but recognises that can be difficult for certain commercial operations. It is urging these businesses to consider whether they can reduce their use of these chemicals and prevent them from getting into streams by following the code of practice, as required by Guernsey's Health and Safety Executive.

Businesses using pesticides who would like advice on how to protect the island's water resources are encouraged to contact Guernsey Water's water quality team.

Where a pollution incident does occur and the source of the incident is identified the Office of Environmental Health and Pollution Regulation has powers under the Environmental Pollution (Water Pollution) Ordinance, 2022 to take action on the person(s) responsible.

The raw water treatment process is not designed to remove the chemicals currently being detected, but they can be managed through a combination of diversion and blending. However, if levels rise, significant investment could be required in the island's water treatment works, which would increase customer bills.

Last year the utility advised that around 250 million litres of water from the Vale Pond water catchment could not be collected due to pesticide levels. Recently these levels have reduced, so this catchment area is now being collected again.

However, pesticide detection is still resulting in significant volumes of water having to be diverted away from storage reservoirs and discharged to sea, increasing the risk of drought if the summer months are dry.

Margaret McGuinness, water quality risk manager at Guernsey Water, said: "Glyphosate has been under the spotlight recently because it is now banned from use in most situations. However, that does not mean we should simply use other pesticides, without any thought to their effects.

"With more severe droughts predicted for the future, the fact we are having to divert millions of litres of water to sea to safeguard the island's water supply is significant and concerning.

"Guernsey's drinking water quality continues to be excellent, and our treatment processes can manage the current levels of pesticides. We protect drinking water quality by monitoring and carefully selecting which streams we collect water from and blending it in our reservoirs. If the level of pesticides in a stream becomes a concern we divert it away from our reservoirs, so we are asking islanders to reconsider their use of pesticides to help us collect more water and protect the island from drought."

Households wishing to dispose of pesticides can take them to the Longue Hougue household waste & recycling centre, where they will be accepted free of charge. More information for both domestic and commercial users is available at

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