When is it OK to use the water after it’s been treated for weeds?

By Jon Jennings, Water Quality Program

Summer. A time of year when recreational activities are at their peak, whether you fish, swim, water ski, or just dip your feet in the water to cool off. It is also the busiest time of year for aquatic herbicide treatments taking place in lakes around Washington under permits from the Department of Ecology.

Its undoubtedly frustrating — you're looking to cool off from the summer heat, you go to a lake to enjoy the water and you see a sign – the lake, or part of it, has been or is about to be treated with aquatic herbicides to control nuisance or noxious weeds.

When can you go swimming, or let your dog into the water to cool off?

Because we get so many questions like this, we’ve created a new website, Quick Reference Guide: Water Use After Herbicide Treatment.

Here, we provide answers to these questions for you. The new web page summarizes how and when you can use the water after waters have been treated.

In the past, the information available on Ecology’s web has been very technical. This new page aims to provide information about when you can use the water after aquatic herbicide treatment in a user friendly, non-technical way, and provide a consistent message from Ecology. Information about each herbicide addresses five use categories:

• Potable (drinking) Water Use.
• Swimming & Water Contact Activities.
• Fishing.
• Irrigation & Home Lawn/Garden Use.
• Livestock/Domestic Animal Water Use.

Each category has an easily identifiable icon that indicates a water-use restriction, advisory, or no restrictions or advisories. Restrictions generally mean that the water should not be used for a specific purpose for a period of time.

Advisories are Ecology’s suggestion that the water not be used for a purpose for a period of time.

We hope you find this information useful.
Learn more about pesticides to control aquatic plants and algae.

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