Aquatic Treatment Background

The Roza Irrigation District follows the requirements of the Irrigation System Aquatic Weed Control, National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge General Permit, WA0991000. The State of Washington, Department of Ecology issues this permit. The permit requires that Roza Irrigation District inform the Central Regional Office in Yakima, Washington 24 hours before an herbicide treatment is released into the Roza Canal.

The Roza Irrigation District places this treatment information on their website 24 hours in advance of the treatment. The treatment locations for laterals and the Canal will be listed on the website at

This link will take you to the actual dates and locations of chemical treatments. It is advised that a landowner who does not want herbicide treated water on their property to deny treated water delivery. Deny the treated water for the day of the posted treatment and for 48 hours after the posted treatment. You may call the Water Quality Supervisor to discuss your individual location(s) at 509-837-6980.

"Working together proactively to preserve, protect and enhance our water and land resources."