Testing River Water with Dye

Scientists from the Washington Department of Ecology will use Rhodamine dye in the Pilchuck river as part of a study to help solve the stream’s water quality problems.

The Pilchuck river currently fails to meet state clean water standards for temperature and oxygen content.

The researchers will use “Rhodamine” dye that is somewhat fluorescent next week as part of their water quality monitoring.

They will release the dye at two locations, where Menzel Lake Rd. and 64th St. NE cross the river.

The tests will take place at dusk on Aug. 16, and on other dates if needed. The dye will look pink- or rust-colored in the water before it dissipates downstream.

This dye does not harm animals, fish, plants or people.

Researchers collect river data

Scientists will track the dye plume with a fluorometer, which detects the small amount of dye in the stream, even after it is no longer visible. They will take measurements at several downstream locations.

Over the following days, a team of four Ecology researchers will collect samples of river water and use electronic probes to gather data on the stream. They will collect information on temperature, dissolved oxygen and nutrients in the Pilchuck.

The river does not meet clean water standards

There isn’t enough oxygen in stretches of the Pilchuck, causing it to fail state clean-water standards for oxygen content. Oxygen is critically important for fish. The river is also too warm. 

High water temperatures harm salmon, trout, and other aquatic life, and decrease the oxygen-carrying capacity of the water. 

“These tests and samples will help us understand river conditions and how long water takes to travel down the river,” said Nuri Mathieu, a scientist with Ecology’s Environmental Assessment Program.

“The information will help calibrate and validate a water-quality computer model that we will use to analyze temperature and dissolved oxygen during critical summer conditions.” 

Data from the field work will be available next year, in advance of a full study that will guide Ecology and local governments' efforts to prepare a cleanup plan for the river.

Rivers like the Pilchuck play an important role in restoring the health of Puget Sound and its troubled salmon runs. 

Source: Washington Department of Ecology

Media

Taxonomy

• Water Quality
• River Studies
• Dyes & Pigments