Since the Sammamamish River fails to meet state clean-water standards for temperature and oxygen content, scientists from the Washington Department of Ecology will place a non-toxic pink- or rust-colored dye in the water for two days of testing on July 27-28.

Researchers will release the “Rhodamine” dye where the river flows under Northeast Marymoor Way in Redmond at dusk on July 27 as part of a study to help solve the stream’s water-quality problems. The dye will dissipate downstream and will not harm people, animals, fish or plants. It may be used on other dates if needed.

“You needn’t worry if you see a slight pink or tan tint in the water,” said Ralph Svrjcek of Ecology’s water-quality program in a press release.

“This dye is commonly used for this type of scientific study,” added Svrjcek, who is coordinating the study. “Research has shown it has no effect at all on human health or aquatic life at the very low concentrations we use.”

The river flows from Lake Sammamish in Redmond to Lake Washington in Kenmore, and Lake Washington empties into Puget Sound.

According to Ecology, stretches of the Sammamish don’t contain enough oxygen, which is critically important for fish. Also, since the river is too warm, the temperature can harm salmon, trout and other aquatic life, and decrease the oxygen-carrying capacity of the water.

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 — and they will take measurements at several downstream locations.

A team of eight Ecology researchers will collect samples of river water and use electronic probes to gather data on the stream. They will collect information on temperature, flow, dissolved oxygen and nutrients in the Sammamish and its tributaries.

“These tests and samples will help us understand river conditions and how long water takes to travel down the river,” said Teizeen Mohamedali, an environmental engineer with Ecology’s Environmental Assessment Program, in the press release. “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 Sammamish play an important role in restoring the health of Puget Sound and its troubled salmon runs.