We've been tackling water quality challenges throughout the Yakima River Basin for nearly 20 years. Then, the river ran muddy from topsoil that washed off fields and remained suspended in the water column, carrying legacy pesticides in the sediments and creating cloudy turbid waters. Now our scientists are conducting a water quality checkup of the river to see how things are doing.
“We have seen tremendous water quality improvements over the years, thanks to the efforts of the watershed community to prevent topsoil from running off into the river,” said Mark Peterschmidt, a supervisor for water quality in our Central Region. “This project will help determine how far we have come and how much further there is to go to meet water quality goals.”
The sampling effort also gives us a chance to gather new data to study new ways to improve dissolved oxygen and temperature levels in the river.
High water temperatures and low dissolved oxygen harm salmon, trout, and other aquatic life. We see river temperatures block fish passage in the summer and fall, due to drought and low flows. We want to learn why and find remedies.
Fluorescent dye helps track heat and oxygen
In October, we are conducting studies along several miles of the river above Selah Gap to establish how streamflow and water velocity affect temperature and dissolved oxygen levels. To do this, we will release small amounts of a tracer dye at eight points in the river to determine how fast water travels down the river (aka water velocity).
Our work will be in the evening to minimize disruptions to activities on the river and to enhance detection by Ecology’s instruments.
Rhodamine Water Tracer is a fluorescent dye commonly used for this type of water study. The amount of dye released is not harmful to animals, fish, plants or people, and will only be visible briefly at the release sites.
“We want to reassure river users, that the concentration of dye we use is very low and is safe to humans and aquatic life," explained Jim Carroll, water quality scientist for Ecology. “After the dye completely mixes with the river downstream of the release sites, people won’t see the dye in the river.”
Scientists will track the invisible dye with fluorometers, which detect small amounts of dye in the river even after it is no longer visible to humans.
Data used to find water quality solutions
Determining the water velocity in the Yakima River will help Ecology understand how fast substances like sediment and heat move through the water column and downstream. Ecology will use that data in water quality models, which help us identify approaches to improving water temperature and dissolved oxygen levels in the river.
“It’s especially important during the summer to improve streamflow temperatures and oxygen levels in the river, when salmon struggle to migrate, and oxygen is low,” explained water quality specialist Jane Creech.
Our dye study is just one facet of an overall checkup of the Yakima River.
Over the years, farmers have introduced better irrigation practices – turning to sprinklers and drip methods to reduce runoff once created by flood irrigation. We saw impressive improvements in the lower river, as reported in 2008. Results showed the water was clearer and fewer pesticides were in the river. Improved conditions led to the lifting of a fish advisory limiting the consumption of white fish on the river.
Now we are conducting a checkup on the upper reaches of the basin, to see if we have successfully met similar targets set there back in 2001. Scientists at Ecology’s central regional office are monitoring the Upper Yakima River to prepare a sort of final report card on our efforts to reduce the amount of sediment and turbidity in that section of the river.
Turbidity sensors in the Yakima River transmit real time readings to our website. That information helps us to analyze when and where problems are occurring, and how to reduce sediment in the river.
So heads up! If you happen to see something fluorescent or our staff out monitoring along the river – it is for a good cause. Good for fish and the Yakima River’s overall health.