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Research / Discovery

Looks aren't everything. . .

March 8, 2010

How can you tell when a stream is just a shadow of its former self -- when it's so polluted that the fish, plants, and bugs you'd expect to find just aren't there anymore?

Will Clements, professor of fish, wildlife, and conservation biology, studies the effects of pollution on streams and rivers.

Point of no return

Scientists used to believe that the effects of pollution were steady — slowly increasing pollution was thought to slowly increase effects on fish, plants, and bugs. Over time, scientists found that streams could suddenly jump from “just a little under the weather” to “hanging on for dear life.”

Will Clements and his team at Colorado State are looking at ways to identify these thresholds — the “points of no return”— in mountain streams. They have a new model — called SiZeR — that can pinpoint the place where a tiny increase in pollution can have very big effect— sometimes so large that the stream cannot easily recover.

What are the warning signs?

Researchers have discovered that sometimes pollution must be cleaned up to lower than what caused the stream to go downhill in the first place and Clements’ model can help water-quality managers figure out the second threshold: How much more to “clean the stream.”

Clements is excited about this project because it’s based on a powerful statistical technique, and it uses diagrams to show where these thresholds are. He likens the thresholds idea to a ski slope: “Imagine skiing on the bunny slope, tooling along, and then suddenly finding yourself on the double black diamond trail,” he said. “Our work is trying to answer the question ‘Are there ways we can put up warning signs?’”

Arkansas River suffered from mining

Professor Will Clement and his team have developed the SiZeR model to pinpoint the threshold where a tiny increase in pollution can have a very big effect.

Other people are excited about this new approach, too. Clements and his team looked at the Arkansas River for the EPA's Superfund program.

The Arkansas River suffered greatly from the effects of mining (which introduced heavy metals, acids; and eroded the nearby soils) and then by remediation (which cleaned up the heavy metals and acids, but made the erosion worse).

SiZeR model for pollution analysis

Clements' team used the SiZeR model to see if different kinds of pollution had different thresholds. They’re also starting to look at whether thresholds are different in different areas.

For instance, the team is also working with the National Park Service to describe thresholds in Yellowstone National Park. They want to understand the effects of volcanic activity, and are using conductivity (the amount of salt and minerals in the water) as a stand-in for volcanism in their model.

Best ways to restore streams

Clements hopes his work will help water-resource managers in states, tribes, and counties identify “how clean is clean” and find the best way to restore fish, plant, and insects (food for the fish!) to streams and rivers. This will benefit other plants and animals that depend on streams and help people enjoy and appreciate them as well.

The team also hopes to identify warning signs of approaching thresholds (like those double black diamond ski slope markers) before they happen and avoid difficult and costly stream restoration.


Originally published by the EPA's National Center for Environmental Research and in the March 2010 issue of the Warner College of Natural Resources e-Resource.