HARRISBURG (AP) — An Oregon State University professor is leading a research project that tracks water temperatures in the Willamette River and could change the future of wastewater management.

Professor Stan Gregory and other researchers are using cutthroat trout to test whether side channels in the river serve as critical cold water refuges for fish.

If they do, cities and other entities pouring warm wastewater into the river could compensate by restoring such channels.

The Oregon Watershed Enhancement Board is providing $450,000 for Gregory’s work. The city of Eugene also is putting money in.

The project involves implanting cutthroat trout with temperature monitors the size of a watch battery and fitting others with radio beacons.

Researchers make sure tracking devices do not add more than 3 percent of the body weight of the fish so as not to stress them.

The research will determine where the fish are spending most of their time and how critical the cool-water refuges are.

Like salmon and steelhead, two species that are also native to the Willamette, cutthroat trout thrive in cool water. Warm water is more inhabitable for nonnative fish such as carp and bass, which eat young salmon.

Studies show that the fish native to the river enter into the river’s side channels to cool themselves before migrating through warmer stretches.

“We’ve been making progress,” Gregory said. “We just need to keep making progress.”

He said the Willamette once had a variety of channels, alcoves and islands but development has constricted much of the river into a single conduit.

“Now it’s more of a pipe, so it warms up more,” he said.

Development has also stifled what is known as hyporheic flow, a natural cooling system in the river, where some water streaming through the channels also passes underground through gravel and sand.

“It’s just these fingers of cool water that feed into the alcoves,” Gregory said. “In some places the underground flow may be close to 10 degrees cooler than the river’s main flow.”

Researchers are now looking at restoring side channels and alcoves that resurrect the cooling underground flow in some places.

The Oregon Department of Environmental Quality is also trying to control the warming trend by limiting the temperature of wastewater that can be discharged into the river.