OREGON STATE UNIVERSITY

Stream temperatures are biologically significant

11/18/1996

CORVALLIS - Ongoing studies are showing that the mere presence of relatively clean water in Pacific Northwest streams isn't enough to keep salmon and trout thriving. The water also has to be cool.

Elevated water temperatures in the summer might mean trouble for salmon and trout and the food they eat, according to Oregon State University hydrologist Bob Beschta.

"Stream temperatures are an indirect indicator of the ecological condition of our rivers and streams - a measure of the state of the system," said Beschta, OSU hydrology professor in forest engineering. "Many of our streams in eastern Oregon are not well. They are too warm in the summer."

Beschta presented a talk entitled, "Stream Temperatures in Eastern Oregon - Are the Fish Really in Hot Water?" at the recent James A. Vomocil Water Quality Conference at OSU.

Recently, more than 500 segments of Oregon's rivers and streams were classified as "water quality limited" based on their high temperatures by the Oregon Department of Environmental Quality (DEQ). OSU scientists, including Beschta and stream ecologist Stan Gregory, helped DEQ develop Oregon's standards for water temperatures necessary to comply with the Federal Clean Water Act.

"Our fish are indeed in hot water," said Beschta. "It amazes me that we still have salmon and trout in some of the places on the east side. It's a testimony to their ability to survive. But ultimately they will be gone if we don't do something.

"The fish are just barely surviving by seeking out cool water seeps on hot days," he added. "High stream temperatures are sometimes lethal for fish. Warm water handicaps their ability to maintain themselves. Temperature regulates the rates of process in biology.

"Everything that lives in a stream is affected by warm temperatures and warm stream temperatures are a common problem in eastern Oregon," he said.

The east side has open country interspersed with forest, more sunny days and relatively hot stream and river temperatures in basins such as the John Day and Grande Ronde.

"I'm not saying these stream systems did not get warm before land use such as logging and grazing in riparian systems," said Beschta. "They probably did. But there was generally more plant cover along steams and their channels were often narrower and more sinuous. There were no roads or ditches blocking the flow of cooler water underneath flood plains into the river. There were probably more cool places for fish to hide.

"Now many of the riparian ecosystems are not intact - streamside vegetation is often gone, channels are wider and shallower, with more sun hitting the water surface," he added. "Temperatures are high and it is tough if you're a fish."

Nevertheless, Beschta remains optimistic that water quality in Oregon's steams and rivers can be improved.

"We have learned that if we can keep streams shaded with vegetation, then we not only get less warming of the water - we also get many other benefits such as more diverse channel morphology, increased plant and animal material in the stream, increased bank strength from plant and tree roots and increased woody debris for fish habitat," he said.

"If we had 20 years of riparian restoration on eastside stream systems, we would see a large change toward better water quality," Beschta said. "We have a lot of opportunity to lower the water temperature through management practices in the state of Oregon. For those that disagree, I say `Let's do the experiments.' Demonstration areas make pretty honest science."

The annual James A. Vomocil Water Quality Conference is sponsored by the OSU Extension Service and the Oregon Water Resources Research Institute.