Rockne Roll / News-Register##The Yamhill River has dropped to a flow of 11-cubic-feet per second, according to the US Geological Survey, despite restrictions imposed by the state on some agricultural water rights. The National Weather Service lists the river level at slightly less than 10 feet. Both measurements are from a monitoring site near McMinnville. Flood stage is 50 feet.

Rockne Roll / News-Register##Luke Westphal, executive director of the Greater Yamhill Watershed Council, checks the calibration of a water temperature sensor in Cozine Creek, south of downtown McMinnville. “Stream temperature can be considered a pollutant,” he said.

Drying Times: Rivers in Crisis

Chinook salmon making their way up the Willamette River can usually count on a cooling flow of freshly melted snow each year when they reach the Santiam. But with this year creating far less snowpack and a lot more hot, dry days, rivers are running warmer and lower.

Normally, salmon carcasses don’t begin to appear until later in the year, after the exhausted fish have reached their traditional spawning grounds.

A look at Oregon’s drought and its effects on local cities, agriculture and recreation.

Now Online:

n Drying Times: Drought in Yamhill County

n Water rights a forbidding tangle in the West

n No letup in sight for Oregon drought

n The Yamhill River is under stress

n Agriculture use strains limited water resources

n Catching raindrops one way to conserve

n Dryland farming provides an alternative

n Fishing in jeopardy as rivers get warmer and flows slow

n Schools and cities discuss how they conserve water

n Cities are trying to plan ahead to ensure a plentiful water supply

But this year, the main stem of the Willamette became so hot, fish began dying off earlier than usual, and in larger quantities. And that doesn’t bode well for future runs.

“Stream temperature can be considered a pollutant,” said Luke Westphal, executive director of Greater Yamhill Watershed Council. “When creeks get too hot, life in the creek has a hard time living and thriving.”

The threshold is about 64 degrees Fahrenheit, he said. Any warmer and it starts to threaten fish.

Westphal said temperature is the most common pollutant for most waterways draining into the Willamette this year, including the Yamhill. He said the changing climate is a significant factor, but man-made changes have contributed as well.

In the 1950s, when it was wrongly thought that large logs and boulders prevented fish from migrating, farmers used to be paid to remove them. This served to straighten out natural meandering paths.

That action had two detrimental effects. It diminished gravel deposits crucial to egg-laying, allowing surface water to seep into the groundwater system.

The reduced streamflow and loss of cooling gravel contributed to the increase in water temperature.

Water temperatures also rose due to the destruction of riparian zones.

Well-watered vegetation normally grows thick and tall along streambanks, creating a canopy of cooling shade. But farmers, ranchers, miners, loggers and homesteaders started reducing or eliminating that vegetation.

Rockne Roll / News-Register##Tim Munro, senior operator and biotech coordinator for McMinnville’s water reclamation facility, checks the clarity of an outflow tank at the plant.

The Watershed Council has been working with the Yamhill Soil and Water Conservation District to reverse that to the maximum extent possible.

“I can’t sell it enough,” Westphal said. “It’s one of the most important things we can do for the watershed.”

Vegetated riparian zones can keep temperatures down, protect banks from eroding, provide wildlife habitat and filter out pollutants.

Watershed Council representative Erik Grimstad said the South Yamhill River has a way to go yet. He said it’s on the state Department of Environmental Quality’s 303 (d) list, which is reserved for waterways still falling short.

“If a river is not meeting the benchmarks, it goes on the list,” he said. He said the South Yamhill was cited for E. coli bacteria, excessive temperature and toxic metal contamination.

“It isn’t great, but the South Yamhill isn’t horrible,” Grimstad said. “I’d swim in it. It’s not worse than the Columbia or Willamette.”

But, like the larger waterways it feeds into, it needs continued attention.

McMinnville’s sewage treatment plant discharges treated effluent into the South Yamhill, which serves to keep up the water level. Wastewater Services Manager David Gehring said farmers pull a lot of irrigation water from the river, which the treatment plant discharge helps offset.

Rockne Roll / News-Register##This pool at McMinville’s water treatment plant collects water after it has been treated with microorganisms and filtered. The water then passes through an anti-bacterial ultraviolet light array before flowing out of the plant and into the Yamhill River. During the summer, it’s among the largest sources of water for the river.

“If our effluent was not in the river, that would affect them in a negative way,” Gehring said. “The water level would be a lot lower.”

The plant treats the effluent to lower the levels of pollutants like phosphorous and ammonia, which can choke off the river’s oxygen supply, killing aquatic life. It’s so clean by the time it’s discharged, he said, “You can’t tell the difference between the effluent and tap water.”

Industrial waste often includes toxic pollutants, so it goes through a pre-treatment regimen before entering the city’s sewage system. The aim is to screen the toxics at the outset.