November 2021. Kym Pokorny, Public Service Communications Specialist. Story Source: Jon Souder, Watershed Management Specialist

CORVALLIS, Ore. – From source to tap, much of Oregon’s water passes through its forests. Along the way quality can be compromised.

Forests – from family outfits to multi-national operations – play a vital role in Oregon’s water system. Activities like logging make a difference in the quality and quantity of the state’s water supply, according to Jon Souder, Oregon State University Extension Service watershed management specialist and assistant professor in the College of Forestry.

Souder is the editor of Tress to Tap: How Forest Practices Affect Oregon’s Municipal Water, a comprehensive new book exploring how forest management impacts Oregon’s water. Three years in the making, the science-based publication is meant to help forest managers, municipal water utilities, conservation groups, government agencies and the public work together to better evaluate and regulate how forests are used in regard to water usage.

“There’s increasing concern about our drinking water,” Souder said. “In writing this book, our goal was to get people together and provide a book rooted in science.”

To help address water quality concerns, the Oregon Forest Resources Institute (OFRI) approached the College of Forestry in 2018 with a request to complete a science review of the most recent studies on the issue. Souder agreed and formed a steering committee to work with him that included forest managers and conservation groups.

“OFRI does public surveys on how people feel about forest management,” Souder said. “The public is saying the part of forest management they are most concerned about is drinking water quality.”

The first part of the Trees to Tap book describes results from a survey of the state’s 156 water utilities conducted by Emily Jane Davis, an Extension specialist in forest ecosystems and society and associate professor in the OSU College of Forestry. This research included three case studies to determine how the utilities work with people who own and manage the watersheds that provide water.

Forestry management practices have markedly improved in the decades since the Clean Water Act was amended with sweeping changes in 1972. Still, a residue of concern remains. Those concerns were on top of the steering committee’s review priorities as they looked at changes in water quality, sedimentation of rivers and streams, herbicide toxicity and wildfire risk.

Since the Clean Water Act amendment, there is still reason for concern, Souder said. For one thing, as trees are cut and replanted, young trees take up more water that could be going to communities.

“As trees regrow, they use a lot of water, more than older plants, he said. “As they grow fast and dense, there’s a period from age 7 to 50 when they are taking more water. You can see that in a reduction of summer flow.”

Herbicides continue to cause controversy, Souder said.

“Many members of the public are concerned about aerial herbicide applications,” Souder said. “They want to know if the spray gets into the water and how far it goes and how long does it last. We reviewed agency reports and records of complaints. We looked at what is the magnitude of chemical use and what is the likelihood it will get into drinking supplies.”

The results showed that contemporary practices have a minimal risk to the drinking water supply. The typical chemicals used in forest management tend to be water soluble and break down quickly so don’t go downstream very far, Souder said. None of the concentrations they saw violated human health standards.

The final part of the study focused on sediment and turbidity or the number of particles floating in water that are difficult to treat for drinking water. Legacy forest roads still cause problems, though new roads mitigate erosion with adequate designs and drainage.

“Forest managers are looking for science to help them manage better,” he said. “That’s how we’re training them in Extension. We help by getting new scientific knowledge into the hands of forest managers. Science is creating a foundation for policy and the policy process that turns into regulations and laws.”