Trees to Tap – Keeping Drinking Water Safe


The Oregon Forest Resources Institute (OFRI) recently released a new special report titled Keeping Drinking Water Safe. It summarizes Trees to Tap, a 30-month study led by Oregon State University’s Institute for Natural Resources (INR), which OFRI commissioned to provide the public with the latest science examining forest management’s impacts on drinking water sources in Oregon.

The study was led by Drs. Jon Souder, Kevin Bladon, Emily Jane Davis and Bogdan Strimbu of the OSU College of Forestry with able assistance from Jeff Behan of the INR. The final Trees to Tap science review report is being published by Oregon State University Extension Service, and is expected this fall. However, the OSU team has made available the “working papers,” which are essentially the final manuscripts of each chapter before they go to the OSU editor.

The Keeping Drinking Water Safe special report, Trees to Tap Science Review Working Papers, a stand-alone chapter on Findings and Recommendations and a Study Summary are all available on the Trees to Tap webpage on OFRI’s website.

The Trees to Tap study focused on four main areas of concern that were identified by a statewide steering committee as the major ways forest management could impact drinking water sources. These include:


- sediment from forestry operations

- forest management chemicals

- water quantity

- organic matter and disinfection byproducts

The Trees to Tap study identified three main forestry activities that have the potential to impact drinking water:

- timber harvest

- forest roads

- chemical application

Timber harvest

Timber harvest reduces canopy coverage and disturbs soils, which can cause erosion and trigger sediment movement until replanted tree seedlings or vegetation reach sufficient size. The sediment risk is clearly related to the type of harvest operation, and is impacted by geology, soil, topography and rainfall patterns. In the short run, timber removal can increase stream flows, which can erode stream banks, saturate soils and scour stream beds, remobilizing sediments from past logging and natural disturbances. Contemporary logging practices are designed to lessen disturbance to the forest floor, and to minimize the possibility of sediment entering streams. The great news is that they work.

Forest roads

Research consistently indicates that unpaved forest roads are a primary source of sediment entering streams and estuaries in forested watersheds. Over the years, best management practices have evolved for forest road design, placement, construction, maintenance, decommissioning and reclamation. Three examples where significant improvements have been made to reduce the amount of sediment entering streams are:

- actively routing runoff away from streams and toward buffer areas

- improving stream crossings by installing bridges or culverts, to keep road traffic from directly crossing stream channels

- upsizing culvert diameters to increase their flow capacity and reduce the likelihood of failure

Forest chemicals

The use of chemicals in the forest raises public concerns about their effect on plants and animals, adjacent properties and downstream community water supplies. Herbicides are the most common chemicals used in Oregon’s forests. Forest landowners use herbicides to aid the re-establishment of tree seedlings following timber harvest. The total number of treatments on a seedling plantation range from one to four. Herbicides are administered in a controlled application either on the ground or by air. However, chemicals can potentially get into water directly by accident, drift during application, volatilization after spraying or through storm water runoff.

Foresters must follow strict rules laid out by a variety of state and federal regulations, as well as the Oregon Forest Practices Act. All of the rules are important and must be followed responsibly for the health and safety of people, aquatic life and drinking water.

Learn more

There is a lot of information contained in the Trees to Tap study, and OFRI will be making a major effort to communicate it. A good place to start to learn more about Trees to Tap is on our webpage devoted to the study.

I will also be giving a presentation on Trees to Tap via Zoom for the Washington County Small Woodlands Association on July 22 at 7 p.m. This meeting is co-sponsored by OFRI and is free and open to the public. Join us here.

A thank you

Finally, I would like to give a special shout-out to Paul Barnum, former OFRI executive director who contracted with us to write the Keeping Drinking Water Safe special report. Well done, Chief.

For the forest,

Mike Cloughesy

Director of Forestry


9755 SW Barnes Rd., Suite 210        
Portland, OR 97225        
Phone: 971-673-2944        
Fax: 971-673-2946

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