A research review and survey of water systems in many Oregon cities suggests that modern forest management can be compatible with a high quality and quantity of water.
       The report, authored by Paul Adams, Extension forest watershed specialist in the Department of Forest Engineering, and Mark Taratoot, former research assistant, was both a review of published studies and a survey of 30 major municipal water systems in the state that are served largely by forested watersheds, including those of Portland, Eugene, and Salem. “When people raise concerns about impacts of forest practices,” says Adams, “one of the first things they mention is water quality. In this report we tried to separate the facts from the myths to better understand how we get clean water.”
       One myth, he says, is the notion of pure water always emerging from pristine forests. “While it’s true that forested watersheds usually deliver a very high quality of water, there’s a wide variation even in nature.” For example, the Flynn Creek watershed in

the Coast Range is a relatively pristine forest, “but even there the suspended sediments have ranged from near zero to about 2,000 parts per million, when the water looks about like a chocolate milkshake.”
      Another myth, he says, is that trees store and release water to streams. Actually a heavy forest canopy in most cases causes a net loss of 15-20 inches a year in water volume. Trees consume water like any plant—it’s the forest soils that store water like a sponge and release it slowly, filtering it in the process.
      Protecting forest soils, then, is the key to water retention, filtering, and quality. Forest cover is important because it protects and nurtures the soils. Occasional timber harvest should not interfere with this process if done carefully, with modern methods and good stream buffers. “Keeping forest lands intact is vital, but in general we’ve found that advanced harvesting practices with proper reforestation has little impact on water quality and quantity for municipal supplies.”
       Because much of the research on the effects of forest practices was done years ago, says Adams, it can give an incomplete picture of the benefits of management tools and techniques now commonly used or required by law. “But this earlier research did help guide us to adopt these improved methods.”
       Highlights of the report, sponsored by the Oregon Forest Resources Institute, were presented at a the conference, “Forests and Drinking Water,”held in Ashland, Ore., in August.
— D.S.

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