This is the first installment of a two-part exploration of the impact of logging on watersheds that supply public water. Part 1 examines the benefits of older forests in providing and protecting water quantity, water quality, and timely release of water. Part 2 offers suggestions to protect watersheds that supply public water in order to improve quantity, quality, and timely release of water while also attaining coincidental conservation benefits for this and future generations.
Top Line: Most Americans get their drinking, bathing, and flushing water from surface sources, most of which are unprotected from logging and other exploitation.
Figure 1. Old-growth-forested watersheds provide the best long-term water quantity and quality for public water supplies. Source: Friends of the Corvallis Watershed.
Logging in watersheds that supply public water can cause cancer. But I digress.
Seventy-one percent of the nation’s daily water supply comes from surface sources. Uses include private domestic (mostly groundwater from wells), public supply (what we drink, wash with, and flush with), industrial, irrigation, thermoelectric (cooling), mining, livestock, and aquaculture. In 2015, Americans consumed 39 billion gallons of water daily from the public supply, three-fifths of which came from surface water. Many municipalities place their water intake facilities on rivers and streams just upstream of the municipality and then treat the hell out of the water to make it potable. Some municipalities are able to run pipeline far uphill into forested mountains to obtain cleaner water that can require far less treatment (but only if unlogged).
Many municipalities in the American West get their public water supply from national forest lands. While there still can be problems with logging of those watersheds, the problems are fewer and can often be addressed. The Forest Service claims that national forests are “the largest source of municipal water supply in the Nation,” serving 60 million people in 3,400 communities, including large cities such as Los Angeles, Portland, Denver, and Atlanta. In Oregon, cities including The Dalles, Dallas, Cottage Grove, Corvallis, Ashland, Medford, Bend, Lakeview, LaGrande, and Baker City have specially designated watersheds on national forest land. However, many watersheds that supply public water are not on national forest or other government land.
Figure 2. All the land in Oregon that is upstream of a community or larger drinking water intake point. Source: Oregon Wild and Oregon Howl.
Figure 3. Designated “Surface Water Drinking Water Source Areas” as determined by the Oregon Department of Environmental Quality; these don’t include all surface waters above a drinking water intake point. Forest Service land is dark green (33 percent); Bureau of Land Management land is dark brown (10 percent); state forest land is light green (1 percent); agricultural lands, including small-owner timberlands, are tan (17 percent); private industrial timberlands are orange (22 percent); and private rural lands are lighter gold (13 percent). Source: Oregon Department of Environmental Quality.
Unfortunately, most surface drinking water supplies in the United States are inadequately protected. This can result in decreased water quantity and higher treatment costs to attain water quality. Intact (older and getting older and not logged) forests provide great “natural infrastructure” that protects the quality and quantity of our drinking water. They also offer coincidental public benefits, including but not limited to biodiversity conservation, carbon storage and sequestration, oxygen that we can breathe, scenic beauty, and recreation (pronounced “re-creation”).
Figure 4. A public recreation trail in the Marys Peak watershed, a source of drinking water for the city of Corvallis. Source: Oregon Wild.
Logged Versus Unlogged Forests: Water Quantity
If one’s sole goal is the maximization of water quantity from a forested watershed, the thing to do is to clear-cut the forest, pave the watershed, and build a reservoir. This prevents trees from transpiring water back into the atmosphere, and soils from retaining water in place. However, it’s cheaper and more effective, not to mention less damaging to the environment, to let a forest—the older the better—do the work of optimizing water quantity.
Water quantity is a matter not only of total water produced by a watershed in the course of a year but also the timing of the release of that water. Late-season (as in late in the irrigation season when it hasn’t rained significantly for several months) flows are much more valuable than heavier spring runoffs—which are exacerbated by logging, resulting in less water being held for longer periods of time in the watershed. As the climate warms—due primarily to the combustion of fossil fuels and the reduction of forests—dry-season water availability has been found to decrease in temperate forests around the world.
That logged forests produce less water is incontrovertible—except to most foresters. The scientific peer-reviewed literature is clear-cut, er I mean clear.
Catalina Segura et al. (2020) examined six decades of data from the Alsea Watershed Study in the Oregon Coast Range. Their findings:
Daily streamflow from a 40- to 53-yr-old Douglas-fir plantation was 25% lower on average, and 50% lower during the summer (June 15 to Sept 15 of 2006 to 2009), relative to the reference watershed containing mature/old forest. Low flow deficits persisted over six or more months of each year. Surprisingly, contemporary forest practices (i.e., clearcutting of the plantation with riparian buffers in 2009 and 2014) had only a minor effect on streamflow deficits. . . . High evapotranspiration from rapidly regenerating vegetation, including planted Douglas-fir, and from the residual plantation forest in the riparian buffer appeared to explain the persistence of streamflow deficits after logging of nearly 100% of the forest plantation. Results of this study indicated that 40- to 50-yr rotations of Douglas-fir plantations can produce persistent, large summer low flow deficits. While the clear-cutting of these plantations, with retention of riparian buffers, increased daily streamflow slightly, flows did not return to pre-first entry conditions. [emphasis added]
Figure 5. City of Hillsboro drinking water watershed. Source: French et al. (2023).
Perry and Jones (2016) analyzed sixty-year records of daily streamflow from eight paired-basin experiments in Oregon. These
revealed that the conversion of old-growth forest to Douglas-fir plantations had a major effect on summer streamflow. Average daily streamflow in summer (July through September) in basins with 34- to 43-year-old plantations of Douglas-fir was 50% lower than streamflow from reference basins with 150- to 500-year-old forests dominated by Douglas-fir, western hemlock, and other conifers. Study plantations are comparable in terms of age class, treatments, and growth rates to managed forests in the region. . . . Reduced summer streamflow in headwater basins with forest plantations may limit aquatic habitat and exacerbate stream warming, and it may also alter water yield and timing in much larger basins. Legacies of past forest management or extensive natural disturbances may be confounded with effects of climate change on streamflow in large river basins. [emphasis added]
Dennis Harr (1982) looked at net precipitation under old-growth Douglas-fir forest in the Bull Run Municipal Watershed (Portland, Oregon) and found that it
totaled 1739 mm during a 40-week period, 387 mm more than in adjacent clearcut areas. Expressing data on a full water year basis and adjusting gross precipitation for losses due to rainfall interception suggest fog drip could have added 882 mm (35 in) of water to total precipitation during a year when precipitation measured 2160 mm in a rain gage in a nearby clearing. Standard rain gages installed in open areas where fog is common may be collecting up to 30 percent less precipitation than would be collected in the [old-growth] forest. Long term forest management (i.e., timber harvest) in the watershed could reduce annual water yield and, more importantly, summer stream flow by reducing fog drip. [emphasis added]
Figure 6. City of Seaside drinking water watershed. Source: French et al (2023).
Logged Versus Unlogged Forests: Water Quality
The quantity and quality of water are the flip sides of the same coin. According to the US Environmental Protection Agency:
Sources of NPS [nonpoint source] pollution associated with forestry activities include removal of streamside vegetation, road construction and use, timber harvesting, and mechanical preparation for the planting of trees. Road construction and road use are the primary sources of NPS pollution on forested lands, contributing up to 90 percent of the total sediment from forestry operations. Harvesting trees in the area beside a stream can affect water quality by reducing the streambank shading that regulates water temperature and by removing vegetation that stabilizes the streambanks. These changes can harm aquatic life by limiting sources of food, shade, and shelter. [emphasis added]
Figure 7. City of Willamina drinking water watershed. Source: French et al. (2023).
Is it possible to log and not harm water quality? No.
Is it possible to log less intensely and therefore harm water quality less? Yes (see USEPA 2005). However, such is not profitable, especially to profit-maximizing entities ranging from transnational corporations to Wall Street hedge funds and even municipal water utilities that own forestland in their own drinking water watershed. In western Oregon, the most profitable plantations are monocultures of Douglas-fir that are clear-cut every forty years and sprayed with harmful pesticides to prevent nature from creeping back in with undesirable vegetation.
Figure 8. A helicopter spraying atrazine on Sierra-Pacific (née Seneca Jones) timberland in Douglas County, Oregon. Lest you think that such spraying is the proverbial pissing in the wind, the helicopter lands to refill every ten minutes. Source: Francis Eatherington.
Forest Management for Drinking Water Protection
Dr. Betsy Herbert, who completed her PhD in environmental studies at UC Santa Cruz in 2004 and now lives in Corvallis, Oregon, focuses on forest management for drinking water protection. Her research question for her PhD dissertation was: When public water utilities own forest land that supplies drinking water, how do they manage that forest land? Herbert’s research first summarized previous research on the subject:
· Most water utilities draw water from watersheds over which they have little or no control.
· 73 percent of water utilities in the rural Pacific Northwest have reported forest management activities as a problem source of pollution.
· Water utility managers view land acquisition as one of the more effective ways to protect water quality.
Figure 9. Drinking water watersheds in the Oregon Coast Range studied by Betsy Herbert. Source: Betsy Herbert.
Herbert then evaluated forty-five public water utilities in Oregon, Washington, and California that owned at least some of their drinking water watershed. She looked at, among other things, (1) logging intensity; (2) old forest (if any) protection; (3) predominant stand age; and (4) road density. Herbert found that city-run utilities
· Claim they manage city-owned watershed lands to protect water quality, but their management focus is on timber extraction, with mitigations to lessen impact on water quality.
· Become dependent on annual timber revenues to fund capital improvements.
· Often close their watershed properties to the public, ostensibly to protect water quality.
Herbert distinguishes water utilities that are protective of their source watersheds and those that are aggressive toward their source watersheds. The former tend to be single-purpose water district governments, allow public access, and have neighbors not practicing commercial forestry. The latter tend to be multi-purpose city governments, prohibit public access, and have neighbors who practice commercial forestry.
She concludes that “public access and grassroots participation is the most effective way to protect watersheds from harmful logging practices.” More on this in the next installment.
Figure 10. Old-growth trees marked for logging (notice the blue paint) by their owners, the City of Corvallis. Fortunately, the City had previously allowed the Corvallis-to-the-Sea Trail to pass over these lands, allowing some members of the public to see the blue paint before they saw just stumps. Source: Friends of the Corvallis Watershed.