There is clear link between forests and water quality, and the preservation of forests is an important tool in long-term, low-cost protection of water supplies.

Runoff from watersheds dominated by other land uses such as agriculture or development is often 3 to 15 times greater than forested watersheds. According to a study by the Trust for Public Land, less forest on water supply lands means lower quality source water and higher treatment costs. Research has shown that concentrations of nitrate from forested watersheds typically average 1 mg/l or less, compared to a drinking water standard of 10 mg/l!

The following video from the PA chapter of The Nature Conservancy looks at how forests improve the quality of source water and make cleaner water possible:

Streamside Forests = Cleaner, Cheaper Water

The development of watershed and aquifer recharge lands results in increased contamination of drinking water. With increased contamination comes increased treatment costs. The costs may be avoided with a greater emphasis on source protection.

The September 2014 Journal of the American Water Works Association featured an article titled, ” Protecting Forested Watersheds is Smart Economics for Water Utilities.” A team of authors explored the issue of forest protection as part of a solution to growing drinking water challenges.  Here is a summary:

Protecting and sustainably managing forested watersheds is an approach that, when used as a complement to traditional infrastructure, may not only reduce costs but also help secure new funding streams.

Increasing evidence suggests that healthy forests produce water that is less expensive to treat, transport and store. These same forests also provide an abundance of other cultural, economic and environmental benefits.

“Forests have a number of characteristics that qualify them alongside retention ponds, filtration technology,and presedimentation basins as critical water infrastructure. With sturdy, long-lived roots, multi layered canopies, and varied soil composition,forests help to regulate water yield and peak flow, as well as mitigate sedimentation and nutrient loading.”

Recent advancements in understanding of the benefits provided by healthy, well-managed forests provide water systems nationwide with a new approach to tackle America’s imposing drinking water infrastructure needs. By harnessing forests as ‘natural infrastructure’ to complement traditional ‘gray’ (built infrastructure) approaches, utilities can help keep costs down, reduce future risks to water supply, enhance resilience to climate change and provide additional benefits for their customers.

AWWA has provided reprint permission for WREN to share the article for educational purposes.   Click here to read.  Reprinted from Journal AWWA 106:9 by permission. Copyright © 2014 the American Water Works Association.

A study of 27 water suppliers conducted by the Trust for Public Land and the American Water Works Association in 2002 found that the more forest cover in a watershed the lower the treatment costs. According to the study:

  • For every 10 percent increase in forest cover in the source area, treatment and chemical costs decreased approximately 20 percent, up to about 60 percent forest cover.
  • Approximately 50-55 percent of the variation in treatment costs can be explained by the percent of forest cover in the source area.
  • Not enough data were obtained on drinking water watersheds with more than 60% forest cover; however, the study authors suggest that treatment costs level off when forest cover is between 70 and 100 percent.

Check out the DetailsThe Cost of Not Protecting Source Waters

Unhealthy streams mean poor water quality, which increases the amount of money we must spend to treat our water supplies. A simple and cost-effective  way to protect and improve the quality of our streams —  and our drinking water —  is to restore trees along the banks.

Learn more about the importance of streamside forests from the experts at Stroud Water Research Center by watching the video below. It looks at the benefits of maintaining forested buffers as part of a “treatment train” in an agricultural setting, and while it focuses on protecting the water flowing from Pennsylvania’s streams to the Chesapeake Bay, the message is clear: forest buffers protect water quality, and that means healthier source water supplies.

Streamside Forest Buffers: Improving Water Quality from GreenTreks Network on Vimeo.

Get the full story at StormwaterPA

To Learn More and download great visual materials, visit Stroud’s website In Support of Streamside Forests

Other SourcewaterPA pages



Several recent studies have addressed the topic of forests and drinking water:

As outlined above, a survey of 27 water suppliers was conducted in 2002 by the Trust for Public Land and the American Water Works Association.  Study Results:  for every 10% increase in forest cover in the source watershed, treatment and chemical costs decreased by approximately 20%, up to about 60% forest cover (see figure below).

A second study conducted by the Trust for Public Land (Freeman et al., 2008) summarized raw water quality data, forest cover data, and drinking water treatment cost data for 60 water treatment plants across the country. This study found that there were significant relationships among percent land cover, source water quality, and drinking water treatment costs.  Decreased forest cover was significantly related to decreased water quality, while low water quality was related to higher treatment cost. The variability associated with the potential treatment costs given a change in watershed land cover precluded the development of a statistical model to predict treatment costs with certainty.


Oct 2013 – Natural Infrastructure: Investing in Forested Landscapes for Source Water Protection in the United States by Todd Gartner, James Mulligan, Rowan Schmidt and John Gunn – (4.3 MB PDF)

8/26/13 Press Release -  SFI and U.S. Endowment for Forestry and Communities Spur Collaboration Among Water Utilities and Forest Landowners to Protect Watersheds

Forests To Faucets - website with variety of resources: The Forest-to-Faucet Partnership is a joint venture of the University of Massachusetts Amherst and the U.S. Forest Service Northeastern Area (State and Private Forestry) Watershed Program.

Forests to Faucets – website of USDA Forest Service; project uses GIS to model and map the continental United States land areas most important to surface drinking water, the role forests play in protecting these areas, and the extent to which these forests are threatened by development, insects and disease, and wildland fire.

“Working Woodlands” Program, by the Pennsylvania Chapter of The Nature Conservancy, has been used by several Pennsylvania water systems to help protect their forested watersheds and provide the utility with a balanced approach to earn revenue.

US Forest Service. 2010. Water, Climate Change and Forests. This publication focuses on watershed stewardship for a changing climate.

2008 White Paper: Land Use and Drinking Water Costs

10,000 Friends of Pennsylvania. 2007. Water and Growth. This report discusses the connection between water supply and land use in southeastern PA.

Ernst, Caryn.  2004.  Protecting the Source. Land Conservation and the Future of America’s Drinking Water. The Trust for Public Land and the American Water Works Association. San Francisco, CA.

Brochure: Working Trees for Water Quality - To learn more about how to use trees to improve water quality, take a look at the brochure produced by the USDA National Agroforestry Center or contact the Agroforestry Center at 402.437.5178 ext. 4011.

Booklet by USDA National Agroforestry –  Conservation Buffers: Design Guidelines for Buffers, Corridors and Greenways. Provides over 80 illustrated design guidelines synthesized and developed from a review of over 1400 research publications.

Each guideline describes a specific way that a vegetative buffer can be applied to protect soil, improve air and water quality, enhance fish and wildlife habitat, produce economic products, provide recreation opportunities, or beautify the landscape.

The importance of forest protected areas to drinking water was discussed in Running Pure, a research report by the World Bank / WWF Alliance for Forest Conservation and Sustainable Use.  Research found that approximately 1/3 of the world’s 105 largest cities obtain a significant portion of their drinking water from protected areas and that well managed natural forests provide benefits to urban populations in terms of high quality drinking water.

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