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Monday
Oct112010

Clean Water

Fresh from the Woods


This map estimates a watershed’s ability to produce clean water, which is largely based on how much forestland is in the watershed. The blue areas provide the greatest amount. (Graphic courtesy of USDA Forest Service)

Clean water: Over the river, through the woods

By Andrew Kekacs

Maine has some of the cleanest water in the nation, and forests are the reason why.

“We know that well-managed forests produce the excellent water quality that Mainers enjoy and depend on,” said Keith Kanoti, water resources forester for the Maine Forest Service. “The state’s clean drinking water is a forest product, just as important as pulpwood and sawlogs.”

The Maine Department of Conservation puts it this way: “The Maine forest – with its vegetation, streams, lakes, wetlands and groundwater aquifers – functions like a huge sponge that collects, cleans and stores water. The forest’s water system is the foundation for wildlife habitats and recreational uses of the forest. It evens out lake levels, [the] flows of streams and rivers, and groundwater levels, throughout wet and dry periods. And it provides Maine people with their drinking and household water.”

A staggering amount of water is filtered through the forest “sponge” each year. In a discussion of the state's water resources at www.state.me.us/doc/nrimc/mgs/explore/water/facts/water.htm, the Maine Geological Survey says about 42 inches of rain fall on the state each year. That equals about 24 trillion gallons of water – enough to fill 40 million Olympic-sized swimming pools.

About half of the precipitation runs off in streams and rivers and collects in ponds and lakes before flowing back to the sea. Some of that surface water is used by Maine utilities to provide “city water” to about 60 percent of state residents.

For example, Sebago Lake is the water source for about 200,000 people in Greater Portland. “Sebago Lake is exceptionally clear and soft - clean enough to be exempt from the expensive filtration process required of most surface water sources,” the Portland Water District says on its Web site. “The lake covers 30,000 acres. The watershed is more than 50 miles long, stretching from Bethel to Standish, and includes parts of 24 towns.”

WoodlandStream
A clean, cold stream flows out of the Maine Woods. (Photo courtesy of Keith Kanoti)

The extent of forest cover in its watershed is one of the chief reasons that Sebago Lake is so clean. Forests remove sediments and capture pollutants before they can reach water bodies. A study of 27 water suppliers conducted by the Trust for Public Land and the American Water Works Association in 2002 found that every 10 percent increase in forest cover in a watershed reduces the cost of treating drinking water by about 20 percent (up to a maximum of 60 percent forest cover).

Not all of the rain and snow that falls on Maine every year runs off to the ocean. Some 30-40 percent evaporates or is returned to the atmosphere by the “breathing” of plants, according to the Maine Geological Survey. That leaves another 10-20 percent – or 2-5 trillion gallons per year – to soak into the soil and refill the underground “aquifers” that serve the 40 percent of Maine residents who get their water from wells.

“Groundwater and surface water are linked,” the Maine Geological Survey says. “Groundwater constantly flows out to surface water, allowing most streams to flow even during the driest periods.”

But whether your water comes from Sebago Lake or a drilled well in Meddybemps, Maine’s 17 million acres of forests help to make sure that it is pure. Forest-to-Faucet, a partnership of the USDA Forest Service Northeastern Area and the University of Massachusetts at Amherst, puts it this way: “People are a forest-dependent species.”

The partnership says the term "forest dependent species" is usually applied to plants or animals with special habitat requirements, such as pileated woodpeckers or pine martens. But millions of people in Maine and the rest of New England rely on lakes, reservoirs and wells for their drinking water.

“In virtually every [water] system, large or small, the faucet is ultimately connected to a forest,” says the Forest-to-Faucet Partnership. “… This underscores the importance of forest conservation to maintain or enhance water resources and many other benefits and values — wildlife habitat, biological diversity, recreation, wood and other forest products, and aesthetics.”

Maine is the most heavily forested state in the nation. Although its population almost doubled from 1900 to 2000, the abandonment of small farms also caused the amount of forest land in Maine to nearly double. That means there is just about as much forestland land per person now (35 acres) as there was 100 years earlier (36.2 acres), according to Forest-to-Faucet.


Flagstaff Lake is surrounded by thousands of acres of forestland. (Photo by Andrew Kekacs)

In an article in the Winter 2006 issue of New England Forests, a publication of the New England Forestry Foundation, Paul K. Barten of the University of Massachusetts at Amherst described how forests serve to protect clean water.

“In forests, rain tumbles through the mature tree canopy, understory trees and shrubs, and herbaceous plants such as ferns before reaching the litter layer,” he wrote. “Renewed by annual additions of leaves, twigs, and branches, the litter layer is a natural mulch that limits evaporation, a shock absorber that protects soil pores, an insulator that inhibits soil freezing, and a slow-release source of nutrients to foster more plant growth and site protection.”

That’s not the case in developed areas, were roofs, driveways, parking lots and roads convert rain directly to storm water, according to Barten.

“With the disappearance of the forest much is changed and, as a result, overland flow, soil erosion and non-point source water pollution become commonplace events,” he wrote. “… The conversion of forest land to developed areas replaces a storm water and pollutant sink with a storm water and pollutant source. This is the two-edged sword of suburban sprawl and forest fragmentation, and the reason why a comprehensive approach to forest conservation and the revitalization of urban areas is at least as important today as it was a century ago.”

Maine streams and lakes also provide abundant wildlife habitat, including one of the few robust populations of native brook trout in the nation. In fact, the USDA Forest Service says about 80 percent of all wildlife species use stream water during some part of their life cycles.

Clean water and wildlife habitat are not the only “ecosystem services” provided by forests, however. Clean air, recreation, wood products, flood control and fuel are other important benefits that -- like water -- can flow forever from well-managed woodlands.

“Ecosystem services are the fundamental link between nature and the well-being of humans,” says Forest-to-Faucet. “Without an understanding or appreciation of the values that ecosystem services have on our quality of life, humans are unlikely to take the steps necessary to protect them.”

Over the next few months, Forests for Maine’s Future will look at other non-timber values that are provided by the state’s vast woodlands.

Fresh from the Woods is produced by Forests for Maine's Future, a collaboration of Maine TREE Foundation, the Small Woodland Owners Association of Maine, the Maine Forest Service, and the University of Maine.