By April Reese

Water Glass

Credit: Greg Riegler/Flickr

This spring and summer, when you quench your thirst with a tall glass of cool, clean water, thank the forests in your local watershed.

Forests provide many benefits, including wildlife habitat, recreational opportunities and carbon sequestration. But they are often under-appreciated for their role in protecting drinking-water supplies. Forests shade snowpack, controlling the rate at which it melts, which keeps water flowing to streams, lakes and aquifers year-round. The trees also work to clean the water, filtering out pollutants and regulating the water’s temperature to keep the aquatic ecosystem in balance.

Federal officials and lawmakers have understood the importance of forests for water supplies for more than a century. Back in 1897, when Congress passed the Organic Act, which created the forest “reserves” that eventually would become our national forests, it specified “favorable conditions of water flow” as one of two purposes for the reserves, in addition to providing a sustainable supply of timber. A few years later, the Transfer Act of 1905, which created the Forest Service within the U.S. Department of Agriculture, directed the new agency to ensure that water from the forests would be available to downstream users.

Unfortunately, since these developments, little has been done to ensure that policies and forest-management methods recognize the vital role that forests play in our water, despite the fact that today, more than half the nation’s drinking water comes from forested ecosystems. Now that climate change has begun pinching already tightly stretched water resources, that’s beginning to change. In fact, the Forest Service, recognizing how crucial forested lands are to maintaining water quality, has made watershed protection one of its main priorities under the Obama administration.

“Clean, healthy forests are vital to our efforts to protect America’s freshwater supply,” Agriculture Secretary Tom Vilsack says in a statement. “Our nation’s economic health, and the health of our citizens, depends on abundant, clean and reliable sources of freshwater.”

Watershed Condition Framework map

In 2011, the USDA Forest Service unveiled this new map that shows the health and condition of national forestlands in more than 15,000 watersheds across the country. Credit: USFS

According to the Forest Service, about 20 percent of the nation’s drinking-water supply comes from watersheds on national forests and grasslands, so it makes sense to start there. Last summer, the Forest Service unveiled a new map that shows the health and condition of national forestlands in more than 15,000 watersheds across the country. The map, which will be used to help establish priorities for watershed restoration, is part of a larger effort to establish a “Watershed Condition Framework” — the first national assessment of the health of watersheds in the 193 million acres that fall under the care of the Forest Service.

As shown in the Watershed Condition Framework map, watersheds from New England down to the Gulf and across the Midwest and Great Plains to the West Coast are functioning at risk or are impaired, including in California where a huge — and growing — population relies on limited water supplies. National forests in California make up about 20 percent of the state’s geographic area, but they provide almost half of its surface water. Every major metropolitan area in the state depends on water imported from distant watersheds, most of which are on national forestlands, according to the Forest Service. For instance, Los Angeles, Oakland and the larger East Bay area all receive much of their water from the Mokelumne watershed, which straddles Stanislaus and El Dorado National Forests miles away in northern California. Los Angeles also funnels water from streams in Inyo National Forest, on the east side of the Sierra Nevada Mountains.

Howard Lake in California’s Mendocino National Forest

Howard Lake in California’s Mendocino National Forest. Credit: USFS Region 5/Flickr

The state’s water system is under tremendous stress from drought, increasing demand, pumping restrictions — some of them to aid endangered fish — and insufficient funding for infrastructure. That means the state’s forested watersheds will be even more vital to California cities in the years to come.

Like other watersheds around the country, California’s face a number of threats that can harm water quality. While several studies indicate that waters on the state’s national forests are of high quality, many streams on national forest lands have been listed as “impaired” by the Environmental Protection Agency. To try to address those problems, the Forest Service is working with state regulators to improve its water-quality-management program.

It can be difficult to balance the legal mandate to protect water resources with other directives to allow “multiple uses,” including logging, grazing and recreation.

“It is a challenge, certainly,” says Barry Hill, a hydrologist with the Forest Service’s Pacific Southwest Region. “It’s not an option to degrade water quality because we’re going to get additional board feet of timber out of it. We still have to follow the law.”

The agency has adopted a number of “best management practices,” or BMPs, that help ensure that water quality is protected when logging and other potentially damaging projects are undertaken, he adds.

“Overall, they’re pretty effective, but there’s room for improvement,” he says. The agency just updated its BMP handbook in December — the first substantive change to the guidelines in 30 years, Hill adds.

Most of the problems with the old practices involved insufficient restrictions on road construction to prevent erosion of sediment into streams. The new BMPs include regulations that prevent bridges or roads from being constructed in a way that obstructs stream flow or fish passage. They also dictate that construction occurs in the dry season to minimize any erosion and that any slopes created must be planted with new vegetation to keep them stable.

San Diego Cedar Fire

The October 2003 Cedar Fire destroyed more than 300 homes in the Scripps ranch neighborhood of San Diego, California. Credit: Michael Campbell/Flickr

Keeping the forest ecosystem healthy as a whole is also crucial to protecting watersheds, Forest Service officials point out. That can include thinning and prescribed burning to clear out forests that have grown too thick thanks to a century of fire suppression. While wildfire plays an important role in forest ecosystems, overstocked fuels can feed unusually large, super-hot fires that deeply burn soils and leave them vulnerable to severe erosion, which can clog streams and water-treatment plants with sediment.

“Our focus is on ecological restoration activities, and that focuses a lot on water quality,” says John Heil, a spokesman for the Forest Service’s Pacific Southwest regional office.

Forest managers and city officials alike are acutely aware that sustainable water supplies are closely tied to forest health. “It’s a primary part of the Forest Service mission and certainly part of our regional leadership’s intent to protect water across the landscapes we manage,” Hill says.

Editor’s Note: Would you like to show support for the USDA Forest Service’s Watershed Condition Framework that aims to protect our forests and drinking water? Take action by submitting a letter about this issue to the U.S. Department of Agriculture (USDA) and the Environmental Protection Agency (EPA). We’ve written a letter that just needs your signature — and additional thoughts, if you’d like — and we’ll send it directly to the top people at the USDA and EPA.