The Link Between Beavers and Water Quality

Beaver 1When you hear of a new development, usually you think of a new business, house or apartment complex. It might surprise you, if you live next to a park, to learn that new houses are rising all the time near you. They’re houses for wildlife, and they’re often built by beavers.

Beaver 2Beavers don’t know the difference between a nice, ornamental crape myrtle in your yard and a Virginia pine standing on parkland. That’s sometimes a source of disagreement as to the true value of beaver houses. However, a three-year study by U.S. Geological Survey (USGS) Ecologist Dan Kroes shows their value in streams.

The USGS study shows that dams and lodges, as beaver houses are properly called, are important to water quality. Dams trap as much as two feet of sediment that would otherwise go downstream. Sediment in water is what makes streams cloudy or murky. Not only are sediment-filled streams unpleasant to look at, they don’t allow sunlight to play its role in aquatic food webs. If there are lakes downstream, the sediment settles and may eventually fill those lakes. Witness Lake Accotink in Springfield. It was 23 feet deep  when it was constructed in the 1940s, and despite numerous dredging efforts, it was a mere four feet deep by 2018.

Beaver dams and lodges also slow the water tumbling downstream. By extension, they reduce stream bank erosion that undercuts banks and fells trees. They slow the pace of streams, which improves drinking water quality, increases stream life and decreases flooding. It’s development that’s good for the environment.


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About Fairfax County Park Authority

About Fairfax County Park Authority HISTORY: On December 6, 1950, the Fairfax County Board of Supervisors created the Fairfax County Park Authority. The Park Authority was authorized to make decisions concerning land acquisition, park development and operations in Fairfax County, Virginia. To date, 13 park bond referenda have been approved between 1959 and 2016. Today, the Park Authority has 427 parks on more than 23,000 acres of land. We offer 325 miles of trails, our most popular amenity. FACILITIES: The Park system is the primary public mechanism in Fairfax County for the preservation of environmentally sensitive land and resources, areas of historic significance and the provision of recreational facilities and services including: • Nine indoor RECenters with swimming pools, fitness rooms, gyms and class spaces. Cub Run features an indoor water park and on-site naturalist • Eight golf courses from par-3 to championship level, four driving ranges including the new state-of-the-art heated, covered range at Burke Lake Golf Center • Five nature and visitor centers. Also nine Off-Leash Dog Activity areas • Three lakefront parks including Lake Fairfax, Lake Accotink and Burke Lake, with campgrounds at Burke Lake and Lake Fairfax. The Water Mine Family Swimmin’ Hole at Lake Fairfax, Our Special Harbor Sprayground at Lee as well as an indoor water park at Cub Run RECenter • Clemyjontri Park, a fully accessible playground in Great Falls featuring two acres of family friendly fun and a carousel, as well as Chessie’s Big Backyard and a carousel at the Family Recreation Area at Lee District Park • An ice skating rink at Mount Vernon RECenter and the Skate Park in Wakefield Park adjacent to Audrey Moore RECenter • Kidwell Farm, a working farm of the 1930s-era at Frying Pan Farm Park in Herndon, now with historic carousel • Eight distinctive historic properties available for rent • A working grist mill at Colvin Run in Great Falls and a restored 18th century home at Sully Historic Site in Chantilly • A horticulture center at Green Spring Gardens in Annandale • Natural and cultural resources protected by the Natural Resource Management Plan and Cultural Resource Plans, plus an Invasive Management Area program that targets alien plants and utilizes volunteers in restoring native vegetation throughout our community • Picnic shelters, tennis courts, miniature golf courses, disc golf courses, off-leash dog parks, amphitheaters, a marina, kayaking/canoeing center • Provides 263 athletic fields, including 39 synthetic turf fields, and manages athletic field maintenance services at 417 school athletic fields. PARK AUTHORITY BOARD: A 12-member citizen board, appointed by the Fairfax County Board of Supervisors, sets policies and priorities for the Fairfax County Park Authority. Visit for Fairfax County Government's Comment Policy.

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