is the Lake Barcroft Watershed? The Lake Barcroft watershed [hyperlink
to watershed map] consists of all the land area that drains into the
lake. Our watershed includes houses, roads, parking lots, schools,
parks, businesses, and other land uses.
Lake Barcroft contains
two main tributaries - Holmes Run and Tripps Run - that drain
approximately 5,400 and 3,700 acres of land, respectively. During a
rainstorm, stormwater runs off the land and into local stormwater
systems, streams, and tributaries that feed into the lake.
is the biggest threat to lake water quality? Fortunately, there is not
much industry or agricultural activity that occurs in the Lake Barcroft
watershed that contribute pollution to lake tributaries and drainage
systems. The biggest threat is urban stormwater runoff.
quantity and quality of stormwater runoff that drains into our lake is
most affected by the land uses and activities that take place in the
watershed. For example, water flowing off the Beltway will be quite
different than water flowing off forested park land and it will likely
contribute more runoff and pollutants.
Since even rain that
runs off land in the upper reaches of the watershed may eventually make
its way into the lake, it’s important to protect all of our watershed.
But watershed protection begins in your back yard.
Sources of Pollution
What are the sources of pollution in our watershed? The Cameron Run Watershed Management Plan (2007)
provides a good overview of the pollution sources as well as
recommendations for the County to protect and improve the watershed
over the next 25 years. The plan notes that the Cameron Run watershed,
which includes the Lake Barcroft watershed, has experienced
environmental degradation primarily as a result of urban and suburban
development and its associated stormwater runoff. The “watershed is
characterized by dense development, significantly degraded instream
habitat conditions, and substantially degraded biological communities”.
Stream bank erosion and instability is widespread.
The amount of stormwater pollution is the result of two primary
When stormwater runs off the land, it picks up nutrients and
pesticides from lawns; oil, metals, and trash from roads and parking
lots; pet waste from parks and yards; and silt and sediment from
construction sites and other areas where soil is exposed. The runoff
carries all these pollutants into drainage systems, streams, and
eventually Lake Barcroft unless some form of treatment is provided to
Many hundreds of years ago, the Lake Barcroft watershed was
completely covered with trees, grasses, and other natural vegetation.
Whenever it rained, the land acted as a sponge soaking up water which
infiltrated the soil and recharged groundwater aquifers. As the area
has become urbanized over the past decades, hardscape impermeable
surfaces such as roads, driveways, roofs, and parking lots have covered
and transformed the land. Now when it rains, much of the water can no
longer soak into the ground. Instead it runs off. This increased amount
of runoff erodes streambanks causing significant increases in sediment
and nutrient loads to the lake. Have you ever noticed how chocolate
brown the lake is after a storm?
We don’t often think of stormwater quantity as a “pollutant”, but a
recent National Research Council Report on Urban Stormwater Management in the United
recommended that flow and related parameters
like impervious cover can serve as proxies for stormwater pollutant
has shown a direct relationship between the amount of impervious cover
and the health of streams. As impervious cover rises above 10% of the
total watershed area, the number and diversity of aquatic species
declines. Sensitive species are lost. A second threshold appears to
exist at around 25 to 30% impervious cover. As streams begin to exceed
this threshold, they essentially become more like conduits or drainage
ditches for conveying stormwater flows and less like healthy streams.
They can no longer support a diverse stream community. “Pool and riffle
structure needed to sustain fish is diminished or eliminated and the
substrate can no longer provide habitat for aquatic insects, or
spawning areas for fish.” Stream water quality is consistently rated as
fair to poor above this threshold.
The percentage of impervious
cover in the Upper Holmes Run and the Tripps Run watersheds is
currently in the range of 25% to 30%, and this percentage is climbing
as neighborhoods infill and roads and businesses expand. For the health
of the lake and its tributaries, it’s important to try to reduce the
amount of impervious cover in the watershed or to implement stormwater
controls to counteract its detrimental effects.
Cameron Run Watershed Management Plan (2007) noted that reducing the
effects of stormwater runoff created by uncontrolled impervious surface
is a critical step to take for restoring the watershed. But how do we
First, watershed restoration begins in your backyard. There
are many things that we can do as individual homeowners to protect the
lake, including planting trees, creating a rain garden
directing gutter downspouts from impervious areas to pervious areas
away from the house foundation, using permeable materials for new or
replacing existing driveways and walkways, minimizing fertilizer use,
and lots more.
The Lake Barcroft Environmental Quality
Committee has developed a Watershed Friendly Garden Certification
Program [hyperlink to document] that has a comprehensive list of things
you can do at your home and in your yard do to control stormwater
runoff and protect water quality.
Did you know that the storm
drains on the streets in Lake Barcroft drain into the lake? Many people
think that these drains go to a treatment plant, but the water flows
untreated into the lake. Therefore never put anything down the storm
drains that you don’t want to end up in the lake such as pet waste,
leaves, grass clippings, trash, used motor oil, paint, or chemicals.
Wash your car at a professional car wash facility or in your yard to
keep dirt and soapy water from running into the storm drain.
The watershed area for Lake Barcroft extends far beyond the
boundaries of the Lake Barcroft community. In fact our community
represents only a small fraction of the watershed as a whole. Thus it
is important to take an active role in Fairfax County issues that may
affect lake water quality, in particular ensuring that any new
development has appropriate stormwater runoff controls, minimizes
impervious cover, and maintains the pre-development hydrology to the
maximum extent feasible. For existing development, it is important to
support the County’s efforts to retrofit stormwater best management
practices, low impact development practices, and green infrastructure
throughout the watershed.
For more information on stormwater management and watershed restoration
Fairfax County - Stormwater
Arlington County - Stormwater
Northern Virginia Soil and Water Conservation District