Poorly planned growth and the subsequent loss of green space that
often accompanies it can affect both surface and groundwater quality.
In the natural environment, rainfall is either intercepted by vegetation
or percolates slowly through the soil to receiving waters.
In urbanized areas, rainfall that once filtered slowly downhill becomes
surface runoff. This water flows across compacted earth and impervious
human-made surfaces, such as asphalt, concrete, and rooftops, and is
channeled into storm drains.
This disruption of the natural hydrologic
cycle causes stormwater runoff to reach streams and rivers more quickly
than these water bodies can absorb it, and often before pollutants can be
filtered through the ground.
Undisturbed forested lands generally have the highest capacity to absorb
water; thus, these areas have the lowest rates of stormwater runoff. In
contrast, impervious surfaces such as concrete have the highest runoff
rates. The volume of stormwater that washes off 1-acre parking lots is
about 16 times greater than the volume that runs off a comparable-sized
meadow. This increased runoff causes increased erosion and stream
siltation and may affect water treatment plants.
An additional threat to water quality posed by uncontrolled growth is the
overuse of septic systems in low-density suburban and rural residential
developments. Overuse of a septic system can result in groundwater
contamination, potentially affecting the health of all people coming into
contact with the water source.
For more information on water quality, refer to the following
resources:
Additional information on water quality and related topics can be found in
the Additional Resources section.
References
Schueler, TR, Holland, HK, editors. Why stormwater matters. The practice of
watershed protection: an edited anthology. Article 63. Center for Watershed Protection;
Maryland: 2000.
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