Stormwater harms our river and streams because it is funneled directly from the stormdrain system into our waterways without being treated.
Frequently Asked Questions
What is stormwater?
Stormwater is water from rainfall or snowmelt that doesn't evaporate or infiltrate into the ground, but instead runs off, either into the storm drain system or directly into our rivers and streams. Increased amounts of impervious surfaces, such as rooftops, driveways and parking lots, increase the amount of stormwater runoff.
Isn't stormwater treated?
Oftentimes not. In many cases, stormwater is funneled directly from the stormdrain system into rivers, streams and lakes without being treated.
Why is stormwater a growing problem?
The increasing and rapid rate of urbanization. Development and construction severely alter the hydrological functioning of the landscape. Soils are compacted by construction equipment and grading. Trees and vegetation are replaced by extensive areas of impervious surface, such as roofs and pavement. Compacted soils cannot infiltrate water as effectively, impervious surfaces prevent water from being absorbed into the ground, and there is less vegetation to soak up, store, and evaporate water. The result is that less water is absorbed into the ground and more runs off as stormwater.
What pollutants are in stormwater?
- Heavy metals and toxic chemicals, including oil and pesticides, which wash off streets, driveways, lawns, and fields.
- Nutrients, especially phosphorous and nitrogen, from landscaping, leaking septic systems, and agriculture.
- Sediment, the largest pollutant load in urban settings, results in high turbidity water, which is harmful to aquatic life.
What problems does stormwater cause?
- Prevents groundwater recharge: Stormwater runs off, instead of seeping into the ground and recharging natural ground water aquifers that people depend on for drinking water and stream recharge.
- Human health: Stormwater picks up bacteria, chemicals and pathogens that can cause illness. In areas with combined sewer systems, it can also overwhelm water treatment systems, causing raw sewage overflows.
- Aquatic wildlife health: The health of fish, aquatic birds and other marine animals is threatened by nutrient-laden stormwater, which causes bay-choking algae growth and low levels of dissolved oxygen, and erosion and sedimentation that can destroy aquatic habitat.
- Recreation: Swimming, fishing and boating on local water bodies can be dangerous and unpleasant due to pollution. In Washington, D.C., swimming in all rivers and streams is illegal due to stormwater pollution.
- Aesthetics: Physical characteristics of water bodies, such as color and smell, can be affected by stormwater pollution, and litter from streets is carried directly into lakes and streams by the storm drain system.
- Increased volume and velocity: Stormwater volume increases can overwhelm stormwater systems, resulting in flooding, sewage releases, and property damage, and in conjunction with increased velocity, results in streambed erosion and large sediment deposits.
- Increased temperature: Impervious surfaces warm the stormwater running off them, affecting stream biology, physiology and aquatic life, which are highly sensitive to temperature changes
- Erosion: One of the worst results of increased volume and velocity is erosion. Erosion not only results in property and stream bed damage, it also can result in loss of fish and wildlife habitat and reduced water quality and clarity from down stream deposits of the eroded soil.
Current Recent and Ongoing Projects:
Maryland's Stormwater Management Act of 2007: Maryland's Stormwater Management Act of 2007 requires that onsite, vegetation-based stormwater management be the presumed norm for all stormwater treatment in the state of Maryland. The Potomac Conservancy is currently working with a coalition of citizen and environmental groups to ensure the regulations and implementation of this cutting-edge bill fulfill its great promise.