Surface Water Quality

​Stormwater & Pollution of Streams and Lakes​


Stormwater is rainwater or snowmelt that isn't absorbed into the ground. Stormwater runs off rooftops, down street curbs, and across parking lots where it enters the storm drains.

Storm drains are often confused with sanitary sewers, but in the City of Charlotte and Mecklenburg County, they are separate systems and very different. Storm drains take rainwater through underground pipes directly into a local stream or lake. Stormwater is not cleaned at a treatment plant.

Sanitary sewers carry sewage from our homes to a wastewater treatment plant to be cleaned before it is released into a stream, river, or lake. Examples of sewage include dirty water from our toilets, showers, kitchens, and laundry machines.

Because stormwater is not cleaned at a treatment plant, the storm drainage system can carry pollution from our yards and streets directly into local streams, rivers, and lakes.

Pollution of Streams and Lakes

Stormwater is the number one pollution problem for our nation's streams and lakes. Rainwater washes off a variety of pollutants from the land into the storm drainage system and into streams, rivers, and lakes.

Nonpoint source pollution is another name for stormwater pollution. Nonpoint source pollution comes from all over the land. Here are some common examples of nonpoint source pollution:

  • Soil from construction sites
  • Oil from cars
  • Fertilizers and pesticides from yards
  • Dog poop from parks and yards
  • Litter from streets

Point source pollution is another problem for our streams and lakes. Point source pollution comes from a single source. Common examples include:

  • Sewage overflows from a sanitary sewer
  • Dumping of wastes from a business or person
  • Illegal discharges
  • Spills from auto accidents

Another problem for streams, rivers, and lakes is the volume of stormwater generated in the urban environment. As a community becomes more urban, there are more impervious surfaces. Impervious surfaces don't allow rain to be absorbed into the ground generating a lot more stormwater. Examples of impervious surfaces include sidewalks, roads, and rooftops.

All that stormwater rushes directly to a stream and acts like a fire hose, eroding stream banks and filling the stream with a lot of sediment or mud. The velocity of stormwater during a storm combined with all the sediment or mud generated makes it difficult for aquatic organisms, like fish, to live.

Consider this example:

one inch of rain on an acre of woods 

produces little to no stormwater runoff. 


one inch of rain on an acre of asphalt 

produces 27,000 gallons of stormwater runoff 

that contains a variety of pollutants 

and causes widespread erosion.

Detention basins and stormwater regulations associated with land development activities help manage volumes of stormwater. Detention basins help slow down stormwater so it can be slowly released to a local stream and pollutants, like sediment, can settle out.

Here are some links to learn more about the quality of our local streams and lakes:

What Can I do to Help Prevent Pollution?