Stormwater Runoff

Stormwater, also spelled storm water, is water that originates from rain, including snow and ice melt. Stormwater can soak into the soil, be stored on the land surface in ponds and puddles, evaporate, or run off.

When land is developed into buildings, roads and parking lots, rainfall runs off these impervious areas and creates ever increasing volumes of rapidly moving water which can carry pollutants, erode streams and cause flooding concerns.

Stormwater runoff collects and transports soil, pet waste, salt, pesticides, fertilizer, oil and grease, litter and other pollutants. This water drains directly into nearby creeks, streams and rivers, without receiving treatment at sewage plants.

Stormwater Runoff Vocabulary

Stormwater: Water that originates from rain, including snow and ice melt. Stormwater can soak into the soil, be stored on the land surface in ponds and puddles, evaporate, or runoff.

Runoff: Surface runoff is the flow of water that occurs when excess stormwater, melt water, or other sources flow over the Earth's surface.

Percolate: The slow movement of water through the pores in soil or permeable rock.

Impervious area: A surface that has been compacted or covered with a layer of material so that it is resistant to ground infiltration by water.

Pollutant: A pollutant is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource.

How does land use impact water?

How we use the land impacts watersheds. Once the land area is disturbed by farming or development, the ecological balance in a watershed is affected. Buildings, roads, parking areas, and other impervious features (where water cannot percolate into underlying soils) eliminate groundwater recharge and convert that volume of water into stormwater runoff. In most communities, this increase in stormwater runoff is quickly diverted through stormdrains to a local stream. To worsen matters, during larger storm events this excess runoff from impervious areas also causes excessive stream channel erosion and increases the frequency and magnitude of flooding.

Nonpoint Source Pollutants are causing widespread impacts to the waters of our watersheds. These pollutants come from diffuse sources such as:

• Excess fertilizers

• Pesticides

• Animal waste

• Sediment

• Gas and oil from vehicles

• And other chemicals on the land surface.

During a rainstorm, these Nonpoint Source Pollutants percolate into the underlying aquifers, and are carried from the land into the streams by stormwater runoff.