Impacts. Warm stormwater from developed areas causes sharp temperature rises when it is discharged into receiving waters. Warmer temperatures in streams and rivers can stress or kill many cold-water species of plants and animals. Higher water temperatures also lower the concentration of oxygen in the water, which may threaten or suffocate certain animals.

Indicator parameters. The temperature of the water can be easily measured with portable thermometers or by simply feeling the water by hand.

Source reduction. Buffer zones and trees planted along streams will help lessen the increase of water temperature. Grassed filter strips, grassed swales and infiltration trenches should be used in residential areas to maximize infiltration and reduce the amount of warm stormwater directly entering streams.

Removal. Temperature impacts can be reduced by using infiltration techniques that prevent discharge of the warm water into receiving waters. Dry detention basins should be designed to release stormwater within a 48-hour period to minimize temperature rise. Trees for shade can be planted around dry detention basins and wet retention ponds to reduce temperatures.

Return to: Surface Water Pollutants and Stormwater Runoff