The Effect of Bioretention on Runoff Temperature in Trout Sensitive Waters

Abstract

As urbanization continues to encroach upon coldwater fisheries, the effect of heated stormwater runoff on the coldwater aquatic ecosystem has been realized; however, the effect of stormwater BMPs on runoff temperature is largely unknown. There are indications that bioretention could discharge cooler effluent than stormwater wetlands and wet ponds, since the outlet is located at the bottom of the system where soil is insulated from elevated temperatures near the surface. Infiltration through soil media is generally considered to reduce runoff temperatures, with many coldwater streams able to maintain their cooler temperatures through influxes of groundwater. A monitoring study was conducted at 4 bioretention areas in western North Carolina, along the southeastern extent of United States trout populations, to determine the effect of bioretention on runoff temperature and identify any design criteria that affect effluent temperatures.