Thermal pollution of streams by runoff from paved surfaces

Abstract

Abstract:Urban development dramatically alters a drainage system by landscaping, changes in surface cover, and addition of stormwater handling systems. Increased and warmer runoff from impervious surfaces into streams can lead to a degradation of habitat for coldwater fish. For the projection of thermal impacts of new land development projects, hydro-thermal simulation models have been developed. With measured climate as input, these deterministic models can be used to predict the thermal impact of individual storm events. Surface runoff and runoff temperature were simulated for an asphalt parking lot using 6 years of climate data from Minnesota, USA, with 282 individual rainfall events. The thermal loading from each rainfall event was quantified by three parameters: runoff temperature (°C), rate of heat export (W/m 2 ) and total (integral) heat export (J/m 2 ). Many storm events were found to have little thermal impact, but a few events per year have high thermal impact, either due to large rainfall amounts at a high dew point temperature or due to high land surface temperature combined with moderate rainfall amounts. The amount of heat added to the runoff is highly dependent on both the characteristics of the rainfall event and the weather conditions prior to the storm event. Runoff temperatures from asphalt were found to be well correlated to a linear combination of three parameters: average dew point temperature during the storm, air temperature prior to the storm, and solar radiation prior to the storm. The study results imply that stormwater thermal pollution is more severe when (1) atmospheric air and dew point temperatures are higher than stream temperature, e.g. for streams that are fed by groundwater that is colder than the ambient air, (2) rainfall events are short, intense and preceded by full or partial sun, and (3) watersheds have a high percentage of impervious, particular paved, surfaces.

Urbanization influences on stream temperature behavior within low-discharge headwater streams

“…The relation between stream temperature and with increasing ISC is seen through (1) increases in average stream temperature; (2) short-term surges in stream temperature due to runoff that increases in amplitude as ISC increases; and (3) a downward trend in correlation of stream and air temperature as ISC increases. We expect these results based on previous work (Herb et al, 2008;Klein, 1979;LeBlanc et al, 1997;Nelson and Palmer, 2007;Pluhowski, 1970); however, unlike previous studies, the data of this study include a much higher level of spatial and temporal resolution and represent a headwater stream in an urban setting.…”

“…Urbanization often results in an increase in impervious surfaces and reduced shading of land surfaces by vegetation (Herb et al, 2008). To examine the effect of these variables upon stream temperature, we use impervious surface coverage (ISC) as a general measure of urbanization within the study area catchment.…”

Changes in stream temperatures in response to restoration of groundwater discharge and solar heating in a culverted, urban stream

“…4) as the result of (1) equilibrium temperature effects (Bogan et al, 2003) and (2) the compounding effects of urbanization (Anderson et al, 2007;Nelson and Palmer, 2007;Herb et al, 2008). Groundwater temperatures that we measured in an observation well in the region average 10.6 ° C with minimal oscillation (<0.1 ° C).…”

Urbanization Effects on Watershed Hydrology and In-Stream Processes in the Southern United States

“…Temperature of runoff from paved surfaces is a function of surface properties, rainfall temperature, air temperature, and solar radiation prior to the storm [94] with temperatures and solar radiation maximized before late afternoon, summer storms. In urbanized watersheds in the MD Piedmont, temperature surges associated with summer thunderstorms averaged 3.7 º C and receded back to pre-storm temperatures over 2.8 hours [95].…”