Thermal enhancement of stormwater runoff by paved surfaces

A methodology for predicting the thermal enhancement of stormwater runoff from paved surfaces is documented for a test facility in Kingston, Ontario, Canada. Prediction of runoff temperature is based on TRMPAVE, a mathematical model that was developed using a thermal energy balance approach and the one-dimensional heat equation to predict the surface temperature and temperature gradient in asphalt during dry-weather and wet-weather periods. Runoff temperature is then estimated as a function of rainwater temperature and surface temperature of the asphalt. In order to supplement wet-weather data, a number of simulated rainfall events were generated over a test plot to help develop, calibrate and verify the wet-weather model. Computer simulations for both dry and wet-weather periods compared well with measurements of temperature from the test plot. In addition, the average temperature of runoff contributed by the entire parking lot area was cooler than the average temperature of runoff from the test plot, but both values were higher than runoff from the upstream catchment. In light of the results obtained, TRMPAVE can be used to predict thermal loading from impervious areas.