Thermal Balance of On-Stream Storm-Water Management Pond

Abstract

Through urbanization, pervious surfaces have been replaced by impermeable surfaces such as rooftops, streets, and parking lots, which act as thermal energy collectors and transfer the thermal energy to stormwater runoff as it passes over the surface. A methodology and assessment of the thermal balance of an on-stream stormwater pond are documented for a test facility in Kingston, Ontario, Canada. An energy balance model was used to estimate average pond water temperature as a function of thermal energy stored in the pond. Major thermal energy fluxes considered within the pond system included radiant heating and cooling of the pond, evaporation, and thermal energy inflow from the upstream catchment and outflow from the pond. A thermal energy balance was achieved between thermal energy input and output measured over the field season. During dry-weather periods, pond temperature increased as a result of solar heating, and thermal energy input exceeded output. Conversely, during wet-weather periods, pond temperature decreased as a result of limited solar radiation and replacement of warm pond water by cool inflow water from the upstream catchment, and thermal energy output exceeded input. A series of discrete temperature surveys in the pond revealed that the location of the stationary temperature probe, used to measure pond temperature, resulted in an underestimation of the average pond temperature during dry- and wet-weather periods. However, this discrepancy was comparable to the difference between measured and modeled values, which further confirmed the model validity.