Modeling Thermal Enrichment of Streams due to Solar Heating of Local Urban Stormwater
This chapter presents a computation of the thermal enrichment of streams due to local urban stormwater. Our earlier study (Xie and James, 1994) confirmed that thermal enrichment is a critical stressor of aquatic habitats and ecology down-stream of urban areas. Previous workers had found a linear relationship between percentage imperviousness and observed thermal enrichment (%I-?T). Here we apply the Hydrological Simulation Program-Fortran (HSPF) to the Speed River at Guelph to check that relationship.
We found that the HSPF processes for heat buildup/wash-off from impervious, urban surfaces during hot weather are somewhat deficient for this work. A simple experiment in a parking lot at the School of Engineering confirmed the importance of these processes. Results were used to re-calibrate HSPF against a large data set collected from various sources for the Speed River at Guelph.
Evidently, this is the first: (i) application of HSPF to examine thermal enrichment due to urban developments; (ii) reproduction of the general linear %I-?T relation using a comprehensive theoretical model; and (iii) application of a model of thermal enrichment of urban streams, treating a large urban area as a solar receptor. Several recommendations are made for developing models of heat in runoff. It is suggested that more experiments, such as those described by James and Verspagen (1996) and Picksley and Deletic (1998), are required.
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