Modeling Thermal Enrichment of Streams due to Solar Heating of Local Urban Stormwater

Abstract

This chapter presents a computation ofthe thermal enrichment of streams local urban stormwater. Our earlier study (Xie and James, 1994) contlnneJ thermal enrichment is a critical stTessor of aquatic habitats and ecology down- stream of urban areas. Previous workers had found a linear relationship between percentage imperviousness and observed thermal enrichment Here we apply the Hydrologicai 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 imper- vious, 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 a large data set coHected from various sources for the 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 ~Yo I-D. T relation using a comprehensive theoretical model; and (iii) application of a rnodel ofthermal enrichment of urban streams, treating a large urban area as a solar receptor. Several recommendations are made for developing models ofheat in runoff. It is suggested that more experiments, such as those described by James and Verspagen (1996) and Picksley and Deletic (1998), are required.