Modelling Changes in Surface Water Quality for Watersheds Undergoing Urbanization.
In this paper we describe a linked cascade of modelling procedures assembled specifically to assess changes created by urbanization in the quantity and quality of streamflow. This assessment is a key to successful integrated watershed management, a concept which has received widespread support in Ontario recently (PCAO, 1991; Queens Printer, 1991; Charlton and Tufgar, 1991).
Subwatershed studies are needed as part of integrated watershed management to determine the impact of development that exists or is anticipated, to evaluate the effectiveness of measures to prevent or remediate damage, and to assist decisions on acceptable levels of urbanization. Urbanization changes both the flow rates of water within varioushydrological processes and the physical, chemical and biological attributes associated with these processes. Techniques used for assessment of the environmental impacts of urbanization must account for all these changes.
The modelling approach that is summarized here has been created as part of the Laurel Creek Watershed Study (Charlton and Tufgar, 1991). This study is being carried out primarily by Triton Engineering Services Ltd. of Kitchener and Ecological Services for Planning Ltd. of Guelph, for the Grand River Conservation Authority, the Regional Municipality of Waterloo and the cities of Kitchener and Waterloo in Ontario. The first three authors of this paper are subconsultants for this study. The model components we assembled and used have been carefully selected to provide the assessments required to meet the objectives of the Laurel Creek Study. The objectives of the study are to establish acceptable levels of urbanization, and to recommend measures to protect, rehabilitate and enhance water quality, associated water resources, fisheries, wetlands and environmentally sensitive areas.
In the following sections of this chapter we describe component modelling procedures and the links among them that were used to assess changes in water quality from urbanization. Typical results from Laurel Creek illustrate the range of impacts that can be assessed. The chapter concludes with comments on the effectiveness and applicability of the methods.
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