A technical basis for analyzing the impact of heat addition from stormwater effluent into receiving water bodies

Darryl A. Dormuth

ABSTRACT

During a rainfall event, stormwater can transport heat from an urban area, which can be significantly warmer than its surrounding region, to a receiving water body, such as a stream, river, lake, or a wetland. An increase of temperature in a water body above ambient levels can adversely affect thermally sensitive aquatic ecosystems, such as those that support cold-water fish habitats. As a consequence, many environmental regulatory agencies have imposed standards or set guidelines on thermal discharges into water bodies. A challenge for municipalities is to determine under what conditions stormwater effluent could violate these temperature standards. If such conditions could be predicted with sufficient accuracy then management practices could be developed to mitigate the adverse impacts on aquatic habitats.

The discharge of urban stormwater runoff into a water body can be categorized as a heated surface plume or jet. Several well-documented models exist to simulate the dynamic behaviour of heated surface jets and plumes and
in this paper the applicability of some of these models to the analysis of heat addition into a water body by
stormwater effluent is discussed. Also presented in this paper is a methodology for determining the impact of heat addition from stormwater efflux into a receiving water body.


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