In-Stream Temperature Modeling to Evaluate Potential Management Practices along the Speed River, Southern Ontario

Abstract

The temperature of the Speed River near the City of Guelph in Southern Ontario is affected by an upstream reservoir, urban runoff, reduced baseflows, in-stream impoundments and development of riparian areas. Mitigating stream temperature increases in this system is desirable because of the direct effects of increased temperature on aquatic organisms but also because of the relationship between stream temperature and dissolved oxygen solubility. Dissolved oxygen levels downstream of the City’s wastewater treatment plant are of particular concern despite high levels of treatment at the plant. Identification of other, less costly, means to sustain acceptable dissolved oxygen levels in the Speed River, in conjunction with nutrient control, would be of interest. The Stream Network Temperature Model (SNTEMP) was linked to a hydrologic watershed model (GAWSER) and applied to the study area to obtain preliminary predictions of the effects of various management practices on the thermal regime of the Speed River. A network of stream temperature loggers was used to calibrate the stream temperature model and identify specific locations on which to focus management efforts. Management practices evaluated were increased riparian vegetation, increased flows from an upstream reservoir, removal of existing in-stream impoundments and decreased stream width. Improvement of the performance of the model is desired along with application of a stream temperature model with a finer temporal resolution.