River modelling

The Grand River Simulation Model (GRSM) is a computer model of the watershed. We use it to understand how changes at wastewater treatment plants might affect water quality. A model is necessary because changes in water quality are caused by a complex interaction of many factors that change over time. For example, we use the model to determine how water quality may change in the future due to improvements in wastewater treatment processes, increases population growth in our towns and cities and changes in river flow or temperature due to climate change.

The model covers 164 kilometres of the Grand River from the Shand Dam to the Six Nations drinking water intake at Ohsweken. It also includes 33 kilometres of the Speed River from Guelph Dam to the Grand River in Cambridge.

The model uses data from the 10 largest wastewater treatment plants in the watershed as well as information about pollution from other sources. It also includes information on river flows, temperatures and dissolved oxygen levels.

We monitor dissolved oxygen levels and water temperature at nine water quality monitoring stations. The information is used for several purposes, including verification that model outputs are realistic. Real-time data from the stations is available on our Water quality data pages.

The model calculates the effect of the effluent coming from all of the wastewater treatment plants, plus other sources of pollution. It predicts the outcome of a variety of scenarios and conditions, providing a dynamic model of the river and its capacity to handle pollutants. Municipalities planning a wastewater plant improvement or expansion can use the model to calculate the probable impact on the river.

For example, the Region of Waterloo used the model for their recent Wastewater Master Plan to analyze a variety of possible scenarios for multiple wastewater treatment plants in Kitchener, Waterloo and Cambridge. The GRSM helped the Region determine which set of improvements would do the most to improve water quality at the most reasonable cost.

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