Water Service - Water Resources

Humber River Watershed Water Balance Modelling and Recharge Mapping

Client:

Toronto Region Conservation Authority
Location:

Toronto, ON
Budget:

$35,000
Biggest Hurdle:

Assessing impact of future urbanization.

Toronto Region Conservation Authority retained XCG Consultants Ltd. (XCG) to develop a hydrologic model of the Humber River watershed and apply the model to estimate groundwater recharge across the watershed. One purpose of the project was to provide input to a groundwater system model being developed by others.

 

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The HSP-F hydrologic modelling platform was used to develop a model of the watershed, based on an earlier model that had been built by XCG for the City of Toronto. To build the Humber model, XCG used HSP-F to develop a set of hydrologic unit-response functions (URFs). Each URF represents a particular combination of land use, land slope, surficial soil type, vegetative cover, and internal drainage connectivity (i.e. how various surfaces such as roads, building roofs, and vegetated areas interconnected in terms of surface drainage pathways). Each URF is effectively a sub-model. Long term simulation of hydrologic response of each URF provided water budget components including direct surface runoff, evapotranspiration, and recharge to the groundwater system.


Geographical Information System (GIS) was used to map out where each URF applies across the watershed. Calibration of the URFs was possible by developing the aggregated watershed response at flow gauge locations. Then, the outputs from the HSP-F model were brought into the GIS to allow mapping of groundwater recharge.