Humber River Watershed Management Plan

Client: Toronto and Region Conservation Authority
Don Ford, P.Geo. Manager, Hydrogeology,
5 Shoreham Drive, Downsview, ON M3N1S4 Tel:416-661-6600×5369
Key Personnel: Dirk Kassenaar and E.J. Wexler

Working for the Toronto and Region Conservation Authority (TRCA), Earthfx provided key surface water and groundwater analysis components of the Humber River Watershed Plan. The watershed is the home to over 800,000 residents, including the western portion of the City of Toronto.

Surface and Groundwater Model Development

A high resolution fully-distributed surface water model was developed using the USGS PRMS code, and this was used to evaluate changes in groundwater recharge under current and future land development and climate scenarios. PRMS recharge estimates were applied to a USGS MODFLOW groundwater model to evaluate long term changes in groundwater levels and baseflow discharge under Official Plan, expanded natural cover and full build-out scenarios.

Low Impact Development (Sustainable Communities)

Future scenarios included assessment of the effects of LID features such as green roofs, permeable paving, and infiltration trenches. These features were represented at the lot level in the high resolution (25 m cell size) PRMS model. Code modifications were made to the PRMS model to allow simulation of lot level LID storage (i.e. rain barrels, galleries) and impervious to pervious runoff routing.

Climate Change

Future climate scenarios were undertaken to assess long term recharge and groundwater levels under a warmer and wetter climate.


Particle tracking simulations using the USGS MODPATH model were used to understand groundwater flow pathways to key baseflow discharge areas. Finally, the coupled SW and GW models were used to estimate all major components of the watershed water budget.

Fully Integrated GSFLOW Simulations

The PRMS and MODFLOW simulations initiated in this project were subsequently merged into a fully-integrated GSFLOW model of the entire TRCA. This model, completed in 2014, further quantified the effects of land development and drought conditions on water resources in the TRCA watersheds.