For 200 years, the Don watershed has been subject to intense pressures from human settlement. Since European settlement, the upper subwatersheds of the Don River have had the healthiest aquatic ecosystems, while the lower sections through Toronto were more degraded. Today, almost the entire Don watershed has been urbanized.
Due to the intense urbanization in the Don watershed, hard paved surfaced now increasingly prevent stormwater from slowly seeping into the soil, or from being taken up by vegetation. Therefore, much of the stormwater runs off the surface into the Don River, resulting in streambank erosion and increased flooding during storm events. Combined sewers (carrying both stormwater and sanitary sewage) still exist in Toronto. Excessive runoff from large storm events can cause these sewers to overflow into the river.
The challenge for the future will be to protect and restore the natural heritage features of the watershed – regenerating what’s been lost, and rehabilitating areas that have been abused – while trying to accommodate the competing recreational demands of a growing number of greenspace users. In addition, a number of serious environmental threats to the watershed have emerged and must be addressed, including global climate change.
In order to build on our past successes, creatively manage future urban intensification, and mitigate the effects of climate change, the following issues and challenges must be addressed:
- Ensure the naturalization of the mouth of the Don River is adequately funded to restore the natural heritage features and reclaim vacant industrial lands for parkland and new neighbourhoods.
- Secure stable, long-term funding for infrastructure renewal, watershed management, land acquisition, and regeneration and protection efforts from both public and private sources.
- Manage stormwater to moderate flows in the river and maintain baseflow levels, while minimizing destructive flood conditions and reducing erosion.
- Reduce the flow of contaminants carried into the river by urban runoff, storm sewer and combined sewer outfalls, leaking historic landfills, and other sources, through a mix of pollution incentives, remediation projects, and restrictions on the use of toxic, stable, and bioaccumulative chemicals.
- Protect and enhance natural heritage features when opportunities arise, while planning for urban intensification and increased pressure by multiple recreational uses. Effort must also be made to protect and restore the deteriorating urban tree canopy.
- Stem the spread of invasive terrestrial and aquatic species through the watershed and attempt to control those that have gained a foothold.