Climate Change

What are the impacts of Climate Change?

• Annual average air temperatures across the province has increased from 0 to 1.4°C; the greatest warming occurred in the spring for the period 1948 to 2006
• Total annual precipitation increased 5‐35% since 1900 and the number of days with precipitation (rain and snow) increased
• Total annual precipitation in Hamilton increased 26mm; this equates to approximately 3% increase in annual average precipitation since 1970
• Heavier, more frequent and intense rainfall events have been detected in the Great Lakes Basin since the 1970s
• Precipitation as snow in the spring and fall has decreased significantly in the Great Lakes ‐ St. Lawrence basin between 1895 and 1995, although total annual precipitation has increased 

Information adapted from Hamilton’s Community Climate Change Action Plan. Read the full plan here

How Does Climate Change Impact Hamilton?

The impacts of climate change would - and already have begun to - affect our community, in particular stormwater management and algal blooms.

 

Stormwater Management

Larger, more intense storms are predicted to occur more frequently in the near future. During a typical rain event, water flowing quickly over impervious surfaces collects in stormdrains (sewers), combines with wastewater from residential and commercial properties (developed before 1970) then flows toward wastewater treatment plants to be cleaned. However, during large rain events, the amount of water entering the system can exceed plant capacity. The excess water is then diverted to nine subterranean tanks, known as combined sewer overflows (CSOs), for storage until the plant is able to process it.

 

In some cases, the sudden flood of rain exceeds even CSO capacity, so untreated water is released into the Harbour, delivering mass amounts of raw sewage (E.coli), fertilizers, pesticides, others hazardous chemicals and suspended sediments.  

 

Algal Blooms

Among the various organic and inorganic materials flowing into the Harbour during stormwater events is the nutrient phosphorus. Urban runoff, fertilized crop-land, animal manure storage areas, disturbed land and exposed soils, rocks, drained wetlands, failing septic systems, commercial cleaning products and wastewater treatment plants all contribute phosphorus to the Harbour. Phosphorus is a nutrient that is essential for the plants and animals of any aquatic food web. However, even small increases in phosphorus in water can cause undesirable events or conditions including accelerated plant growth, algae blooms, low dissolved oxygen, and the death of certain fish, invertebrates and other aquatic wildlife (Toward Safe Harbours Report, 2014). 

 

Unlike traditional aquatic “plants”, algal blooms are a threat to restoring healthy Harbour water quality. Progressively intense rain events are predicted to increase the amount of phosphorus entering the Harbour system. The continued restoration of Hamilton Harbour - notably improvements to water quality – will depend on the actions of its citizens in order to identify and mitigate the effects of climate change in ways that simultaneously support the rehabilitation of our watershed. Photo to right: Workers skim algae off water at Bayfront Park to prevent toxic blue-green algae blooms (2016).