Spring brings heavy rains, high river flows, flood warnings, and stormwater which poses considerable risk to water quality at this time of year. Alberta government annually reports on water quality in our rivers in the River Water Quality Index. Although results for 2006-7 indicate relatively good water quality, the heavy rains and extensive flooding in 2005-06 translated to poorer water quality in the central and southern rivers. Heavy rain events “cleanse” the land surface but results in more pollution to the river. This runoff water rushes into water bodies and contains all the substances it has picked up off the land — including pollution. These events are particularly problematic in urban areas, where impervious surfaces create higher volumes of runoff and where more pollutants exist, such as oil products, which can be picked up by the runoff water.

What contaminants come from stormwater?

Sediment can increase turbidity, making food less available for fish and impairing water quality.

• Sediments come from landscaping, construction projects, and riverbank erosion.
• Sediments increase turbidity making it difficult for plants to access sunlight, which in turn make less food available for fish and other aquatic species.
• Pathogenic bacteria and viruses more easily cling to sediment in the water.
• Sediments decrease reservoir capacity by collecting upstream of dam walls.
• Sediments can destroy aquatic habitat by settling on spawning habitat and fish eggs.

Bacteria, viruses, and other pathogens wash off lawns, dog parks, and agricultural areas into water bodies and create health hazards for drinking water and swimming areas.

• Sources of pathogens include pet, wildlife, and livestock waste.
• Heavy stormwater can sometimes overload municipal wastewater treatment plants forcing them to release untreated or partially treated sewage into the river.

Toxic chemicals and hazardous substances from our roads, lawns, and many other land uses poison aquatic and terrestrial life, including humans, fish, and pets. Source include:

• Oil, gasoline, and automotive products
• Heavy metals
• Cleaners, pool chemicals, paint solvents
• Insecticides, pesticides, lawn care products
• Pesticides (from lawn care, golf courses, and agriculture)

Nutrients and fertilizers impair water quality and cause algal blooms.

• As algae die and decompose they remove oxygen from the water, a necessity for aquatic organisms such as fish.
• Fertilizers for lawn care, golf courses, and agriculture contribute considerable amounts of nutrients (e.g., nitrogen and phosphorous).
• Municipal wastewater treatment, septic systems, and livestock waste also add nutrients to our natural water systems.

Salts disrupt the balance of salt in our water sources, particularly groundwater, and can corrode infrastructure and harm aquatic life.

• Salts come from salting our roads for ice.

Litter can choke, suffocate, or disable wildlife such as fish, ducks, and turtles.

• Litter comes from human carelessness and waste mismanagement.

Reducing Stormwater Impact

Changing our built environment and our personal and industrial practices are critical to reduce the volume and impact of stormwater. Stormwater affects on our water systems and our drinking water sources and ultimately points back to the effects of land-use activities.

Sources

United States Environmental Protection Agency (EPA). 2003. After the Storm.

United States Environmental Protection Agency (EPA). Source Water Protection Bulletin: Managing Stormwater Runoff to Prevent Contamination of Drinking Water.