Water Quality in the Great Lakes: How It Affects Our Drinking Water

The Great Lakes are an abundant source of freshwater

The Great Lakes are a vast system of five interconnected lakes that stretch from west of Thunder Bay, Ontario to the Atlantic Ocean. Although the lakes contain an abundance of fresh water, this huge resource is threatened by human activity and pollution. Reports of “boil water advisories,” closed beaches, toxic algae, and high mercury levels in fish make it important to ask if drinking water from the Great Lakes is safe?

The lakes provide fresh drinking water for the 34 million people who call its shores home, including about 32% of the population of Canada. The Great Lakes also hold almost 6 quadrillion gallons of water, which is one fifth of the fresh water on the planet. 

Water Quality in the Great Lakes

The Great Lakes Consist of:

  • Lake Superior - The largest, coldest, and deepest, Lake Superior contains 10% of the world’s surface water—an amount that could cover the entirety of North and South America under one foot of water!
  • Lake Huron - Second largest of the lakes by surface area, Lake Huron also contains Manitoulin Island, the world’s largest freshwater island and site of more than 1,000 shipwrecks. (It was coined “the sweet sea” by early French explorers due to its pristine fresh water.)
  • Lake Michigan - The third largest Great Lake and the only one entirely contained within the United States.
  • Lake Erie - The fourth largest lake but shallowest with an average depth of 62 metres.
  • Lake Ontario - The smallest in terms of surface area, but more than one-quarter of Canada’s population lives along its shores.

The Great Lakes support diverse and unique ecosystems

The lakes connect Canada to the United States and (except for Lake Michigan) provide a natural border between the two countries. Known for their beautiful sandy beaches and wetlands (and an abundance of water activities and fishing opportunities), more than 3,500 species of plants and animals and over 170 types of fish live in their waters. They also provide hydro-electricity, transportation, and manufacturing and agriculture support. The Great Lakes are vital to our health, economy, and way of life; we must protect them to ensure safe drinking water for decades to come.

Over 34 million people depend on the Great Lakes for drinking water

What’s in the Water?

The Great Lakes are an incredible resource to those that live on their shores. Unfortunately, the last 200 years have introduced toxic chemicals, pollutants, and invasive species that continue to put the lakes at risk. In the 1960s, pollution was so bad that a Cleveland newspaper declared, “Lake Erie is dead!” because of the high levels of toxic industrial and agricultural sewage that had flowed into its waters.

Since then, conditions have improved as a result of governments and industries working alongside communities to protect the lakes. However, development and expanding infrastructure continue to severely impact the water and have resulted in:

  • Closed beaches due to harmful levels of bacteria.
  • Boil-water advisories for communities that rely on the Great Lakes for their drinking water.
  • Clogged intake pipes (as a result of toxic algae) that makes beaches unsafe for swimming.
  • Introduction of invasive species (such as zebra mussels and Asian carp) that threaten native organisms.
  • Fresh fish that are unsafe to eat because of dangerous levels of mercury and other chemicals.
  • A “dead zone” in Lake Erie that forms each summer when cold water at the bottom of the lake separates from warmer surface water. Oxygen from the top layer can’t penetrate, trapping organisms in the lower layer; as they decay, they use more oxygen. Fertilizers and nitrogen from agricultural runoff have also increased the size and severity of the dead zone.

Human activity threatens the state of the Great Lakes

Current State of the Great Lakes

The State of the Great Lakes report (created in 2017 by Canada and the U.S. as part of the Great Lakes Water Quality Agreement) is a commitment to work together to restore and protect the water quality and aquatic ecosystem of the lakes. The report gives an overview of the current water conditions using nine indicators of ecosystem health, with data collected from 180 government and non-government scientists. Research shows the following:

  • If treated, Great Lakes water is safe to drink.
  • Some beaches are unsafe for swimming due to bacterial contamination.
  • Due to known contaminants in certain types of fish, recommended limits on seafood consumption have been created to reduce the risk of exposure.
  • The lakes are generally free from pollutants at levels deemed harmful to humans and the environment, but some pollutants in local areas contain unhealthy concentrations.
  • Nutrient loadings in Lake Erie (and some nearshore areas of Lakes Huron, Michigan, and Ontario) cause severe impact due to the formation of toxic algae.
  • While the introduction of new non-native species has declined, the spread of aquatic invasive species in the lakes continues.

Largest Threats to the Water in the Great Lakes

  • Untreated sewage - Many communities around the Great Lakes dump untreated sewage into the water. A 2018 report found that in one year alone, 20 cities in the U.S. and Canada allowed 92 billion gallons of untreated sewage and storm water to flow into the lakes.
  • Phosphorus runoff from farms and fields - After a rainstorm, phosphorus and nitrogen (both found in agricultural fertilizers) wash off fields and enter the lakes. These contribute to the algae blooms by increasing the nutrients in the water, making the algae grow to dangerous levels and threatening other species.

Water treatment plants struggle to keep up during heavy storms

  • Storm water runoff - Strong, heavy rains cause problems for treatment plants that may not be able to manage high levels of water; untreated excess water gets released into the lakes.
  • Zebra and quagga mussels - These invasive species have spread from Lake St. Clair and Lake Erie into all the lakes. They are thought to come from the Black and Caspian Seas through ballast water released from cargo ships.

Lake Ontario is one of the most vulnerable bodies of water

Is Your Drinking Water Safe?

Millions of people rely on the Great Lakes for their drinking water, which is considered safe if filtered properly. The city of Toronto treats over 1 billion litres of drinking water every day. That water is collected from Lake Ontario through intake pipes deep below the surface and at least 1 km from the shore. First, it passes through multiple screens and filters and is disinfected with chlorine or ozone. To remove suspended impurities and bacteria, it goes through gravel and sand filters. Other chemicals are then added:

  • Chlorine (destroys bacteria and viruses)
  • Ammonia (keeps chlorine levels consistent)
  • Phosphoric acid (creates a barrier between the water and any lead in the pipes)
  • Fluoride (prevents tooth decay)

The taste of chlorine (or other chemicals) in tap water can be off-putting. A home water filter system can remove those impurities without losing the healthy minerals that your water provides.

The Great Lakes are an abundant source of fresh drinking water; with proper treatment, that water is safe to enjoy. At Efilters.net, our experts provide high-quality water filtration systems for your home or business. Give us a call at 1(866) 283-9919. We’ll help you find the best filtration system for your water treatment needs.