Pollution

Water quality in the Bow River varies greatly. Generally, the lower stretches of the system tend to be more degraded than those closer to the headwaters.

The Headwaters

Water quality in the upper Bow River is relatively good. However water at the headwaters of the Bow River is not pristine. Samples taken at the headwaters contain pesticides and persistent organic pollutants such as PCBs and DDT — these contaminants are also found in the resident fish. These pollutants leach into Bow Lake from glaciers that contain a legacy of long-range atmospheric transport of pollution from around the world.

Water quality above Lake Louise is generally excellent but that has not always been the case for the water below Lake Louise. Historically, the water quality between Lake Louise and Canmore was "degraded" due to poor sewage treatment. Over the years, however, water quality in this stretch of river has improved as a result of sewage treatment upgrades in the towns of Lake Louise, Banff, and Canmore.

But these improvements may not be enough. The Bow River is "nutrient limited" which means that the addition of even small quantities of nutrients (such as phosphorus) can negatively impact the health of the river. Higher levels of nutrients encourage the growth of algae. The decomposition of algae depletes oxygen supplies in the river, and puts pressure on fish populations.

Additionally, new municipal developments, increased populations, golf courses, and increased water withdrawals are potential future stresses on water quality.

Calgary's State-of-the-art Sewage Treatment

The City of Calgary has a state-of-the-art sewage treatment plant that serves as a model nationwide. Despite this high level of treatment, growth in Calgary has put significant pressure on the river. Even the best water treatment plants still do release pollution into the river, and when water quantity in the river is low, the capacity of the Bow River to assimilate the treated effluent is compromised.

Untreated Runoff from Cities and Farms

Urban development increases the volume of pollution running off into the river. This pollution - called "storm water runoff" - is comprised of grime from our automobiles and roads. Storm water runoff can be captured and treated, but in many municipalities some, or even most, storm water runoff enters rivers untreated.

Some of the more significant sources of pollution on the Bow River are storm water from Calgary and runoff from sources such as agriculture and livestock operations. The growth of the cattle industry in the past 25 years has tripled the number of farm acres on which pesticides and fertilizers are used.Metals, salts, pesticides, and disease-carrying organisms all flow into our river untreated.

Each year, nearly 11.4 million kilograms of waste (including 768,000 kg of iron, 219 kg of aluminum, 33,800 kg of phosphorus, and 16,200 kg of lead) is washed into the Bow from Calgary storm sewers.

Presently, runoff from lawns, golf courses, agriculture and livestock operations, leaking septic tanks, and other developments all deteriorate water quality in the Bow River.