Water quality results released for the Hay and Slave Rivers

News Releases

Yellowknife — September 11, 2020

Results of water quality monitoring conducted by the Department of Environment and Natural Resources in July indicate this year’s prolonged high water levels have resulted in more suspended sediment than usual in the Hay and Slave Rivers.

As a result of the increased sediment, many metals associated with silt and clay particles were also found at higher than usual concentrations in both rivers for July. In the Slave River, some concentrations of dissolved metals were also elevated, but most were within the range of what has been measured historically in the rivers.

It is normal to see increased metal concentrations due to high water, as particles along the river bed and shores are carried downstream. Under these conditions, nutrients such as phosphorus also accumulate in the suspended sediment. These spikes are observed every spring with snowmelt, and have been amplified this year due to long-lasting high water levels across most of the Mackenzie River Basin, including the Athabasca, Peace, Hay and Liard Rivers.

The Government of the Northwest Territories (GNWT) monitored water quality in the Slave River during the spring breakup and in both the Hay and Slave Rivers through the summer, with some delays beginning summer sampling due to the COVID-19 pandemic. Water quality results for samples collected in August from the Great Slave Lake plume as well as additional samples collected from the Hay and Slave Rivers for the analysis of hydrocarbons and pesticides will be released on the Environment and Natural Resources website as they are available.



“All summer we’ve been seeing extreme high water levels, not just in the Northwest Territories but throughout much of the Mackenzie Basin in British Columbia, Alberta and Saskatchewan. For example, water levels on the Athabasca River this year are among the highest ever recorded. High water levels have affected water quality. The water quality data being shared by upstream jurisdictions as part of our transboundary agreements can help us get a better understanding of what is happening in our lakes and rivers.”

- Shane Thompson, Minister of Environment and Natural Resources


Quick facts

  • The GNWT monitors water quality within the NWT, including at transboundary sites on the Slave, Hay, Liard and Peel rivers. Long-term monitoring provides a record of changes over time, and will help detect differences and trends in water quality.
  • Water quality is also measured upstream in Alberta and British Columbia by the provincial and federal governments (Environment and Climate Change Canada). While some water quality monitoring was temporarily suspended during the COVID-19 pandemic, most has now resumed.
  • An agreement was recently reached with Environment and Climate Change Canada for the GNWT to collect water samples on behalf of ECCC at four important transboundary sites near the Alberta-NWT border (Peace River at Peace Point, Slave River at Fitzgerald, Slave River above the Mouth and Hay River near the Alberta-NWT border). Samples were collected in August and are currently being analyzed.
  • The toxicity of a metal depends on the form in which it occurs. When a metal is attached to sediment in the water, it is less likely to be absorbed by aquatic organisms. Dissolved metals are more likely to affect aquatic organisms.
  • High turbidity in water can interfere with the disinfection process for drinking water. The Department of Health and Social Services issues boil water advisories when there is a risk that microbiological contamination may be present in the water supply. When out on the land, no matter how pristine the water, the water should always be boiled at a rolling boil for at least one complete minute to remove harmful microbes.

Related Links


For more information, please contact:

Public Affairs and Communications

Department of Environment and Natural Resources

Government of the Northwest Territories