High water levels caused more sediment in Hay and Slave rivers

The Northwest Territories government says this year’s prolonged high water levels have resulted in more suspended sediment that usual in the Hay and Slave rivers.

In a Friday press release, the Department of Environment and Natural Resources said its water quality monitoring found metals associated with silt and clay particles at higher than usual levels in both rivers in July. That included total arsenic, barium, cesium, chromium, iron, and zinc.

The government said while these spikes happen every spring when the snow melts, they have been amplified because of the high water levels across most of the Mackenzie River Basin this summer. It’s normal to see increases in metal concentrations when water levels are high, it said, as particles along the river bed and shores are carried downstream. 


According to the government, the metals are not likely to affect aquatic organisms as they’re attached to dirt in the water. In this form, it said, metals are not easily absorbed by fish and other aquatic life.

Levels of dissolved metals, which are more likely to affect aquatic organisms, were slightly elevated but within the normal range for these rivers.

The NWT’s chief environmental health officer issued a boil-water advisory for Hay River, Enterprise, Kakisa and the Kátł’odeeche First Nation on September 2. It’s one of several boil advisories that has been issued for the region throughout the summer.

The territorial government is responsible for monitoring transboundary waters to ensure upstream provinces don’t cause downstream effects in the NWT. Monitoring currently takes place on the Slave, Hay, Liard and Peel rivers. 

“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,” Minister Shane Thompson was quoted as saying.