HRM staff revising saltwater plan amid high levels of chloride in freshwater lakes

A report from a local organization shows that “most lakes” around Halifax Regional Municipality are suffering from consistently high salt levels, posing a threat to freshwater ecosystems.

In the 2022-23 LakeWatchers report discussed at city council on Nov. 12, researchers found chloride (salt) levels in 17 of 73 lakes in Halifax are approaching or exceeding levels set under the Canadian Water Quality Guidelines. The policy sets out that samples of water deep within lakes should not reach a chloride concentration of over 120 milligrams per litre (mg/l) of water.

Some of those bodies of water include Lovetts Lake, Lake Banook and Lake Micmac.

Lakes around Halifax are salty in part from de-icing and anti-icing processes used in winter to help break down snow-covered roads. The compounds used — sodium chloride (NaCl) —  melts ice and dissolves into stormwater systems or becomes runoff into lakes.

“This has the effect of increasing concentrations of chloride in lakes beyond their naturally occurring levels,” the report to HRM council reads.

Higher levels of chloride, or salinization, can make the lake saltier over time, which can result in a loss of biodiversity due to the difficulty of organisms in freshwater lakes, such as fish, plants and plankton to adapt.

Ambient chloride concentrations in freshwater lakes within the Atlantic region, including Nova Scotia, are normally less than 10 mg/L for inland lakes, with concentrations as high as 20 to 40 mg/L in lakes located closer to coastal areas, HRM staff note.

As a result of the LakeWatches report, council has directed the Chief Administrative Officer to review the municipality’s saltwater management plan and explore areas where setbacks for stormwater discharge locations can be implemented.