Okanagan Lake is not going to turn into an ocean-like salty body of water anytime soon.
But recent chloride measurements at various points along the lake taken by the Ministry of Environment do indicate an upward trend.
And while the Okanagan Basin Water Board (OKWB) has no imminent concerns about the current threat the lake water getting saltier poses on aquatic life or drinking water, it remains on its monitoring radar.
“It is trending up but that is partly because of the increase in the number of people living (in the valley),” said Corinne Jackson, communications director for the OKWB.
In 1973, the chloride level was 1.5 milligrams/litre (mg/L) in Okanagan Lake. Last fall, almost 50 years later, that reading came in at 5.73 mg/L.
The threshold of concern for aquatic life in Okanagan Lake would be to exceed 150 mg/L, for drinking water it would be 250 mg/L. As a comparison, the chloride content of ocean-water is about 19,400 mg/L.
Jackson said salinity levels of the lake are a key reason why the OKWB encourages both the City of Kelowna and property owners to avoid using road salt.
The city prioritizes the use of sand, followed by calcium chloride, before reverting to road salt to keep roadways drive-able when winter snow storms occur.
She said the road and driveway runoff salt migrates into storm drains eventually and flows directly into the lake.
“The same thought goes into encouraging people not to use chemical fertilizers in the summer because of the runoff, and instead use natural compost or other natural products,” she said.
“All pollutants getting into the lake are a concern.”
She said the road salt issue is an ongoing concern in Ontario, where road salt is commonly used for roads and sidewalks.
“Unfortunately, salt has some real negative effects on the environment that are all too often ignored for the sake of how well it works,” stated a report from Lake Ontario Waterkeeper, a group started in 2001 in response to environmental impact concerns affecting the Lake Ontario Watershed.
“It’s the chloride ions that’s the real problem. Health Canada estimates that five per cent of aquatic species would be affected (median lethal concentration) at chloride concentrations of about 210 mg/L, and 10 per cent would be affected at chloride concentrations of about 240 mg/L.”
UBC Okanagan did a provincially funded study of endocrine disruptors, such as dioxins and various pesticide products, in Okanagan Lake several years ago.
The study found treated waste water in the North Okanagan exposed to another natural filtration process, such as being sprayed on golf courses, helped reduce the endocrine content while in the Central Okanagan the lake depth and water volume negated the issue.
In the South Okanagan, because the lake feeds into the salmon spawning Okanagan River, a project was initiated to create a wetland to allow treated water to filter through it before accessing the river.
The OBWB has partnered with Larrat Aquatic to create a webpage with the chloride and other chemical element contents of Okanagan Lake at multiple water test measurement points from Vernon to Osoyoos.
Recent readings show a 5.73 mg/L near Bennett Bridge; 5.5 mg/L on the Okanagan River channel at Penticton; and 6.73 mg/L on Osoyoos Lake.
The webpage can be found at https://www.obwb.ca/wqdb/.
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