Water levels on Chestermere Lake are returning to normal after an upstream oil spill prompted the temporary shutdown of water entering the lake over the weekend.
The City of Chestermere said inflows were stopped Saturday, July 25, as a precaution while containment and cleanup work was carried out within the Western Irrigation District’s canal system.
According to information available to the City, the oil did not reach Chestermere Lake.
The Western Irrigation District has since reopened the canal, allowing water to once again enter the lake and levels to begin recovering.
For residents watching the shoreline, the temporary drop was a visible reminder that Chestermere Lake is part of a much larger water-management system stretching from Calgary into agricultural areas east of the city.
When the inflow was closed Saturday, water continued moving out of Chestermere Lake through the irrigation system. With no replacement water entering from upstream, lake levels temporarily declined.
That relationship is part of the normal operation of Chestermere Lake, which functions not only as the recreational centrepiece of the community but also as an important reservoir within the Western Irrigation District system.
Water for the district is diverted from the Bow River at Harvie Passage in Calgary and travels east through the Western Headworks Canal before reaching Chestermere. From the lake, water continues through a network of canals, pipelines and reservoirs serving agricultural and other water users farther east.
The Western Irrigation District normally operates its water-delivery system from the beginning of May until the end of September, with water levels and flows managed throughout the season.
That interconnected system also means events occurring upstream can sometimes require operational changes in Chestermere even when the lake itself is not directly affected.
In this case, the City said shutting off the inflow was a precautionary step while crews dealt with the spill elsewhere in the canal system.
The City has been supporting the response alongside the Western Irrigation District and emergency services partners. However, officials said the irrigation district is leading the cleanup and investigation because the incident occurred within its infrastructure.
No information provided by the City identified the source of the oil or what caused the spill. Questions surrounding the origin of the spill, the investigation and the cleanup are being handled by the Western Irrigation District.
That distinction is important for residents concerned about what happened upstream. Based on the information released by the City, there is no indication that oil entered Chestermere Lake itself.
The immediate local effect was instead a temporary change in water level caused by stopping the inflow while water continued leaving the lake.
With the canal reopened, that imbalance has ended and lake levels are recovering as normal operations resume.
The City said it will continue monitoring conditions and will provide further information should circumstances change or additional impacts to Chestermere residents be identified.
For now, the incident appears to have resulted in a short-term operational impact on the lake rather than contamination of the lake itself, based on the information currently available.