Lac St. Cyr Water Quality Assessment

Lac St. Cyr is 16 km southeast of the Town of St. Paul in the Frog sub‐watershed, a hydrological component of the larger North Saskatchewan River (NSR) watershed. The Town of St. Paul has withdrawn its raw drinking water supply from Lac St. Cyr since 1951. Lake levels declined by approximately two metres between 1959 and 1971 due to increased water demand.

In 1978, Alberta Environment and Sustainable Resource Development allowed raw water diversion from the NSR into the lake over winter. This diversion continues to present.

Initially, nutrient levels in the lake increased to a eutrophic level due to the river diversion, but over time the levels have declined due to improvements in river water quality. The lake has returned to a mesotrophic level of productivity.
Trace organics and metal concentrations did not appear to be a concern within the lake; however the data record ended in 2000. New research on the NSR between 2004 and 2009 has revealed that pharmaceuticals and personal care product residues are now detectable in the river, and are presumably also present in the lake. The long‐term effects of these compounds is unknown at this point, but their presence is worthy of further investigation.

Students at King’s College University calibrated a lake water quality model (BATHTUB) as a research project during the winter semester 2013. The model is now available to support future management discussions regarding increased diversions from the NSR and any land management changes for the watershed.

Lac St. Cyr Water Quality Assessment Report

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