U of S researchers explore the health of Lake Diefenbaker

Researchers from the University of Saskatchewan have released findings on the health of Lake Diefenbaker that identify water flowing in from the South Saskatchewan River as the principal factor affecting the lake’s water quality.

The researchers contributed to a special issue of the Journal of Great Lakes Research that showed what happens upstream has the most impact on the reservoir’s water quality.

The special issue’s 15 articles—contributed by researchers from the U of S College of Arts & Science, the School of Environment and Sustainability, the Global Institute for Water Security (GIWS) and the Toxicology Centre—examine the physical, chemical and biological properties of Lake Diefenbaker and assess the reservoir’s susceptibility to increasing stress.

“Lake Diefenbaker is an important source of drinking water, irrigation, hydroelectricity and recreation for the province, yet we had little baseline knowledge or historical data on the reservoir as a whole when it comes to ecosystem health,” said Rebecca North, GIWS research associate and one of the guest editors working on the issue. “Our goal was to understand how the reservoir has changed since its formation and identify stressors affecting its water quality.”

The researchers found that while there has been public concern about the potential for declining Lake Diefenbaker water quality, especially related to surface algal blooms, they found little evidence that supported this perception.

“Algal blooms do occur in a portion of the reservoir—the Qu’Appelle arm—but in the rest of the lake, blooms are generally infrequent and even less frequent than other lakes with similar nutrient concentrations,” said North.

More than half of the papers in the special issue identified changes in hydrology as a principle factor affecting water quality.

“We are predicting that the risk of algal blooms may be more prevalent during years of lower water flow, which we will continue studying in order to fully understand the factors affecting the water quality of Lake Diefenbaker,” said North.

North added that for Lake Diefenbaker, it is the upstream activities and precipitation patterns in the Saskatchewan River basin that primarily dictate what happens to the flow levels and the potential for algal blooms. For example, one study released in the special issue shows that the South Saskatchewan River is a major source of phosphorus flowing into and settling in the reservoir. The majority of phosphorus coming into Lake Diefenbaker is not leaving it.

The institute’s findings suggest that land management practices and efforts to reduce nutrient input should be focused at sites upstream to Lake Diefenbaker, in addition to managing activities along its shorelines.

The Lake Diefenbaker program represents a major research effort initiated by U of S researchers in collaboration with the Saskatchewan Water Security Agency and scientists from the Universities of Regina, Waterloo, Minnesota and Oregon.

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