Lake Diefenbaker Updates
Lake Diefenbaker Updates
Updated September 10, 2026
Current Conditions
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Flows in the Oldman River basin increased following rainfall received last weekend. Flows are generally between median and upper quartile levels for this time of year and have begun to recede.
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Flows in the Bow and Red Deer River basins remain near lower quartile levels for this time of year.
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The rainfall received in the headwaters was less than forecast in last week’s update. As a result, inflows into Lake Diefenbaker are now expected to peak at approximately 229 m³/s on September 12, lower than previously forecast, before gradually declining. The forecast peak remains above the upper quartile for this time of year.
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Lake Diefenbaker water levels are currently below the seasonal median but remain within the historical interquartile range.
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Conditions will continue to be monitored closely, and outflows may be adjusted as needed based on updated forecasts and observed basin conditions
Forecast Overview
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Inflows into Lake Diefenbaker are expected to peak near 230 m³/s on September 12, before gradually declining to approximately 150 m³/s by the end of the forecast period.
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Daily mean outflows are expected to remain steady at approximately 130 m³/s throughout the forecast period.
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Lake Diefenbaker levels are expected to gradually increase from approximately 555.48 m to 555.58 m over the forecast period.
Note: Flows shown in the table above are mean (average) daily flows. Actual releases from Lake Diefenbaker may fluctuate throughout the day as SaskPower adjusts operations at Coteau Creek Hydro Station to meet the Province’s electricity demands.
Hydrologic / Weather Conditions
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Most areas in the mountain headwaters received approximately 10 to 35 mm of rainfall, with localized amounts of approximately 30 to 40 mm in the southern portion.
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Approximately 10 to 30 mm of precipitation is forecast for the southern portion of the mountain headwaters over the next 3 days. This precipitation may increase flows in the Bow and Oldman river basins, depending on the location and intensity of the rainfall.
Below are the updated plots showing 2026 observed inflows and reservoir elevations compared to historical ranges.
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