River Report #15 – Growing season nears end, harvest begins in southern Alberta
The South Saskatchewan River at Medicine Hat running at 124 cubic metres a second on Aug. 26. (Photo Alex McCuaig)
It’s been a rollercoaster of a season for southern Alberta rivers with historic low streamflows in June rebounding by the end of July and into August with above normal levels.
And irrigation reservoir levels across the region appear to be in good shape with nearly all of them at normal seasonal capacity, if not better, heading into the tail end of the growing season and beginning of harvest.
The exception, as it has been for much of the past two years, is the Oldman reservoir.
Despite timely and even heavy rains hitting the Eastern Slopes since the spring, the reservoir hasn’t reached a level that has allowed the Municipal District of Pincher Creek to remove its Stage 1 water restrictions.
In April, the Lethbridge Northern Irrigation District announced its goal to see the Oldman reservoir be at 55 per cent capacity by the end of the irrigation season.
With about two months left before the taps are turned off, the province’s largest irrigation reservoir is sitting at 63.5 per cent capacity.
The Oldman River downstream of the reservoir is feeling the pinch with streamflows at Lethbridge skirting a little above the 20 cubic metre as second level.
Environment Canada hydrometric water level data for the Oldman reservoir from Jan. 1, 2024 to Aug. 27, 2025. Levels at the reservoir recovered from near historic lows at the end of 2023 by July 2024 but have yet to sustain levels above the lower quartile since then.
But the water basin has seen improvement from earlier in the season and is currently at the provincial Stage 1, abnormally dry, drought rating.
The Bow basin continues to be rated as having adequate water supplies while the situation along the South Saskatchewan River basin continues to be rated at Stage 3, severe drought, despite the most recent provincial river forecast rating river conditions at normal.
Southern Alberta crops and pastures – both irrigated and dryland – appear to have fared well this season except for Cypress County which declared an agricultural disaster earlier this year. The other notable exception was the 350,000 acres across a 400-kilometre swath of farmland running from south of Bassano to near the Saskatchewan border plowed down by baseball-sized hail last weekend.
The latest and last provincial crop report for August released on Friday is rating conditions in the south region crop conditions to be well above the five-year average for this time of year.
Sub-surface moisture levels across the region are rated 80 per cent in either fair or good condition. Second cut dryland hay is at 60 per cent harvested while irrigated second cut is at more than 70 per cent. Yields are 1.2 tons and 2.1 tons per acre respectively.
Major crop yields estimates are also improving and are expected to be better than both five- and ten-year averages in southern Alberta.
Harvesting of fall seeded crops is well underway along with pulse crops.
Statistics for the South Saskatchewan River at Medicine Hat for Aug. 29
Upper quartile – 170 m³/s
Lower quartile – 63 m³/s
Aug. 29, 2024 – 92 m³/s
Aug. 29, 2025 – 107 m³/s
Statistic for the Oldman River at Lethbridge for Aug. 29
Upper quartile – 45 m³/s
Lower quartile – 14 m³/s
Aug. 29, 2024 – 20 m³/s
Aug. 29, 2025 – 22 m³/s
Statistics for the Bow River at Calgary for Aug. 29
Upper quartile – 119 m³/s
Lower quartile – 80 m³/s
Aug. 29, 2024 – 98 m³/s
Aug. 29, 2025 – 78 m³/s
*Upper and lower quartile averages are based on data collected between 1911 and 2024.
Oldman Reservoir for Aug. 29 level (metres above sea level)
Upper quartile – 1115.312 m
Lower quartile – 1111.443 m
Aug. 29, 2024 – 1110.735 m
Aug. 29, 2025 – 1109.497 m
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Past River Reports