River Report #12 - Precipitation Welcome, But Dry Conditions Forecast to Return
The low streamflows seen on the South Saskatchewan River at Medicine Hat on Wednesday should see a significant recovery starting Thursday with streamflows in the 200 cubic metres per second range. (Photo Alex McCuaig)
The Oldman and South Saskatchewan river basins continue to be in a severe hydrological drought but they’ve seen relief as widespread rains continue to fall in the region.
The South Saskatchewan River at Medicine Hat briefly fell below the instream objective of 42.5 cubic metres a second (m³/s) on Tuesday but bounced back with a strong recovery by Thursday. Streamflows at the Hat are anticipated to continue rise as the Bow River at the forks rose from 17 m³/s on Monday to approaching 200 m³/s mid-day Thursday.
The Oldman River has also seen substantial rainfall accumulations this week but not enough to see substantial improvement of streamflows at Lethbridge. Those streamflows are into a third year of highly managed levels to support the Oldman Reservoir’s recovery that has yet to bounce back from the 2023 drought.
Some localized areas in the southwestern portion of the province near Pincher Creek reported up to 120 mm of precipitation while much of the southern portion of the province saw accumulations of 35 mm or more earlier this week.
The rainfall has again come during a particularly timely fashion as levels at the Oldman Reservoir have dropped below 60 per cent capacity and dryland soil moisture levels had been drying up in the southern portion of the province.
Despite the recent rains, dryland crops and pastures in Cypress County surrounding Medicine Hat haven’t fared well.
“Recent rains came too late for many farmers and Cypress County has now declared a local state of agricultural disaster for the fourth time in the past five years,” read a media release posted by the rural municipality on Tuesday.
However, many cereal crops in the southern region continue to develop ahead of long-term averages.
(Graphic courtesy of Alberta Environment)
Alberta Environment’s July water supply outlook report is forecasting continuing below normal conditions heading into the next few months.
“Observed river flows thus far this season rank on average 10th lowest out of 99 years for the Red Deer, Bow, Oldman, and Milk river basins,” read the report regarding southern Alberta. “Summer precipitation thus far (May to June) is below normal to well below normal across most regions of the province.”
Some notable exceptions include the Special Areas around Oyen where seasonal precipitation is well above normal.
But the report notes a high likelihood for below normal precipitation for the next three months across southern and central Alberta based on Environment Canada forecasts.
Eastern Irrigation District’s Lake Newell continues to report normal seasonal levels with the Bow River Irrigation District’s largest reservoirs also in good shape. However, the Bow River basin continues to be rated at Stage 2, moderate drought, on the provincial five-stage drought scale.
St. Mary River Irrigation District and Lethbridge Northern Irrigation District are continuing to see challenges though recent rains are anticipated to moderate the situation.
Scattered showers are forecast across southern Alberta going into the weekend.
A irrigation pivot remains turned off at a Medicine Hat city corn field following recent rains. (Photo Alex McCuaig)
Statistics for the South Saskatchewan River at Medicine Hat for July 17
Upper quartile – 378 m³/s
Lower quartile –133 m³/s
July 17, 2024 – 156 m³/s
July 17, 2025 – 98 m³/s
Statistic for the Oldman River at Lethbridge for July 17
Upper quartile – 128 m³/s
Lower quartile – 33 m³/s
July 17, 2024 – 26 m³/s
July 17, 2025 – 98 m³/s
Statistics for the Bow River at Calgary for July 10
Upper quartile – 221 m³/s
Lower quartile – 135 m³/s
July 17, 2024 – 192 m³/s
July 17, 2025 – 162 m³/s
*Upper and lower quartile averages are based on data collected between 1911 and 2024.
Oldman Reservoir for July 17 level (metres above sea level)
Upper quartile – 1117.952 m
Lower quartile – 1116.514 m
July 17, 2024 – 1116.485 m
July 17, 2025 – 1107.783 m