River Report #8 - High Streamflow Advisory Issued Across Southern Alberta
The South Saskatchewan River at Medicine Hat on Thursday June 19. A high streamflow advisory has been issued by the province as a heavy rain is expected to see river levels rise by as much as two metres over the weekend. (Photo Alex McCuaig)
Rain is expected across southern Alberta over the weekend, and it certainly meets all definitions of timely if the forecast amounts come through.
Those amounts have resulted in the province issuing a general high streamflow advisory for the Oldman, Bow and South Saskatchewan rivers which will impact the communities of Lethbridge, Calgary and Medicine Hat.
Warnings have also been issued for the Red Deer River upstream of Dickson Dam as well as the Little Red Deer basin.
While no major flooding is anticipated, Albertans are being warned that river levels could rise rapidly by one to two metres. Log jams caused by the sudden rise could see levels increase rapidly if they release. Anyone situated close to river tributaries and streams are being advised to take caution.
Barring too much precipitation falling too fast, the situation could boost the outlook for both crops and river health.
An early completion of seeding this year followed by corresponding early emergence has now resulted in advanced development for this time of year, requiring a good soaking to keep the crops growing and to keep irrigation to a minimum to support river levels.
“Despite the favourable emergence rates and crop development progress, the current limited soil moisture is not supportive, particularly in advanced crops where deeper soil moisture reserves are needed,” stated the latest Alberta Ag crop report. “Reports indicate that precipitation is anticipated across most of the province prior to the release of the next report.”
An irrigated corn crop in Medicine Hat showing good development. (Photo Alex McCuaig)
Rivers across southern Alberta have seen record lows in June and on the anniversary dates of flooding in 1995, 2005 and culminating with record highs seen in 2013.
The Oldman River basin is reported to be in a Stage 3, severe drought, with the Bow basin in Stage 2, moderate drought. The South Saskatchewan basin is in Stage 1, abnormally dry.
While the short-term outlook is promising with precipitation expected to move into the province on Friday and continue through the weekend, Alberta Environment’s June Water Supply Outlook is predicting some tough times ahead.
“Much below average to below average May precipitation in southern Alberta combined with a relatively early mountain snowmelt runoff resulted in the classifications for the majority of these water supply forecasts to remain or become much below average for the March to September forecast period,” according to the provincial report.
The Oldman Reservoir has seen levels start to drop in the past week while streamflows through Lethbridge and Medicine Hat have regained some higher levels, at worst, maintained a status quo compared to the beginning of June. Reservoir levels have dropped by four percent over the past dozen days.
Levels at the Oldman Reservoir will impact its connected irrigation waterbody at Keho.
Other irrigation reservoirs are at or near normal seasonal averages.
The Medicine Hat Owl will have the latest information on severe impacts of associated with the high streamflow advisory and any advancement of the alert status.
The confluence of the Ross, Seven Persons creeks and South Saskatchewan River on June 19, 2025. (Photo Alex McCuaig)