Water Supply Outlook for Alberta

May 2015

Water Supply Forecast as of May 1, 2015 - Oldman River Basin (Natural Flows)

Volume Forecast for May 1 to September 30, 2015 Year to date
Locations Volume in dam3 Volume as a % of Average Probable Range as a % of Average Reasonable Minimum as % of Average Forecast Ranking (lowest to highest) Recorded March-April 2015 Volume as a % of Average Ranking (lowest to highest)
St. Mary River 505,000** 85 75-95 66 22/99 181*** 92/99
Belly River 171,000* 82 94-110 88 19/99 166*** 96/99
Waterton River 394,000* 80 70-90 61 19/99 186*** 93/99
Oldman River near Brocket 667,000* 77 65-104 54 24/99 204*** 95/99
Oldman River at Lethbridge 1,858,000* 74 61-88 50 31/99 168*** 85/99

*NOTE: The forecast shown is the March to September 2015 forecast minus the recorded volume to date

** - This value is the natural volume and includes the U.S. share
*** - Recorded 2015 natural volumes are preliminary and subject to change
Average is calculated for the March 1 to September 30 period 1981 to 2009

NOTE: There is: a 50% chance that the actual natural flow will fall within the probable range given; a 25% chance that the actual flow will be less than the lower bound of the probable range given; and a 10% chance that the actual natural flow will be less than the reasonable minimum. Actual day to day streamflow conditions may vary throughout the season as a result of the effects of streamflow diversion and reservoir storage.


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