Water Supply Outlook for Alberta

May 2003

Table 3b - Water Supply Forecast as of May 1, 2003 - Oldman River Basin (Natural Flows)

Volume Forecast for May 1 to September 30 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 2003 Volume as a % of Average Ranking (lowest to highest)
St. Mary River 481,000** 71 56-92 53 16/85 124*** 64/85
Belly River 171,000* 77 53-105 48 16/85 139*** 73/85
Waterton River 437,000* 73 60-109 58 19/85 107*** 53/85
Oldman River near Brocket 744,000* 76 55-103 45 23/85 121*** 60/85
Oldman River at Lethbridge 1,816,000* 69 50-92 44 17/85 128*** 69/85

*NOTE: The forecast shown is the March to September 2003 forecast minus the recorded volume to date

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** - This value is the natural volume and includes the U.S. share
*** - Recorded 2003 natural volumes are preliminary and subject to change
Average is calculated for the period 1912 to 1995

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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