Water Supply Outlook for Alberta

May 2002

Table 3b - Water Supply Forecast as of May 1, 2002 - 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 2002 Volume as a % of Average Ranking (lowest to highest)
St. Mary River 679,000** 100 75-122 64 46/84 54*** 14/84
Belly River 199,000* 89 65-113 60 27/84 112*** 57/84
Waterton River 568,000* 96 67-115 53 38/84 60*** 17/84
Oldman River near Brocket 808,000* 83 57-120 49 30/84 52*** 9/84
Oldman River at Lethbridge 2,312,000* 88 60-111 51 35/84 57*** 15/84

*NOTE: The forecast shown is the March to September 2002 forecast minus the recorded volume to date

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** - This value is the natural volume and includes the U.S. share
*** - Recorded 2002 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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