Water Supply Outlook for Alberta

May 2005

Table 3b - Water Supply Forecast as of May 1, 2005 - Oldman River Basin (Natural Flows)

Volume Forecast for May 1 to September 30, 2005 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 2005 Volume as a % of Average Ranking (lowest to highest)
St. Mary River 484,000** 72 59-98 50 18/91 54*** 16/91
Belly River 165,000* 74 63-99 55 15/91 90*** 43/91
Waterton River 385,000* 70 58-97 51 17/91 75*** 32/91
Oldman River near Brocket 653,000* 68 54-104 49 21/91 85*** 40/91
Oldman River at Lethbridge 1,742,000* 66 52-92 46 18/91 64*** 24/91

*NOTE: The forecast shown is the March to September 2005 forecast minus the recorded volume to date

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** - This value is the natural volume and includes the U.S. share
*** - Recorded 2005 natural volumes are preliminary and subject to change Average is calculated for the period 1912 to 2001

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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