Water Supply Outlook for Alberta

April 2005

Oldman River Basin - Water Supply Forecasts

As of April 1, 2005, natural runoff volumes for the March to September 2005 period are forecast to be below to much below average (Table 3).

Current forecasted values for the March to September 2005 period for the Oldman River at Lethbridge would rank 18th lowest in 91-years of record (1912-2001). Current natural runoff volume forecasts range from 68 to 79% of average. The March to September 2005 forecast volumes are 4% higher than those recorded during the same period last year for Brocket, and 1 to 13% lower than last year for the Belly, Waterton and St. Mary Rivers and for Lethbridge. The April forecasts are 2% lower than last month's for Brocket, 1 to 3% higher for the Belly, Waterton and St. Mary Rivers and similar to last month's for Lethbridge.

The first month of the forecast period has been completed, with March 2005 recorded natural runoff volumes ranging from 55 to 111% of average. Runoff was above average in the Belly River and at the Oldman Reservoir, below average to average in the Waterton River and at Lethbridge, and below to much below average in the St.Mary River. Recorded volume data is preliminary, due to ice effects, and is subject to change. March volumes typically comprise a small portion of the March to September total. The remaining volume forecast, which is the March to September 2005 forecast minus the recorded volume to date, is available in Table 3b.

Although snowpack in the area was severely depleted in January, future precipitation can still heavily influence the forecast runoff. If minimal precipitation occurs during the coming months, near record low volumes are possible. Conversely, above normal precipitation could yet result in average runoff volumes.

Also, reservoirs were able to store some of the early runoff volume in January, and as a result most are currently at above average levels.

For technical enquires about this web page please contact Alberta Environment - Environmental Management Water Management Operations Branch at AENV-WebWS@gov.ab.ca