Water Supply Outlook for Alberta

April 2005

Mountain Water Supply Forecast Summary

As of April 1, 2005, natural runoff volumes are forecast to be below to much below average for the Milk and Oldman River basins, below average to average for the Bow River basin, and near average for the Red Deer and North Saskatchewan River basins for the March to September 2005 period (Table 1). Forecasts are for higher volumes than during the same time period last year in the North Saskatchewan, Red Deer, and Milk River basins and in most of the Bow River basin, but lower than last year in most of the Oldman River basin. Forecasts are similar to or slightly lower than last month's forecasts for most basins due to below average precipitation in the mountains during March, but slightly higher for the Waterton, Belly and St. Mary Rivers.

Natural flow volumes were above normal in most mountain-fed rivers during March, due mainly to an early start to snowmelt this year. As a result of prior depletion of the snowpack from January melting in the Oldman and Milk River basins, and below normal March precipitation, natural runoff volumes during March were generally below average to average in the Oldman River basin, and much below average in the Milk River basin. March volumes typically comprise a small portion of the March to September total, ranging from 15% for the Milk River basin to less than 5% for the other major basins.

April 1, 2005 mountain snow accumulations are generally much below average in the Oldman River basin. Mountain snowpack conditions elsewhere are generally below average in the Bow River basin, average in the North Saskatchewan River basin, and above average in the Red Deer River basin.

Although snowpack in the Oldman and Milk River basins was severely depleted in January, future precipitation can still heavily influence the March-September forecast runoff. The forecasts described above assume that precipitation over the summer period will be normal. However, if minimal precipitation occurs during the coming months, near record low volumes are possible. Conversely, above normal precipitation could yet result in near average runoff volumes. Also, reservoirs were able to store some of the early runoff volume in January, and most are currently at above average levels.

Future precipitation could have a major impact on all the water supply forecasts between now and the end of September. Streamflow volume forecasts will be updated monthly until mid-summer. Check our Forecaster's Comments throughout the month for updated information regarding runoff conditions.

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