Water Supply Outlook August 2009

Updated: August 14, 2009

Mountain runoff forecasts (natural volumes for March to September 2009)

Forecasts in most areas of the Oldman and Bow River basins have increased since July 1 due to much above normal precipitation. Exceptions are forecasts for Lake Minnewanka which decreased, and Bow River at Banff which decreased by a large amount. Forecasts for the Bighorn and Dickson Dam reservoir inflows and for the North Sakatchewan River at Edmonton also decreased.

Milk River basin Oldman River basin Bow River basin
  • Much below average, except below to much below average for the Highwood River and Lake Minnewanka and below average for the Elbow River. Banff is expected to record among the 6 lowest volumes on record.
  • Below to much below average for August to September, except below average for the Spray and Cascade Reservoirs and the Elbow and Highwood Rivers, and much below average for the Bow River at Banff
  • March - July recorded volumes much below average, except below to much below average for the Highwood River and Spray reservoir, and below average for the Elbow River and Lake Minnewanka. The Bow River at Banff was 2nd lowest in 91 years of record, and at Calgary and at the Kanaskis River volumes were 10th lowest.
Red Deer River basin
  • Much below average
  • Below average for August to September at Red Deer and below to much below average at Dickson Dam.
  • March - July recorded volumes much below average, 12th and 9th lowest on record at Red Deer and Dickson Dam, respectively
North Saskatchewan River basin
  • Much below average, among the ten lowest on record
  • Much below average August to September
  • March - July recorded volumes much below average, 3rd lowest on record (41 years) for Brazeau, 5th lowest in 91 years for Edmonton, and second lowest in 30 years for Bighorn

Precipitation can have a major impact on water supply between now and the end of September. The forecasts above assume that precipitation through the remainder of summer will be normal. The range of possible precipitation scenarios is large however, and as a result, probable range forecasts and a minimal precipitation forecast of natural runoff volume are also provided for each individual basin. Since more information becomes known over time, March-September volume forecast ranges will narrow. Streamflow volume forecasts are updated monthly from February to May, and again in July, and due to the dry conditions, this August report. Recorded 2009 volumes are preliminary and subject to change.

Check our Forecaster's Comments for updated information regarding runoff conditions.


Contoured maps of precipitation amounts and as a percent of normal for the past month and for current and recent seasons are available here. Maps of precipitation amounts for the most recent day, week and month to date are available here.

Soil Moisture

Alberta Agriculture models soil moisture for non-mountainous, agricultural areas of Alberta. Modelled soil moisture compared to average as of August 12, 2009 is available here.

Long Lead Precipitation Outlooks

Environment Canada (issued on August 1, 2009): temperature and precipitation for the August through October 2009 period:

  • below normal precipitation in the northeast corner of the province and in southern Alberta, normal to above normal in the northwest corner, and normal elsewhere in Alberta
  • above normal temperatures

National Oceanic and Atmospheric Administration (NOAA) (issued on July 16, 2009): below normal precipitation for southwestern Alberta and an even chance of below normal, normal or above normal precipitation for southestern Alberta, and an even chance of below normal, normal or above normal temperatures in southern Alberta, for August through October 2009.

Climate indicators: The NOAA reported on August 6, 2009 that El Nino conditions are expected to strengthen and last through the coming winter.

Note that forecasting weather for such a long time period into the future is very difficult, and so the historical accuracy has been variable, dependent on location and time period, and is often low, more so for precipitation than temperature. Environment Canada provides an assessment of their forecast method's historical accuracy on their website.

Reservoir storage

Water storage volumes in the major irrigation and hydroelectric reservoirs of the Milk, Oldman, Bow, Red Deer North Saskatchewan, and Athabasca River basins is updated each weekday and is available in the Provincial Reservoir Storage Summary.


Background information on the Water Supply Outlook is available in Frequently Asked Questions

Media Contact:
Communications Division, Alberta Environment
Phone: (780) 427-6267