Water Supply Outlook April 2012

Updated: April 12, 2012

Mountain runoff forecasts (natural volumes for March to September 2012)

Forecasts have remained the same for the Bow River basin and decreased for the North Saskatchewan River basin. Forecasts have increased for the Milk, Oldman and Red Deer River basins since March 1.

Milk River basin Oldman River basin
  • Average
  • Average for April to September
  • March recorded volumes are much below average for the St. Mary, Oldman River at Brocket, and the Oldman River near Lethbridge; and average to above average for the Waterton River and Belly River
Bow River basin
  • Average to slightly above average
  • Average to slightly above average for April to September
  • March recorded volumes are average for the Bow River at Banff and Spray River near Banff; slightly above average for the Kananaskis River, Bow River at Calgary and the Elbow River; below average for the Cascade Reservoir and the Highwood River
Red Deer River basin North Saskatchewan River basin
  • Slightly above average for the Brazeau Reservoir, average for the Bighorn Reservoir and the North Saskatchewan River at Edmonton
  • Slightly above average for the Brazeau Reservoir, average for the Bighorn Reservoir and the North Saskatchewan River at Edmonton for April to September
  • March recorded volumes much below average for the Brazeau reservoir, much above average for the Bighorn reservoir, and below average for the North Saskatchewan River at Edmonton

Precipitation can have a major impact on water supply between now and the end of September. The forecasts above assume that precipitation over the remainder of the winter period and through the 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, forecast ranges will narrow. Streamflow volume forecasts are updated monthly from February to May, and again in July.

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

Mountain snowpack

Snow accumulations measured in the mountains as of April 1, 2012: Mountain snow accumulation percent of averages continue to rise in the Bow, Red Deer, North Saskatchewan, Athabasca and Oldman River basins.

  • Oldman River basin: Average to much above average.
  • Bow River basin: Above average to much above average.
  • Red Deer, North Saskatchewan, Athabasca River basins: In general, above average to much above average in all three basins, except below average in foothill areas.
  • Upper Peace River basin in British Columbia: 126% of normal at most locations as indicated in British Columbia's Snowpack and Water Supply Outlook

Mountain snowpack is an important source of water supply to reservoirs in the spring. Accumulation at this time of year typically accounts for about 80-95% of the seasonal total.

Plains Spring Snowmelt Runoff Forecasts

Conditions are variable across the province, please refer to the map in the Plains Runoff Forecast section of our Maps and Data Summaries webpage.

Plains snowpack

  • Snow course measurements were taken at the end of March and the beginning of April in many areas of central and northern Alberta.
  • Environment Canada map of satellite estimation of plains snow water equivalent (SWE) as of April 8, 2012 is shown here.
  • Alberta Agriculture publishes maps of modelled plains snow accumulations and accumulations as compared to normal.


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 March 31, 2012 is available here.

Long Lead Precipitation Outlooks

Environment Canada (issued on April 1, 2012): Above normal temperature in the south and above normal precipitation for southern and western Alberta for the April through June 2012 period.

National Oceanic and Atmospheric Administration (NOAA) (issued on March 15, 2012): An even chance of below normal, normal or above normal temperature and precipitation in southern Alberta, for April through June 2010. For April alone; slightly above normal for southwestern Alberta and slightly colder for southwestern Alberta (issued March 31, 2012).

Climate indicators : The NOAA reported on April 5, 2012 that La Nina is expected to continue to weaken in the Northern Hemisphere and transition to ENSO neutral conditions for late Spring 2012.

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 and Water
Phone: (780) 427-6267