Water Supply Outlook April 2009

Updated: April 15, 2009

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

Forecasts have increased for the Milk and Oldman River basins since March 1, by a significant amount at many locations. In the Bow, Red Deer and North Saskatchewan River basins, forecasts are similar to March 1 forecasts.

Milk River basin Oldman River basin Bow River basin Red Deer River basin North Saskatchewan River basin

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. Recorded 2009 volumes are preliminary and subject to change.

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, 2009: Mountain snow accumulations have improved significantly in the Oldman River basin since March 1, improved slightly in the area upstream of Banff and in the upper Highwood and Peace River basins, and decreased slightly in the Athabasca River basin. Accumulations were similar to last month in other areas.

  • Oldman River basin: below average to average in the Waterton, St. Mary and Belly River basins. Below average in the upper Oldman River basin. of record.
  • Bow River basin: below to much below average upstream of Banff and in the Highwood River basin. Much below average in the remainder of the basin, ranking from third to eighth lowest in generally 25 to 30 years of record.
  • Red Deer, North Saskatchewan, Athabasca River basins: below to much below average, except average to much above average at four locations in the foothills.
  • Upper Peace River basin in British Columbia: 95 to 125% 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. On average, the accumulation of snow by April 1 is nearing the seasonal total in the Oldman River basin and is normally 80 to 95% of the seasonal total in mountain areas north of this basin.

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 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 4, 2009 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, 2009 is available here.

Long Lead Precipitation Outlooks

Environment Canada (issued on April 1, 2009): below normal temperature and precipitation for the April through June 2009 period, except:

  • normal to above normal precipitation in most of northern Alberta
  • normal temperatures in the north eastern corner of the province

National Oceanic and Atmospheric Administration (NOAA) (issued on March 19, 2009): below normal to normal precipitation and below normal temperatures in southern Alberta, for April through June 2009.

Climate indicators: The NOAA reported on April 9, 2009 that La Nina conditions are transitioning to neutral conditions during April, and that neutral conditions are expected to persist through the rest of 2009.

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