Water Supply Outlook May 2017

Updated: May 9, 2017

Mountain runoff forecasts (natural volumes for March to September 2017)

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.

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

Mountain snowpack

Snow accumulations measured in the mountains as of May 1, 2017:

  • Oldman River basin: Much above average, ranging from 107% at Ptarmigan Lake to 157% at Josephine Lower (11 sites surveyed).
  • Bow River basin: Much above average, ranging from 112% at Lost Creek South to 248% at Wilkinson Open (17 sites surveyed).
  • Red Deer, North Saskatchewan, Athabasca River basins:

    Red Deer River basin: (2 sites surveyed) Gable Mountain at 131% and McConnell Creek at 172%.

    North Saskatchewan River basin: High variability – ranging from average at Job Lake (105%) to much above average at Limestone Ridge (148%).

    Athabasca River basin: (2 sites surveyed) Sunwapta Falls at 143% and Marmot-Jasper at 136%.

  • Upper Peace River basin in British Columbia: as indicated in British Columbia's Snow Survey and Water Supply Bulletin

Mountain snowpack is an important source of water supply to reservoirs in the spring. Accumulation at this time of year typically accounts for nearly three-quarters of the seasonal total.

Plains Spring Snowmelt Runoff Forecasts (issued in March and April each year)

Plains Snowpack (issued in March and April each year; Cypress Hills mid to late January and February)


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 as of May 3, 2017 is available here.

Long Lead Precipitation Outlooks

Environment Canada (issued on April 30, 2017): Temperatures is forecast to be normal for the May through July 2017 period, except for east-central Alberta, which is forecast to be below average. Precipitation is forecast to be normal for the May through July 2017 period.

National Oceanic and Atmospheric Administration (NOAA) (issued on April 20, 2017): An equal chance of below normal, normal or above normal temperature in southern Alberta for May to July 2017. Above normal precipitation in the extreme south east corner of Alberta for May to July 2017.

Climate indicators: The NOAA reported on April 13, 2017 that ENSO-neutral conditions are favored to continue through at least the Northern Hemisphere spring 2017, with increasing chances for El Niño development by late summer and fall.

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 Parks
Phone: (780) 427-8636