Water Supply Outlook May 2015

Updated: June 3, 2015

Mountain runoff forecasts (natural volumes for March to September 2015)

Milk River basin
  • Average for the Milk River at Western Crossing for the March to September period
  • Below average for the Milk River at Milk River and Eastern Crossing for the March to September period
  • Below average for May to September
  • March-April recorded volumes are above average for the Milk River at Western Crossing and below average for the Milk River at Milk River and Eastern Crossing, due to spring melt starting earlier than normal at lower elevations

Oldman River basin
  • Below average for the Belly River, Waterton River and Oldman River at Lethbridge for the March to September period
  • Average for the St. Mary River and Oldman River near Brocket for the March to September period
  • Below average for May to September, except for Belly River which is much below average.
  • March-April recorded volumes are much above average, due to spring melt starting earlier than normal at lower elevations

Bow River basin  Correction made to the May to September Forecast: June 3, 2015
  • Below average for the March to September period.
  • Below average except for the Highwood and Elbow Rivers which are slightly below average for May to September
  • March-April recorded volumes are above average to much above average, due to spring melt starting earlier than normal at lower elevations

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, 2015:

Field teams have noted that for those survey locations with reasonable snow accumulation the nearby valleys are bare which in their experience is very unusual. The early melt this year is very similar to the conditions in 2005 in southern Alberta.

  • Oldman River basin: Much below average: ranges from 0% (Josephine Lower and Many Glacier) to 81% (Gardiner Creek) of average.
  • Bow River basin: Below average: ranges from 15% (Mist Creek) to 97% (Katherine Lake) of average.
  • Red Deer, North Saskatchewan, Athabasca River basins:

    Much below average for the Red Deer River basin: two sites surveyed in this basin – Gable Mountain at 57% and McConnell Creek at 34% of average.

    Much below average to above average for the North Saskatchewan River basin: ranges from 41% (Limestone Ridge) to 108% (Job Creek and Southesk) of average.

    Below average to above average for the Athabasca River basin: two sites surveyed in this basin – Marmot-Jasper at 119% and Sunwapta Falls at 72% of average.

  • 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)

Precipitation

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 April 30, 2015 is available here.

Long Lead Precipitation Outlooks

Environment Canada (issued on April 30, 2015): Temperatures is forecast to be above normal across the entire province for the May through July 2015 period. Precipitation is forecast to be above normal across the province, excluding the north east corner which is normal, for the May through July 2015 period.

National Oceanic and Atmospheric Administration (NOAA) (issued on April 16, 2015): Above normal temperatures in the province for May to July 2015 and an equal chance of below normal, normal or above normal precipitation for May to July 2015.

Climate indicators: The NOAA reported on May 4, 2015 that an El Niño Advisory is still in place. El Niño conditions are present. There is an approximately 70% chance that El Niño conditions will continue through Northern Hemisphere summer 2015, and a greater than 60% chance it will last through autumn.

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.

Questions

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

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