Water Supply Outlook November 2017

Updated: November 14, 2017

Recorded natural runoff volumes from March to September 2017

Natural flow volumes from March to September 2017 showed extreme variability from river basin to river basin. Locations in the Milk River basin ranged from much above normal too much below normal, while the Oldman, Bow, Red Deer and North Saskatchewan ranged from below normal to much above normal.

Natural runoff volumes recorded from March to September 2017 for rivers in the Milk River basin ranked between 23 and 56 in 98 years of record. Rankings are from lowest to highest. The rivers in the Oldman River basin ranked between 32 and 59 in 99 years of record. The rivers in the Bow River basin ranked between 31 and 74 in 99 years of record. The rivers in the Red Deer River basin ranked between 31 and 61 in 99 years of record. The rivers in the North Saskatchewan River basin ranked between 20 and 74 in 100 years of record.

The average difference between all forecasts from the beginning of the year through August and the preliminary recorded natural volumes were 23% for the Milk River basin, 12% for the Oldman River basin, 10% for the Bow River basin, 18% for the Red Deer River basin, and 12% for the North Saskatchewan River basin.

The forecast accuracy between the first month’s forecast and the July forecast saw, on average, an increase in accuracy from 24% to 13% for the average difference between recorded and forecasted volumes.

However, to fully understand the runoff conditions in 2017 the year should be separated into two distinct periods. The first is the snowpack runoff period from March to June and the second is the rainfall runoff period from July to September. When the recorded natural flow volumes are compared in this way the May much above average snowpack is apparent in the much above average March to June flows and the much below average precipitation in late summer is apparent in the much below average runoff from July to September.

March to June Period
  • Milk River Basin 80-176% of average for the period; ranked between 25 and 65 in 98 years
  • Oldman River Basin 107-137% of average for the period; ranked between 54 and 83 in 99 years
  • Bow River Basin 99-141% of average for the period; ranked between 45 and 91 in 99 years
  • Red Deer Basin 110-152% of average for the basin; ranked between 60 and 81 in 99 years
  • North Saskatchewan River Basin 109-160% of average for the basin; ranked between 53 and 94 in 100 years
July to September Period
  • Milk River Basin 6-28% of average for the period; ranked between 1 and 10 in 98 years
  • Oldman River Basin 40-87% of average for the period; ranked between 4 and 39 in 99 years
  • Bow River Basin 43-92% of average for the period; ranked between 7 and 23 in 99 years
  • Red Deer Basin 48-56% of average for the basin; ranked between 7 and 10 in 99 years
  • North Saskatchewan River Basin 58-98% of average for the basin; ranked between 2 and 47 in 100 years
Milk River basin
  • March - September recorded volumes were below average for Milk River at Eastern Crossing, average for Milk River at Milk River and above average for Milk River at Western Crossing.
  • The lack of precipitation in the Milk River basin in the late summer significantly affected the localized runoff contributions to the basin during that period.
  • The recorded volumes were higher than was forecasted during the January to March period for the Milk River at Western Crossing and for the January period for Milk River at Milk River. For all other periods the recorded volumes were lower or very close to forecast volumes. The average difference between forecasted and recorded volumes was 23%.
Oldman River basin
  • March - September recorded volumes were below average for the Oldman at Lethbridge average for Oldman River at Brocket and Belly River and above average for the St Mary and Waterton Rivers.
  • The recorded volumes were higher than was forecasted in the March water supply outlook, a mix of higher and lower in the April to May outlook and lower than forecast in the June to August outlook. The average difference between forecasted and recorded volumes was 12%.
Bow River basin
  • March - September recorded volumes were below average for Spray, Elbow, Kananaskis and Highwood, average for Cascade and Calgary and much above average for Banff.
  • The recorded volumes were higher than was forecasted during the March to April water supply outlook and lower than those forecasted from May through August. The difference between forecast and recorded volumes were on average 10%.
Red Deer River basin
  • March - September recorded volumes were average for the Red Deer River at Dickson Dam and below average for the Red Deer River at the City of Red Deer.
  • All of the recorded monthly volumes at Dickson Dam were lower than was forecast. At the City of Red Deer recorded volumes were higher than forecast in March and April and lower from May-September. On average the difference between the forecasted and recorded volumes was 18%.
North Saskatchewan River basin
  • March - September recorded volumes were much above average for Lake Abraham (Bighorn Reservoir), above average for the North Saskatchewan River at Edmonton and below average for the Brazeau Reservoir.
  • The recorded volumes were a mix of greater than and lower than forecast for all locations due to lower then average snow early in the year followed by late April and May snow storms that brought the snowpack up significantly which was then followed by a below normal rainfall period late in the season. On average, the difference between the forecasted and recorded volumes was 12%.

Note: The recorded 2017 natural flow volumes are preliminary and subject to change.

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

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 October 31, 2017 is available here.

Long Lead Precipitation Outlooks

Environment Canada (issued on October 31, 2017): temperature and precipitation for the November 2017 through January 2018 period:

  • above normal precipitation for the province except for the northern east slopes, which is normal.
  • below normal temperatures for all of Alberta.

National Oceanic and Atmospheric Administration (NOAA) (issued on October 19, 2017): equal chance of above normal, normal and below normal temperatures and precipitation for the province for the November 2017 through January 2018 period.

Climate indicators: The NOAA reported on November 9, 2017 that La Niña conditions are predicted to continue (~65-75% chance) at least through the Northern Hemisphere winter 2017-18.

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 and Parks
Phone: (780) 427-8636