Water Supply Outlook November 2010
Updated: November 5, 2010
Recorded natural runoff volumes from March to September 2010
Natural runoff volumes from March to September 2010 were generally much above average in the Milk River Basin, average to above average in the Oldman River Basin and below average in the Bow, Red Deer and North Saskatchewan River Basins. The heavy precipitation in southern Alberta this summer produced much above normal runoff particularly in the Milk River and St. Mary River.
Natural runoff volumes recorded from the March to September 2010 for the Milk River, St. Mary River, Belly River and Oldman River at Lethbridge ranked from 59 to 80th highest in 91 years of record. However, the Bow River at Banff, Spray River, Kananaskis River, Bow River at Calgary, ranked the lowest, 7th, 10th and 11th lowest in 91 years of record respectively (Banff and Calgary similar to 2009 and 1984 respectively). Lake Abraham Inflow and Brazeau Reservoir Inflow ranked from 4 to 12th lowest in 30 and 41 years of record respectively. The Red Deer River at Red Deer and North Saskatchewan River at Edmonton ranked 28th and 25th lowest in 91 years of record respectively.
The runoff volume forecasts were generally accurate within 2 to 7% on average for the Bow, Red Deer and North Saskatchewan River Basins. However, due to much above normal precipitation in southern Alberta in June, runoff volume forecasts were underestimated in the Milk River (106%) and Oldman River (19%) basins.
Milk River basin- March - September recorded volumes much above average for the Milk River due to heavy precipitation in southern Alberta this summer.
- Runoff in this basin is naturally highly variable. With very high precipitation totals this year, volumes were closer to the high end of the forecast range (upper quartile forecasts).
- March - September recorded volumes slightly below average for the Waterton River and Oldman River near Brocket and above average for the St. Mary River, Belly River and Oldman River at Lethbridge.
- Six months forecasts (February to August, excluding June) issued this past year for 5 locations were on average, accurate within 1 - 44% (departure from forecast volume by location) and basin average accuracy equals 19%. St. Mary River had a 44% forecast volume departure from measured volumes. Runoff was closer to the upper quartile forecasts due to high precipitation totals.
- March - September recorded volumes below average for the Bow River, Spray River, Kananaskis River, Bow River, Elbow River Highwood River and Lake Minnewanka inflow.
- Six months forecasts (February to August, excluding June) issued this past year for 7 locations were on average, accurate within 1 - 18% (departure from forecast volume by location) and basin average accuracy equals 7%. Spray River near Banff had a 18% forecast volume departure from measured volumes. Runoff was closer to the lower quartile and decile forecasts due to low precipitation totals.
- March - September recorded volumes below average for the Red Deer River at Dickson Dam and City of Red Deer.
- Six months forecasts (February to August, excluding June) issued this past year for 2 locations were on average, accurate within 3 - 14% (departure from forecast volume by location) and basin average accuracy equals 5%. Red Deer River at Dickson Dam had a 14% forecast volume departure from measured volumes. Runoff was closer to the lower quartile forecasts due to low precipitation totals.
- March - September recorded volumes below average for Lake Abraham inflow, Brazeau Reservoir inflow and North Saskatchewan River at Edmonton.
- Six months forecasts (February to August, excluding June) issued this past year for 3 locations were on average, accurate within 1 - 6% (departure from forecast volume by location) and basin average accuracy equals 2%. Lake Abraham Inflow had a 6% forecast volume departure from measured volumes. Runoff was closer to the lower quartile forecasts due to low precipitation totals.
Note: The recorded 2010 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 25, 2010 is available here.
Long Lead Precipitation Outlooks
Environment Canada (issued on November 1, 2010): temperature and precipitation for the November 2010 through January 2011 period:
- normal precipitation, except below normal in northeastern Alberta.
- normal to above normal temperatures in central and southern Alberta and below normal temperatures in northern Alberta.
National Oceanic and Atmospheric Administration (NOAA) (issued on October 21, 2010): above normal precipitation and normal temperature for southern Alberta for November 2010 through January 2011.
Climate indicators: The NOAA reported on November 4, 2010 that La Nina conditions are expected to strengthen and last through the coming winter. Below average temperatures and above average snowfall is most likely for the Northern Rockies and Plains.
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