Water Supply Outlook for Alberta

December 2005

Mountain Snowpack

Snow accumulations in the mountains as of December 1, 2005 are below to much below average for this time of the year in the Oldman and Highwood River basins, average to above average in the remainder of the Bow River basin, and average in the Red Deer River basin. The mountain snowpack is an important source of water supply to reservoirs in the spring. On average, the accumulation of snow at this time of the year accounts for nearly one-fifth of the seasonal total.

Three snow courses and two automated snow pillow readings were taken at the end of November in the Oldman River basin, with values ranging from 57 to 77% of average for this time of year, which is below to much below average (Table 1). Generally, snow accumulations are lower than in December 2004, but much higher than those observed in December 2000, 2001 and 2002.

Eight snow courses were measured at the end of November in the Bow River basin, with values ranging from 97 to 129% of average, except in the Highwood River basin where snowpack ranged from 52 to 93% of average (Table 2). Snow accumulations at two of three snow course locations in the Highwood River basin are third lowest in fifteen years of record, but are much higher than accumulations in the two lower years of 1987 and 1992. In the rest of the Bow River basin, measured snow accumulations are average to above average and greater than in December 2004.

Two snow pillows in the Red Deer River basin show snowpack ranging from 93 to 97% of average on December 1, 2005 which is similar to the snowpack last December (Table 3).

No snow course measurements were made in the upper North Saskatchewan or Athabasca River basins this month. More comprehensive snow course measurements of basin snowpack begin at the end of January.

Four snow pillows in the upper Peace River basin in British Columbia indicate snowpack ranging from below average to average, as seen in the snow pillow plots available at: http://wlapwww.gov.bc.ca/rfc/river_forecast/spdn_east.html.

At twelve snow course sites, real-time snow accumulation can be monitored using snow pillows. Snow pillows can be viewed by choosing any mountainous southern basin, and snow data, in the two drop down menus at:


Snow water equivalent values on the snow pillow may or may not match the snow course value at a particular location. While snow pillow data is very valuable information, the quantity of snow on the pillow is only representative of the accumulation at that specific spot. A snow course survey is measured at numerous spots and provides a more representative value of snow in the area. In some locations, there can be considerable difference between the snow pillow and snow course values. Factors such as wind and exposure of the site can cause the snow pillow values to be significantly different from the snow course survey. The snow pillow graphs on our website show the daily average snow water equivalent. The monthly snow survey is the average of all measurements conducted within five days of the end of the month. Also, where snow pillow and snow course measurements are available for the same site, snow pillow records tend to be much shorter (10-15 years) in length compared to the snow course sites. As a result, the difference in the average value between the snow pillow and the snow course can be attributed to snow water equivalent being derived two different ways (physically measured compared to an instrument reading), site location and length of data record. In some cases, the values can deviate by 10-20%. Therefore, while snow pillows are excellent for analyzing trends and for monitoring accumulation between snow surveys, snow course values should always be used when considering the quantity of snow at a particular location as they best represent that area.

Click here to see a map of snow course locations

Plains Snowpack

Satellite estimation of plains snowpack as of December 1, 2005 shows little to no snowpack throughout the province (Figure 1). Point measurements of snow depth on this map indicate snowpack is well below normal in almost all plains areas of Alberta, although a couple of locations along the southwestern foothills recorded above normal snow depths. More detailed information on plains area snowpack will appear in the March Water Supply Outlook as snow course measurements will be conducted at the end of February.

For technical enquires about this web page please contact Alberta Environment - Environmental Management Water Management Operations Branch at AENV-WebWS@gov.ab.ca