Water Supply Outlook for Alberta

December 2002

Mountain Snowpack

Snow accumulations in the mountains as of December 1, 2002 are below-normal to much-below-normal for this time of the year. The exception is one location in the foothills of the Red Deer basin, which is much-above-normal. Much-above-normal temperatures combined with much-below-normal precipitation in November resulted in a decrease in snowpack in some areas. The mountain snowpack is an important source of water supply to reservoirs in the province. On average, the accumulation of snow at this time of the year accounts for nearly one-fifth of the seasonal total.

There were a limited number of snow course measurements taken at the end of November. More comprehensive measurements of basin snowpack begin at the end of January.

Two snow courses and one automated snow pillow reading were taken at the end of November in the Oldman River basin, with values ranging from 26 to 34% of average for this time of year (Table 1). Snow accumulations are much-below-normal and are similar to those observed last year at this time.

Four snow courses and four automated snow pillow readings were made at the end of November in the Bow River basin, with values ranging from 23 to 75% of average (Table 2). Snow accumulations are below-normal to much-below-normal, and are much lower than those observed last year at this time.

One snow pillow in the foothills of the Red Deer River basin shows accumulation of 180% of average on December 1, while one snow pillow in the upper elevations of the basin had 48% of average snowpack (Table 3).

No snow course measurements were made in the upper North Saskatchewan or Athabasca River basins in November.

At twelve snow course sites, real-time snow accumulation can be monitored using snow pillows. Snow pillows can be viewed by choosing any 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.

Plains Snowpack

As of December 1, 2002, the snowpack in most plains areas of the province is much-below-average. Satellite estimation of snow water equivalent shows plains area snowpack is much-below-normal (Figure 1). The Paddle River basin north of Edmonton had a little more snow, with one of two snow pillows there showing normal accumulation. Additional 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