Water Supply Outlook for Alberta

April 2002

Mountain Snowpack

Snow accumulations in the mountains as of April 1, 2002 are above-average for this time of the year with the exception of the headwaters of the Oldman River basin, which have average accumulations and the Highwood and Kananaskis headwaters, which are much-above-average for this time of the year (Table 1). The mountain snowpack is an important source of water supply to reservoirs in the province. On average, the accumulation of snow for this time of the year is nearing the seasonal total in the Oldman River basin and is normally 80 to 95 % of the seasonal total in areas north of this basin.

Eight snow course measurements were made in the Oldman River basin in late March and early April, with values ranging from 90 to 131% of average (Table 2). Above-average accumulation in March brought many of the higher elevation stations to average or above-average values for this time of the year. Snow accumulations are significantly above values observed last year at this time. While the higher elevations of the basin have average or above-average accumulations, areas below 6000 feet have improved to average values.

Snow water equivalent values on the snow pillow may or may not be close to 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 point. 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. A snow course survey is measured at numerous points and provides a more representative value of snow at that location. The snow pillow graphs on our website shows 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.

Fifteen snow course measurements were made at the end of March in the Bow River basin with values ranging from 98 to 148% of average (Table 3). Snow accumulations were above-average during March, particularly in the Highwood and Kananaskis headwaters. Current snow accumulations in the Bow River basin are one and a half to two times the seasonal maximum recorded last year. All snow surveys measured above 6000 feet indicate snow accumulations are above-average. The three sites located below 6000 feet (Bow River, Chateau Lawn and Pipestone Upper) all showed significant increases during March and have accumulations nearing average conditions.

Ten snow course measurements were completed in the headwaters of the Red Deer, North Saskatchewan and Athabasca River basins during the last week of March (Table 4). Snow accumulations ranged from 101 to 138% of average at the ten sites. Eight of the ten snow surveys indicated that snow accumulations were above-average while two (Nigel Creek and Sunwapta Falls) were in their normal range for this time of the year.

Snow course measurements are completed monthly. At twelve of the snow course sites, real-time snow accumulation can be monitored using snow pillows. The snow pillow plots can be found on the department website in the Weekly River Report.

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