Water Supply Outlook for Alberta

March 2003

Mountain Snowpack

Mountain snow accumulations as of March 1, 2003 are much-below-average for this time of year. Thirty-eight of thirty-nine snow course measurements taken at the end of February ranged from 40 to 75% of average (Table 1). These snowpacks are the lowest to ninth-lowest in the last 30 years of record, for this time of year. The current snowpack is generally much lower than last year at this time but higher than in 2001, which was the lowest on record in many 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 three-quarters of the seasonal total.

Twelve snow course measurements were taken at the end of February in the Oldman River basin. The snowpack is much-below-average for this time of year, ranging from 38 to 67% of average (Table 2). These values are similar to those recorded at the end of February in 2001 and 1988. The March 1, 2003 snowpacks rank from lowest to sixth lowest in up to 32 years of record. Record low snowpack was measured at two of the seven snow course sites this months. End of February measurements were done for the first time this year at five of the snow course sites.

Eighteen snow courses were done at the end of February in the Bow River basin. Snowpacks ranged from 46 to 72% of average, which is much-below-average for this time of year (Table 3). Similar snow conditions were seen in 1988, 1993, and 1998. This year's snowpacks are generally better than the record-low of March 1, 2001, especially in the upper Highwood, Elbow, and Kananaskis River basins, where there is approximately one-and-a-half times more snow than in March 2001. The March 1, 2003 snowpacks rank from lowest to sixth lowest in up to 37 years of record. Record-low snowpacks were measured at two sites in the upper Bow River basin, near Lake Louise. End of February measurements were done for the first time this year at one of the snow course sites.

Ten snow courses were performed in the Red Deer, North Saskatchewan, and Athabasca River basins at the end of February. Generally, much-below-average snowpacks were recorded, ranging from 52% to 75% of average (Table 4). Snow conditions in these basins rank from second to ninth lowest in up to 32 years of record and are similar to or better than in 2001 in most areas. The Limestone snow course, in the foothills of the Red Deer River basin, is much-above-average (146% of average) due to a localized snowfall in early October.

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:

http://environment.alberta.ca/apps/basins/default.aspx

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.


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