Water Supply Outlook for Alberta

June 2002

Mountain Snowpack

Snow accumulations in the mountains as of June 1, 2002 are much-above-average for this time of the year due to the late spring. The 19 snow courses measured in the last week of May are near record maximums for this time of the year. The percent of average snow accumulations are also very high because there is generally no snowpack remaining at this time of the year, which causes the values to be artificially high this month. The mountain snowpack is an important source of water supply to reservoirs in the province. The snow course measurements that were completed in late May for the Oldman (Table 1), Bow (Table 2) and Red Deer (Table 3) River basins are provided in the specified tables. Typically the peak snowmelt runoff from the mountain areas occurs in late May or in June.

Snow water equivalent values on the snow pillow may or may not match the snow course value at a particular location, especially at this time of the year. 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.

There will be no further snow course measurements this year. However, 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 Alberta River Basins portion of the water page by selecting a basin and asking for snow data in the second box.

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