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Snow Survey Bulletin
Snowpack and Water Supply Outlook for British
Columbia
June 15, 2009
Every
effort is made to ensure that data reported on these
pages are accurate. However, in order to update the graphs
and indices as quickly as possible, some data may have
been estimated. Please note that data provided on these
pages are preliminary and subject to revision on review.
The June 15th snow survey is now complete.
Data from 3 snow courses and 57 snow pillows around the province
have been used to form the basis for the following reports.
This is the final Snow Survey Bulletin for the 2008/09
snow season.
Snowpack
The 2009 spring snowmelt is almost complete. Low and mid elevation snow is gone,
and the melt of high elevation
snow is well advanced. Many high elevation snow pillows across the province are now recording zero snow. For the remaining pillows, about one-third of their maximum snow water remains to melt.
Weather
Following cool weather in April and May, the weather across most of British Columbia turned hot in early June, as a result of a high pressure ridge centred over the Alaska panhandle. Temperatures across BC were well above seasonal normals for 8 or 9 days, with record or near-record highs in some areas for 4-5 days (particularly the north-west). This hot weather produced extremely rapid melt of the late season snow, and produced high streamflows in some areas.
Spring weather has been dry. April and May brought below normal rainfall to most parts of BC; the first half of June has brought almost no rain to BC (generally, 0-5 mm) to the south and central interior. June is typically the wettest month of the year in the south and central interior.
Most mainstem rivers in the province experienced
their freshet peak flows in late May or early June. Since
then, most rivers have been receding. The Upper Fraser and Quesnel rivers are experiencing a 2nd peak this week (June 18-20) as a result if rainfall, which will result in a 2nd peak on the Fraser River through the Lower Mainland over the June 21-23 period. In areas with below normal snowpacks at the end of the winter (the southern half of British Columbia), the peak flows experienced this spring were below average. In areas with well above normal snowpacks (the Skeena, Nass, Stikine, and Liard basins), high steamflows and occurred in early June, with flooding on some rivers. The Skeena, Nass and Stikine rives all peaked at <5-year return period levels; the Liard River peaked at a 5-10 year return period level.
Outlook
There is a high likelihood for water-supply challenges in some parts of British Columbia this summer. For the south and central interior (Okanagan, Kettle, Similkameen, Nicola, Thompson, and Kootenay basins), as well as Vancouver Island and the South Coast, the cumulative effects of the low winter snowpack and dry spring is a high likelihood for below normal summer streamflow and water-supply. This will be reflected in such things as lower than normal lake and reservoir levels, lower than normal recharge of groundwater aquifers, and lower than normal river levels during summer. Okanagan Lake inflows for Jan-May are the 6th lowest of record (based on the 1921-2009 record), and are slightly lower than 2003, which was a notable dry year in the interior.
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