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Snow Survey Bulletin
Snowpack and Water Supply Outlook for British
Columbia
June 15, 2006
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 5 snow courses and 57 snow pillows around the province
have been used to form the basis for the following reports.
This is final Snow Survey Bulletin for the 2005/06
snow season.
Snowpack
The 2006 spring snowmelt is largely
complete. The snow water indices for most basins are at or
near zero. The largest amount of snow still being recorded
is on Vancouver Island (snow water index = 907 mm, 125% of
normal) and the South Coast (index = 572 mm, 87% of normal).
However, these amounts represent only about one-third of the
peak snow water in the basins measured on May 1st.
Weather
The last half of May and the first
half of June have been wet, with well above normal rainfall
recorded throughout the southern half of the province and
near normal rainfall in the northern half. Temperatures were
generally near normal.
Most mainstem rivers in the province experienced
their freshet peak flows in late May or early June. In many
cases, the peaks were as much as two to three weeks earlier
than usual. Since then, most rivers have been receding. Rainfall
during early June has moderated the flow recession in some
areas.
The snowmelt and wet weather produced high
flows (in the 2-10 year return period range) in small and
mid-sized rivers throughout much of the southern interior
(Kootenay, Columbia, Okanagan and South Thompson), with significant
flooding (in the 25-50 year return period range) concentrated
in the Grand Forks - Slocan - Nelson area of the Boudary and
West Kootenay. Mission Creek at Kelowna experienced a 30-year
return period high flow on June 15, following an intense convective
rain storm centred over the upper watershed.
Most gauged rivers in the province are at
or above median flows for mid-June. The Similkameen is slightly
below median, but is not at a level of concern.
Outlook
There are no water supply issues
for the province evident at this time.
June 15
The upper Fraser snow index was only 70% of normal at May
1. The index is now at zero, while the Nechako index is near
zero. Precipitation in the Upper
Fraser was slightly below normal for May and early June.
The Fraser River at Shelley (at Prince George)
peaked on May 25, near 2800 cubic metres per second..
Hydrograph of the Fraser River at Shelley
June 15
Snow water equivalencies throughout the Middle and Lower Fraser
are very low, as a result of significant melt during late
May. The Middle Fraser overall had a June 15 Snow Water Index
of 51%, while the lower Fraser was 61%.
The Fraser River at Hope experienced a peak
discharge of 7700 on May 27. Flows are currently receding,
and are below normal for mid-June.
Hydrograph of the Fraser River at Hope
June 15
The Thompson basin experienced above normal loss of snow water
during late May. The North Thompson Snow Water Index is 35%
of normal for June 15. Low and mid elevation snow has melted
off. The South Thompson Snow Water Index is at 60%.
The North Thompson River at McLure peaked
on May 25 ay 2080 cms, while the Thompson River near Spences
Bridge peaked on May 27 at 2630 cms. They are currently receding
are are near normal for the date.
Hydrograph of
the North Thompson River at McLure
Hydrograph of the Thompson River near Spence's Bridge
June 15
Relatively very few snow surveys are conducted in the Columbia
basin at this sampling date. Based on the limited sample,
snowpacks in Columbia are at 50% of normal.
Streamflows in the region, as represented
by the mean monthly flow in the Columbia River at Donald,
are currently receding, after experiencing their freshet peaks
in mid-June.
Hydrograph
of the Columbia River at Donald
June 15
Based on a limited sample, the Kootenay Snow
Water Index has fallen to 24% of normal on June 15. All low
and mid elevation snow thoughout the Kootenays is gone, with
less than 50% of normal June 15 snow remaining at high elevation.
Most rivers throughout the West and East Kootenay
experienced high flows or floods over the May 19-23 period,
produced by accelerated snowmelt from record or near record
heat, followed by frontal and convective rain. A number of
rivers experiecned significant flooding, including the Salmo,
Slocan, Lardeau, Kettle and Granby rivers.
.
June 15
All but one of the Kettle, Okanagan and Similkameen snow courses
measured for the June 15th survey are at zero snow. Virtually
all the Okanagan basin appears to be snow free as of June
15, with the exception of remnant patches at high elevation.
Small streams (e.g., Trout Creek, Vaseux Creek,
Mission Creek, Kettle River, etc.) experienced their largest
peak flow of the snowmelt freshet period near May 21. These
and other small and mid-sized rivers throughout the Okanagan,
Kettle and Similkameen basins are currently receding to well
below normal levels for mid-June. Mission Creek experienced
a significant high flow (approximately 30-year return period)
on June 15, following a convective rain storm centred over
the upper watershed.
The Similkameen River and Tulameen Rivers
experienced their freshet peak flows in mid-May. They are
currently slightly below normal for mid-June.
Hydrograph
of the Similkameen River near Hedley
June 15
Vancouver Island and the South Coast continue with significant
high elevation snow. The Vancouver Island index is 125% of
normal, while the South Coast index is 87%.
May and the first half of
June were wet throughout the coast, with above normal precipitation.
The rain and continuing snowmelt have maintained streamflows
at above normal levels, and bodes well for abobe normal flows
during summer.
June 15
Based on a limited survey, the Peace River basin Snow Index
is well below normal (10%) for June 15.
June 15
The Skeena/Nass basin Snow Water Index is at zero.
Regional stream flows, as
reflected by the mean monthly flows in the Skeena River at
Usk, were above normal during early June. The Skeena River
experienced a freshet peak of 5300 cms on June 4th.
Hydrograph for
the Skeena River at Usk
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