RIVER
FORECAST CENTRE
Water-Supply
& Stream Flow Conditions
Commentary
updated July 24, 2006
Rivers
in a large portion of the province are continuing to experience
low streamflow conditions for the date. In some areas, streams
flows are very low. These areas include the most of the Peace
River basin, along with some streams in the upper Fraser,
middle Fraser, eastern Nechako, Thompson, and elsewhere. The
Fraser River at Hope and the Thompson River at Spences Bridge
are both currently at 20-year return period low flows.
SYNOPSIS:
Winter snow water accumulation was near normal or above
normal for many areas (Vancouver Island, South Coast, Okanagan,
Kootenay, Columbia, South Thompson), but below normal in the
middle and upper Fraser River basin, the eastern Nechako,
and the north-east corner of the province. Much of that snow
melted early, in mid-May, during a period of near-record high
temperatues. Since then, rainfall during June and July has
been below normal in most areas. For the north and central
interior, rain during May and June was only about 50% of normal.
As
a result of the intense mid-May heat and early snowwmelt,
followed by the drier than normal June and July, most rivers
throughout the of the province are currently below their long-term
median flows for the date. Some rivers are currently experiencing
very low flows, and are at record low flows for the date
BC
INTERIOR:
Thompson
Basin: All gauged rivers are currently below median flows
for the date (generally in the 5-10 year return period low
flow range). The Eagle River at Malakwa is currently at a
record low for the date, and the Coldwater River at Merrit
is approaching a record low for the date. The Thompson River
at Spences Bridge is below a 20-year low flow.
Upper
Fraser: All gauged rivers are currently below median flows
for the date (generally near a 10-year return period low flow).
.
Middle
Fraser: Most rivers in the middle Fraser are near 10-20
year return period low flows. The Horsefly River is at a 20-year
low flow. Cayoosh Creek near Lilloet is at a 20-year low flow.
Some rivers along the western side are currently above median
flow levels, reflecting glacial melt. The Fraser River at
Hope is at a 20-year return period low flow.
Peace:
Most gauged rivers in the Peace are currently experiencing
very low flow, generally in the 10-20 year return period low
flow range. The Finlay River, Halfway, Osilanka and Nation
rivers are currently at record low flows for the date. Other
rivers (Ospika R., Mesilinka R., Omineca R.) are below 20-year
return period lows.
Okanagan:
Many rivers are in the 5-10 year return period low flow range.
The Tulameen and Similkameen rivers are at 20-year return
period lows. Coldstream Creek and Whiteman River in the north
Okanagan are slightly above median for the date, likely reflecting
runoff from some rainfall in mid-July.
Kootenay/Columbia:
Most gauged rivers are currently slightly below median flows
for the data. The Kootenay River is near a 20-year return
period low flow.
BC
COAST: Most coastal
rivers are currently in the 80-120% of normal range. The Tsolum
River on Vancouver Island is currently recording below its
previous record low for the date, however, other rivers on
the east side of Vancouver Island are near long-term median
levels. The Skeena River is at a 10-year return period low
flow, while the Bulkley River is at a 20-year low. The Saloomt
River (at Hagensborg, near Bella Coola) is currently at a
record low flow for the date.
OUTLOOK:
The warm and dry weather of the past week will be reflected
in continuing decline in water levels, particularly in the
areas of concern noted above. Without a significant and prolonged
period of wet weather, rivers in these areas, along with the
Fraser River mainstem (as far downstream as Mission) and the
Thompson River mainstem, will continue to recede, and will
remain at well below normal levels into August.
Indicators
We
are currently monitoring five indicators. These are:
- Basin Snow Indices (in Snow Survey
Bulletin)
- Standaridized Precipitation Indices
- Monthly Precipitation, %
of Normal
- Streamflow
conditions
- Groundwater conditions
During
the winter & early spring, we utilize Basin Snow Indices
and Standardized Precipitation Indices (SPI) as indicators
of future drought conditions. Basin Snow Water Indices can
be found in the Snow Survey Bulletin.
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