High streamflow advisory issued for local rivers

By on May 15, 2014

With warmer temperatures and rapidly melting snowpack, the B.C. River Forecast Centre today issued a High Streamflow Advisory affecting the South Okanagan.

The advisory affects both the Okanagan and Similkameen rivers and their tributaries.

A High Streamflow Advisory means that river levels are rising or are expected to rise rapidly, but no major flooding is expected. Minor flooding in low-lying areas is possible.

The bulletin notes that high temperatures in recent days have led to rapid melt of mid-elevation snowpack causing river levels to rise.

“Another hot day on Thursday will contribute to on-going rises in rivers into Friday,” the bulletin says.

Last week the River Forecast Centre issued a report warning that a delayed melt in April has caused snow basin indexes to be substantially higher in the Similkameen and Okanagan than is normal at this time of year. The Similkameen was at 172 per cent of normal and the Okanagan was at 128 per cent of normal.

The increased water volumes in the last few days are especially noticeable on the Similkameen, but the water level on Osoyoos Lake has continued to rise, though not yet to the point of flooding.

The volume of water measured on the Similkameen near Nighthawk has risen to 12,700 cubic feet per second by 2:30 p.m. Thursday from just 8,580 cubic feet per second on Tuesday.

The level of Osoyoos Lake had reached 911.79 feet above sea level by Thursday afternoon.

With an upper trough of low pressure moving across the B.C. Interior over the weekend, moderate to heavy rainfall is expected in the Southern Interior, the River Forecast Centre said.

“The combination of snowmelt and rainfall may cause localized issues, particularly for smaller river systems and in areas which receive the heaviest precipitation,” the advisory said.

Flows on the Similkameen River are expected to approach or exceed the mean annual peak flow level, the advisory added.

The advisory also covers rivers of the Thompson Region as well as the Boundary, which includes the West Kettle and Kettle Rivers.


Osoyoos Times


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