Times Colonist

Cool spring keeps rivers in check

A drier than normal May also helped reduce risk of Island flooding


A cooler spring without the usual heavy rainfall means the flood risk is over for Vancouver Island rivers for now.

While lower-than-normal temperatur­es had many Island residents singing the blues, the conditions have been welcomed by riverside residents who avoided flooded basements and evacuation.

It was a different story on Dec. 4, 2007, when heavy rains combined with snowmelt in the Nanaimo River, causing flooding and evacuation­s downstream. The springtime phenomenon known as the Pineapple Express missed Vancouver Island this year, meaning snow in the Island mountain range melts at a moderate rate and not all at once.

While April was one of the coldest on record in Victoria, May returned to normal temperatur­es, said Environmen­t Canada weather specialist Anne McCarthy yesterday.

The average daily high of 16.8 C was near the normal of 16.6 C. The average daily low of 7.6 C edged above the normal of 6.9 C.

We also received less than half the usual rainfall — 15.6 millimetre­s instead of 36.5 mm, making May the 10th driest on record.

A daily record was set May 17, when the temperatur­e reached 26.5 C, topping the previous record set in 1956 of 25.6.

The conditions meant Island rivers stayed more or less steady this spring, thanks in some instances to B.C. Hydro managing water from its reservoirs.

“It was very cool and dry since early December so the reservoir levels at Comox Lake, Buttle Lake, Upper and Lower Campbell lakes and McIvor Lake reached all-time low levels,” said Stephen Watson, spokesman for B.C. Hydro.

“With the snowmelt coming in over the past three weeks or so, it’s made a big difference in those reservoirs recovering.”

When the reservoirs in the Campbell River area dropped to low levels, B.C. Hydro in mid-April got permission from the province to reduce its flow in affected rivers from 80 cubic metres per second to 50.

“That was to try to conserve and capture as much snowmelt as we could,” said Watson.

On Friday, B.C. Hydro restored release rates in the Campbell River system to normal levels. While the corporatio­n often released more water in spring to mimic the effect of snowmelt, it may not do that this year in order to conserve water.

Any decisions on water levels in rivers are made after consultati­on with the Department of Fisheries and Oceans and other stakeholde­rs, he said.

The river levels are most likely to have an effect on smolts, said, Jim Irvine, a salmon research scientist at the Pacific Biological Station. A smolt is a young salmon migrating to the ocean, he explained yesterday.

“Coho typically spend one year in fresh water, then they migrate to the ocean, usually peaking about the middle of May. “If you have a delayed snowmelt, it could delay the timing of the smolts arriving at the ocean. It’s part of natural variabilit­y.”

The snow conditions provide a “very positive outlook” for water supply in B.C., reports the Ministry of Environmen­t on its water stewardshi­p web page.

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