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Dams keep Trail safe from swelling river

Over 53 years ago the Columbia River flooded Trail and Castlegar, but now the Columiba River Treaty dam keeps rising waters at bay.

It was over 53 years ago the waters of the Columbia River rose up and flooded in the cities of Trail and Castlegar, causing extensive damage in waterfront neighbourhoods.

Today, a combination of heavy spring runoff and record rainfall has swelled the Columbia River near those record levels once again, but the city is safe from flooding, according to a BC Hydro spokesperson.

Mary Ann Coules noted that without the Columbia River Treaty dams, the river flows at Birchbank would have peaked at 10,165 cubic metres per second (359,000 cubic feet per second) this year, only 425 m3/s below the highest ever river flow of 10,590 m3/s (374,000 cfs) in 1961.

Without the operation of upstream Columbia River Treaty dams, the peak flow in the Columbia River in Trail would be approximately double its current flow and within five per cent of the historic maximum flows ever seen in the major pre-dam flood years of 1948 and 1961.

“Under the current conditions, BC Hydro is maintaining the Columbia River flows at Trail to a manageable level,” said Coules. “Without the Columbia River Treaty dams, these flows would have more than doubled, resulting in major flooding damage.”

Currently there are high water conditions throughout the Columbia basin and across B.C. In addition to a higher than average snow pack in the Columbia basin the region has seen record rainfalls during the month of June with 227 millimetres of rainfall, three times its average amount for the month.

As a result, BC Hydro allowed the Arrow Lakes Reservoir to reach its full pool level of 440.1 m. (1,444 ft.) earlier this week and it will continue to rise as much as 0.6 m. (two ft.) above normal full pool over the next several weeks depending on weather conditions.

This year recorded inflows to Arrow Lakes Reservoir from February to July 3 are the fourth highest since 1970.

BC Hydro recently increased releases from the Hugh L. Keenleyside dam to 1,557 m3/s or 55,000 cfs to manage the rate of refill for the reservoir.

Although uncommon in recent years, BC Hydro regularly operated Arrow Lakes Reservoir above 440.1 m. (1444 ft.) during the 1970’s and 1980’s, a typical operation under high water conditions.

The last time was 1997 and 1991 when the reservoir level went slightly above 440.1 m. The last time the reservoir level went to 440.7 m. was in 1990.