DEH CHO - Heavy rain last week in the Deh Cho region put a damper on some summer activities as rivers rose to unusually high levels for this time of year.

"The Liard River came up over two metres, over four days, which is pretty rare for this time of year," said Roger Pilling, hydrometric supervisor with Water Survey of Canada.

Andrew Smith lowers a weighted cable into the Blackstone River on Sept. 9, to measure its depth and velocity. Torrential rain caused the river to rise to its highest point since 2002. - photo courtesy of Andrew Smith

"It was just one of those big rain events and it came right up the river valley, so it resulted in quite a significant increase in the flow," said Pilling.

"For us (in Fort Simpson) a big rain is about 25 millimetres, and we got close to 80 millimetres here (last week), which is a lot for Fort Simpson," Pilling continued.

Pilling said it was the highest fall flow on record for the Liard River and the Blackstone River since 2002, excluding flows during spring breakup when river levels are commonly much higher.

Blackstone was higher this year than it was in 2002, according to Pilling. The previous highest recorded level for the river was 220 cubic metres, and last week it was nearly double - 405 cubic metres.

Pilling said the river levels are already receding now. The Liard River, he said, peaked last Friday.

"It'll probably take at least a good week to get back to where it was 10 or 12 days ago," said Pilling.

Pilling said the water will flow into the Mackenzie and make its way to the Arctic Ocean.

He said it takes the water about 10 days to get from Fort Simpson to Inuvik.

Pilling made the trip to measure the rivers last Wednesday through Friday with his colleague, Andrew Smith, a hydrometric technician with Water Survey of Canada.

"We usually go around and measure, I'd say, about every six to eight weeks. Of course when you get your big flood events or rain events, we go right away," said Smith.

"We want to capture those peaks," said Smith.

Smith said when the water is low they wade in and measure the levels. When levels are high, they attach an apparatus to a bridge over the river and then lower into the waters.

The device consists of a 70-pound weigh attached to a cable. When lowered, another attached device gathers depth information and measures the velocity at which the river is traveling.

Spring breakup, Pilling said, is the only time Fort Simpson is ever in danger of flooding.

The record for high water levels in the Deh Cho region was set in 1988.

"In 1988 we had a very historic flood," said Pilling.

"The Mackenzie Highway was closed for a week and the Liard Highway was closed for about three months because they had flooded."