Friday, October 24, 2014

Rainy Lake level close to peaking

The level of Rainy Lake is close to peaking at its highest level since 1950.
At the Fort Frances-International Falls dam, all 15 spill gates have been open since June 6.

As well, the overflow weir that spans the centre of the dam began passing water last week for the first time since 1950.
Although the dam has been fully opened, record high rainfall in June in Minnesota led to inflow to Rainy Lake that far exceeded the outflow capacity of the dam.
As a result, Rainy Lake continued to rise throughout the month.
The high water levels have caused significant damage in communities, for individual property owners, and for businesses on both sides of the border.
Emergency declarations have occurred in several communities, with co-ordinated efforts at sandbagging and other protective measures being carried out over the last few weeks by various levels of government and volunteers.
Along the Namakan chain of lakes, the peak level occurred June 18—the highest level since 1968.
Many properties and businesses have been contending with flooding in this area, as well.
Particularly hard hit have been the lakes upstream of Namakan Lake such as Crane Lake, which rose several inches higher than the main body of Namakan.
Since June 18, the level has been declining but Namakan Lake remains 15 cm (six inches) above the emergency level defined by the International Joint Commission, known as the “All Gates Open” level.
Crane Lake, meanwhile, is 25 cm (10 inches) above this level.
The “All Gates Open” level is nearly a foot higher than the top of the rule curve band—the target lake level range defined by the IJC for this reservoir.
The dams at Squirrel Falls and Kettle Falls, the principal outlets of Namakan Lake, have been fully opened since May 16.
These dams now are providing slightly more than half of the flow entering Rainy Lake, although at the peak of the inflow to Rainy Lake, the dams at Namakan Lake provided roughly one-third of the flow.
Over the past week, the International Rainy-Lake of the Woods Watershed Board has received a number of inquiries as to whether there will be action taken to reduce flow out of Namakan Lake to help the level of Rainy Lake decline faster.
The option of a flow reduction out of Namakan Lake requires serious consideration as it would involve increasing risk to one area to reduce it in another.
The Water Levels Committee of the International Rainy-Lake of the Woods Watershed Board, which advises the IJC on emergency conditions within the Rainy River watershed, is reviewing possible options.
But it would like to advise the public of the facts considered in such a decision.
The surface area of Namakan Lake is much smaller than that of Rainy Lake. As a result, for every inch that would be saved on Rainy Lake by holding back water in Namakan, the level of Namakan would be nearly four inches higher.
While Namakan Lake has been declining, water is leaving the lake only slightly faster than it is flowing in.
Reducing flow now would postpone the decline below the “All Gates Open” emergency level at a time when the Namakan chain of lakes still is at the second-highest level since 1968 (2002 was slightly higher than the current level).
While the short-term forecast is favorable, there is still the risk that the rest of July could see wet weather.
Reducing flow from Namakan Lake now would place interests in this basin at significant additional risk for a small benefit to Rainy Lake.
If the level of Namakan Lake declines below the “All Gates Open” emergency level, as expected later in July, the Water Levels Committee will review whether to recommend to the IJC to reduce Namakan Lake outflow until Rainy Lake also has declined below its emergency level.
The IJC has no authority over dams in the watershed other than those at the outlets of Namakan Lake and Rainy Lake.
However, the Water Levels Committee has been working closely with operators of smaller upstream dams, including the Ministry of Natural Resources, to determine if there is any capacity to store water safely without compromising upstream interests.
The MNR has stated its primary concern is to ensure their dam structures are not compromised by high water levels.
Since water levels remain high throughout the basin, no flow reductions currently are planned at smaller control structures.
Along the Seine River system, some small flow reductions have occurred over the past couple of weeks.

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