Monday, September 1, 2014

Dam outflow raised

The late spring melt is working its way through the Rainy-Namakan system.
These flows, in combination with recent rainfall amounts, have led to steep rises in tributary flow rates to these lakes.

Many of these tributaries have water levels and flows greater than that seen on average once every 10 years, historically.
The owners of the dams on Namakan Lake and Rainy Lake have been increasing the flow out of these lakes over the past few weeks to maintain their levels within the rule curve prescribed by the International Joint Commission (IJC).
At Namakan Lake, all logs had been removed from the dams at Squirrel Island and Kettle Falls as of Friday, allowing for maximum outflow, which is 478 m³/s at the current lake level elevation.
The lake level is at 79 percent of the IJC’s rule curve band, and has been rising at about 30 cm (or 12 inches) per week over the past week.
At the Rainy Lake dam at Fort Frances, two additional spill gates were opened Friday, making 10 of the 15 opened since April 30.
Rainy Lake outflow increased from ~665 m³/s to ~755 m³/s as a result of this change.
The level of Rainy Lake is 337.34 metres (or 1,106.7 feet), which is 67 percent of the IJC’s rule curve band.
The level of the Rainy River below the dam has risen by roughly 3.3 metres (11 feet) since early April as a result of the outflow increases from Rainy Lake.
The level of the Rainy River at Manitou Rapids has risen by 3.5 metres (11.5 feet) since early April—due to the Rainy Lake outflow increases plus significant local inflow, including from the Fork Rivers.
Further outflow increases from Rainy Lake tentatively are scheduled for this week—potentially raising the outflow to the Rainy River by an additional 100 m³/s to 900 m³/s.
Each additional outflow increase will contribute to rising river levels downstream until there is a decline in the local inflow, which currently is very high.
The Water Levels Committee regularly is monitoring conditions in the watershed and will post updates as conditions warrant.
The latest information on lake levels, dam settings, and basin flows can be found at www.ijc.org/en_/RLWWB

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