Lake Reservoir Levels
Minnesota Power operates Birch and Garden Lake Reservoirs’ water levels to maintain a target parameters throughout the year as required by a Federal Energy Regulatory Commission (FERC) License. An upper and lower limit has been established around the target parameters to allow for limited flexibility in level operations as hydrologic conditions vary.
Current Lake / Reservoir Levels, Current Flow Information and Target Parameters:
Historical Highest and Lowest lake level records, as well as data over the last 10 years:
USGS stream flow report covering the South Kawishiwi inflow to Birch Lake Reservoir:
Birch Lake Reservoir Operating Objectives
- May 15th thru Sept 1st; Manage lake levels for recreation purposes and to allow for a 1’ gradual drawdown to mimic natural lake drawdown while not impacting shorefront property, recreation residences, recreation businesses, and recreation users.
- Sept 1st thru Nov 15th; Refill up to target levels
- Nov 15th thru April 1st; Manage lake levels to allow for a drawdown and refill cycle to capture a portion of spring runoff as well as to allow for increased Winton Hydroelectric generation during the winter.
- Manage the winter drawdown to ensure that Birch Lake refills to target elevation no later than May 15th.
- Instream seasonal minimum flows are maintained for the protection and enhancement of aquatic resources in the South Kawishiwi River.
Garden Lake Reservoir Operating Objectives
- Feb 1st thru April 1st; Manage lake levels to allow for a 2’ drawdown to capture a portion of spring runoff and to alleviate some flooding on Garden and White Iron Lakes.
- May 15th thru June 15th; Maintain stable lake levels for recreation purposes.
- June 15th thru Sept 15th; Manage lake levels for recreation purposes and to allow for a 0.5’ gradual drawdown to mimic natural lake drawdown while not impacting shorefront property, shorefront residences, recreation businesses, and recreation users.
White Iron Lake:
Though MN Power monitors White Iron Lake water levels, this lake is not a part of the regulatory requirements for Minnesota Power. During low flow conditions, the elevation at the hydroelectric dam, Garden, Farm, South Farm and White Iron Lakes are an essentially flat pool elevation. The narrows at White Iron Rapids are a pinch point limiting the amount of water able to pass through at any given time, thereby raising the water levels of White Iron during high flow conditions.
Consultation Requirements to Allow Deviation from Lake Level Operating Bands
In some instances, Minnesota Power may need to operate Lake Levels outside the operating band due to hydrologic conditions or planned maintenance activities. If the deviations are not an emergency, MN Power will consult with the US Forest Service and members of the Winton Collaborative Team at least 5 days prior to a change that would cause operation outside the operating band. Upon Team agreement and after advising WICOLA, MN Power may make changes. If such an operational change were to occur, MN Power will provide a report to the regulatory agencies within 10 days of the change.
Consultation between Minnesota Power and the regulatory agencies during the last several years has determined it is appropriate to allow Birch Lake Reservoir’s elevation to fall below the lower band during drought and late spring run-off periods, discharging an amount equal to inflow, to mimic a natural lake. However, in May of 2015, the drought was so intense that the regulatory agencies approved an adaptive management plan to temporarily decrease the minimum flow requirements in an attempt to balance the impacts of the drought on both the reservoir and the downstream river section. Shortly after the change, precipitation increased filling the reservoir to normal levels.
Emergency Conditions to Allow Deviation from Lake Level Operating Bands
Deviations from the lake level operating bands without any prior consultation shall be permitted only for the purposes of Urgent Dam Safety, immediate protection of human life and property, rescue activities, or Mid-Continent Area Power Pool emergencies. In these cases, MN Power will notify and provide a report as soon as possible, but no later than 10 days.
