Blanche Lake Reservoir Report
Nearby: Otter Tail Lake Dead Lake East
Last Updated: December 13, 2025
Blanche Lake, located in Otter Tail, Minnesota, is a state-regulated reservoir with a gravity dam constructed in 1938 by the WPA-C.
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Summary
The dam stands at a height of 7 feet and has a hydraulic height of 1.5 feet, providing a maximum storage capacity of 24,500 acre-feet and a normal storage capacity of 20,400 acre-feet. The reservoir covers a surface area of 1352 acres and has a drainage area of 160 square miles, with a maximum discharge of 2569 cubic feet per second.
Despite being classified as having a low hazard potential and fair condition assessment, Blanche Lake poses a very high risk due to its location and potential impact on the surrounding area. The reservoir is equipped with a controlled spillway and has a controlled outlet structure. The last inspection conducted in August 2016 indicated that the dam was in fair condition, with an inspection frequency of every 8 years. The reservoir is primarily used for purposes other than flood control or water supply, making it a unique and valuable resource for the community.
Blanche Lake, with its picturesque location and historical significance, serves as a vital water resource for the region. Managed by the Minnesota Department of Natural Resources, the reservoir plays a crucial role in water management and conservation efforts. With its rich history and strategic location on Blanche Creek, this gravity dam stands as a testament to the ingenuity and foresight of its designers, providing both recreational opportunities and essential water supply for the surrounding area.
Year Completed |
1938 |
Dam Length |
83 |
Dam Height |
7 |
River Or Stream |
BLANCHE CREEK |
Primary Dam Type |
Gravity |
Surface Area |
1352 |
Hydraulic Height |
1.5 |
Drainage Area |
160 |
Nid Storage |
24500 |
Structural Height |
7 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
7 |
Seasonal Comparison
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Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
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Blanche Lake
State Highway 78 305, Ottertail