Lake Jefferson Reservoir Report

Last Updated: December 6, 2025

Lake Jefferson, located in Le Sueur, Minnesota, is a state-owned reservoir with a primary purpose classified as "Other." Built in 1938 by WPA-BC, this gravity dam stands at a height of 7.25 feet and a length of 15 feet.


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Summary

With a normal storage capacity of 18,544 acre-feet and a maximum storage of 25,489 acre-feet, Lake Jefferson covers a surface area of 700 acres and serves a drainage area of 16.3 square miles. The dam's hazard potential is rated as low, and its condition assessment is deemed satisfactory as of 2009.

Situated in the city of Waterville, Lake Jefferson is fed by the Big Cannon River and falls under the jurisdiction of the St. Paul District of the US Army Corps of Engineers. Despite not being regulated by the state or requiring inspections, the dam remains an integral part of the area's water resource management system. With its historical significance as a Works Progress Administration project, Lake Jefferson continues to provide essential water storage and recreational opportunities for residents and visitors alike. The dam's low hazard potential and satisfactory condition underscore its importance in ensuring water security and climate resilience in the region.

Year Completed

1938

Dam Length

15

Dam Height

7.25

River Or Stream

BIG CANNON RIVER - TR

Primary Dam Type

Gravity

Surface Area

700

Drainage Area

16.3

Nid Storage

25489

Structural Height

9

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

9
       
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Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.