Heron Lake Outlet Reservoir Report

Last Updated: December 10, 2025

Heron Lake Outlet in Windom, Minnesota, is a state-regulated dam completed in 1937 with a primary purpose designated as "Other." This gravity dam, standing at a height of 10 feet and a length of 133 feet, serves the Heron Lake Outlet river and has a normal storage capacity of 72,571 acre-feet.


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Summary

The dam's hazard potential is rated as low, with a satisfactory condition assessment as of April 2010.

Located in Jackson County, Minnesota, the Heron Lake Outlet dam plays a crucial role in managing water resources in the region, with a maximum discharge capacity of 4,889 cubic feet per second. The dam's hydraulic height is recorded at 3.2 feet, serving a drainage area of 448 square miles. Despite its age, the dam remains structurally sound and is inspected regularly by the Minnesota Department of Natural Resources to ensure its continued safe operation.

Overall, Heron Lake Outlet dam represents a vital piece of infrastructure within the Rock Island District, providing flood control, water storage, and regulation services for the surrounding community. With its moderate risk assessment and history of satisfactory performance, this dam exemplifies the importance of effective water resource management in maintaining the resilience of local ecosystems and communities in the face of changing climate conditions.

Year Completed

1937

Dam Length

133

Dam Height

7

River Or Stream

HERON LAKE OUTLET

Primary Dam Type

Gravity

Surface Area

2845

Hydraulic Height

3.2

Drainage Area

448

Nid Storage

100000

Structural Height

10

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

10
       
Seasonal Comparison

Weather Forecast

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.