South Zumbro Wr-4 Reservoir Report

Last Updated: December 7, 2025

South Zumbro Wr-4 is a local government-owned earth dam located in Olmsted County, Minnesota, specifically in Rochester.


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Summary

Built in 1988 by the USDA NRCS, this dam serves the primary purpose of flood risk reduction along the Willow Creek-TR. With a height of 46 feet and a length of 1100 feet, South Zumbro Wr-4 has a storage capacity of 968 acre-feet and covers a surface area of 40 acres, draining an area of 4.3 square miles.

Managed by the Minnesota Department of Natural Resources, this dam is regulated, permitted, inspected, and enforced by state agencies to ensure its structural integrity and operational efficiency. Despite being categorized as having a high hazard potential, the condition assessment as of June 2017 was deemed satisfactory. The dam's emergency action plan was last updated in April 2015, and it meets guidelines for risk management, with a very high risk assessment rating of (1).

South Zumbro Wr-4 plays a crucial role in safeguarding the surrounding area from potential flooding events, with controlled spillways and uncontrolled outlet gates in place. The dam's design and construction by the Natural Resources Conservation Service highlight the collaborative efforts to manage water resources effectively and mitigate climate-related risks in the region. As water resource and climate enthusiasts, staying informed about the maintenance and management of structures like South Zumbro Wr-4 is essential for ensuring the resilience of our communities in the face of changing environmental conditions.

Year Completed

1988

Dam Length

1100

Dam Height

21

River Or Stream

WILLOW CREEK-TR

Primary Dam Type

Earth

Surface Area

40

Drainage Area

4.3

Nid Storage

968

Structural Height

46

Outlet Gates

Uncontrolled

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

46
       
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.