Little Grassy Lake Reservoir Report

Last Updated: December 5, 2025

Little Grassy Lake, located in Washburn, Wisconsin, is a picturesque reservoir with a rich history dating back to its completion in 1981.


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Summary

This local government-owned dam, standing at a height of 9 feet, serves multiple purposes including flood control and water supply management. With a normal storage capacity of 50 acre-feet and a maximum storage of 140 acre-feet, the lake covers a surface area of 28 acres and has a drainage area of 0.2 square miles.

The dam at Little Grassy Lake boasts a controlled spillway type and a maximum discharge capacity of 40 cubic feet per second, ensuring the safety of the surrounding area in the event of heavy rainfall or flooding. Despite its low hazard potential, the dam's risk assessment indicates a very high risk level, emphasizing the importance of regular inspections and maintenance. The last inspection in October 2011 was rated as "Not Rated," highlighting the need for ongoing assessment and management to mitigate any potential risks associated with the dam.

As an essential water resource in the region, Little Grassy Lake serves as a hub for water-based recreational activities and wildlife habitat. Its strategic location and design make it a vital component of the local ecosystem, highlighting the importance of sustainable water resource management practices in the face of evolving climate patterns. With a commitment to regulatory compliance and regular inspections, Little Grassy Lake stands as a testament to the intersection of water resource management and climate resilience in the region.

Year Completed

1981

Dam Length

230

Dam Height

9

River Or Stream

LITTLE GRASSY LAKE OUTLET

Primary Dam Type

Earth

Surface Area

28

Hydraulic Height

9

Drainage Area

0.2

Nid Storage

140

Structural Height

9

Hazard Potential

Low

Nid Height

9
       
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.