Totagatic Reservoir Report

Last Updated: December 5, 2025

Totagatic, also known as Nelson Lake, is a gravity dam located in Sawyer, Wisconsin, with a primary purpose of recreation.


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Summary

Completed in 1936, Totagatic stands at a height of 20 feet and has a maximum storage capacity of 38,000 acre-feet and a normal storage capacity of 21,000 acre-feet. The dam has a surface area of 2,503 acres and a drainage area of 49.8 square miles, with a controlled spillway width of 37 feet.

Managed by the Wisconsin Department of Natural Resources, Totagatic is regulated, permitted, inspected, and enforced by state authorities. The dam has a low hazard potential and has not been rated for its current condition. While it has a very high risk assessment rating due to its age and other factors, the emergency action plan for Totagatic meets guidelines and is regularly updated to ensure the safety of the surrounding area in case of a potential breach.

With its scenic location and recreational opportunities, Totagatic serves as a popular destination for water resource and climate enthusiasts. Its historical significance, combined with its natural beauty and the efforts to maintain its safety and functionality, make it a noteworthy site for those interested in the intersection of water management and environmental conservation.

Years Modified

1937 - Other

Year Completed

1936

Dam Length

556

Dam Height

20

River Or Stream

TOTAGATIC

Primary Dam Type

Gravity

Surface Area

2503

Hydraulic Height

11

Drainage Area

49.8

Nid Storage

38000

Structural Height

20

Hazard Potential

Low

Nid Height

20
       
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.