Johnston Reservoir Report

Last Updated: December 5, 2025

Johnston, also known as Johnston Surprise, is a federal-owned fish and wildlife pond located in Bayfield, Wisconsin.


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Summary

Completed in 1960, the dam stands at a height of 10 feet and has a hydraulic height of 5 feet. With a storage capacity of 120 acre-feet, Johnston serves as a vital resource for supporting the local ecosystem and wildlife in the area.

Despite its low hazard potential and fair condition assessment, Johnston poses a moderate risk level (3) according to the data. The dam has a controlled spillway type and covers a surface area of 15 acres, with a drainage area of 1.2 square miles. The last inspection of Johnston took place on May 30, 2019, with an inspection frequency of every 10 years.

While Johnston has not undergone any significant modifications in recent years, it remains an important structure for the conservation of fish and wildlife in the region. As climate change continues to impact water resources, Johnston serves as a reminder of the crucial role that well-maintained dams and ponds play in maintaining biodiversity and ecological balance in our changing environment.

Year Completed

1960

Dam Length

22

Dam Height

10

Surface Area

15

Hydraulic Height

5

Drainage Area

1.2

Nid Storage

120

Structural Height

10

Hazard Potential

Low

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.