Gimlet Reservoir Report

Last Updated: December 13, 2025

Gimlet is a privately owned water resource located in Ketchum, Idaho, with a primary purpose of recreation.


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Summary

This earth dam, constructed in 1987, stands at a height of 24 feet and has a hydraulic height of 19.9 feet. The dam spans 800 feet in length and has a storage capacity of 16 acre-feet, serving a drainage area of 0.6 square miles.

The dam on Gimlet is regulated by the Idaho Department of Water Resources and is subject to regular inspections to ensure its structural integrity. Its hazard potential is considered significant, with a fair condition assessment as of May 2018. The area surrounding the dam poses a very high risk of inundation, indicating the need for robust risk management measures.

Water and climate enthusiasts interested in the intersection of water resource management and recreation in the Idaho wilderness will find Gimlet to be a fascinating case study. As a vital structure in the region, the dam's design, construction, and ongoing maintenance serve as a critical aspect of environmental conservation and public safety, highlighting the intricate balance between human recreation and nature preservation in this picturesque setting.

Year Completed

1987

Dam Length

800

Dam Height

24

River Or Stream

UNNAMED STREAM BIG WOOD RIVER

Surface Area

2.5

Hydraulic Height

19.9

Drainage Area

0.6

Nid Storage

16

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

24
       
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.