Mcginnis Evaporation Reservoir Report

Last Updated: January 12, 2026

Mcginnis Evaporation, located in Sublette, Wyoming, is a privately owned earth dam structure designed by Joseph C.


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Summary

Lord in 1984. This offstream reservoir has a dam height of 24 feet and a length of 456 feet, providing a storage capacity of 64 acre-feet. With a surface area of 5 acres, the dam serves a primary purpose other than flood control or water supply, reflecting its unique role in managing water resources in the region.

Despite its low hazard potential and fair condition assessment, Mcginnis Evaporation poses a high risk due to its location and design characteristics. The dam lacks a spillway and outlet gates, potentially increasing the risk of flooding in the event of heavy rainfall or snowmelt. Regular inspections are conducted every 5 years to ensure the structure's integrity and safety, with the last assessment performed in May 2021.

For water resource and climate enthusiasts, Mcginnis Evaporation presents an intriguing case study in dam design and risk management. Understanding the complexities of this earth dam structure, its purpose, and the challenges it faces in a changing climate can provide valuable insights into the sustainable management of water resources in arid regions like Wyoming.

Year Completed

1984

Dam Length

456

Dam Height

24

River Or Stream

OFFSTREAM

Primary Dam Type

Earth

Surface Area

5

Nid Storage

64

Structural Height

24

Outlet Gates

None

Hazard Potential

Low

Foundations

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.