Patch Reservoir Report

Last Updated: December 5, 2025

Located in Johnson, Wyoming, the Patch dam on Muddy Creek serves primarily for irrigation purposes.


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Summary

Completed in 1958, this privately owned structure stands at a height of 44 feet and boasts a storage capacity of 473 acre-feet. Despite its age, the dam's hazard potential is classified as low, with a moderate risk assessment rating.

With a spillway type of "Uncontrolled" and a single valve outlet gate, Patch dam's condition assessment is marked as poor as of August 2018. The dam's structural height matches its dam height at 44 feet, with a hydraulic height of 38 feet. Although the dam has not been modified over the years, regular inspections every five years ensure its ongoing safety and functionality.

Despite its modest surface area of 26.14 acres and lack of a drainage area, Patch dam plays a critical role in supporting local agriculture through its irrigation capabilities. Enthusiasts of water resources and climate will find Patch's unique design and historical significance to be a compelling case study in sustainable water management practices within the state of Wyoming.

Year Completed

1958

Dam Length

916

Dam Height

44

River Or Stream

MUDDY CREEK

Primary Dam Type

Earth

Surface Area

26.14

Hydraulic Height

38

Nid Storage

473

Structural Height

44

Outlet Gates

Valve - 1

Hazard Potential

Low

Foundations

Soil

Nid Height

44
       
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.