Nicolaysen Reservoir Report

Last Updated: December 14, 2025

Nicolaysen Dam, located in the Big Muddy Oil Field of Natrona, Wyoming, is a privately owned structure primarily used for irrigation purposes.


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Summary

Completed in 1899, this Earth-type dam stands at a height of 22 feet and has a storage capacity of 475 acre-feet, with a normal storage level of 330 acre-feet. The dam spans a length of 1500 feet and is situated on the Dry Muddy Creek, within the jurisdiction of the Wyoming State Regulatory Agency.

With a significant hazard potential and fair condition assessment as of 2017, Nicolaysen Dam poses a moderate risk according to a risk assessment evaluation. It features an uncontrolled spillway with a width of 4 feet and an outlet gate controlled by a single valve. The dam has a hydraulic height of 15 feet and a structural height of 20 feet, serving the surrounding area with water for irrigation needs.

Despite its age, Nicolaysen Dam continues to be inspected every five years to ensure its structural integrity and safety. As water resource and climate enthusiasts, it is crucial to monitor and manage the risk associated with dams like Nicolaysen to safeguard communities and maintain the sustainable use of water resources in the region.

Year Completed

1899

Dam Length

1500

Dam Height

22

River Or Stream

DRY MUDDY CREEK

Primary Dam Type

Earth

Surface Area

30

Hydraulic Height

15

Drainage Area

5.9

Nid Storage

475

Structural Height

20

Outlet Gates

Valve - 1

Hazard Potential

Significant

Foundations

Soil

Nid Height

22
       
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.