Hidden Reservoir Report

Last Updated: December 9, 2025

Hidden, also known as Hidden Lake, is a private dam located in Mason, Oklahoma.


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Summary

Completed in 1950, this recreational dam stands at 25 feet high with a length of 370 feet, providing a storage capacity of 90 acre-feet. Situated on the TR-Little Walnut Creek, Hidden offers a surface area of 2 acres and a controlled spillway for managing water discharge.

Owned privately, Hidden is regulated by the Oklahoma Water Resources Board, with state permitting, inspection, and enforcement in place to ensure its safety and compliance. Despite being categorized as having a low hazard potential, the dam is rated as having a very high risk due to its condition not being assessed. With a single valve outlet gate and emergency action plan details being unclear, there may be room for improvement in risk management measures for this hidden gem in Okfuskee County.

For water resource and climate enthusiasts, Hidden represents a recreational structure with potential environmental and safety implications. As a privately owned dam nestled in the picturesque landscape of Oklahoma, its risk assessment and management strategies may warrant further attention to ensure the sustainable enjoyment of Hidden Lake for future generations.

Year Completed

1950

Dam Length

370

Dam Height

25

River Or Stream

TR-LITTLE WALNUT CREEK

Primary Dam Type

Earth

Surface Area

2

Hydraulic Height

25

Nid Storage

90

Structural Height

25

Outlet Gates

Valve - 1

Hazard Potential

Low

Foundations

Soil

Nid Height

25
       
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.