Hidden Dam Reservoir Report

Last Updated: December 5, 2025

Hidden Dam, also known as Hensley Lake, is a Federal-owned structure located in Madera, California.


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Summary

Built in 1975 by the US Army Corps of Engineers, the dam stands at 140 feet tall and has a maximum storage capacity of 116,727 acre-feet. Its primary purpose is flood risk reduction, but it also serves for hydroelectric power generation, irrigation, and recreation. The dam is situated on the Fresno River and covers a surface area of 1570 acres.

With a high hazard potential, Hidden Dam is continuously monitored and managed by the US Army Corps of Engineers to mitigate flood risks. The agency regularly inspects the dam, updates emergency action plans, and collaborates with local emergency managers to ensure preparedness in case of a dam-related emergency. Despite its risk management measures, the dam's limited water storage capacity and the potential for severe weather events to overwhelm the system highlight the importance of ongoing vigilance and maintenance. As the agency works to address all types of flood risks associated with the dam, additional details specific to Hidden Dam will be provided in the future to enhance understanding and preparedness.

Year Completed

1975

Dam Length

5730

Dam Height

140

River Or Stream

FRESNO RIVER

Primary Dam Type

Earth

Surface Area

1570

Hydraulic Height

163

Drainage Area

234

Nid Storage

90000

Structural Height

184

Hazard Potential

High

Nid Height

184
       
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.