Lake Mamie Reservoir Report

Last Updated: December 5, 2025

Located in Mono County, California, Lake Mamie is a Federal-owned water supply reservoir with a primary purpose of providing water.


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Summary

Built in 1968, this concrete dam stands at a height of 6 feet and stretches 50 feet in length. Situated in Mammoth Lakes, the reservoir is fed by Mammoth Creek and serves multiple purposes including fish and wildlife pond, flood risk reduction, and recreation in addition to water supply.

The dam at Lake Mamie has a significant hazard potential and a very high risk assessment, making it a crucial structure for water resource and climate enthusiasts to monitor. With a controlled spillway and a valve outlet gate, the dam underwent mechanical modifications in 1968. Despite not being rated for its condition assessment, Lake Mamie remains an essential resource in the region, providing vital water supply and recreational opportunities while managing flood risks in the area.

Managed by the Forest Service, Lake Mamie's risk management measures remain unspecified, but its strategic location near Mammoth Lakes and Mammoth Creek highlights its importance in the local ecosystem. As a part of the Los Angeles District, this reservoir is a key component in the water infrastructure of Mono County, California, attracting both water resource professionals and outdoor enthusiasts alike.

Years Modified

1968 - Mechanical

Year Completed

1968

Dam Length

50

Dam Height

6

River Or Stream

MAMMOTH CREEK

Primary Dam Type

Concrete

Outlet Gates

Valve

Hazard Potential

Significant

Foundations

Rock

Nid Height

6
       
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.