Upper Twin Lake Reservoir Report

Last Updated: December 5, 2025

Upper Twin Lake is a privately owned water resource located in Bridgeport, California, within the Mono County.


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Summary

The dam, completed in 1905, stands at a height of 14 feet and serves primarily for irrigation and water supply purposes. With a storage capacity of 2070 acre-feet and a surface area of 286 acres, Upper Twin Lake is a vital source of water for the surrounding area. The dam is regulated and inspected by the California Department of Water Resources to ensure its safety and compliance with state regulations.

Situated along Robinson Creek, Upper Twin Lake has a drainage area of 30.05 square miles and a hydraulic height of 11 feet. Despite being classified as having a high hazard potential, the dam's condition is assessed as fair as of September 2017, with regular inspections carried out to ensure its integrity. The emergency action plan for the dam was last revised in August 2019, indicating proactive measures in place to mitigate potential risks and ensure the safety of the surrounding community in case of emergencies. Enthusiasts of water resources and climate will find Upper Twin Lake an intriguing case study of sustainable water management in a region prone to drought and water scarcity challenges.

Year Completed

1905

Dam Length

160

Dam Height

14

River Or Stream

Robinson Creek

Primary Dam Type

Earth

Surface Area

286

Hydraulic Height

11

Drainage Area

30.05

Nid Storage

2070

Hazard Potential

High

Nid Height

14
       
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.