Upper Rock Lake Main Reservoir Report

Last Updated: December 5, 2025

Upper Rock Lake Main in California is a privately owned dam regulated by the Department of Water Resources (DWR) for the safety of dams.


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Summary

Completed in 1855, this earth dam stands at 17 feet high and serves primarily for hydroelectric purposes. Located in Nevada County, the dam impounds Texas Creek and has a storage capacity of 190 acre-feet, with a surface area of 0.06 square miles and a drainage area of 0.1 square miles.

Despite its low hazard potential, Upper Rock Lake Main is under the oversight of the Federal Energy Regulatory Commission for inspections and regulatory measures. The dam has not been assessed for its current condition, but an Emergency Action Plan (EAP) was last revised in October 2020. With a high risk assessment score of 2, there are likely management measures in place to ensure the safety and integrity of the structure in the event of an emergency.

Water resource and climate enthusiasts interested in the history and details of Upper Rock Lake Main will find its location, design, and operational characteristics intriguing. As a part of the hydroelectric infrastructure in the region, this dam plays a crucial role in water management and energy production, contributing to the overall resilience of the water resource system in the area.

Year Completed

1855

Dam Length

60

Dam Height

17

River Or Stream

Texas Creek

Primary Dam Type

Earth

Surface Area

0.06

Hydraulic Height

14.5

Drainage Area

0.1

Nid Storage

190

Structural Height

17

Hazard Potential

Low

Nid Height

17
       
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.