Black Reservoir Reservoir Report

Last Updated: December 7, 2025

Black Reservoir, also known as Junction Reservoir, is a privately owned water storage facility located in Sonora Junction, California.


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Summary

Built in 1905, this earth dam stands at 18 feet tall and spans a length of 1330 feet, with a storage capacity of 185 acre-feet. The reservoir serves primarily for irrigation and water supply purposes, drawing water from Black Creek to support agricultural activities in the area.

Managed by the California Department of Water Resources (DWR) and the Safety of Dams, Black Reservoir is subject to state regulations, permitting, inspection, and enforcement to ensure its safe operation. Despite its low hazard potential and satisfactory condition assessment, regular inspections are conducted to maintain the reservoir's integrity. The dam has a spillway type and width unspecified, but with a drainage area of 0.2 square miles, it plays a crucial role in managing water resources in the region.

Situated in Mono County, California, Black Reservoir offers a vital water storage solution for the surrounding community. With its historical significance and ongoing state oversight, this reservoir stands as a testament to sustainable water management practices in the face of a changing climate. For water resource and climate enthusiasts, Black Reservoir serves as a fascinating example of how private ownership and state regulation can work together to ensure the reliability and safety of essential water infrastructure.

Year Completed

1905

Dam Length

1330

Dam Height

18

River Or Stream

Black Creek

Primary Dam Type

Earth

Surface Area

21

Hydraulic Height

15.4

Drainage Area

0.2

Nid Storage

185

Hazard Potential

Low

Nid Height

18
       
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.