Briones Dam Reservoir Report

Last Updated: December 5, 2025

Briones Dam is located in Contra Costa County, California, and was completed in 1964.


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Summary

Its primary purpose is to provide flood control and water supply to the region. The dam impounds the Bear Creek tributary of the San Pablo Reservoir. The hydrology of the area is influenced by the Mediterranean climate, with most of the rainfall occurring between November and April. The dam is primarily fed by surface flows from Bear Creek, but it also receives water from snowpack melt in the surrounding hills during the spring and early summer. The water from the reservoir is used for irrigation and municipal supply, and there are also recreational opportunities such as fishing and hiking in the surrounding Briones Regional Park.

Reservoir Details

Storage 24hr Change -0.02%
Percent of Normal 105%
Minimum 49,150.0 acre-ft
2021-10-19
Maximum 59,250.0 acre-ft
2023-03-29
Average 53,570 acre-ft
Nid_Height 273
Hydraulic_Height 261.2
Drainage_Area 8.6
Year_Completed 1964
Dam_Height 273
Primary_Dam_Type Earth
Surface_Area 735
Hazard_Potential High
Nid_Storage 67520
River_Or_Stream Bear Creek
Dam_Length 2100
       
Seasonal Comparison
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Pool Elevation Levels
Top Conserv Storage Levels
Inflow Levels

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.