Decoto Reservoir Reservoir Report

Last Updated: December 5, 2025

Decoto Reservoir, located in Fremont, California, is a vital offstream water supply structure primarily owned by the local government.


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Summary

Completed in 1966, this Earth type dam stands at a height of 33 feet, with a hydraulic height of 30.5 feet and a length of 1360 feet. It has a storage capacity of 46 acre-feet, serving the purposes of irrigation and water supply for the region.

Despite its satisfactory condition assessment as of September 2017, Decoto Reservoir is classified as having a high hazard potential. Regular inspections are conducted, with the last one taking place in February 2021. The dam is regulated, permitted, and inspected by the California Department of Water Resources' Safety of Dams program, ensuring its compliance with state safety standards. In the event of an emergency, the reservoir's Emergency Action Plan is expected to be readily available, although details on its preparation and adherence to guidelines are currently unspecified.

For water resource and climate enthusiasts, Decoto Reservoir offers a fascinating case study in water management and infrastructure. With its location in Alameda County, the reservoir plays a crucial role in supporting local agricultural activities and providing a reliable water supply to the surrounding communities. As efforts continue to maintain its structural integrity and emergency preparedness, Decoto Reservoir stands as a testament to the ongoing importance of sustainable water resource management in the face of changing climate conditions.

Year Completed

1966

Dam Length

1360

Dam Height

33

River Or Stream

Offstream

Primary Dam Type

Earth

Surface Area

3

Hydraulic Height

30.5

Nid Storage

46

Hazard Potential

High

Nid Height

33
       
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.