La Herradura Reservoir Report

Last Updated: December 5, 2025

La Herradura is a privately owned earth dam located in Napa, California, along the Tr Conn Creek.


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Summary

Built in 1948, this dam serves multiple purposes including flood risk reduction, irrigation, and water supply. With a height of 73 feet and a storage capacity of 110 acre-feet, La Herradura plays a crucial role in managing water resources in the region.

Managed by the California Department of Water Resources and regulated by the Safety of Dams program, La Herradura has a low hazard potential and is deemed to be in satisfactory condition. The dam underwent its last inspection in December 2020, with inspections occurring annually to ensure its structural integrity and safety. Despite its relatively small surface area of 5 acres, the dam contributes significantly to the drainage area of 0.52 square miles.

As a key component of flood risk reduction efforts in the area, La Herradura underscores the importance of effective water management practices in the face of a changing climate. With its strategic location and vital functions, this dam exemplifies the intersection of water resource management and climate resilience, making it a noteworthy site for water resource and climate enthusiasts to study and appreciate.

Year Completed

1948

Dam Length

285

Dam Height

73

River Or Stream

Tr Conn Creek

Primary Dam Type

Earth

Surface Area

5

Hydraulic Height

67.4

Drainage Area

0.52

Nid Storage

110

Hazard Potential

Low

Nid Height

73
       
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.