Henry J. Mills Reservoir Reservoir Report

Last Updated: December 5, 2025

Henry J.


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Summary

Mills Reservoir is a vital water resource located in Riverside, California, completed in 1979 with a capacity of 83 acre-feet. This offstream reservoir primarily serves as a water supply for the region, crucial for sustaining local communities and ecosystems. Managed by a public utility, the dam stands at a height of 23 feet and has a hydraulic height of 19.3 feet, ensuring a steady water supply for the area.

The reservoir is under the jurisdiction of the California Department of Water Resources (DWR) and is regulated for safety by the Safety of Dams agency. Despite its high hazard potential, the dam has been assessed as satisfactory and is regularly inspected to maintain its structural integrity. With a solid condition assessment in place, emergency action plans are prepared to address any potential risks, ensuring the safety and security of the surrounding area in case of emergencies. The reservoir's location, design, and purpose make it a key player in water resource management in the region.

Overall, Henry J. Mills Reservoir stands as a critical infrastructure for water supply in Riverside, California, demonstrating proper regulatory oversight and safety measures. As a significant component of the local water management system, the reservoir plays a crucial role in ensuring water security for the community. With its strategic location and design, the reservoir serves as a testament to effective water resource management and climate resilience efforts in the region.

Year Completed

1979

Dam Length

2038

Dam Height

23

River Or Stream

Offstream

Primary Dam Type

Earth

Surface Area

6

Hydraulic Height

19.3

Nid Storage

83

Hazard Potential

High

Nid Height

23
       
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.