Lake Mission Viejo Reservoir Report

Last Updated: December 5, 2025

Lake Mission Viejo, located in Mission Viejo, California, is a privately owned reservoir on Oso Creek that serves primarily as a water supply source.


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Summary

Built in 1976, this earth-type dam stands at 123 feet in height and spans 1750 feet in length, with a storage capacity of 4300 acre-feet. The reservoir covers a surface area of 150 acres and has a drainage area of 3.6 square miles, making it a vital resource for the local community.

Despite its primary purpose of water supply, Lake Mission Viejo also offers recreational opportunities for residents and visitors to enjoy. With its picturesque setting and varied activities such as boating and fishing, the reservoir serves as a popular destination for outdoor enthusiasts. The dam's satisfactory condition assessment and high hazard potential highlight the importance of regular inspections and emergency preparedness to ensure the safety and security of the surrounding areas.

Managed by private owners and regulated by the California Department of Water Resources, Lake Mission Viejo plays a crucial role in sustaining the region's water resources and supporting the needs of the community. With its strategic location and significant storage capacity, this reservoir stands as a key asset in managing water supply and promoting resilience in the face of changing climate conditions.

Year Completed

1976

Dam Length

1750

Dam Height

123

River Or Stream

Oso Creek

Primary Dam Type

Earth

Surface Area

150

Hydraulic Height

114

Drainage Area

3.6

Nid Storage

4300

Hazard Potential

High

Nid Height

123
       
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.