Upper Lake Mary Reservoir Report

Last Updated: December 5, 2025

Upper Lake Mary, located in Coconino, Arizona, is a captivating destination for water resource and climate enthusiasts.


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Summary

This local government-owned reservoir, completed in 1941, serves primarily for recreation and water supply purposes. With a capacity of 21,041 acre-feet and a surface area of 1,058 acres, Upper Lake Mary is a significant water source in the region, drawing from a drainage area of 54.3 square miles.

Standing at a height of 38 feet with a structural height of 49 feet, the earth dam on Upper Lake Mary impounds water from Walnut Creek. The reservoir boasts a spillway width of 360 feet and a maximum discharge capacity of 11,000 cubic feet per second. Despite its significant hazard potential, the dam's condition assessment in 2015 deemed it satisfactory, ensuring the safety and stability of the structure for water storage and recreational activities.

With its scenic location near Walnut Canyon National Monument and I-40, Upper Lake Mary offers a serene and picturesque setting for outdoor enthusiasts. The reservoir's moderate risk assessment and regular inspection schedule, every three years, highlight its commitment to safety and environmental stewardship. Whether for boating, fishing, or simply enjoying the natural beauty of the area, Upper Lake Mary is a must-visit destination for those interested in water resources and climate conservation.

Year Completed

1941

Dam Length

845

Dam Height

38

River Or Stream

WALNUT CREEK

Primary Dam Type

Earth

Surface Area

1058

Drainage Area

54.3

Nid Storage

21041

Structural Height

49

Hazard Potential

Significant

Foundations

Rock

Nid Height

49
       
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.