Lyman Dam Reservoir Report

Last Updated: December 13, 2025

Lyman Dam, located in St.


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Summary

Johns, Arizona, along the Little Colorado River, was completed in 1912 and serves as a crucial water resource for irrigation purposes. The dam is privately owned and state-regulated by the Arizona Department of Water Resources, with a height of 60 feet and a length of 800 feet. With a maximum storage capacity of 44,500 acre-feet and a normal storage of 30,600 acre-feet, the dam covers a surface area of 1,324 acres and has a drainage area of 790 acres.

The dam's spillway type is uncontrolled, with a width of 160 feet, and it has a maximum discharge capacity of 15,000 cubic feet per second. Despite its high hazard potential, Lyman Dam is currently assessed as being in satisfactory condition as of October 2017, with regular inspections taking place every year. The risk assessment for the dam is moderate, with a DSAC (Dam Safety Action Classification) rating of 3, indicating that risk management measures are in place to ensure the safety and reliability of the structure in the face of potential emergencies.

For water resource and climate enthusiasts, Lyman Dam presents an intriguing case study of a historic rockfill dam that continues to play a vital role in supporting agricultural irrigation and recreational activities in the region. With ongoing state regulation and maintenance efforts, the dam stands as a testament to the importance of proper infrastructure management in ensuring the sustainability of water resources amid changing environmental conditions.

Year Completed

1912

Dam Length

800

Dam Height

60

River Or Stream

LITTLE COLORADO RIVER

Primary Dam Type

Rockfill

Surface Area

1324

Drainage Area

790

Nid Storage

44500

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

60
       
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.