Horse Mesa Reservoir Report

Last Updated: December 5, 2025

Horse Mesa is a Federal-owned concrete dam located on the Salt River in Maricopa, Arizona.


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Summary

Completed in 1926, this hydroelectric structure stands at a towering height of 305 feet, with a storage capacity of 261,335 acre-feet. The dam serves multiple purposes including hydroelectric power generation, irrigation, and water supply for the region.

With a hazard potential rated as high and a risk assessment indicating a very high risk level, Horse Mesa is a critical infrastructure requiring constant monitoring and maintenance. The dam underwent modifications in 1999 for foundation and seismic upgrades to ensure its structural integrity and safety. Bureau of Reclamation is the primary agency responsible for the operation, inspection, and regulatory oversight of this essential water resource.

Water resource and climate enthusiasts would be fascinated by the historical significance and engineering marvel of Horse Mesa. As a key component of the water management system in Arizona, this dam plays a crucial role in providing water for irrigation, power generation, and municipal use. Its strategic location on the Salt River highlights the importance of sustainable water resource management in arid regions like Maricopa County.

Years Modified

1999 - Foundation, 1999 - Seismic

Year Completed

1926

Dam Length

660

Dam Height

305

River Or Stream

SALT RIVER

Primary Dam Type

Concrete

Surface Area

2660

Hydraulic Height

272

Drainage Area

210

Nid Storage

261335

Structural Height

305

Hazard Potential

High

Foundations

Rock

Nid Height

305
       
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.