Cortez #1 Reservoir Report

Last Updated: December 5, 2025

Cortez #1 is a vital earth dam located in Colorado, specifically in Montezuma County near the city of Cortez.


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Summary

Completed in 1938, this dam serves the primary purpose of providing water supply, with a capacity to store up to 145 acre-feet of water. With a height of 38 feet and a structural height of 44 feet, Cortez #1 plays a significant role in managing water resources in the region.

Managed by the local government and regulated by the Colorado Department of Water Resources, Cortez #1 has been designated as a state-regulated structure. The dam's condition was last assessed as fair in October 2020, with a significant hazard potential and a moderate risk assessment rating. Despite the need for regular inspections and maintenance, Cortez #1 continues to play a crucial role in water management and supply in the area, ensuring the safety and reliability of its operations.

With an uncontrolled spillway and valve outlets, Cortez #1 is equipped to handle a maximum discharge of 253 cubic feet per second. The dam's location on the McElmo Creek-TR river system adds to its importance in water resource management. As an essential part of the region's infrastructure, Cortez #1 stands as a testament to the ongoing efforts to safeguard and optimize water resources in Colorado.

Year Completed

1938

Dam Length

875

Dam Height

38

River Or Stream

MCELMO CREEK-TR

Primary Dam Type

Earth

Surface Area

9

Hydraulic Height

41

Nid Storage

145

Structural Height

44

Outlet Gates

Valve - 1, Valve - 2

Hazard Potential

Significant

Nid Height

44
       
Seasonal Comparison

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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.