Upper Highline Reservoir Report

Last Updated: December 5, 2025

Upper Highline, also known as Highline Lake, is a state-owned recreational reservoir located in Mesa County, Colorado.


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Summary

Built in 1967, this earth dam stands at a height of 87 feet and has a maximum storage capacity of 7,125 acre-feet. The reservoir covers a surface area of 155 acres and is fed by the Mack Wash-TR river or stream, providing water for various recreational activities.

The dam underwent modifications in 1969 for structural improvements, followed by hydraulic, mechanical, and additional structural enhancements in 1997. With a spillway width of 40 feet and a high hazard potential, Upper Highline is inspected annually, with its condition assessed as fair in the latest evaluation conducted in April 2020. Despite the moderate risk associated with the reservoir, it continues to be a popular destination for water resource and climate enthusiasts, offering opportunities for boating, fishing, and wildlife observation in a picturesque setting.

Situated within the Omaha District, Upper Highline is regulated by the Colorado Division of Water Resources, ensuring compliance with state permitting, inspection, and enforcement requirements. With its scenic surroundings and recreational offerings, this reservoir serves as a vital water resource for the local community while also providing a glimpse into the intersection of water management and environmental stewardship in the region.

Years Modified

1969 - Structural, 1997 - Hydraulic, 1997 - Mechanical, 1997 - Structural

Year Completed

1967

Dam Length

1440

Dam Height

87

River Or Stream

MACK WASH-TR

Primary Dam Type

Earth

Surface Area

155

Hydraulic Height

84

Drainage Area

13

Nid Storage

7125

Structural Height

98

Outlet Gates

Slide (sluice gate) - 1

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

98
       
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.