Hinkley Reservoir Report

Last Updated: December 5, 2025

Hinkley, also known as Mountain Supply #18, is a private irrigation dam located in Larimer County, Colorado.


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Summary

Completed in 1906, this earth dam stands at a height of 26 feet and spans a length of 1125 feet, providing a storage capacity of 1099 acre-feet. Situated on Boxelder Creek, Hinkley serves as a vital source of water for agricultural purposes in the region.

Managed by the Colorado Department of Water Resources (DWR), Hinkley is regulated, permitted, inspected, and enforced by the state to ensure its safety and functionality. With a low hazard potential and satisfactory condition assessment as of September 2019, this dam plays a crucial role in water resource management in the area. Its uncontrolled spillway, with a width of 55 feet, can handle a maximum discharge of 892 cubic feet per second.

Climate enthusiasts and water resource experts interested in the infrastructure and management of dams will find Hinkley to be a fascinating case study. From its historical significance to its current regulatory framework and risk assessment, Hinkley represents a balance between human intervention in water systems and the need for sustainable resource management. As part of the larger network of dams in Colorado, Hinkley contributes to the irrigation needs of the region while also highlighting the importance of maintaining infrastructure for future generations.

Year Completed

1906

Dam Length

1125

Dam Height

26

River Or Stream

BOXELDER CR-TR

Primary Dam Type

Earth

Surface Area

80

Hydraulic Height

26

Nid Storage

1099

Structural Height

26

Hazard Potential

Low

Nid Height

26
       
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.