Great Western Reservoir Report

Last Updated: December 5, 2025

Great Western is a vital water supply dam located in Westminster, Colorado, along the Walnut Creek.


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Summary

Built in 1903, this Earth-type dam stands at a height of 70 feet and has a maximum storage capacity of 4,459 acre-feet. It serves as a critical resource for the local government and is regulated by the Colorado Department of Water Resources.

With a high hazard potential and fair condition assessment, Great Western is closely monitored for safety and underwent its last inspection in May 2020. The dam has a spillway width of 113 feet and a maximum discharge capacity of 6,600 cubic feet per second. Despite its age, the dam continues to play a crucial role in water management for the region, with a moderate risk level assigned to it.

As an essential infrastructure for water supply purposes, Great Western's historical significance and ongoing operational relevance make it a noteworthy site for water resource and climate enthusiasts. Its location in Broomfield County, Colorado, and association with the Omaha District highlight the collaborative efforts required to maintain and manage water resources effectively in the region.

Year Completed

1903

Dam Length

1885

Dam Height

70

River Or Stream

WALNUT CREEK

Primary Dam Type

Earth

Surface Area

150

Hydraulic Height

54

Drainage Area

4

Nid Storage

4459

Structural Height

83

Hazard Potential

High

Nid Height

83
       
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.