Monarch Lake Reservoir Report

Last Updated: December 4, 2025

Monarch Lake, located in Grand County, Colorado, is a federally-owned recreational water body that serves as a fish and wildlife pond.


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Summary

Managed by the USDA Forest Service, this Earth-type dam was completed in 1929 and stands at a height of 18 feet, with a storage capacity of 2000 acre-feet. The dam holds back Arapaho Creek, providing a serene setting for outdoor enthusiasts to enjoy activities such as fishing and boating.

With a drainage area of 47 square miles and a maximum discharge of 3300 cubic feet per second, Monarch Lake has a high hazard potential but is currently rated as "Not Rated" in terms of condition assessment. Despite its age, the dam has not been modified in recent years, raising some concerns about its maintenance and potential risks. While the dam is uncontrolled, the Forest Service conducts regular inspections to ensure its safety and manage any potential emergencies.

In the event of a dam failure, there are no specific emergency action plans in place, highlighting the need for improved risk management measures. Despite these concerns, Monarch Lake remains a popular destination for outdoor recreation, attracting visitors from near and far to enjoy its scenic beauty and abundant wildlife.

Year Completed

1929

Dam Length

1005

Dam Height

18

River Or Stream

ARAPAHO CREEK

Primary Dam Type

Earth

Hydraulic Height

13

Drainage Area

47

Nid Storage

2000

Structural Height

25

Outlet Gates

Uncontrolled

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

25
       
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.