Zimmerman Lake Reservoir Report

Last Updated: December 4, 2025

Zimmerman Lake in Larimer County, Colorado, is a state-regulated earth dam built in 1913 for the primary purpose of creating a fish and wildlife pond.


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Summary

The dam stands at a height of 10 feet and has a length of 600 feet, with a storage capacity of 238 acre-feet. The lake covers an area of 20 acres and is fed by the Joe Wright Creek. Despite its low hazard potential, the dam's condition was assessed as unsatisfactory during the last inspection in July 2013.

Located just 42 miles from Fort Collins, Zimmerman Lake offers a serene setting for outdoor enthusiasts and nature lovers. Its controlled spillway, with a width of 11 feet, helps manage the lake's water levels, while the moderate risk assessment rating indicates a need for ongoing monitoring and risk management measures. The dam is subject to state regulation, permitting, inspection, and enforcement by the Colorado Division of Water Resources, ensuring the safety and integrity of the structure for both recreational and environmental purposes.

With its picturesque surroundings and crucial role in supporting local wildlife, Zimmerman Lake serves as a vital water resource in the region. Whether it's for fishing, wildlife observation, or simply enjoying the beauty of the outdoors, this historic lake continues to be a cherished destination for those passionate about water resources and climate conservation in Colorado.

Year Completed

1913

Dam Length

600

Dam Height

10

River Or Stream

JOE WRIGHT CR-TR

Primary Dam Type

Earth

Surface Area

20

Hydraulic Height

10

Nid Storage

238

Structural Height

10

Hazard Potential

Low

Nid Height

10
       
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.