Rainbow Lake Reservoir Report

Last Updated: December 4, 2025

Rainbow Lake in Larimer, Colorado, is a private earth dam completed in 2016 with a primary purpose of water supply.


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Summary

Located in Pinewood Springs, this dam on the West Fork Little Thompson River has a height of 16 feet and a length of 300 feet, providing a storage capacity of 69 acre-feet. While its hazard potential is rated as low, the risk assessment indicates a moderate level of risk.

This picturesque reservoir covers 7 acres and offers recreational opportunities in addition to its water supply function. Designed by GEI and Nick Miller, Rainbow Lake is regulated by the Colorado Division of Water Resources, with permitting, inspection, and enforcement carried out by state authorities. Despite its relatively small size, the dam serves a vital role in the local water management system, ensuring a stable supply for the surrounding community.

Water resource and climate enthusiasts will appreciate Rainbow Lake as a well-maintained and regulated structure that contributes to water supply and recreation in the area. With its low hazard potential and moderate risk assessment, this earth dam represents a balanced approach to water management, emphasizing safety and sustainability. Its location in the scenic Colorado landscape adds to its charm, making it a noteworthy site for those interested in the intersection of water resources and environmental conservation.

Year Completed

2016

Dam Length

300

Dam Height

16

River Or Stream

W FORK LITTLE THOMPSON

Primary Dam Type

Earth

Surface Area

7

Nid Storage

69

Structural Height

20

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

20
       
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.