Rainbow Lake Reservoir Report

Last Updated: December 4, 2025

Rainbow Lake, also known as Mt Yale Reservoir, is a private water resource located in Chaffee County, Colorado, near the city of Buena Vista.


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Summary

Built in 1965, this rockfill dam stands at a height of 23 feet and has a storage capacity of 196 acre-feet, primarily serving recreational purposes such as fishing and wildlife preservation. With a surface area of 19 acres and a drainage area of 32 square miles, Rainbow Lake is fed by the Middle Cottonwood River and boasts a maximum discharge of 1730 cubic feet per second.

Despite its low hazard potential and satisfactory condition assessment, Rainbow Lake is subject to state regulation and inspection by the Colorado Division of Water Resources. The reservoir's uncontrolled spillway, with a width of 61 feet, ensures the safe release of excess water during periods of high flow. Its emergency action plan status and risk assessment indicate a moderate level of risk, with measures in place to mitigate potential hazards. While the dam has not been significantly modified since its construction, regular inspections every six years help to ensure its continued safety and reliability for the surrounding community and ecosystem. Overall, Rainbow Lake stands as a vital water source and recreational haven in the heart of Colorado's scenic landscape.

Year Completed

1965

Dam Length

120

Dam Height

23

River Or Stream

MIDDLE COTTONWOOD

Primary Dam Type

Rockfill

Surface Area

19

Hydraulic Height

23

Drainage Area

32

Nid Storage

196

Structural Height

23

Outlet Gates

Slide (sluice gate) - 0

Hazard Potential

Low

Nid Height

23
       
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.