Lake Ann Reservoir Report

Last Updated: December 5, 2025

Lake Ann, also known as Dinkle Lake, is a private reservoir located in Pitkin County, Colorado, near the city of El Jebel.


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Summary

The dam, completed in 1912 and designed by BOND Engineering, stands at a height of 40 feet and serves primarily for irrigation purposes. With a storage capacity of 562 acre-feet, the reservoir covers an area of 20 acres and is fed by the West Sopris Creek.

Despite its age, Lake Ann has been regularly inspected and maintained by the Colorado Department of Water Resources (DWR), with a fair condition assessment as of July 2020. The dam's spillway, an uncontrolled type with a width of 40 feet, has a high hazard potential but is considered to have a moderate risk level. The reservoir's emergency action plan (EAP) was last revised in December 2015, and the facility is equipped with a slide (sluice gate) outlet gate for water release.

Lake Ann offers not only essential irrigation functions but also recreational opportunities for the local community. With its picturesque location and historical significance, this reservoir serves as a vital water resource in the region while maintaining a balance between water management and environmental preservation.

Year Completed

1912

Dam Length

580

Dam Height

40

River Or Stream

WEST SOPRIS CREEK-OS

Primary Dam Type

Earth

Surface Area

20

Hydraulic Height

40

Nid Storage

562

Structural Height

42

Outlet Gates

Slide (sluice gate) - 1

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

42
       
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.