Cobb Lake Reservoir Report

Last Updated: December 5, 2025

Cobb Lake, located in Larimer County, Colorado, is a privately owned reservoir primarily used for irrigation purposes.


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Summary

The earth dam, standing at 58 feet high, was completed in 1953 and has a storage capacity of 28,200 acre-feet. With a normal storage level of 22,300 acre-feet, the reservoir covers a surface area of 765 acres and serves a drainage area of 2 square miles.

Managed by the Colorado Division of Water Resources, Cobb Lake poses a high hazard potential due to its size and location. Despite this, the dam's condition is rated as satisfactory, with the last inspection conducted in May 2020. The spillway, of uncontrolled type and 130 feet wide, aids in managing excess water flow. Additionally, the reservoir has a maximum discharge capacity of 9,110 cubic feet per second, ensuring effective flood control measures.

As a vital water resource in the Cache La Poudre River basin, Cobb Lake plays a crucial role in supporting agricultural activities in the region. With its strategic location and storage capacity, the reservoir contributes to the sustainable management of water resources while also serving as a potential recreational site for residents and visitors alike.

Year Completed

1953

Dam Length

1000

Dam Height

58

River Or Stream

CACHE LA POUDRE RIVER-OS

Primary Dam Type

Earth

Surface Area

765

Hydraulic Height

43

Drainage Area

2

Nid Storage

28200

Structural Height

58

Hazard Potential

High

Nid Height

58
       
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.