Cattail #1 Reservoir Report

Last Updated: December 5, 2025

Cattail #1 is a privately owned Earth dam located in Larimer, Colorado, along the Big Thompson River.


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Summary

Built in 1966 by the USDA NRCS, this dam stands at a height of 22 feet and has a length of 1,172 feet, providing flood risk reduction to the surrounding area. With a storage capacity of 91 acre-feet and a maximum discharge of 5,733 cubic feet per second, Cattail #1 plays a crucial role in managing water flow and protecting the local community from potential flooding events.

The dam is regulated by the Colorado Department of Water Resources and undergoes regular inspections to ensure its structural integrity and safety. Despite being classified as having a low hazard potential, the dam is considered to have a moderate risk level, highlighting the importance of proper risk management measures. While the condition assessment of Cattail #1 is currently listed as "Not Rated," the dam continues to serve its primary purpose of flood risk reduction effectively and remains a key component of Colorado's water resource infrastructure.

Overall, Cattail #1 serves as a vital piece of water resource management in the region, showcasing the collaboration between private owners and government agencies to protect the community from potential flooding risks. With its strategic location along the Big Thompson River and its significant storage capacity, this Earth dam plays a critical role in safeguarding the surrounding area and managing water flow effectively. As climate change continues to impact water resources, dams like Cattail #1 will become increasingly essential in ensuring the resilience and sustainability of water infrastructure in Colorado.

Year Completed

1966

Dam Length

1172

Dam Height

10

River Or Stream

BIG THOMPSON RIVER-TR

Primary Dam Type

Earth

Surface Area

19

Hydraulic Height

15

Drainage Area

1

Nid Storage

91

Structural Height

22

Hazard Potential

Low

Nid Height

22
       
Seasonal Comparison

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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.