Hourglass Reservoir Report

Last Updated: December 4, 2025

Hourglass, also known as Big Beaver, is a vital water resource located in Larimer County, Colorado.


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Summary

Built in 1898, this Earth-type dam stands at 45 feet high and serves primarily for irrigation and water supply purposes. With a maximum storage capacity of 2180 acre-feet and a normal storage of 1729 acre-feet, Hourglass plays a crucial role in supporting the water needs of the surrounding area.

Managed by the local government, Hourglass is regulated by the Colorado Department of Water Resources, ensuring that the dam meets state standards for inspection, permitting, and enforcement. The dam's spillway, with a width of 120 feet, is uncontrolled, adding to the high hazard potential of the structure. Despite the moderate risk assessment, Hourglass has been assessed as in satisfactory condition as of July 2020, highlighting its importance in maintaining a reliable water supply for the region.

With its strategic location on Beaver Creek-TR, Hourglass serves as a key component of the water infrastructure in Fort Collins, Colorado. As water resource and climate enthusiasts, understanding the intricacies of Hourglass and its role in water supply management is essential for ensuring the sustainability and resilience of the region's water resources in the face of changing climate patterns and increasing water demands.

Year Completed

1898

Dam Length

2400

Dam Height

45

River Or Stream

BEAVER CREEK-TR

Primary Dam Type

Earth

Surface Area

76

Hydraulic Height

41

Nid Storage

2180

Structural Height

46

Hazard Potential

High

Nid Height

46
       
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.