Black Hollow Reservoir Report

Last Updated: December 5, 2025

Black Hollow is a privately owned irrigation dam located in Weld County, Colorado, specifically in the city of Severance.


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Summary

Built in 1918, this Earth-type dam stands at 40 feet tall and stretches 1,260 feet in length, creating a reservoir with a storage capacity of 9,300 acre-feet. The dam regulates Black Hollow Creek, with a drainage area of 21 square miles, and has a spillway width of 1,820 feet to manage maximum discharge of 38,200 cubic feet per second.

Despite being classified as having a high hazard potential, Black Hollow Dam is currently in satisfactory condition according to its last inspection in June 2020. It is under the regulatory oversight of the Colorado Division of Water Resources and undergoes regular inspections and enforcement to ensure its safety and functionality. The dam serves a crucial purpose in providing irrigation water to the surrounding area, showcasing the intersection of water resource management and climate considerations in the region.

With its historical significance and vital role in water management, Black Hollow Dam serves as a key infrastructure in Weld County. Its presence highlights the importance of maintaining and regulating dams for irrigation purposes, while also emphasizing the need for continued monitoring and risk assessment to address climate-related challenges in water resource management. As water resource and climate enthusiasts, understanding the intricacies of dams like Black Hollow is essential in safeguarding our environment and ensuring sustainable water practices for the future.

Year Completed

1918

Dam Length

1260

Dam Height

40

River Or Stream

BLACK HOLLOW CREEK

Primary Dam Type

Earth

Surface Area

371

Hydraulic Height

39

Drainage Area

21

Nid Storage

9300

Structural Height

42

Hazard Potential

High

Nid Height

42
       
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.