Green Lake No. 3 Reservoir Report

Last Updated: December 4, 2025

Green Lake No.


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Summary

3, located in Boulder, Colorado, is a rockfill dam completed in 1907 for the primary purpose of water supply. With a dam height of 28 feet and a storage capacity of 345 acre-feet, this structure plays a crucial role in managing water resources in the region. Situated on North Boulder Creek, the dam has a low hazard potential and a moderate risk assessment rating, indicating its importance for mitigating potential water-related risks in the area.

Owned by the local government and regulated by the Colorado Department of Water Resources, Green Lake No. 3 undergoes regular inspections, permitting, and enforcement to ensure its structural integrity and functionality. Despite being last inspected in 1990, this dam continues to serve as a vital infrastructure for water management and supply in the region. With a spillway width of 15 feet and a maximum discharge capacity of 205 cubic feet per second, Green Lake No. 3 is equipped to handle water flow and maintain water levels within safe limits.

For water resource and climate enthusiasts, Green Lake No. 3 represents a historic and essential piece of infrastructure in Boulder, Colorado. As a key element in the local water supply system, this dam plays a critical role in ensuring water security and management in the region. With its low hazard potential and moderate risk assessment, Green Lake No. 3 stands as a testament to effective water resource management and infrastructure development in the face of changing climate conditions.

Year Completed

1907

Dam Length

315

Dam Height

28

River Or Stream

NORTH BOULDER CREEK

Primary Dam Type

Rockfill

Surface Area

20

Hydraulic Height

28

Drainage Area

1

Nid Storage

345

Structural Height

28

Hazard Potential

Low

Nid Height

28
       
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.
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