Grand Lake Reservoir Report

Last Updated: December 5, 2025

Grand Lake is a natural lake located in the Rocky Mountains of Colorado.


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Summary

The lake has a long history, with Native American tribes using it as a hunting and fishing ground for centuries. During the late 1800s, the area around the lake was settled and transformed into a tourist destination, with steamboats and hotels catering to visitors. Today, Grand Lake is a popular destination for fishing, boating, and hiking.

The lake is fed by several streams, including the North Inlet and the Tonahutu Creek. Its waters flow into the Colorado River, making it an important part of the state's hydrology. Snowpack in the surrounding mountains is a significant source of water for the lake, and the Colorado-Big Thompson project diverts water from the lake to provide irrigation for agricultural land in northeastern Colorado. Despite its many uses, Grand Lake remains a pristine natural resource that is treasured by locals and visitors alike.

Reservoir Details

Storage 24hr Change 3.28%
Percent of Normal 100%
Minimum 585.3 acre-ft
2018-07-01
Maximum 964.1 acre-ft
2010-06-07
Average 820 acre-ft
       
Seasonal Comparison
Water Surface Elevation Levels
Storage Levels
Pool Elevation Levels
Storage Levels
Pool Elevation Levels

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.