Boulder Lake Reservoir Report

Last Updated: December 15, 2025

Boulder Lake, located in Valley County, Idaho, is a privately owned reservoir with a primary purpose of irrigation.


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Summary

The dam, a masonry structure with a multi-arch core, stands at a height of 15 feet and was completed in 1902. With a storage capacity of 1310 acre-feet and a surface area of 114 acres, Boulder Lake serves as a vital resource for the surrounding agricultural community.

The reservoir is fed by Boulder Creek, a tributary of the North Fork Payette River, and has a drainage area of 1.8 square miles. The spillway, which is uncontrolled and 480 feet wide, allows for a maximum discharge of 160 cubic feet per second. The dam's condition was last assessed as "fair" in July 2018, with a significant hazard potential and a moderate risk assessment score of 3. Despite its age, Boulder Lake continues to play a crucial role in water resource management and agricultural irrigation in the region.

Water resource and climate enthusiasts interested in the history and engineering of irrigation infrastructure will find Boulder Lake to be a fascinating case study. From its construction over a century ago to its continued operation and maintenance today, the reservoir exemplifies the intersection of human ingenuity and natural resource management. With its location in the scenic town of McCall, Idaho, Boulder Lake is not just a functional reservoir but also a reminder of the importance of sustainable water utilization in a changing climate.

Year Completed

1902

Dam Length

450

Dam Height

15

River Or Stream

BOULDER CREEK NORTH FORK PAYETTE RIVER

Surface Area

114

Hydraulic Height

15

Drainage Area

1.8

Nid Storage

1310

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

15
       
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.