Blanchard Creek Reservoir Report

Last Updated: December 21, 2025

Blanchard Creek, located in Bonner County, Idaho, is a privately owned irrigation dam completed in 1910.


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Summary

The dam, made of concrete with a multi-arch core and supported by rock and soil foundations, stands at a height of 19 feet with a hydraulic height of 16 feet. The reservoir created by the dam has a storage capacity of 240 acre-feet and covers a surface area of 37.5 acres, serving the primary purpose of irrigation for the surrounding area.

With a drainage area of 34 square miles, Blanchard Creek has a maximum discharge of 108 cubic feet per second and features an uncontrolled spillway 7 feet wide. Despite its age, the dam is in poor condition and has a significant hazard potential, requiring inspections every 4 years. The risk assessment for the dam is moderate, and while emergency action plans have not been updated recently, the dam is regulated and permitted by the Idaho Department of Water Resources.

Given its historical significance and importance for irrigation in the region, efforts to improve the structural integrity and safety of Blanchard Creek Dam are essential to ensure its continued function and minimize risks to downstream communities and the environment. Climate enthusiasts and water resource advocates may find opportunities to support restoration and maintenance initiatives for this vital water infrastructure in Bonner County, Idaho.

Year Completed

1910

Dam Length

60

Dam Height

19

River Or Stream

BLANCHARD CREEK BLANCHARD LAKE

Surface Area

37.5

Hydraulic Height

16

Drainage Area

34

Nid Storage

240

Outlet Gates

Slide (sluice gate)

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

19
       
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.