Post Falls South Channel Reservoir Report

Last Updated: December 7, 2025

Post Falls South Channel is a gravity dam located in Greenacres Subdivision, Idaho, on the Spokane River.


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Summary

Built in 1906, this hydroelectric dam stands at a height of 25 feet with a hydraulic height of 18 feet and a structural height of 25 feet. It serves multiple purposes including fish and wildlife pond, recreation, and hydroelectric power generation, with a normal storage capacity of 225,000 acre-feet.

With a hazard potential rated as high and a risk assessment indicating a very high risk level, the dam is under the regulatory oversight of the Federal Energy Regulatory Commission. It boasts a spillway width of 127 feet and features six vertical lift outlet gates. The dam's drainage area covers 3,784 square miles and its surface area spans 48,000 acres, making it a significant water resource structure in the region.

Despite its age, Post Falls South Channel remains a vital component of the water infrastructure in Kootenai County, Idaho. With its rich history and ongoing importance for both water management and energy production, this dam exemplifies the intersection of hydrology, engineering, and environmental stewardship in the face of changing climate conditions.

Year Completed

1906

Dam Length

127

Dam Height

25

River Or Stream

Spokane River

Primary Dam Type

Gravity

Surface Area

48000

Hydraulic Height

18

Drainage Area

3784

Nid Storage

225000

Structural Height

25

Outlet Gates

Vertical Lift - 6

Hazard Potential

High

Foundations

Rock

Nid Height

25
       
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.