Dry Falls Reservoir Report

Last Updated: December 22, 2025

Dry Falls, also known as Banks Lake South Dam or South Coulee Dam, is a federal-owned structure located in Grant County, Washington.


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Summary

Completed in 1949 by the Bureau of Reclamation, this earth dam stands at a height of 63 feet and serves multiple purposes including flood risk reduction, hydroelectric power generation, irrigation, and navigation. Situated on the Upper Grand Coulee River, Dry Falls has a storage capacity of 1,275,000 acre-feet and covers a surface area of 27,000 acres.

The dam, with a length of 9,800 feet, is designed with a multi-arch core and is supported by rock and soil foundations. Despite its high hazard potential, the condition assessment of Dry Falls is currently not available, and the last inspection was conducted in June 2020. The Emergency Action Plan (EAP) for the dam was last revised in September 2020, ensuring that the necessary measures are in place to address any potential risks or emergencies associated with the structure.

Dry Falls plays a crucial role in managing water resources in the region, offering flood protection, irrigation water, and hydroelectric power while also providing recreational opportunities for visitors. As a key component of the Bureau of Reclamation's infrastructure, this dam remains an essential asset for the community and a symbol of sustainable water resource management in Washington state.

Year Completed

1949

Dam Length

9800

Dam Height

63

River Or Stream

UPPER GRAND COULEE RIVER

Primary Dam Type

Earth

Surface Area

27000

Hydraulic Height

53

Drainage Area

263

Nid Storage

1275000

Structural Height

123

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

123
       
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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.