Wenas Dam Reservoir Report

Last Updated: December 15, 2025

Wenas Dam, located in Selah, Washington, along Wenas Creek, is a rockfill dam primarily used for recreation and irrigation purposes.


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Summary

Built in 1911 by Gray and Osborne, this dam stands at a hydraulic height of 90 feet and a structural height of 86 feet. With a storage capacity of 5,500 acre-feet and a normal storage of 3,200 acre-feet, Wenas Dam covers a surface area of 142 acres and serves a drainage area of 114 square miles.

The dam, managed by the Washington Department of Ecology, has a high hazard potential but is deemed to be in satisfactory condition as of the last assessment in February 2018. Despite its age, Wenas Dam has been regularly inspected every 5 years to ensure its safety and functionality. The dam's maximum discharge capacity is 29,000 cubic feet per second, making it a crucial water resource for the surrounding area.

With its picturesque location and vital role in water management, Wenas Dam stands as a testament to the ingenuity of early 20th-century engineering. As a popular spot for recreational activities, the dam continues to attract water resource and climate enthusiasts who appreciate its historical significance and environmental impact on the Yakima region.

Year Completed

1911

Dam Length

525

River Or Stream

Wenas Creek

Primary Dam Type

Rockfill

Surface Area

142

Hydraulic Height

90

Drainage Area

114

Nid Storage

5500

Structural Height

86

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

90
       
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.