Rimrock Lake Reservoir Report

Last Updated: December 13, 2025

Rimrock Lake, located in Harney, Oregon, is a privately owned earth dam built in 1905 primarily for irrigation purposes.


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Summary

With a height of 10 feet and a length of 200 feet, this dam holds a maximum storage capacity of 200 acre-feet and covers a surface area of 134.6 acres. The reservoir's drainage area is 4.6 square miles, with a maximum discharge capacity of 75 cubic feet per second.

Despite being classified as having a low hazard potential, Rimrock Lake is regulated and inspected by the Oregon Water Resources Department. The dam features a slide gate as its outlet gates and has not been rated for its condition assessment as of the last inspection in June 2017. The surrounding area does not have any downstream settlements, adding to the remote and natural beauty of the location.

For water resource and climate enthusiasts, Rimrock Lake offers a glimpse into early 20th-century water management practices and the vital role of irrigation in agricultural areas like Harney County. The dam's historical significance, combined with its peaceful and undisturbed setting, makes it a noteworthy site for those interested in water infrastructure and its impact on the surrounding environment.

Year Completed

1905

Dam Length

200

Dam Height

10

River Or Stream

RIMROCK LAKE

Primary Dam Type

Earth

Surface Area

134.6

Hydraulic Height

8

Drainage Area

4.6

Nid Storage

200

Structural Height

12.5

Outlet Gates

Slide (sluice gate)

Hazard Potential

Low

Nid Height

13
       
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.
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