South Arm Reservoir Reservoir Report

Last Updated: December 5, 2025

Located in Lake County, Oregon, the South Arm Reservoir is a significant water resource utilized primarily for irrigation purposes.


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Summary

Built in 1908, this earth dam stands at a height of 19 feet, with a storage capacity of 560 acre-feet. The reservoir covers a surface area of 128.6 acres and is situated on Hay Creek, providing vital water supply to the surrounding agricultural lands in the area of WEST SIDE.

With a low hazard potential and a condition assessment marked as "Not Rated," the South Arm Reservoir is a well-maintained structure that is regulated, inspected, and enforced by the Oregon Water Resources Department. The reservoir features a slide (sluice gate) as its outlet gates and has a maximum discharge capacity of 180 cubic feet per second. Despite its age, the dam remains a crucial piece of infrastructure for water management in the region.

Enthusiasts of water resources and climate will appreciate the historical significance and the ongoing operational relevance of the South Arm Reservoir. As a private-owned facility, the reservoir plays a key role in sustaining agricultural activities in the area and showcases the importance of water management and irrigation systems in supporting local economies and communities. With its picturesque location and vital function, the South Arm Reservoir stands as a testament to the ingenuity and foresight of early water resource developers in Oregon.

Year Completed

1908

Dam Length

170

Dam Height

19

River Or Stream

HAY CREEK

Primary Dam Type

Earth

Surface Area

128.6

Hydraulic Height

14

Drainage Area

5.2

Nid Storage

560

Structural Height

19

Outlet Gates

Slide (sluice gate)

Hazard Potential

Low

Nid Height

19
       
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.