Star Mountain Reservoir Reservoir Report

Last Updated: December 13, 2025

Star Mountain Reservoir, also known as Lower Chapman Dam, is a privately owned water resource located in Malheur County, Oregon.


°F

°F

mph

Wind

%

Humidity

Summary

Built in 1961, this earth dam stands at a height of 66 feet and has a storage capacity of 1460 acre-feet, primarily used for irrigation purposes. Situated on the No. Fork Granite Creek, this reservoir covers a surface area of 25 acres and has a drainage area of 87 square miles.

Managed by the Oregon Water Resources Department, Star Mountain Reservoir poses a significant hazard potential and undergoes inspections every 3 years. With a moderate risk assessment rating, the dam features an uncontrolled spillway and slide gates for outlet control. Its location in Riverside, Oregon, makes it an essential component of the local water supply infrastructure, ensuring water availability for agriculture in the region.

For water resource and climate enthusiasts, Star Mountain Reservoir represents a vital piece of Oregon's irrigation network, serving as a strategic water storage facility for the surrounding area. As a privately owned structure regulated by the state, its role in water management and conservation is crucial for sustaining agricultural activities in Malheur County. With its historical significance and ongoing maintenance, this reservoir continues to play a key role in ensuring water security and resource sustainability in the region.

Year Completed

1961

Dam Length

285

Dam Height

66

River Or Stream

NO. FORK GRANITE CREEK

Primary Dam Type

Earth

Surface Area

25

Hydraulic Height

66

Drainage Area

87

Nid Storage

1460

Structural Height

68

Outlet Gates

Slide (sluice gate)

Hazard Potential

Significant

Nid Height

68
       
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.