Cinnabar Reservoir Report
Last Updated: December 16, 2025
Cinnabar, also known as Swain Number Two, is a privately owned irrigation dam located in Weiser, Idaho.
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Summary
Built in 1975, this earth dam stands at a height of 26 feet and has a hydraulic height of 21.5 feet. With a storage capacity of 173 acre-feet and a surface area of 22 acres, Cinnabar plays a crucial role in providing water for agricultural purposes in the area.
Managed by the Idaho Department of Water Resources, Cinnabar is regulated, permitted, inspected, and enforced to ensure its safe operation. The dam has a low hazard potential and is currently assessed to be in fair condition. With a moderate risk level, measures for risk management are in place to address any potential issues that may arise. In the event of an emergency, protocols are in place to ensure that appropriate action can be taken swiftly and effectively.
Situated on unnamed streams and Cove Creek in Washington County, Cinnabar serves as a key infrastructure for water resource management in the region. With its controlled spillway and moderate risk assessment, the dam continues to support the irrigation needs of the local community while maintaining a focus on safety and environmental responsibility.
Year Completed |
1975 |
Dam Length |
480 |
Dam Height |
26 |
River Or Stream |
UNNAMED STREAMS COVE CREEK |
Surface Area |
22 |
Hydraulic Height |
21.5 |
Drainage Area |
1.7 |
Nid Storage |
173 |
Hazard Potential |
Low |
Foundations |
Rock, Soil |
Nid Height |
26 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Weiser River Nr Weiser Id
|
281cfs |
Crane Creek At Mouth Nr Weiser Id
|
6cfs |
Snake River At Weiser Id
|
10100cfs |
Payette River Nr Payette Id
|
1590cfs |
Weiser River Nr Cambridge Id
|
172cfs |
Payette River Nr Letha Id
|
1270cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Cinnabar