Onwatt Reservoir Report
Last Updated: December 5, 2025
Onwatt is a privately owned water resource located in Phillips County, Montana, specifically in the city of Malta.
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Summary
Completed in 1932, this earth dam serves multiple purposes, including fire protection, stock, and a small fish pond. It has a dam height of 20 feet, a length of 200 feet, and a storage capacity of 81 acre-feet. Onwatt is regulated by the Montana Department of Natural Resources and Conservation (DNRC), with state jurisdiction, permitting, inspection, and enforcement in place.
Situated on TR-ALKALI CREEK, Onwatt contributes to the overall water management system in the area, providing essential resources for fire protection and agricultural use. With a low hazard potential and a condition assessment that is currently not rated, the dam plays a crucial role in the local ecosystem. Although the dam has not been modified in recent years, its emergency action plan status, risk assessment, and inundation maps remain under evaluation, reflecting a proactive approach to ensure safety and sustainability.
Overall, Onwatt represents a valuable asset for water resource and climate enthusiasts, showcasing the importance of private water infrastructure for community resilience and ecosystem health. The dam's historical significance, functional versatility, and regulatory compliance demonstrate a commitment to responsible water management practices in the state of Montana. As efforts continue to monitor and improve the dam's safety features, Onwatt remains a cornerstone of water resource management in the region, serving as a model for sustainable infrastructure development.
Year Completed |
1932 |
Dam Length |
200 |
Dam Height |
20 |
River Or Stream |
TR-ALKALI CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
20 |
Nid Storage |
81 |
Hazard Potential |
Low |
Nid Height |
20 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
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.
Onwatt