Jawbone Dam #1 Reservoir Report
Nearby: Jawbone Dike #1 Jawbone Dam #2
Last Updated: December 5, 2025
Jawbone Dam #1, located in Harlowton, Montana, was completed in 1966 by the USDA NRCS for the purpose of flood risk reduction along Jawbone Creek.
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Summary
This earth dam stands at a height of 31 feet and a structural height of 35 feet, with a length of 650 feet and a drainage area of 1.97 square miles. The dam has a spillway width of 20 feet and an uncontrolled spillway type, with a maximum discharge capacity of 140 cubic feet per second.
With a hazard potential rated as high and a risk assessment of moderate, Jawbone Dam #1 has undergone satisfactory condition assessments and inspections. The dam is owned and regulated by the local government, with state jurisdiction and permitting, inspection, and enforcement carried out by the DNRC. Emergency action plans have been prepared, although last updated in May 2020, to ensure the safety and protection of nearby residents and infrastructure in the event of a dam failure.
Water resource and climate enthusiasts interested in the engineering and management of dams will find Jawbone Dam #1 to be an intriguing case study. The dam's unique design, construction, and purpose, as well as its risk assessment and emergency preparedness, offer valuable insights into the challenges and considerations involved in safeguarding communities from the impacts of flooding. As a key flood risk reduction structure in Wheatland County, Montana, Jawbone Dam #1 plays a critical role in protecting lives and property along Jawbone Creek.
Year Completed |
1966 |
Dam Length |
650 |
Dam Height |
31 |
River Or Stream |
JAWBONE CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
31 |
Drainage Area |
1.97 |
Nid Storage |
1933 |
Structural Height |
35 |
Outlet Gates |
Vertical Lift |
Hazard Potential |
High |
Foundations |
Rock, Soil |
Nid Height |
35 |
Seasonal Comparison
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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.
Jawbone Dam #1