Lake Desmet (South Dam) Reservoir Report
Last Updated: December 5, 2025
Lake Desmet (South Dam) in Wyoming is a vital water supply source with a storage capacity of 234,987 acre-feet and a surface area of 2,653 acres.
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Summary
Completed in 1975, this earth dam stands at a height of 80 feet and has a structural height of 120 feet, serving the purpose of water supply for the local government in Ucross. The dam is regulated, inspected, and enforced by the Wyoming State Engineer's Office, ensuring its safety and functionality.
Located on the Piney and Rock Creek rivers, Lake Desmet (South Dam) has a high hazard potential and a fair condition assessment as of the last inspection in July 2019. The dam features an uncontrolled spillway with a width of 200 feet and a maximum discharge capacity of 8,520 cubic feet per second. With a moderate risk assessment rating, the dam's emergency action plan (EAP) status and risk management measures are currently under review, highlighting the importance of ongoing monitoring and maintenance to ensure the safety of the surrounding community and water resources.
Managed by the local government, Lake Desmet (South Dam) plays a crucial role in providing water supply for the region while also posing potential risks that require proactive management. With Liz Cheney representing the Congressional District in Wyoming where the dam is located, stakeholders and authorities must work together to ensure the dam's integrity, emergency preparedness, and risk mitigation strategies are up to date and in line with regulatory standards to safeguard both the environment and the community.
Year Completed |
1975 |
Dam Length |
4000 |
Dam Height |
80 |
River Or Stream |
PINEY AND ROCK CREEK |
Primary Dam Type |
Earth |
Surface Area |
2653 |
Hydraulic Height |
70 |
Drainage Area |
40.5 |
Nid Storage |
234987 |
Structural Height |
120 |
Outlet Gates |
Valve - 1 |
Hazard Potential |
High |
Foundations |
Soil |
Nid Height |
120 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Piney Creek At Kearny
|
113cfs |
Rock Creek Near Buffalo
|
70cfs |
Clear Creek Near Buffalo
|
12cfs |
South Piney Creek At Willow Park
|
0cfs |
Powder River At Arvada
|
156cfs |
Goose Creek Near Acme
|
123cfs |
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.
Lake Desmet (South Dam)