Fairfax Lake Reservoir Report
Nearby: Baker Dam Bonesteel Lake
Last Updated: December 13, 2025
Fairfax Lake in Gregory, South Dakota, is a state-regulated dam on South Scalp Creek with a low hazard potential.
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Summary
Built in 1934, this earth dam stands at 28 feet in height and spans 500 feet in length, providing a maximum storage capacity of 468 acre-feet. The reservoir has a normal storage of 264 acre-feet and drains a 3-square-mile watershed, with a maximum discharge of 1428 cubic feet per second.
Despite not being rated for condition assessment, Fairfax Lake is inspected every 3 years, with the last inspection conducted in May 2017. The dam does not have an Emergency Action Plan (EAP) in place, and there are no inundation maps prepared or risk assessment measures documented. Located within the St. Paul District of the US Army Corps of Engineers, Fairfax Lake is maintained by the South Dakota state agency DANR. For water resource and climate enthusiasts, Fairfax Lake offers a glimpse into the management and regulation of a vital water resource in the region.
Year Completed |
1934 |
Dam Length |
500 |
Dam Height |
28 |
River Or Stream |
SOUTH SCALP CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
28 |
Drainage Area |
3 |
Nid Storage |
468 |
Hazard Potential |
Low |
Nid Height |
28 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Platte Creek Near Platte
|
3cfs |
Niobrara River At Mariaville
|
1650cfs |
Ponca Creek At Verdel
|
23cfs |
Niobrara River Nr. Verdel
|
517cfs |
Keya Paha R At Wewela Sd
|
54cfs |
Long Pine Creek Near Riverview
|
191cfs |
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.
Fairfax Lake
Gregory County