Isabel Reservoir Report
Nearby: John Meginess R. Clark No.3
Last Updated: December 12, 2025
Isabel is a state-regulated dam located in South Dakota, specifically in Dewey County.
°F
°F
mph
Wind
%
Humidity
Summary
Built in 1935 by the Works Progress Administration (WPA), this earth dam stands at a height of 30 feet with a length of 1200 feet. It holds a maximum storage capacity of 2432 acre-feet, with a normal storage level of 537 acre-feet and a drainage area of 10 square miles.
The dam's primary purpose and associated structures are not specified, but it is classified as a high hazard potential structure with a fair condition assessment as of October 2018. The spillway type is uncontrolled, with a width of 90 feet. Isabel is situated on the TR. of Firesteel Creek and falls under the jurisdiction of the South Dakota Department of Agriculture and Natural Resources (DANR). Despite its age, the dam continues to be inspected every 3 years and has a moderate risk assessment rating.
Given its historical significance and ongoing regulatory oversight, Isabel serves as a critical water resource management infrastructure in the region. Climate and water resource enthusiasts may find interest in studying the dam's design, construction, and maintenance practices to ensure its continued safety and effectiveness in mitigating flood risks and providing essential water storage capacity for the surrounding area.
Year Completed |
1935 |
Dam Length |
1200 |
Dam Height |
30 |
River Or Stream |
TR. OF FIRESTEEL CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
30 |
Drainage Area |
10 |
Nid Storage |
2432 |
Outlet Gates |
None |
Hazard Potential |
High |
Foundations |
Soil |
Nid Height |
30 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Moreau R Near Whitehorse Sd
|
35cfs |
Grand R At Little Eagle Sd
|
47cfs |
Moreau R Near Faith Sd
|
14cfs |
Cedar Creek Nr Raleigh
|
20cfs |
Oak Cr Near Wakpala Sd
|
10cfs |
Cannonball River Nr Raleigh
|
40cfs |
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.
Isabel