Bismark Lake Reservoir Report

Last Updated: December 5, 2025

Located in the picturesque NORBECK WILDLIFE PRESERVE in Custer, South Dakota, Bismark Lake is a serene body of water fed by BISMARK CREEK.


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Summary

Managed by the USDA Forest Service, this Federal-owned recreational spot offers a tranquil escape for nature enthusiasts and climate advocates alike. The Earth-type dam, completed in 1937, stands at 38 feet high and stores 626 acre-feet of water for fish and wildlife purposes, as well as recreational activities.

With a maximum storage capacity of 626 acre-feet and a normal storage level of 297 acre-feet, Bismark Lake is a vital resource for the surrounding ecosystem. The dam's spillway, uncontrolled with a width of 30 feet, ensures the safe release of excess water during periods of high discharge, with a maximum capacity of 2087 cubic feet per second. Despite being rated as having a high hazard potential, the dam's condition remains unassessed as of the last inspection in 2019, presenting a moderate risk that requires ongoing monitoring and management measures.

As a key site for outdoor recreation and conservation efforts, Bismark Lake serves as a valuable asset in the preservation of South Dakota's water resources and natural environment. Its significance extends beyond its physical structure, embodying a harmonious balance between human enjoyment and ecological stewardship in the face of climate challenges.

Year Completed

1937

Dam Length

280

Dam Height

38

River Or Stream

BISMARK CREEK

Primary Dam Type

Earth

Hydraulic Height

28

Drainage Area

4

Nid Storage

626

Structural Height

40

Outlet Gates

Uncontrolled

Hazard Potential

High

Nid Height

40
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.