Lake Wanalain Dam Reservoir Report

Last Updated: December 13, 2025

Lake Wanalain Dam, located in Chamberlain, South Dakota, was completed in 1936 by the Works Progress Administration (WPA).


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Summary

This earth dam stands at a height of 21 feet and has a hydraulic height of 21 feet, with a length of 250 feet. The dam's primary purpose is to regulate the flow of the TR-MISSONot RatedI river, with a drainage area of 70 square miles.

With a normal storage capacity of 460 acre-feet and a maximum storage of 8378 acre-feet, Lake Wanalain Dam serves as a vital water resource for the region. The dam's spillway, which is uncontrolled and 100 feet wide, helps manage excess water flow during heavy rainfall events. The dam is under state regulation by the South Dakota Department of Agriculture and Natural Resources (DANR), with regular inspections and enforcement to ensure its structural integrity and safety.

Despite being classified as having a high hazard potential and fair condition assessment, Lake Wanalain Dam continues to provide essential water management services for the community. With its historical significance and ongoing role in safeguarding the surrounding area from flooding, this earth dam stands as a testament to the enduring value of sustainable water resource management in the face of changing climate conditions.

Year Completed

1936

Dam Length

250

Dam Height

21

River Or Stream

TR-MISSONot RatedI

Primary Dam Type

Earth

Hydraulic Height

21

Drainage Area

70

Nid Storage

8378

Outlet Gates

None

Hazard Potential

High

Foundations

Soil

Nid Height

21
       
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.