H.K. Thatcher Lock And Dam Reservoir Report

Last Updated: December 5, 2025

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Summary

Thatcher Lock and Dam, also known as Calion Lock and Dam, is a federal-owned structure located in Moro Bay, Arkansas, along the Ouachita River. Completed in 1983, it serves primarily for navigation purposes but also supports recreation and water supply. This gravity dam stands at a structural height of 80 feet and has a spillway width of 350 feet. Managed by the US Army Corps of Engineers, the dam has a significant hazard potential and a very high risk assessment rating, emphasizing the importance of continuous monitoring and risk management measures.

The dam has a storage capacity of 108,000 acre-feet and a maximum discharge of 250,000 cubic feet per second. With a drainage area of 6,569 square miles, the dam plays a crucial role in managing water levels and mitigating flood risks in the region. The USACE regularly updates the emergency action plan for the dam, conducts maintenance and repairs as needed, and collaborates with local emergency managers to ensure preparedness for any potential dam-related emergencies. As severe weather events can pose challenges, the dam's risk management measures aim to address all types of flood risks associated with the structure, safeguarding both the dam's structural integrity and downstream communities.

Overall, H.K. Thatcher Lock and Dam is a vital piece of infrastructure in Arkansas, providing essential services for navigation, recreation, and water supply. Its management by the US Army Corps of Engineers ensures that the dam is well-maintained and monitored to address any potential risks effectively, showcasing a commitment to public safety and environmental stewardship in the face of changing climate conditions.

Year Completed

1983

Dam Length

698

River Or Stream

OUACHITA

Primary Dam Type

Gravity

Surface Area

12200

Length Of Locks

600

Hydraulic Height

33

Drainage Area

6569

Nid Storage

108000

Structural Height

80

Hazard Potential

Significant

Foundations

Soil

Nid Height

80
       
Seasonal Comparison

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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.