Ninety Nine Islands Reservoir Report

Last Updated: December 6, 2025

Ninety Nine Islands is a stunning hydroelectric dam located in South Carolina, specifically in the city of Lockhart.


°F

°F

mph

Wind

%

Humidity

Summary

Built in 1909 by the Southern Power Company, this concrete gravity dam stands at a height of 72 feet and stretches 1568 feet in length. With a storage capacity of 2300 acre-feet and a maximum discharge of 145,000 cubic feet per second, this dam plays a crucial role in power generation and water management in the region.

The dam's high hazard potential and moderate risk assessment highlight the importance of its maintenance and emergency preparedness. The Federal Energy Regulatory Commission oversees its operations and inspections, ensuring its structural integrity and adherence to safety protocols. The surrounding area, including the Broad River and its drainage area of 1550 square miles, benefits from the dam's regulation of water flow and storage capacity.

Enthusiasts of water resources and climate change will appreciate the significance of Ninety Nine Islands in providing renewable hydropower and managing water resources in Cherokee County, South Carolina. Its historical significance, engineering marvel, and environmental impact make it a fascinating site for exploration and study in the realm of water resource management and climate resilience.

Year Completed

1909

Dam Length

1568

Dam Height

72

River Or Stream

Broad

Primary Dam Type

Concrete

Surface Area

350

Drainage Area

1550

Nid Storage

2300

Structural Height

72

Hazard Potential

High

Foundations

Rock

Nid Height

72
       
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.