Lake Jb Thomas Dam Reservoir Report

Last Updated: December 5, 2025

Lake Jb Thomas Dam, located in Colorado City, Texas, is a vital water resource and recreational site managed by the local government.


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Summary

Built in 1952 by design firm FREESE AND NICHOLS, the dam stands at a height of 105 feet and has a storage capacity of 430,600 acre-feet. The dam primarily serves the purposes of recreation and water supply, attracting visitors with its sprawling surface area of 7,820 acres for various outdoor activities.

The dam's infrastructure includes an uncontrolled spillway with a width of 1834 feet, ensuring efficient water discharge during high-flow events. With a fair condition assessment as of April 2021, the dam undergoes inspections every five years to maintain safety standards. Despite its moderate risk level, Lake Jb Thomas Dam remains a reliable structure for water management and recreational enjoyment in the region, showcasing a harmonious blend of functionality and leisure for water resource and climate enthusiasts to explore and appreciate.

Years Modified

2007 - Other

Year Completed

1952

Dam Length

9200

Dam Height

105

River Or Stream

COLORADO RIVER

Primary Dam Type

Earth

Surface Area

7820

Hydraulic Height

100

Drainage Area

997

Nid Storage

430600

Structural Height

105

Outlet Gates

Uncontrolled - 3, Valve - 1

Hazard Potential

Not Available

Foundations

Rock, Soil

Nid Height

105
       
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.