Thannas Dam Reservoir Report

Last Updated: December 5, 2025

Thannas Dam, located in Travis County, Texas, is a locally owned earth dam with a primary purpose classified as "Other".


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Summary

Standing at a height of 17.3 feet, the dam has a storage capacity of 50 acre-feet and a maximum discharge rate of 2 cubic feet per second. The dam features an uncontrolled spillway with a width of 23 feet and two uncontrolled outlet gates.

Managed by the Texas Commission on Environmental Quality (TCEQ), Thannas Dam was last inspected in May 2013 and was rated in fair condition as of April 2021. The dam poses a moderate risk with a hazard potential that is not available. While no significant modifications or upgrades have been reported in recent years, the dam is under state regulation, inspection, and enforcement to ensure its safety and functionality for the surrounding area.

Thannas Dam, although not extensively studied or modified, remains a vital structure for water resource management in the region. With its unique design features and risk assessment, the dam serves as a key element in the local water infrastructure, highlighting the importance of regular maintenance and monitoring to mitigate potential hazards and ensure long-term resilience in the face of changing climate conditions.

Dam Height

17.3

River Or Stream

Primary Dam Type

Earth

Hydraulic Height

17.3

Nid Storage

50

Structural Height

17.3

Outlet Gates

Uncontrolled - 2

Hazard Potential

Not Available

Foundations

Unlisted/Unknown

Nid Height

17
       
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.