Armstrong Lake Dam Reservoir Report

Last Updated: December 6, 2025

Armstrong Lake Dam, located in Bandera, Texas, along the West Prong Medina River, is a privately owned structure primarily used for recreational purposes.


°F

°F

mph

Wind

%

Humidity

Summary

Completed in 1964, this earth dam stands at 26 feet in height and spans a length of 1750 feet, with a storage capacity of 220 acre-feet. The dam has undergone modifications over the years, with updates to its structural and hydraulic components in 1982, 1989, and 2005.

Managed by the Texas Commission on Environmental Quality (TCEQ), Armstrong Lake Dam is subject to state regulations, inspections, and enforcement measures to ensure its safety and compliance with standards. The dam has been assessed to be in fair condition as of February 2016, with a moderate risk rating of 3. With an uncontrolled spillway and two outlet gates, the dam has a spillway width of 174 feet and a maximum discharge of 2 cubic feet per second.

Despite its relatively small drainage area of 0.32 square miles, Armstrong Lake Dam serves as an important recreational resource in the region, offering a surface area of 14 acres for activities such as fishing, boating, and picnicking. With its scenic location and historical significance, the dam continues to be a popular destination for water resource and climate enthusiasts seeking to explore the natural beauty of the West Prong Medina River.

Years Modified

1982 - Structural, 1989 - Hydraulic, 2005 - Hydraulic

Year Completed

1964

Dam Length

1750

Dam Height

26

River Or Stream

WEST PRONG MEDINA RIVER

Primary Dam Type

Earth

Surface Area

14

Hydraulic Height

26

Drainage Area

0.32

Nid Storage

220

Structural Height

26

Outlet Gates

Uncontrolled - 2, Valve - 1

Hazard Potential

Not Available

Foundations

Unlisted/Unknown

Nid Height

26
       
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.