Johnston Dam No 1 Reservoir Report

Last Updated: December 5, 2025

Johnston Dam No 1, located in Harrison, Texas, was completed in 1950 for the primary purpose of irrigation along the TR-BIG MASON CREEK.


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Summary

This private earth dam stands at a height of 20 feet and has a length of 700 feet, providing a storage capacity of 260 acre-feet. Despite its age, the dam's condition assessment is not rated, with a high risk potential noted, making it a subject of interest for water resource and climate enthusiasts.

The dam, designed as an earth buttress structure, does not have a spillway and is not regulated by the state. With no inspections or enforcement in place, the dam's operational and safety aspects remain unclear. The lack of hazard potential assessment and emergency preparedness further add to the intrigue surrounding Johnston Dam No 1, making it a notable feature in the water resource landscape.

As water scarcity and climate change continue to impact regions like Texas, understanding the state of dams like Johnston Dam No 1 becomes crucial in ensuring water security and disaster resilience. Despite its historical significance in irrigation, the dam's condition and risk assessment raise questions about its long-term viability and the need for proactive management measures to address potential hazards. For enthusiasts interested in water resource management and climate adaptation, Johnston Dam No 1 presents a case study worth exploring in the context of evolving environmental challenges.

Year Completed

1950

Dam Length

700

Dam Height

20

River Or Stream

TR-BIG MASON CREEK

Primary Dam Type

Earth

Hydraulic Height

20

Nid Storage

260

Structural Height

20

Outlet Gates

None - 1

Hazard Potential

Not Available

Foundations

Unlisted/Unknown

Nid Height

20
       
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.