Johnson Dam Reservoir Report

Last Updated: December 10, 2025

Johnson Dam, located in Princeton, MO, is a privately owned structure designed by USDA NRCS to regulate the TR-Weldon River in Iowa.


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Summary

Completed in 1974, this earth dam stands at a height of 32 feet and spans 370 feet in length, with a storage capacity of 59 acre-feet. Its primary purpose is to provide water supply for the surrounding area, with a low hazard potential and moderate risk assessment.

The dam is under the regulatory jurisdiction of the Iowa DNR and undergoes regular inspections, permitting, and enforcement to ensure its structural integrity and safety. Although the dam is not rated for its condition assessment, it is considered to meet guidelines for emergency action planning and risk management measures. The surrounding area benefits from the dam's water storage capabilities, especially during times of water scarcity or drought.

With its strategic location and efficient design, Johnson Dam plays a crucial role in water resource management and climate resilience in Decatur County, Iowa. As a key piece of infrastructure in the Rock Island District, this dam serves as a vital asset for water supply and flood control, highlighting the importance of sustainable water management practices in the region.

Year Completed

1974

Dam Length

370

Dam Height

32

River Or Stream

TR-WELDON RIVER

Primary Dam Type

Earth

Surface Area

4

Drainage Area

0.06

Nid Storage

59

Hazard Potential

Low

Foundations

Soil

Nid Height

32
       
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.