Thomas Dam Reservoir Report
Nearby: Lake Homestead Dam Von Maur Dam
Last Updated: December 13, 2025
Thomas Dam, located in Jackson County, Iowa, was completed in 1959 by the USDA SCS and serves multiple purposes including fire protection, stock, and small fish pond.
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Summary
The earth dam stands at 19 feet high and stretches 350 feet in length, with a storage capacity of 55 acre-feet. Situated on the TR-South Fork Maquoketa River, the dam has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment.
Despite not being federally owned or funded, Thomas Dam is regulated and permitted by the Iowa DNR, with state jurisdiction, inspection, and enforcement in place. The dam is in compliance with state regulations and has a moderate risk assessment rating of 3. Although the last inspection date was in 1980, the dam continues to meet guidelines and has not experienced any major modifications in recent years. While the spillway is uncontrolled, the dam poses minimal risk to the surrounding area and remains a vital resource for water management in the region.
For water resource and climate enthusiasts, Thomas Dam serves as a fascinating example of sustainable infrastructure in a rural setting. With its strategic location on the Maquoketa River and multiple uses, the dam highlights the importance of maintaining and regulating water resources for various purposes. Additionally, the dam's low hazard potential and moderate risk assessment demonstrate effective management and monitoring practices, ensuring the safety and functionality of the structure for years to come.
Year Completed |
1959 |
Dam Length |
350 |
Dam Height |
19 |
River Or Stream |
TR-SOUTH FORK MAQUOKETA RIVER |
Primary Dam Type |
Earth |
Surface Area |
4.5 |
Drainage Area |
0.84 |
Nid Storage |
55 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
19 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
North Fork Maquoketa River Near Fulton
|
245cfs |
Maquoketa River Near Maquoketa
|
569cfs |
Wapsipinicon River Near Anamosa
|
321cfs |
Sinsinawa River Near Menominee
|
19cfs |
Apple River Near Hanover
|
110cfs |
Wapsipinicon River Near De Witt
|
559cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Maquoketa Caves State Park Campground
Maquoketa Caves State Park
Eden Valley Park
Joinerville County Park
Fillmore County Rec Area
Fillmore Recreation Area Campground
Thomas Dam