Nashua Milldam Reservoir Report

Last Updated: December 13, 2025

Nashua Milldam, located in Nashua, Iowa along the Cedar River, was completed in 1917 and serves as a recreational site for water resource and climate enthusiasts.


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Summary

Managed by the local government, the dam stands at a height of 20 feet with a gravity design and rock foundation. With a storage capacity of 5,242 acre-feet and a surface area of 405 acres, the dam provides opportunities for leisure activities in the surrounding area.

Despite its low hazard potential and satisfactory condition assessment, Nashua Milldam is regulated by the Iowa Department of Natural Resources, with state permitting, inspection, and enforcement in place to ensure its safety and functionality. The dam features a controlled spillway with a width of 260 feet, and its risk assessment indicates a very high level of risk, possibly due to its age and the potential impact of climate change on water levels in the Cedar River. As a site of historical significance and natural beauty, Nashua Milldam continues to be a popular destination for outdoor enthusiasts and water resource advocates alike.

Year Completed

1917

Dam Length

1170

Dam Height

20

River Or Stream

CEDAR RIVER

Primary Dam Type

Gravity

Surface Area

405

Hydraulic Height

17

Drainage Area

1113

Nid Storage

5242

Hazard Potential

Low

Foundations

Rock

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.