Lake Delhi Dam Reservoir Report

Last Updated: December 5, 2025

Lake Delhi Dam, located in Hopkinton, Iowa, serves as a recreational haven nestled along the Maquoketa River.


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Summary

Built in 1922, this gravity dam stands at a height of 55 feet and spans 750 feet in length, with a storage capacity of 9,920 acre-feet and a surface area of 440 acres. The dam's primary purpose is recreation, offering locals and visitors alike a tranquil escape for various water activities.

Managed by a private owner, Lake Delhi Dam is regulated and inspected by the Iowa Department of Natural Resources, ensuring its structural integrity and safety for the surrounding community. Despite being classified as having a significant hazard potential, the dam's condition is deemed satisfactory as of the last inspection in July 2020. With a risk assessment rating of very high, measures are in place to mitigate potential risks and ensure the dam's resilience in the face of climate challenges.

As a vital component of the local landscape, Lake Delhi Dam not only provides recreational opportunities but also plays a crucial role in water resource management within the region. With its controlled spillway and rock and soil foundations, this historic dam continues to stand as a testament to engineering ingenuity and environmental stewardship, attracting water resource and climate enthusiasts to appreciate its significance in sustaining the surrounding ecosystem.

Year Completed

1922

Dam Length

750

Dam Height

55

River Or Stream

MAQUOKETA RIVER

Primary Dam Type

Gravity

Surface Area

440

Drainage Area

347

Nid Storage

9920

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

55
       
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.