Mottville Reservoir Report

Last Updated: December 5, 2025

Mottville is a captivating hydroelectric dam located in St.


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Summary

Joseph, Michigan, along the scenic St. Joseph River. Built in 1920, this gravity dam stands at 23 feet tall and spans 846 feet in length, providing a storage capacity of 4256 acre-feet. With a maximum discharge of 20610 cubic feet per second and a controlled spillway width of 241 feet, Mottville plays a crucial role in regulating water flow and generating hydropower for the region.

Managed by the Federal Energy Regulatory Commission, Mottville serves as a hub for both hydroelectric power generation and recreational activities. The dam features a Tainter radial gate system with 10 gates for controlled water release, ensuring safety and efficiency in operations. Despite its high hazard potential, Mottville's risk management measures are in place to mitigate any potential risks, with a detailed emergency action plan last revised in May 2019.

With its rich history, impressive engineering design, and essential role in water resource management, Mottville stands as a symbol of sustainable energy production and environmental stewardship. Visitors to Mottville can witness the harmonious blend of human ingenuity and natural beauty, making it a must-visit destination for water resource and climate enthusiasts seeking to explore the intersection of technology and nature.

Year Completed

1920

Dam Length

846

Dam Height

23

River Or Stream

St Joseph River

Primary Dam Type

Gravity

Surface Area

378

Hydraulic Height

13

Drainage Area

1866

Nid Storage

4256

Outlet Gates

Tainter (radial) - 10

Hazard Potential

High

Foundations

Rock, Soil

Nid Height

23
       
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.