Mendota Locks Reservoir Report

Last Updated: December 6, 2025

Mendota Locks, also known as Tenney Park Locks, located in Madison, Wisconsin, play a crucial role in navigation and recreation along the Yahara River.


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Summary

Constructed in 1849, these locks have a dam height of 16 feet and a hydraulic height of 5 feet, with a total length of 100 feet. The locks provide a normal storage capacity of 132,000 acre-feet and serve a drainage area of 254 square miles, making them integral to managing water resources in the region.

With a high hazard potential and a satisfactory condition assessment, Mendota Locks have been inspected regularly, with the last assessment conducted in December 2018. The locks have a very high risk assessment level, denoting their critical importance in flood control and water management. Managed by the Wisconsin Department of Natural Resources, the locks are subject to state regulations, permitting, inspection, and enforcement, ensuring their safe operation and maintenance for the benefit of the community and the environment.

As a historic structure that has been modified over the years, Mendota Locks continue to serve as a vital component of the water resource infrastructure in Dane County, Wisconsin. The locks' controlled spillway, efficient navigation system, and significant storage capacity make them essential for managing water levels, ensuring recreation opportunities, and safeguarding against flood risks in the region.

Years Modified

1959 - Other

Year Completed

1849

Dam Length

100

Dam Height

16

River Or Stream

YAHARA RIVER

Primary Dam Type

Other

Surface Area

9730

Length Of Locks

102

Hydraulic Height

5

Drainage Area

254

Nid Storage

160000

Structural Height

16

Hazard Potential

High

Nid Height

16
       
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.