Dorchester Reservoir Report

Last Updated: December 13, 2025

Dorchester, located in Clark County, Wisconsin, is a gravity dam on the North Fork Poplar River with a primary purpose of recreation.


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Summary

Completed in 2011, this dam stands at a height of 12.5 feet and has a hydraulic height of 11 feet. With a capacity of 177 acre-feet, it provides a normal storage of 30 acre-feet and covers a surface area of 7 acres. The dam has a low hazard potential and was last inspected in August 2013, with a satisfactory condition assessment.

Managed by the Wisconsin Department of Natural Resources, Dorchester is state-regulated and meets all permitting, inspection, and enforcement requirements. The dam's spillway is uncontrolled, and it has a maximum discharge capacity of 1360 cubic feet per second. Despite its moderate risk level, the dam has not had any major modifications in recent years and is considered to be in good condition. The surrounding area offers opportunities for outdoor recreation, making Dorchester a popular destination for water resource and climate enthusiasts in the region.

Year Completed

2011

Dam Length

400

Dam Height

12.5

River Or Stream

N.FORK POPLAR RIVER

Primary Dam Type

Gravity

Surface Area

7

Hydraulic Height

11

Drainage Area

1.6

Nid Storage

177

Structural Height

12.5

Hazard Potential

Low

Nid Height

13
       
Seasonal Comparison

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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.