Lake Nessmuk (Pa-601) Reservoir Report

Last Updated: December 7, 2025

Lake Nessmuk (Pa-601) in Tioga, Pennsylvania, is a state-owned recreational lake built in 1968 for flood risk reduction and leisure activities.


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Summary

The earth dam, standing at 52.2 feet tall and 870 feet long, holds a storage capacity of 1453 acre-feet with a surface area of 60 acres. The dam's spillway type is uncontrolled and has a width of 166 feet, making it a critical structure with a high hazard potential.

Managed by the Pennsylvania Department of Environmental Protection, Lake Nessmuk is regularly inspected and found to be in satisfactory condition as of April 2020. The dam's risk assessment is moderate, with an overall risk rating of 3. Despite its moderate risk, the dam meets guidelines for emergency action plans, although specifics on preparedness and inundation maps are not provided in the data. The surrounding area is under the jurisdiction of the state, ensuring that regulatory agencies oversee the proper maintenance and operation of the dam to protect the community downstream along the Morris Branch Marsh Creek.

With its scenic location in Delmar Township and its primary purpose of recreation, Lake Nessmuk offers both a tranquil retreat for visitors and a crucial infrastructure for flood risk reduction. As climate change continues to impact water resources, the maintenance and regulation of dams like Lake Nessmuk become increasingly important to ensure the safety and enjoyment of those who rely on its services.

Year Completed

1968

Dam Length

870

Dam Height

52.2

River Or Stream

MORRIS BRANCH MARSH CREEK

Primary Dam Type

Earth

Surface Area

60

Drainage Area

1.6

Nid Storage

1453

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

52
       
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.