Loch Alsh Reservoir Reservoir Report

Last Updated: December 6, 2025

Loch Alsh Reservoir, located in Montgomery, Pennsylvania, is a picturesque water resource managed by the local government for recreational purposes.


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Summary

Built in 1915, this earth dam structure stands at a height of 16 feet and has a storage capacity of 41 acre-feet. With a surface area of 6 acres and a drainage area of 0.25 square miles, the reservoir is a popular spot for outdoor enthusiasts to enjoy water-based activities.

Under the jurisdiction of the Pennsylvania Department of Environmental Protection, Loch Alsh Reservoir is regularly inspected and regulated to ensure its safety and functionality. The dam has a high hazard potential but has been assessed as satisfactory in condition, with the last inspection conducted in November 2020. While no emergency action plan (EAP) has been reported, the reservoir meets regulatory guidelines and continues to be a valuable water resource for the community.

Surrounded by the tranquility of Upper Dublin Township and fed by the Wissahickon Creek, Loch Alsh Reservoir remains a vital part of the local landscape. Its historical significance, combined with its recreational value, makes it a cherished destination for water resource and climate enthusiasts seeking to connect with nature and appreciate the beauty of Pennsylvania's diverse water ecosystems.

Year Completed

1915

Dam Length

513

Dam Height

16

River Or Stream

TR WISSAHICKON CREEK

Primary Dam Type

Earth

Surface Area

6

Drainage Area

0.25

Nid Storage

41

Hazard Potential

High

Foundations

Unlisted/Unknown

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.