Longham Reservoir Dam Reservoir Report

Last Updated: December 19, 2025

Longham Reservoir Dam, located in Wenham, Massachusetts, is a vital structure owned and regulated by the local government for water supply purposes.


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Summary

The dam, constructed of earth and buttress core types, stands at a height of 15 feet and has a hydraulic height of 13.5 feet. It holds a maximum storage capacity of 150 acre-feet and covers a surface area of 0.14 acres, serving the Longham Brook and surrounding areas in Essex County.

With a low hazard potential and satisfactory condition assessment, Longham Reservoir Dam poses a moderate risk level, prompting a 10-year inspection frequency to ensure its continued safety and functionality. The dam's uncontrolled spillway type and lack of outlet gates indicate its reliance on natural drainage and water flow management. Despite its modest size and capacity, the dam plays a crucial role in water resource management and climate resilience efforts in the region.

Managed by the Department of Conservation and Recreation, Longham Reservoir Dam remains a key infrastructure for water security in the area, supported by the state's permitting, inspection, and enforcement mechanisms. As climate change impacts water resources worldwide, structures like Longham Reservoir Dam are essential for maintaining a stable water supply and mitigating the risks of droughts and floods. Its strategic location and design contribute to the overall resilience of the local water infrastructure, highlighting the importance of sustainable water management practices for the future.

Dam Length

240

Dam Height

15

River Or Stream

LONGHAM BROOK

Primary Dam Type

Earth

Surface Area

0.14

Hydraulic Height

13.5

Drainage Area

3.5

Nid Storage

150

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

15
       
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.