Happy Hollow Reservoir Report

Last Updated: December 6, 2025

Happy Hollow is a privately-owned dam located in Linwood, Kansas, designed by the USDA NRCS and regulated by the Kansas Department of Agriculture.


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Summary

Built in 1962 for flood risk reduction, this earth dam stands at a height of 37 feet and has a storage capacity of 324.4 acre-feet, with a normal storage level of 131 acre-feet. With a low hazard potential and a moderate risk assessment rating, Happy Hollow serves as a vital structure in the Pony Creek watershed, providing protection against floods while also offering recreational opportunities.

Managed by the Natural Resources Conservation Service, Happy Hollow features an uncontrolled spillway with a width of 140 feet and a maximum discharge capacity of 1017 cubic feet per second. The dam's primary purpose of flood risk reduction is complemented by its secondary function of recreational use, attracting visitors to its 12-acre surface area. Although its condition is currently not rated, the dam undergoes regular inspections by state agencies to ensure its safety and effectiveness in managing water resources in the region.

Despite its age, Happy Hollow continues to play a crucial role in water resource management in Leavenworth County, Kansas. With a history of successful flood risk reduction and a commitment to regulatory standards, this earth dam stands as a testament to the importance of proper infrastructure in mitigating the impacts of climate change on local communities. Water resource and climate enthusiasts can admire the engineering prowess behind Happy Hollow while appreciating its role in safeguarding the environment and enhancing recreational opportunities for residents and visitors alike.

Year Completed

1962

Dam Length

720

Dam Height

37

River Or Stream

PONY CREEK-TR

Primary Dam Type

Earth

Surface Area

12

Hydraulic Height

35

Drainage Area

0.88

Nid Storage

324.4

Structural Height

37

Outlet Gates

None

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

37
       
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.