Mompano Reservoir Report

Reservoir Report

Oregon

Nearby: Briscoe Reservoir Willamette Falls

Last Updated: December 13, 2025

Mompano, also known as Beaver Lake Dam, is a privately owned structure located in Echo Dell, Clackamas County, Oregon.

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Summary

Built in 1971, this earth dam stands at a height of 39 feet and has a hydraulic height of 35 feet, with a maximum storage capacity of 780 acre-feet. It serves as a crucial water resource on Abernethy Creek, with a drainage area of 12.7 square miles and a maximum discharge capacity of 1400 cubic feet per second.

With a high hazard potential, Mompano has been regulated and permitted by the Oregon Water Resources Department, ensuring regular inspections and enforcement to maintain its structural integrity. Classified as a needle-gated dam, it spans 720 feet in length and covers a surface area of 56 acres, providing essential flood control and irrigation benefits to the surrounding area. Despite its satisfactory condition assessment as of November 2020, the dam's emergency action plan and risk management measures warrant further attention for potential improvements and preparedness.

As a significant component of the water infrastructure in the region, Mompano plays a vital role in supporting water supply and management efforts in Clackamas County. Its location within the Portland District of the US Army Corps of Engineers underscores its importance in safeguarding against potential flooding events and ensuring the resilience of Abernethy Creek's ecosystem. Climate and water resource enthusiasts can appreciate the complexities and importance of structures like Mompano in maintaining a balance between water conservation, safety, and environmental protection in Oregon's diverse landscape.

Year Completed	1971
Dam Length	720
Dam Height	39
River Or Stream	ABERNETHY CREEK
Primary Dam Type	Earth
Surface Area	56
Hydraulic Height	35
Drainage Area	12.7
Nid Storage	780
Structural Height	44
Outlet Gates	Needle
Hazard Potential	High
Nid Height	44

Explore Interactive Map

MOMPANO

Reservoir Report • Water Levels • Weather Forecast

December 13, 2025

Year_Completed	1971
Dam_Length	720
Dam_Height	39
River_Or_Stream	ABERNETHY CREEK
Primary_Dam_Type	Earth
Surface_Area	56
Hydraulic_Height	35
Drainage_Area	12.7
Nid_Storage	780
Structural_Height	44
Outlet_Gates	Needle
Hazard_Potential	High
Nid_Height	44

Seasonal Comparison

Weather Forecast

Nearby Streamflow Levels

Clackamas River Near Oregon City 6250.0cfs	6250cfs
Clackamas River At Estacada 3970.0cfs	3970cfs
Tualatin River At West Linn 4260.0cfs	4260cfs
Nate Creek Tributary Near Colton 5.7cfs	6cfs
Molalla River Near Canby 3060.0cfs	3060cfs
Kelley Creek At Se 159th Drive At Portland 8.98cfs	9cfs

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.