Lower Monumental Lock And Dam Reservoir Report
Last Updated: December 15, 2025
Lower Monumental Lock and Dam, located on the Snake River in Pasco, Washington, serves multiple purposes including navigation, fish and wildlife habitat, hydroelectric power generation, and recreation.
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Summary
Completed in 1969 by the US Army Corps of Engineers, this concrete dam stands at a height of 226 feet and has a length of 3800 feet. With a storage capacity of 432,000 acre-feet and a maximum discharge capacity of 850,000 cubic feet per second, the dam plays a crucial role in managing water levels and mitigating flood risks in the region.
The dam's controlled spillway, 400 feet wide, helps regulate water flow while a single lock facilitates navigation along the river. Lower Monumental Lock and Dam is maintained and operated by the US Army Corps of Engineers, who continuously monitor its condition and manage flood risks associated with the structure. With a high hazard potential and very high risk assessment rating, the agency collaborates with local emergency managers and the public to raise awareness and prepare for potential dam-related emergencies. Despite the inherent risks, this dam remains a vital component of the region's water resource management infrastructure.
As water resource and climate enthusiasts, the Lower Monumental Lock and Dam represents a fascinating intersection of engineering, environmental conservation, and disaster risk management. Its role in balancing competing needs for water use, power generation, and flood protection underscores the complexity and importance of sustainable water resource management in the face of changing climate conditions. With ongoing risk management measures in place and a commitment to public safety, this dam stands as a symbol of resilience in the face of natural challenges.
Year Completed |
1969 |
Dam Length |
3800 |
River Or Stream |
SNAKE RIVER |
Primary Dam Type |
Concrete |
Surface Area |
6590 |
Length Of Locks |
650 |
Hydraulic Height |
100 |
Drainage Area |
108500 |
Nid Storage |
432000 |
Structural Height |
226 |
Hazard Potential |
High |
Nid Height |
226 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Tucannon River Near Starbuck
|
174cfs |
Palouse River At Hooper
|
1030cfs |
Mill Creek At Walla Walla
|
216cfs |
Mill Creek At Five Mile Rd Br Nr Walla Walla
|
634cfs |
Walla Walla River Near Touchet
|
1040cfs |
Mill Creek Near Walla Walla
|
71cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Area Campgrounds
| Location | Reservations | Toilets |
|---|---|---|
Devils Bench - Snake River
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Mathews- Snake River
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Windust - Lake Sacajawea
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Ayer Boat Basin - Snake River
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Walker Park - Lake Sacajawea
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Lower Monumental Lock And Dam