Merwin Dam

Merwin Dam Quick Facts

Location: Cowlitz, Washington
Coordinates: 45.9572, -122.5562
River: Lewis River
Primary Purpose: Hydroelectric
Type: Arch Concrete Gravity
Commissioned: 1931
Dam Height: 313 ft (95 m)
Dam Length: 1,250 ft (381 m)
Dam Capacity: 422,000 acre-ft (520,529 Ml)
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Merwin Dam Map

Merwin Dam Information

Merwin Dam is an arch concrete gravity dam located about 11 miles from Woodland, Wa, Cowlitz, Washington.

The dam, which is on the Lewis River, was primarily built for Hydroelectric purposes, but also serves for Fish and Wildlife Pond and Recreation benefits.

The dam was designed by and commissioned in 1931 and is currently owned by PacifiCorp.

Merwin Dam Structure

The Merwin Dam is approximately 1,250 feet (381 m) long, 313 feet (95 m) high and has a structural volume of cubic yards (0 cubic metres).

Merwin Dam Storage Capacity & Surface Area

The reservoir has a normal storage capacity of 422,000 acre-ft (520,529 Ml) and maximum capacity of 422,000 acre-ft (520,529 Ml).

The surface area of the reservoir is 3,921 acres (1,587 ha) and the total catchment area is 726 square miles (1,880 square kilometres).

Merwin Dam Spillway

The dam spillway has a maximum discharge capacity of 120000 cubic feet per second (3398 cubic metres per second).

Merwin Dam Compared to Five Famous American Dams

Height (ft)
Length (Ft)
Storage Volume (acre-ft)
Drainage Area (sq miles)
 
Merwin Dam
Cowlitz, Washington
Height (ft)
313
Length (Ft)
1,250
Storage Volume (acre-ft)
422,000
Drainage Area (sq miles)
726
Hoover Dam
Clark County, Nevada
Height (ft)
730
Length (Ft)
1,244
Storage Volume (acre-ft)
30,237,000
Drainage Area (sq miles)
167,800
Grand Coulee Dam
Okanogan County, Washington
Height (ft)
550
Length (Ft)
5,673
Storage Volume (acre-ft)
9,562,0000
Drainage Area (sq miles)
74,100
Theodore Roosevelt Dam
Maricopa County, Arizona
Height (ft)
357
Length (Ft)
1,208
Storage Volume (acre-ft)
3,411,500
Drainage Area (sq miles)
5,736
Oroville Dam
Butte County, California
Height (ft)
235
Length (Ft)
6,920
Storage Volume (acre-ft)
3,540,000
Drainage Area (sq miles)
3,611
Glen Canyon Dam
Coconino County, Arizona
Height (ft)
216
Length (Ft)
1,565
Storage Volume (acre-ft)
29,875,000
Drainage Area (sq miles)
108,355

Merwin Dam Weather

Current Conditions at Merwin Dam

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7-Day Forecast for Merwin Dam

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Merwin Dam Frequently Asked Questions

In which state is the Merwin Dam?

Merwin Dam is in Washington.

In which county is the Merwin Dam?

Merwin Dam is in Cowlitz County.

How high is the Merwin Dam?

Merwin Dam is 313 feet high.

How long is the Merwin Dam?

Merwin Dam is 1,250 feet long.

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More Dams in Cowlitz County:

Castle Lake Debris Dam
Centralia Coal Mine Dam No 3c South
Coldwater Debris Dam
Merwin Dam
Yale Dam

Condition Assessment Classification

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.

Source: National Inventory of Dams

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