Mount St. Helens, Washington -
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The major eruption of Mount St. Helens, Washington, on May 18, 1980, deposited
tons of ash, mud, logs, and other debris into more than 30 near-pristine lakes
in the immediate vicinity of the volcano. Even lakes in parts of eastern
Washington received deposits of windblown ash as much as 3 inches
thick.2
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Lake/Reservoir |
Information |
Comments/Remarks |
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Boot Lake |
Location: Skamania County
Altitude: 4,550 feet10 Surface Area: 16 acres10 |
Trees were felled or topped but not removed; lake was free of floating timber. 7 | |
Castle Lake(physical characteristics after construction of outlet and stabilization of lake) |
Location: Cowlitz County
Altitude: 2,560 feet2; 2,510 feet10 Surface Area: 480 acres2 Volume: 19,000 acre-feet2,8 Maximum depth: 100 feet2 Mean depth: 40 feet2 Drainage area: 1,980 acres2 |
New lake as result of May 18, 1980, debris avalanche
blocking tributary to North Fork Toutle River; lake flows into North Fork
Toutle Drainage via COE-constructed outlet channel.
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Coldwater Lake(physical characteristics after construction of outlet and stabilization of lake) |
Location: Cowlitz and Skamania Counties
Altitude: 2,480 feet2; 2,490 feet10 Surface Area: 900 acres2; 766 acres10 Volume: 70,000 acre-feet2 Maximum depth: 190 feet2 Mean depth: 78 feet2 Drainage area: 11,200 acres2 |
New lake as result of May 18, 1980, debris avalanche
blocking tributary to North Fork Toutle River; lake flows into North Fork
Toutle Drainage via COE-constructed outlet channel.
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Curtis Lake |
Location: NE of volcano; Skamania County | Trees were felled or topped but not removed; lake was free of floating timber. 7 | |
Deadmans Lake |
Location: Skamania County
Altitude: 4,330 feet2,10 Surface Area: 32 acres2; 34 acres10 Volume: 1,100 acre-feet2 Maximum depth: 97 feet2 Mean depth: 34 feet2 Drainage area: 170 acres2 |
Outside of Blast Zone | |
Elk Lake |
Location: Skamania County | In Blast Zone | |
Fawn Lake |
Location: 9 miles NNW; 10N-4E-25; Cowlitz County
Altitude: 3,700 feet1,2 Surface Area: 20 acres1,2 Volume: 430 acre-feet1,2 Maximum depth: 54 feet1,2 Mean depth: 22 feet1,2 Drainage area: 140 acres2 |
Received heavy deposits of ash; most nearby
trees were uprooted, blown down, or completely stripped.1 ---
Trees were felled or topped but not removed; lake was free of floating timber.
7
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Hanaford Lake |
Location: Skamania County | Trees were felled or topped but not removed; lake was free of floating timber. 7 | |
Merrill Lake |
Location: Cowlitz County |
Merrill Lake (344 acres):
This fly-fishing-only lake is located north of Cougar near Mount St. Helens.
Merrill contains coastal cutthroat,
brown trout to several pounds, and some rainbow trout.
Special bag and size limits are in effect; please check the regulations pamphlet.
Internal combustion engines are prohibited on boats that are used for fishing.
Merrill is open year-round, but action is usually slow during the
winter months. There is a DNR campground and boat ramp.9
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Merwin Reservoir |
Location: Clark and Cowlitz Counties |
Merwin Reservoir is formed by a combination gravity-concrete-arch dam.
Some storage began March 1931; completed May 13, 1931.
Usable capacity: 245,600 acre-feet
between elevations 165 feet (lower limit of regulation set by Federal Energy
Regulatory Comission), and 235 feet (top of spillway gates). Additional storage
of 18,200 acre-feet is provided by flashboards to elevation 239.6 feet. Unused
storage below elevation 165 fett: 159,000 acre-feet. Water is used by
PacifiCorp for power development.
4
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Meta Lake |
Location: 8.5 miles NE; Skamania County
Altitude: 3,580 feet10 Surface Area: 9 acres10 |
Lake within May 18, 1980, blast zone; trail through
downed timber to lake that was only moderately disturbed by blast;
small trees on shore and fish in lake survived because they were under
snowpack.5 ---
Trees were felled or topped but not removed; lake was free of floating timber.
7
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Ryan Lake |
Location: 12 miles N; Cowlitz County
Altitude: 3,310 feet10 Surface Area: 4 acres10 |
Lake provides good overview of
effects and dynamics of May 18, 1980 blast at a point
12 miles north of crater; temperature of
blast at this site reached an estimated 300 degrees C (572 degrees F);
as much as 6 inches of ash fell here;
locally trees on lower parts of valley wall were blown
down, those on upper parts of valley wall were not.
6
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Silver Lake |
Location: Cowlitz County |
Lake is shallow (maximum depth 16 feet)
and was formed and is partially underlain by lahar deposits.
About 2,500 years ago during the Pine
Creek eruptive period, a series of very large lahars traveled down the Toutle
River from Mount St. Helens. Lahars flowed into Outlet Creek (east of the
lake) and dammed its valley to produce Silver Lake. These lahars were generated
by the catastrophic draining of a lake (presumably an older Spirit Lake) or
lakes that had been dammed by debris avalanches from Mount St. Helens.
Level of Silver Lake is now controlled by a dam.
6
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Spirit Lake(Prior to May 18, 1980 eruption) |
Location: 4 miles NE; 9N-5E-15; Skamania County
Altitude: 3,198 feet1,2 Surface Area: 1,300 acres1,2 Volume: 160,000 acre-feet1,2 Maximum depth: 190 feet1,2 Mean depth: 130 feet1; 123 feet2 Drainage area: 10,900 acres2 |
The water in Spirit Lake was heated to more than
32 degrees C by influx of hot volcanic material during May 18,
1980 eruption, but the surface temperature had decreased to near preeruption
levels (13 degrees C) by October 1980;
because of this heating and change in
lake's altitude, Spirit Lake can be considered a completely
different lake after May 18.2
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Spirit Lake(After May 18, 1980 eruption) |
Location: 4 miles NE; 9N-5E-15; Skamania County
Altitude: 3,440 feet (1981)1; 3,408 feet10 Surface Area: 2,200 acres (1981)1; 2,817 acres10 Maximum depth: 110 feet (1983)2 |
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St. Helens Lake |
Location: north; 9N-5E-3; Skamania County
Altitude: 4,567 feet1,2; 4,570 feet10 Surface Area: 79 acres1,2,10 Volume: 13,000 acre-feet2 Maximum depth: 280 feet2 Mean depth: 165 feet2 Drainage area: 350 acres2 |
St. Helens Lake is immediately north of Mount St.
Helens and was in direct line of initial blast. Unlike Spirit Lake,
St. Helens Lake did not receive a direct flow of volcanic material; much of
surface of lake was covered by logs, and much volcanic material
undoubtedly fell into lake or slid into it from steep slopes
surrounding lake1
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Swift Reservoir |
Location: Skamania County |
The uppermost lake in the Lewis River valley, Swift Reservoir,
receives drainage from the volcano via
Swift Creek, Pine Creek, and Muddy River. In 1980,
lahars descending these streams
dumped about 14 million cubic meters (18 million cubic yards)
of sediment and water into the lake,
abruptly raising the lake level 0.85 meters (2.8 feet).3
Swift Reservoir is formed by a rock and earthfill dam. Storage began
September 19, 1958; the dam was completed in December 1958. Usable capacity:
446,600 acre-feet between elevations 878 feet (lower limit for economic
operation), and 1,000.5 feet (maximum operating limit). Dead storage is unknown.
Water is used by PacifiCorp for power development.4
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Tradedollar Lake |
Location: Skamania County | In Blast Zone | |
Venus Lake |
Location: 10 miles NNE; 10N-5E-14; Skamania County
Altitude: 4,920 feet1,2,10 Surface Area: 20 acres1,2; 21 acres10 Volume: 930 acre-feet1,2 Maximum depth: 47 feet1; 46 feet2 Mean depth: 140 feet1,2 Drainage area: 130 acres2 |
Received heavy deposits of ash; most nearby
trees were uprooted, blown down, or completely stripped.1
Trees were felled or topped but not removed; lake was free of floating timber.
7
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Walupt Lake |
Location: 37 miles NE; 11N-11E-20; Lewis County
Altitude: 3,926 feet1; 3,930 feet2,10 Surface Area: 354 acres1; 350 acres2; 384 acres10 Volume: 62,300 acre-feet1; 62,000 acre-feet2 Maximum depth: 295 feet1; 300 feet2 Mean depth: 176 feet1; 177 feet2 Drainage area: 8,830 acres2 |
Outside of Blast Zone | |
Yale Lake |
Location: Clark and Cowlitz Counties |
Yale Reservoir is formed by a rock and earthfill dam. Storage began July
31, 1952; the dam was completed in 1952. Usable capacity: 189,500 acre-feet
between elevations 430 feet (lower limit for economic operation), and 490 feet
(top of spillway gates). Dead storage below elevation 417 feet: 178,000
acre-feet. Water is used by PacifiCorp for power development.4
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Sources
1
Dion and Embrey, 1981,
Effects of Mount St. Helens Eruption on Selected Lakes in Washington:
USGS Circular 850-G
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