EFFECTS OF MOUNT ST. HELENS 

ERUPTION ON SELECTED LAKES 

IN WASHINGTON 
Aerial view of Mount Saint Helens, Spirit Lake, and Saint Helens Lake after the eruption. 
Effects of Mount St. Helens 

Eruption on Selected lakes 

in Washington 

By N. P. Dian and S. S. Embrey 

Hydrologic Effects of the Eruptions of 

Mount St. Helens, Washington, 1980 

GEOLOGICAL SURVEY CIRCULAR 850-G 

1981 
United States Department of the Interior 

JAMES G. WATT, Secretary 

Geological Survey 

Doyle G. Frederick, Acting Director 

Library of Congress catalog-card No. 81-600041 

Free on application to Distribution Branch, Text Products Section, 

U. S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
FOREWORD 

On May 18, 1980, after more than a month of earthquakes and eruptions, Mount St. 

Helens, in southwestern Washington, exploded in a volcanic eruption more violent than 

any in the conterminous .United States during the 20th century. A lateral blast of hot gas 

and rock particles devastated an area of about 150 square miles on the northern side 

of the mountain knocking down trees to a distance of 15 miles. Several minutes later, a 

giant ash cloud rose to about 60,000 feet. Winds then carried the ash cloud across the 

United States, with heavy fallout and deposition in eastern Washington and parts of 

Idaho and Montana. Earlier, smaller eruptions deposited ash in western Washington 

and parts of Oregon and Canada. 

The hydrologic effects of the May 18 eruption have been both widespread and intense. 

During the eruption, a massive debris avalanche moved down the north flank of the 

volcano depositing about 3 billion cubic yards of rock, ice, and other materials in the 

upper 17 miles of the North Folk Toutle River valley. The debris deposits are about 

600 feet thick in the upper reaches of the valley. Following the avalanche, runoff from 

the melted glaciers and snow, and possible outflow from Spirit Lake, caused an extraordinary mudflow in the North Fork Toutle River. The mudflow shattered and uprooted 

thousands of trees, destroyed most of the local bridges, and deposited an estimated 

25,000 acre-feet of sediment in the Cowlitz River channel. A considerable amount of 

additional sediment was conveyed through the lower Cowlitz into the Columbia River 

where it was deposited and formed a shoal that blocked the shipping channel. Mudflows 

also occurred in the South Fork Toutle River and in tributaries on the east flank of 

Mount St. Helens which enter Swift Reservoir. 

As part of a concerted Geological Survey effort to study the volcanic event and to 

identify potential hazards, Survey hydrologists have mounted an intensive program to 

document the hydrologic effects of the eruptions. The major initial hydrologic findings 

are reported in this circular series. Quick, useful assessment was made possible only 

because the Survey has long conducted extensive water-resources investigations in the 

affected areas of Washington, Oregon, and Idaho. Hence, there was a well-defined basis 

for identification and documentation of the types and magnitudes of hydrologic changes. 

The Geological Survey Circular 850, "Hydrologic Effects of the Eruptions of Mount 

St. Helens, Washington, 1980," consists of individually published short chapters that 

emphasize data collection activities, field observations, and initial comparisons of preand post-eruption conditions. The series will cover hydrologic events occurring on 

May 18 in the Toutle and Cowlitz River; physical alteration of the Toutle River system; 

the chemical and physical quality of precipitation, streams, and lakes affected by volcanic ash fall; ash-leaching studies; and Mount St. Helens glaciers. 

Doyle G. Frederick 

Acting Director 

m 
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METRIC CONVERSION FACTORS 

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IV 
CONTENTS 

Page 

Abstract -------------------------------------- G 1 

Introduction ---------------------------------- 1 

Effects of volcanic eruption-Continued 

Chemical-Continued 

Page 

E~ffects of volcanic eruption _____________________ 3 Venus Lake ___________________________ G17 

Physical ----------------------------------- 3 

Chemical --------------------------------- 4 

Spirit Lake --------------------------- 4 

St. Helens Lake ________________________ 16 

Fawn Lake --------------------------- 16 

Walupt Lake --------------------------- 17 

Warden, Sprague, and Amber Lakes ---- 17 

Biological -------------------------------- 18 

Summary and conclusions ----------------------- 23 

References cited ------------------------------ 24 

ILLUSTRATIONS 

Page 

FIGURE 1. Map showing distribution of volcanic ash and locations of lakes studied G2 

2. Bathymetric map of Spirit Lake before the eruption _________________ 5 

3-10. Photographs showing: 

3. Spirit Lake before the eruption ------------------------------ 6 

4. Spirit Lake after the eruption ------------------------------- 7 

5. St. Helens Lake before the eruption ------------------------- 8 

6. St. Helens Lake after the eruption ------------------------- 9 

7. Fawn Lake before the eruption ----------------------------- 10 

8. Fawn Lake after the eruption ----------------------------- 11 

9. Venus Lake before the eruption ----------------------------- 12 

10. Venus Lake after the eruption ----------------------------- 13 

11. Graphs of surface-water temperatures of Spirit Lake _______________ 14 

TABLES 

Page 

TABLE 1. Locations and physical features of study lakes ----------------------- G2 

2-9. Water-quality data for: 

2. Spirit Lake ------------------------------------------------ 15 

3. St. Helens Lake ------------------------------------------- 16 

4. Fawn Lake ----------------------------------------------- 17 

5. Venus Lake ------------------------------------------------ 18 

6. Walupt Lake --------------------------------------------- 19 

7. Warden Lake ---------------------------------------------- 20 

8. Sprague Lake --------------------------------------------- 21 

9. Amber Lake ----------------------------------------------- 22 

10. Generalized water-quality conditions in lakes at various distances 

from the volcano --------------------------------------------- 23 

v 

HYDROLOGIC EFFECTS OF THE ERUPTIONS OF MOUNT ST. HELENS, WASHINGTON, 1980 

EFFECTS OF MOUNT ST. HELENS ERUPTION ON SELECTED LAKES 

IN WASHINGTON 

By N. P. DroN and S. S. EMBREY 

ABSTRACT 

The cataclysmic eruption of Mount St. Helens May 

18, 1980, altered the physical, chemical, and biological 

characteristics of numerous Washington lakes. As 

would be expected, those lakes closest to the volcano 

were the ones affected most by the eruption. Spirit Lake 

can now be considered a completely different lake because of its higher altitude, larger area, shallower 

depth, and changed hydrology, biology, and water 

chemistry. 

Water-quality changes were observed only in the 

lakes situated in the blast zone of the volcano. The 

changes included increases in most chemical constituents and reductions in transparency. Productivity levels 

in these lakes, as estimated by chlorophyll a concentrations, probably increased. No chemical or biological 

changes were observed in lakes that received only 

ash fall. 

INTRODUCTION 

The major eruption of Mount St. Helens on 

May 18, 1980, dumped tons of ash, mud, logs, 

and 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 that locally 

measured up to 7.6 centimeters thick (SarnaWojicki and others, 1980). 

The objective of this report is to describe 

the preliminary findings of a long-term study 

that was designed to (1) describe the present 

physical, chemical, and biological conditions in 

selected Washington lakes affected by volcanic 

activity; (2) compare present conditions in the 

lakes to pre-eruption conditions; and (3) document the recovery of the lakes. This report 

summarizes the first 5 months of a 3-year investigation that began in June 1980. 

The study lakes, whose locations are shown in 

figure 1, were selected on the basis of the following criteria: 

1. All the lakes received significant amounts of 

ash as a result of the May 18 eruption; 

2. Most of the lakes had been studied previously by the U.S. Geological Survey, and 

some background data are available for 

comparison ; 

3. The lakes in the immediate vicinity of the 

volcano were sufficiently close to be impacted by the deposition of pyroclastic 

material, ash, ice, mud, or timber; and 

4. The lakes distant from the volcano (that is, 

in eastern Washington) were at least 

moderately productive of aquatic plants 

and animals and showed a distinct seasonal succession of the algal community. 

General descriptions of the locations and 

physical features of the eight lakes selected for 

study are summarized in table 1. Background 

data for most of the lakes are contained in 

Washington Department of Ecology Bulletins 

42 (parts 2, 4, 5, and 6) and 43 (vol. 4); the 

detailed references are given at the end of this 

report. St. Helens Lake had not been studied 

by the U.S. Geological Survey prior to this investigation; consequently, no background data 

exist for that lake. 

Gl 
480 

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,~ \ I 4 ~305~· ',fp:..-..- ------l.O-~CHLAND MOUNT --_-:_--------o--------

ST. HELENS ---... WALLA WALLA 

0 STUDY LAKES 

0 50 100 MILES 1 Spirit 5 Walupt 

I I I 

I 

I I 2 St. Helens 6 Warden 

0 50 1 00 KILOMETERS 3 Fawn 7 Sprague 

4 Venus 8 Amber 

-1.0- Ash fall depth, in millimeters 

FIGURE 1.-Map showing distribution of volcanic ash and locations of lakes studied. 

TABLE 1.-Locations and physical features of study lakes 

Township, Altitude Area Volume Maximum Mean 

Lake County Range, and (ft) (acres) (acre-ft) depth depth 

Section (ft) (ft) 

Spirit 1 -------------------------- Skamania 9N-5E-15 3,198 1,300 160,000 190 130 

St. Helens ----------------------- Skamania 9N-5E-3 4,567 79 

Venus --------------------------- Skamania 10N-5E-14 4,920 20 930 140 47 

Fawn ---------------------------- Cowlitz 10N-4E-25 3,700 20 430 54 22 

Walupt -------------------------- Lewis llN-llE-20 3,926 354 62,300 295 176 

Warden -------------------------- Grant 17N-29E-15 1,076 200 5,300 71 27 

Sprague -------------------------- Adams 20N-37E-12 1,878 1,800 19,000 20 11 

Amber --------------------------- Spokane 21N-40E-2 2,160 120 2,000 40 17 

1 Prior to May 18, 1980, eruption. 

G2 
EFFECTS OF VOLCANIC ERUPTION 

PHYSICAL 

The four study lakes in the blast zone of 

Mount St. Helens (Spirit, St. Helens, Fawn, 

and Venus Lakes) received varying amounts of 

pyroclastic material, mud, ice, ash, and downed 

timber. The blast zone, as used in this report, 

is defined as the area immediately north of the 

volcano that was affected by the violent outburst, or explosion, that marked the beginning 

of the eruption. A detailed description of conditions in the blast zone at the time of the 

eruption was given by Korosec and others 

(1980). 

Because of its proximity to the volcano, 

Spirit Lake was the most affected of the four 

lakes. A comparison of aerial photographs 

taken before (fig. 3) and after (fig. 4 ) the 

eruption shows that the lake increased in size 

and rose in altitude. The surface area of the 

lake increased from 1,300 acres to about 2,200 

acres. Soundings of the east bay of the lake on 

October 16, 1980, indicated that the depth at 

the midpoint of the east bay, originally 190 ft 

(fig. 2 ) , was less than 50 ft. Because of an 

extensive cover of logs on the surface of Spirit 

Lake, a post-eruption bathymetric map could 

not be constructed. The rise in lake level, estimated to be about 240 ft, is due to the blockage of the North Fork Toutle River, floods 

from melting snow on the volcano, and partial filling of the lake with debris (Youd and 

Wilson, 1980). Because of the blockage of the 

original outlet, surface outflow to North Fork 

Toutle River will not occur until the lake rises 

from its present altitude of about 3,440 ft to 

about 3,600 ft. The pre-eruption altitude of 

the lake was 3,198 ft. 

St. Helens Lake is immediately north of the 

volcano and was in the direct line of the initial 

blast. Unlike Spirit Lake, St. Helens Lake did 

not receive a direct flow of volcanic material, 

so it was affected differently from Spirit Lake. 

Aerial photographs taken before (fig. 5) and 

GS 

after (fig. 6) the eruption depict the devastation resulting from the volcanic blast. As shown 

in figure 6, much of the surface of the lake is 

covered by logs, and much volcanic material 

undoubtedly fell into the lake or slid into it 

from the steep slopes that surround the lake. 

The outlet of the lake, which allows water to 

flow across a bedrock lip and into Spirit Lake, 

appears to have been unaffected. Water was 

observed flowing out of the lake when the area 

was visited in July and August 1980. Because 

bathymetric maps are not available for St. 

Helens Lake, the effects of the eruption on the 

depth of the lake cannot be accurately determined. Sporadic soundings of the lake with a 

handline suggest that the post-eruption lake is 

more than 250 ft deep. 

Fawn Lake, about 9 miles north-northwest 

of the volcano, and Venus Lake, about 10 miles 

north-northeast of the volcano, were also impacted by the eruption; but, because they are 

farther from the volcano, they were less impacted than Spirit and St. Helens Lakes. Both 

Fawn and Venus Lakes received heavy deposits of ash, and most nearby trees were 

uprooted, blown down, or completely stripped 

of their bark, branches, and leaves (figs. 7 to 

10). The stages of the lakes have not changed 

significantly because of the eruption, and when 

they were visted in August 1980, water was 

draining from both lakes. Comparisons of preand post-eruption bathymetric maps (not 

shown in report) indicate that the basins of 

Fawn and Venus Lakes have not changed significantly, despite the deposition of ash in the 

lakes. 

The configurations of the basins of other study 

lakes also were unchanged. For this reason, 

photographs and bathymetric maps of these 

lakes have not been included in this report. 

Readers desiring that information are referred 

to reports by Bartleson and others (1974, 

1976), Dion and others (1976, 1980), and 

McConnell and others (1976). 
CHEMICAL 

The May 18, 1980, eruption introduced huge 

quantities of volcanic debris into nearby lakes 

and varying quantities of ash into all lakes 

beneath the ash plume depicted in figure 1. 

Constituent 

Calcium 

Chlorine 

Magnesium 

Manganese 

Potassium 

Sodium 

Sulfate 

Concentration 

(micrograms per 

gram dry ash) 

151 

178 

27 

2.0 

20 

143 

534 

The leachate also contained high concentrations of ammonia, nitrate, phosphate, and up 

to 225 mg/L (milligrams per liter) of dissolved organic carbon. Taylor and Lichte theorized that the source of the organic material 

in the ash was the atmospheric condensation of 

the products formed by the burning of vegetation surrounding the volcano. 

In order to determine the effects of the debris 

and ash on the chemical characteristics of lake 

water, comparisons were made of chemical 

conditions in the study lakes before a1',r1 after 

the eruption. Those conditions are summarized 

in tables 2-9, at the end of the report. Posteruption vertical profiles of water temperatures 

and dissolved-oxygen concentrations were completed for most of the lakes studied and were 

compared with pre-eruption profiles, if available. These comparisons indicated that, except 

for Spirit Lake, no significant changes harl 

occurred in the temperatures and dissolvedoxygen concentrations of the lakes ; therefore, 

the profiles have not been included in this report. Because of the lack of either pre- or posteruption data, however, this comparison was 

not made for St. Helens Lake. 

Most of the water samples were collected 

over the deepest part of each lake ; however, 

for logistical reasons, some of the samples from 

lakes in the blast area of the volcano were collected from the littoral (nearshore) zone of the 

lake. The amount of pre-eruption chemical data 

available for Fawn and Venus Lakes is limChemical analyses of the leachate of volcanic 

ash collected near Moses Lake (Taylor and 

Lichte, 1980) indicate that the ash contains 

the following, and possibly other, soluble constituents: 

Constituent 

Arsenic 

Barium 

Beryllium 

Cadmium 

Copper 

Iron 

Lead 

Mercury 

Selenium 

Zinc 

Concentration 

(nanograms per 

gram dry ash) 

2 

51 

0.5 

5 

24 

24 

5 

0.1 

3 

12 

ited to that collected as part of a reconnaissance 

investigation of Washington lakes. 

SPIRIT LAKE 

In addition to the logs covering its surface, 

Spirit Lake contains large amounts of organic 

debris that impart an unpleasant odor to the 

water and give it a dark color. In fact, the 

water looks and smells very much like the 

effluent liquor from a pulp mill. The lake is rich 

in organic compounds (H. E. Taylor and J. M. 

Klein, U.S. Geological Survey, oral commun., 

November 4, 1970), especially gases (R. A. 

Rasmussen, Oregon Graduate Center, oral 

commun., October 10, 1980), as a result of the 

thermal, chemical, and biological alteration of 

organic matter introduced at the time of eruption. When visited on September 4, 1980, the 

surface of the lake was emitting large quantities of gas, some of it in "boils" 2 to 3 ft in 

diameter and some of it in almost continuous 

"streamers" of gas bubbles. On the October 1980 

visit, the gas activity of Spirit Lake was considerably less. According to Rasmussen, nlore 

than 50 gases have been identified, including 

H2S (hydrogen sulfide), CS2 (carbon disulfide), 

and COS (carbonyl sulfide). Many of the gases 

identified are toxic, and some are flammable. 

The concentrations of the gases within the lake, 

however, are unknown. Rasmussen also reported that there is a large amount of chlorine 

gas present. 

G4 
EXPLANATION 

-------- 40------

Line of equal water depth 

Interval 20 feet 

0 1000 2000 3000 4000 FEET 

FIGURE 2.-Bathymetric map of Spirit Lake before the eruption. 

G5 

N 
Q 

C') 

FIGURE 3.-Spirit Lake before the eruption. Top of Mount St. Helens in foreground. View is to the northeast. 
~ 

FIGURE 4.-Spirit Lake after the eruption. View is to the northeast. 
4.l 

00 

FIGURE 5.-St. Helens Lake before the eruption. View is to the south. Photograph from the Washington Game Department. 
C) 

c.o 

FIGURE 6.-St. Helens Lake after the eruption. View is to the south. 
FIGURE 7.-Fawn Lake before the eruption. View is to the southeast. 

GlO 
FIGURE 8.-Fawn Lake after the eruption. View is to the southeast. 

Gll 
FIGURE 9.- Venus Lake before the eruption. Photograph from the Washington Game Department. 

G12 
FIGURE 10.-Venus Lake after the eruption. 

G13 
On May 19, 1980, one day after the eruption 

and the subsequent influx of hot volcanic material into Spirit Lake, the temperature at the 

water surface (fig. 11) was 32.7°C (T. J. Casadevall, U.S. Geological Survey, written commun., October 8, 1980). By October 16,.19SO, 

the temperature at the water surface had 

decreased to 12.7°C and was only slightly 

higher than on October 9, 197 4. The maximum 

temperature observed in 1974 was 16.1 °C, in 

August. 

The heating of Spirit Lake and the introduction of organic matter have contributed to the 

depletion of the DO (dissolved-oxygen) concentration of the water. On October 16, 1980, 

the DO concentration in the epilimnion (top 

100 

Iw 90 I 

z 

w 

0::: 

I 

<( 

LL.. 

(/) 80 

w 

w 

0::: 

<..9 

w 

0 

z 70 

w 

0::: z 

:::> 0 

I-

<( I0.... 0::: 

w 60 :::> 

0::: 0.... 

~ w 

w 

I50 

May June July 

water layer) of Spirit Lake was only 0.8 mg/L; 

on October 9, 1974, before the eruption, the DO 

concentration in the epilimnion was 9.2 mg/L. 

The chemical data in table 2 indicate that, as 

a result of the eruption, there were significant 

increases in the dissolved-solids concentration, 

specific conductance, hardness, and alkalinity of 

the water in Spirit Lake. The concentrations 

of dissolved iron and manganese also greatly 

increased, although the iron concentration had 

decreased by June 8, 1980. Significant increases 

were also noted in the concentrations of metals 

(calcium, magnesium, sodium, and potassium), 

I 

nutrients (nitrogen and phosphorus), sulfate, 

chloride, and silica. 

35 

en 

::::> 

30 ~ UJ 

() 

en 

UJ 

UJ 

25 0::: <.!' 

UJ 

0 

z 

20 u.i 

0::: 

::::> 

I-

< 0::: 

15 UJ 

a.. 

~ 

UJ 

I10 

Aug. Sept. Oct. 

FIGURE 11.-Surface-water temperatures of Spirit Lake before (1974) and after (1980) the eruption of Mount 

St. Helens. (Based in part on data from T. J. Casadevall, U.S. Geological Survey, written commun., October 

8, 1980.) 

G14 
TABLE 2.-Water-quality data for Spirit Lake 

[In milligrams per liter unless otherwise indicated] 

Pre-May 18, 1980,eruption Post-May 18, 1980,eruption 

Date of collection (mo/day/yr) ----------- 6/27/74 8/7/74 9/11/74 10/9/74 3/28/80 6/6/80 6/8/80 7/28/80 

---- Sample depth (ft) ----------------------- 3 171 3 171 3 164 3 164 Outlet Littoral Littoral Littoral 

Specific conductance ( micromhos at 25 ° C)_ 27 35 25 35 26 33 19 20 30 844 828 860 

pH (units) ----------------------------- 6.9 6.4 8.3 8.2 6.6 6.2 7.2 7.2 7.1 6.4 6.0 6.8 

Temperature (degrees Celsius) ----------- 10.0 4.0 16.0 4.0 15.0 3.0 12.3 3.5 2.6 26.0 26.0 20.6 

Transparency, Secchi-disk (ft) ----------- 23 36 46 41 

Dissolved oxygen (DO) ------------------ 10.4 -- 9.0 1.9 8.9 2.8 9.2 3.2 

Hardness, as CaC03 (Ca,Mg) ------------- -- -- -- -- -- -- 12 17 9 240 230 240 

Noncarbonate hardness ------------------ __ -- -- -- -- -- 0 0 1 130 110 54 

Calcium, dissolved ( Ca) ------------------ __ -- -- -- -- -- 5.0 3.5 2.8 74 74 76 

Magnesium, dissolved (Mg) -------------- -- -- -- -- -- -- .o 1.9 .6 13 12 13 

Sodium, dissolved ( N a) ------------------ __ -- -- -- -- -- 1.8 2.1 2.0 68 68 78 

0 Potassium, dissolved (K) ----------------- -- -- -- -- -- -- .4 .4 .6 15 15 15 

1--l Bicarbonate (HCOs) --------------------- 14 20 u 21 14 20 16 20 en Alkalinity, total, as CaCOs --------------- 11 16 11 17 11 16 13 16 8 110 120 190 

Carbon dioxide ( C·02) -------------------- 2.8 13 .1 .2 5.6 20 1.6 2.0 1.2 85 

Sulfate, dissolved ( S04) ------------------ -- -- -- -- -- -- 1.3 1.3 .0 190 160 150 

Chloride, dissolved ( Cl) ------------------ __ -- -- -- -- -- 1.3 1.5 1.5 86 86 83 

Silica, dissolved ( Si02) ------------------ 12 15 11 16 11 15 12 15 12 46 46 50 

Dissolved solids, calculated, sum of 

constituents --------------------------- -- -- -- -- -- -- 30 36 25 574 543 

Nitrate plus nitrite, total as N ----------- .00 .17 .00 .20 .00 .19 .02 .16 .06 .07 -- .00 

Nitrogen, ammonia, total as N ----------- .01 .01 .01 .01 .01 .02 .02 .02 .14 .19 -- .00 

Nitrogen, total organic, as N ------------- .03 .04 .09 .05 .04 .01 .13 .04 .80 1.5 -- 1.2 

Nitrogen, total, as N -------------------- .04 .22 .10 .26 .05 .22 .17 .22 1.0 1.8 -- 1.2 

Phosphorus, total, as P ------------------ .01 .02 .00 .01 .00 .01 .01 .01 .03 1.8 .40 .34 

Phosphate, ortho, dissolved (P04) -------- .00 .03 .00 .03 .00 .00 .oo .00 

Iron, dissolved, as Fe (p,g/L) ------------ 20 230 50 180 80 180 50 50 10 8,800 2,100 420 

Manganese, dissolved,. as Mn ( p,g/L) ---- 0 260 10 70 0 40 0 0 6 5,000 4,900 4,800 

Carbon, organic, total, as C -------------- 2.7 -- 1.7 -- -- -- 1.4 -- -- -- -- 40 

Chlorophyll a (p,g/L) ------------------- 0.7 0.3 0.6 1.3 
ST. HELENS LAKE 

Because no pre-eruption data were available 

for this lake, it was assumed that the quality of 

the water prior to the eruption was similar to 

that of Spirit Lake. Previous studies (Dethier 

and others, 1979) have shown that most alpine 

lakes without significant cultural development 

have similar chemical and biological characteristics. A comparison of pre-eruption waterquality conditions in Spirit Lake (table 2) with 

post-eruption conditions in St. Helens Lake 

(table 3) suggests that the changes brought 

about by the volcano were similar to those 

observed in Spirit Lake, but not as great. This 

generalization holds true for such characteristics as dissolved solids, specific conductance, 

hardness, metals, phosphorus, sulfate, and 

chloride. The concentrations of silica and DO 

in the epilimnion may have decreased, whereas 

the nitrogen, iron, and manganese may have increased. Assuming that the transparency of 

pre-eruption St. Helens Lake was as great as 

that of Spirit Lake, the transparency of St. 

Helens Lake, as measured by Secchi disc, was 

substantially decreased because of the suspended mud and ash. On August 28, 1980, the 

water was grayish brown and transparency 

was only 1 ft. No significant change in the 

water temperature has been observed. 

FAWN LAKE 

The pre-eruption water-quality data for this 

lake are sparse, making comparisons difficult. 

The small amount of available information 

(table 4) suggests that the specific conductance, 

hardness, and concentrations of metals, sulfate, 

chloride, dissolved solids, organic nitrogen, 

iron, manganese, and chlorophyll a increased 

while the transparency and concentration of 

dissolved silica decreased as a result of the 

TABLE 3.-Water-quality data for St. Helens Lake 

[In milligrams per liter unless otherwise indicated] 

Date of collection (mo/day/yr) ___________________ _ 

Sample depth (ft) --------------------------------

Specific conductance (micromhos at 25oC) _________ _ 

pli (units) --------------------------------------- Temperature (degrees Celsius) ___________________ _ 

Transparency, Secchi-disk (ft) ___________________ _ 

Dissolved oxygen (DO) ---------------------------- Hardness, as CaCOa (Ca,Mg) _____________________ _ 

N oncarbonate ha1·dness ___________________________ _ 

Calcium, dissolved (Ca) __________________________ _ 

Magnesium, dissolved (Mg) _______________________ _ 

Sodium, dissolved (Na) __________________________ _ 

Potassium, dissolved (K) --------------------------

Bicarbonate (liCOa) ------------------------------

Alkalinity, total as CaCOa --------------------------

Carbon dioxide ( C02) -----~------------------------

Sulfate, dissolved ( S04) __________________________ _ 

Chloride, dissolved ( Cl) __________________________ _ 

Silica, dissolved ( SiO~) ---------------------------

Dissolved solids, calculated, sum of constituents _____ _ 

Nitrate, plus nitrite, total as N ____________________ _ 

Nitrogen, ammonia, total as N _____________________ _ 

Nitrogen, total organic as N _______________________ _ 

Nitrogen, total as N -------------------------------

Phosphorus, total as P ----------------------------

Phosphate, ortho, dissolved ( P04) _________________ _ 

Iron, dissolved as Fe (,ug/L) ______________________ _ 

Manganese, dissolved as Mn (,ug/L) _______________ _ 

Carbon, organic, total as C ________________________ _ 

Chlorophyll a (,ug/L) ------------------------------

G16 

6/6/80 

Littoral 

150 

7.1 

5.4 

7.2 

40 

31 

14 

1.3 

8.9 

2.5 

0 

9 

1.4 

36 

16 

7.6 

93 

.01 

.09 

.13 

.23 

.17 

.52 

75 

320 

Post-eruption 

7/28/80 8/28/80 

Littoral 3 240 

161 154 164 

6.4 6.6 6.6 

17.0 11.0 5.3 

1.0 

7.0 2.6 

42 44 43 

30 35 36 

14 15 15 

1.6 1.5 1.4 

8.8 9.2 9.3 

2.8 2.4 2.2 

12 9 9 

43 38 44 

12 12 14 

8.7 5.8 5.7 

99 90 98 

.09 .00 .05 

.02 .02 .02 

.88 .56 .58 

.99 .58 .65 

.11 .05 .16 

.34 .06 .06 

140 150 50 

330 330 360 

5.5 

3.1 
TABLE 4.-Water-quality data for Fawn Lake 

[In milligrams per liter unless otherwise indicated] 

Pre-eruption Post-eruption 

Date of collection (mo/day/yr) ___________________ _ 9/14/74 8/27/80 

----------------------- Sample depth (ft) --------------------------------

Specific conductance (micromhos at 25°C) _________ _ 

pH (units) ---------------------------------------- Temperature (degrees Celsius) ___________________ _ 

Transparency, Secchi-disk (ft) ___________________ _ 

Dissolved oxygen (DO) ---------------------------- Hardness, as CaCOa (Ca,Mg) _____________________ _ 

Noncarbonate hardness ---------------------------- Calcium, dissolved (Ca) __________________________ _ 

Magnesium, dissolved (Mg) _______________________ _ 

Sodium, dissolved (Na) --------------------------- Potassium, dissolved (K) _________________________ _ 

Bicarbonate (HCOa) ------------------------------

Alkalinity, total as CaCOa _________________________ _ 

Carbon dioxide ( C02) ______________________________ _ 

Sulfate, dissolved ( S04) __________________________ _ 

Chloride, dissolved (Cl) __________________________ _ 

Silica, dissolved ( Si02) ---------------------------

Dissolved solids, calculated, sum of constituents _____ _ 

Nitrate, plus nitrite, total as N ____________________ _ 

Nitrogen, ammonia, total as N _____________________ _ 

Nitrogen, total organic as N _______________________ _ 

Nitrogen, total as N --------------------------------

Phosphorus, total as P ----------------------------

Phosphate, ortho, dissolved (P04) _________________ _ 

Iron, dissolved as Fe (,ug/L) ______________________ _ 

Manganese, dissolved as Mn (,ug/L) _______________ _ 

Carbon, organic, total as C -------------------------

Chlorophyll a (,ug/L) ------------------------------

eruption. The decrease in silica concentration 

may have been the result of changes in the 

algal diatom population and not a direct result 

of the eruption. The water transparency observed on August 27, 1980, was 7 ft, but it 

had increased to 12 ft by October 28, 1980. 

VENUS LAKE 

The paucity of chemical data available for 

this lake prevents a complete discussion of the 

effects of the eruption. However, the observed 

increase in the specific-conductance value, from 

9 to 233 micromhos (table 5), suggests that 

the lake water has undergone some type of 

alteration because of the eruption. 

WALUPT LAKE 

On the basis of available chemical data, the 

eruption had no effect on the water quality of 

Walupt Lake, about 37 miles northeast of the 

3 

30 

14.8 

8.8 

.02 

.06 

.05 

.13 

.00 

.00 

21 

72 

46 

3.7 

1.0 

.01 

.27 

.02 

.30 

.05 

.02 

3 

666 

6.5 

15.7 

9.2 

200 

180 

68 

6.2 

46 

10 

19 

170 

71 

8.1 

392 

.00 

.02 

.56 

.58 

.02 

.03 

1.9 

50 

760 

6.5 

9.9 

7 

.6 

210 

190 

74 

6.8 

47 

11 

25 

180 

76 

9.5 

414 

.00 

.21 

.79 

1.0 

.06 

.03 

3.6 

volcano. The relatively low transparency observed on June 23, 1980 (3.5 ft--table 6), 

occurred at a time of high runoff and inflow, 

and the exact source of the inorganic suspended 

sediment that caused the low transparency is 

not known. The source of the sediment may 

have been ash that was deposited either directly 

in the lake or on snow in the drainage basin 

of the lake. The sediment may also have been 

the result of normal spring runoff, although the 

minimum transparency value observed prior to 

the eruption was 20ft (in 1971). 

WARDEN, SPRAGUE, AND AMBER LAKES 

For the most part, on the basis of chemical 

and physical characteristics documented in this 

report, the study lakes in eastern Washington 

appear to have been unaffected by the volcanic 

eruption, despite the deposition of up to 3 

inches of ash in some areas. The chemical data 

G17 
TABLE 5.-Water-quality data for Venus Lake 

[In milligrams per liter unless otherwise indicated] 

Pre-eruption 

Date of collection (mo/day/yr) 

Sample depth (ft) --------------------------------------------

Specific conductance (micromhos at 25°C) _____________________ _ 

pii (units) --------------------------------------------------- Temperature (degrees Celsius) _________________________ _ 

Transparency, Secchi-disk (ft) --------------------------------

Dissolved oxygen (DO) _________ --------------------------------

IIardness, as CaC03 (Ca,Mg) ----------------------------------

~oncarbonate hardness ----------------------------------------

Calcium, dissolved ( Ca) ---------------------------------------

Magnesium, dissolved (Mg) ------------------------------------ Sodium, dissolved (~a) ______________________________________ _ 

Potassium, dissolved (K) _____________________________________ _ 

Bicarbonate (II C03) ------------------------------ ___________ _ 

Alkalinity, total as CaC03 -------------------------- ___________ _ 

Carbon dioxide ( C02) ----------------------------- ___________ _ 

Sulfate, dissolved ( S04) --------------------------- ___________ _ 

Chloride, dissolved ( Cl) ---------------------------------------

Silica, dissolved ( Si02) ---------------------------------------

Dissolved solids, calculated, sum of constituents _________________ _ 

~itrate, plus nitrite, total as ~ ---------------------------------

~itrogen, ammonia, total as ~ ----------------------------------

~itrogen, total organic as ~ ------------------------------------

~itrogen, total as ~ -------------------------------------------

Phosphorus, total as P ----------------------------------------

Phosphate, ortho, dissolved (P04) _____________________________ _ 

Iron, dissolved as Fe (Mg/L) -----------------------------------

Manganese, dissolved as Mn (Mg/L) ----------------------------

Carbon, organic, total as C ------------------------------------- Chlorophyll a (f.tg/L) _________________________________________ _ 

3 

9 

9.4 

9.5 

.01 

.04 

.10 

.15 

.00 

.00 

9/14/74 

66 

125 

12 

3.8 

7.2 

.02 

.03 

.08 

.13 

.01 

.00 

Post-eruption 

7/28/80 

Littoral 

233 

6.3 

17.8 

60 

58 

20 

2.4 

13 

2.7 

2 

61 

19 

8.2 

.00 

.00 

.74 

.74 

.16 

51 

370 

3.1 

(tables 7-9) suggest that the dissolved-iron 

concentration in the hypolimnion (bottom 

water layer) of Amber Lake and the dissolvedmanganese concentration in the hypolimnion 

of both Warden and Amber Lakes have increased. However, the data for Sprague Lake 

suggest that the iron and manganese concentrations in that lake have decreased. Given 

this set of seemingly contradictory data, it is 

difficult to ascribe changes in the water chemistry of the lakes to the erpution with any 

degree of certainty. 

are available for the post-eruption period, but, 

because corresponding pre-eruption data are 

not available, the post-eruption data have not 

been included in this preliminary report. Productivity levels can be approximated, however, 

by the concentration of chlorophyll a in the 

water. Chlorophyll a is a green photosynthetic 

pigment present in all groups of algae. 

BIOLOGICAL 

Very little pre-eruption biological information is available for lakes in the blast zone of 

Mount St. Helens, and, therefore, the biological 

effects of the eruption can only be surmised. 

Qualitative and quantitative data pertaining to 

populations of phytoplankton and zooplankton 

Chlorophyll a concentrations in Spirit Lake 

in 1974 ranged from 0.3 to 1.3 f-tg/L (micrograms per liter). If the assumption can be 

made that pre-eruption concentrations in other 

alpine study lakes (St. Helens, Fawn, Venus, 

and Walupt Lakes) were similar to that in 

Spirit Lake, it appears that the productivities of all lakes mentioned were increased as a 

result of the eruption. The possibility exists, 

however, that the very fine suspended sediment 

in the water samples interfered with the optical technique of determining chlorophyll a 

G18 
0 

'"'"' co 

TABLE 6.-Water-quality data for W alupt Lake 

[In milligrams per liter unless otherwise indicated] 

Pre-eruption 

Date of collection (mo/day/yr) -------------------------------------------- 7/8/71 8/18/71 10/5/71 

Sample depth (ft) 50 

Specific conductance (micromhos at 25°C) ---------------------------------- 25 

pH (units) ---------------------------------------------------------------- 7.2 

Temperature (degrees Celsius) ---------------------------------------------

Transparency, Secchi-disk (ft) ---------------------------------------------

Dissolved oxygen (DO) ----------------------------------------------------

Hardness, as CaCOa ( Ca,Mg) ----------------------------------------------

Noncarbonate hardness -----------------------------------------------------

Calcium, dissolved ( Ca) ----------------------------------------------------

Magnesium, dissolved (Mg) ------------------------------------------------

Sodium, dissolved ( Na) ----------------------------------------------------

Potassium, dissolved (K) --------------------------------------------------

Bicarbonate (HCOa) -------------------------------------------------------

Alkalinity, total as CaCoa --------------------------------------------------

Carbon dioxide ( C02) ------------------------------------------------------

Sulfate, dissolved ( S04) ----------------------------------------------------

Chloride, dissolved ( Cl) ----------------------------------------------------

Silica, dissolved (Si02) ----------------------------------------------------

Dissolved solids, calculated, sum of constituents -----------------------------

Nitrate, plus nitrite, total as N --------------------------------------------

Nitrogen, ammonia, total as N ---------------------------------------------

Nitrogen, total organic as N -----------------------------------------------

Nitrogen, total as N -------------------------------------------------------

Phosphorus, total as P -----------------------------------------------------

Phosphate, ortho, dissolved (P04) ------------------------------------------

Iron, dissolved as Fe (11-g/L) -----------------------------------------------

Manganese, dissolved as Mn (~/L) ----------------------------------------

Carbon, organic, total as C -------------------------------------------------

Chlorophyll a. (11-g/L) ------------------------------------------------------

6.0 

20 

11.2 

12 

0 

4.3 

.4 

1.7 

.3 

17 

14 

.0 

.3 

8.0 

23 

10 

0 

.06 

.00 

.00 

3 

27 

7.9 

17.5 

8.8 

.05 

.12 

.01 

.00 

26 

200 

28 

7.9 

4.0 

9.2 

.02 

.11 

.01 

.00 

3 

10.5 

9.8 

.01 

.07 

.01 

.01 

32 

285 

4.0 

3.8 

.01 

.07 

.01 

.01 

6/23/80 

3 

38 

6.4 

11.2 

3.5 

10.0 

11 

0 

3.6 

.5 

2.0 

.4 

-

12 

3.0 

1.4 

8.6 

30 

.00 

.00 

.19 

.19 

.02 

.00 

<10 

10 

0.74 

Post-eruption 

8/11/80 

240 3 240 

32 38 34 

6.1 6.9 7.1 

4.4 16.7 4.0 

24 

10.6 8.6 9.7 

9 14 10 

0 6 0 

3.1 4.0 3.0 

.4 1.0 .6 

1.8 2.2 2.1 

.4 .5 .5 

--

13 8 15 

-- -- 3.4 1.5 1.9 

1.1 2.3 1.7 

8.4 6.4 6.4 

34 23 25 

.00 .00 .00 

.00 .00 .00 

.25 .21 .22 

.25 .21 .22 

.02 .01 .01 

.00 .00 .00 

<10 20 0 

20 0 0 

-- 2.5 
TABLE 7.-Water-quality datw for Warden Lake 

[In milligrams per liter unless otherwise indicated] 

Pre-eruption Post-eruption 

Date of collection (mo/day/yr) ----------- 4/21/75 5/27/75 8/18/75 9/15/75 6/24/80 8/12/80 

Sample depth (ft) ----------------------- 3 66 3 66 3 62 3 60 3 65 3 65 

Specific conductance (micromhos at 25°C) _ 592 578 630 660 531 584 532 580 550 630 548 632 

ph (units) ------------------------------ 9.2 9.2 8.8 7.9 9.4 7.4 9.0 7.2 9.5 7.8 9.3 7.6 

Temperature (degrees Celsius) ----------- 10.7 6.8 14.9 7.7 21.4 9.0 19.9 9.1 21.8 9.3 22.7 8.7 

Transparency, Secchi-disk (ft) ----------- 8.0 9.5 2.7 8.5 4.5 10 

Dissolved oxygen (DO) ------------------ 11.0 8.0 10.8 .3 11.9 0 13.4 0 15.8 .2 10.0 .0 

Hardness, as CaCOs ( Ca,Mg) ------------ 180 -- -- -- -- -- 160 -- 140 160 140 180 

Noncarbonate hardness ------------------ 0 -- -- -- -- -- 0 -- 0 0 0 0 

Calcium, dissolved ( Ca) ----------------- 26 -- -- -- -- -- 19 -- 17 25 16 30 

Magnesium, dissolved (Mg) -------------- 27 -- -- -- -- -- 27 -- 23 24 24 25 

~ Sodium, dissolved (Na) ------------------ 71 -- -- -- -- -- 74 -- 72 69 73 70 

1.\:) Potassium, dissolved (K) ---------------- 8.7 -- -- -- -- -- 10 -- 8.1 8.8 9.1 9.0 

0 Bicarbonate (HCOa) -------------------- 253 200 256 280 164 297 256 307 

Alkalinity, total, as CaCOa --------------- 222 164 220 230 206 244 210 252 210 240 200 250 

Carbon dioxide ( C02) ------------------- .3 .2 .7 5.6 .2 19 .4 31 

Sulfate, dissolved (804) ----------------- 71 -- -- -- - - 77 -- 60 57 59 53 

Chloride, dissolved (Cl) ------------------ 22 -- -- -- -- -- 22 -- 20 15 18 17 

Silica, dissolved (Si02) ------------------ 29 29 26 30 26 31 27 81 21 82 15 24 

Dissolved solids, calculated, sum of 

constituents --------------------------- 389 -- -- -- -- -- 382 -- 348 376 335 379 

Nitrate plus nitrite, total as N ----------- .20 .15 .95 .25 .01 .01 .01 .00 .11 .00 .35 .00 

Nitrogen, ammonia, total as N ----------- .06 .23 .08 .80 .09 2.4 .11 2.9 .06 1.7 .01 3.7 

Nitrogen, total organic, as N ------------- .55 .69 .5'Z .50 1.0 .60 .71 .90 .78 .60 .62 .70 

Nitrogen, total, as N -------------------- .81 1.1 1.6 1.6 1.1 3.0 .83 3.8 .95 2.3 .98 4.4 

Phosphorus, total, as P ------------------ .02 .03 .02 .02 .04 .16 .03 .21 .02 .11 .01 .25 

Phosphate, ortho, dissolved (P04) -------- .00 .00 .00 .00 .00 .43 .00 .55 .00 .06 .00 .43 

Iron, dissolved, as Fe (,ug/L) ------------ 20 so 30 40 30 20 20 40 <10 <10 20 20 

Manganese, dissolved, as Mn ( ~/L) ---- 4 70 20 260 20 290 20 270 4 440 10 400 

Carbon, organic, total, as C -------------- -- -- 7.9 -- 11 -- 12 

Chlorophyll a (p,g/L) ------------------- 6.8 4.2 19 7.9 8.2 8.2 
TABLE 8.-Water-quality data for Sprague Lake 

[In milligrams per liter unless otherwise indicated] 

Pre-eruption Post-eruption 

Date of collection (mo/day/yr) ----------- 4/16/75 5/19/75 8/13/75 9/30/75 6/25/80 8/13/80 

Sample depth (ft) ----------------------- 3 16 3 16 3 14 3 13 3 15 3 15 

Specific conductance (micro mhos at 25°C) _ 308 309 326 326 304 341 338 337 384 383 379 388 

pH (units) ------------------------------ 8.9 9.1 8.6 8.6 9.1 8.4 8.2 8.1 8.5 8.5 8.8 8.6 

Temperature (degrees Celsius) ----------- 8.1 8.1 13.1 12.6 22.0 20.0 15.1 14.7 19.4 19.4 20.8 19.8 

Transparency, Secchi-disk (ft) ----------- 3.5 2.8 1.9 1.8 1.5 1.5 

Dissolved oxygen (DO) ------------------ 12.2 12.0 9.4 8.6 14.4 3.8 8.9 8.7 7.9 7.3 9.7 7.6 

Hardness, as CaCOa (Ca,Mg) ------------ 130 -- -- -- -- -- 150 -- 130 130 140 150 

Noncarbonate hardness ------------------ 0 -- -- -- -- -- 0 -- 0 0 0 0 

Calcium, dissolved ( Ca) ----------------- 29 -- -- -- -- -- 34 -- 28 28 27 30 

Magnesium, dissolved ( Mg) -------------- 14 -- -- -- -- -- 15 -- 15 15 17 17 

G":) Sodium, dissolved (Na) ------------------ 19 -- -- -- -- -- 22 -- 24 24 28 28 !:':) Potassium, dissolved (K) ---------------- 6.9 -- -- -- -- -- 8.8 -- 8.5 8.6 9.5 9.8 ...... Bicarbonate (HCOa) -------------------- 189 189 195 196 202 215 224 223 

Alkalinity, total, as CaCOa --------------- 155 155 160 161 166 176 184 183 160 160 160 160 

Carbon dioxide ( C02) ------------------- .4 .2 .8 .8 .3 1.4 2.3 2.8 

Sulfate, dissolved (S04) ----------------- 13 -- -- -- -- -- 12 -- 30 29 16 16 

Chloride, dissolved (Cl) ------------------ 4.8 -- -- -- -- -- 5.2 -- 6.3 6.8 9.4 9.6 

Silica, dissolved ( Si02) ------------------ 13 14 3.3 3.3 .4 5.6 2.5 2.9 1.0 1.1 7.4 7.3 

Dissolved solids, calculated, sum of 

constituents --------------------------- 193 -- -- -- -- 210 -- 209 209 211 214 

Nitrate plus nitrite, total as N ----------- .08 .07 .00 .00 .01 .01 .02 .03 .00 .00 .02 .00 

Nitrogen, ammonia, total as N ----------- .15 .13 .10 .13 .29 .32 .07 .08 .08 .09 .23 .16 

Nitrogen, total organic, as N ------------- .75 .73 .80 .82 1.7 .78 1.1 1.1 1.4 .85 1.3 1.1 

Nitrogen, total, as N -------------------- .98 .93 .90 .95 2.0 1.1 2.0 1.2 1.5 .94 1.5 1.3 

Phosphorus, total, as P ------------------- .06 .07 .09 .10 .10 .12 .08 .08 .05 .05 .07 .07 

Phosphate, ortho, dissolved (P04 ) -------- .00 .00 .00 .00 .03 .06 .03 .03 .00 .00 .00 .00 

Iron, dissolved, as Fe (p,g/L) ------------ 80 90 250 310 130 340 260 290 <10 <10 20 20 

Manganese, dissolved., as Mn (~/L) ---- 30 30 30 40 30 50 30 40 <3 0 10 10 

Carbon, organic, total, as C -------------- 8.5 -- 7.9 -- 22 -- 28 

Chlorophyll a (p,g/L) ------------------- 35 23 29 15 11 133 
TABLE 9.-Water-quality data for Amber Lake 

[In milligrams per liter unless otherwise indicated] 

Pre-eruption Post-eruption 

Date of collection (mo/day/yr) ----------- 4/4/73 5/22/73 7/10/73 10/2/73 6/26/80 8/14/80 

Sample depth (ft) ----------------------- 3 34 3 34 3 32 3 30 3 36 3 36 

Specific conductance ( micromhos at 25°C) _ 250 240 267 264 260 272 249 255 274 290 266 292 

pH (units) ----------------------------- 6.9 7.2 8.2 7.6 8.8 7.4 9.4 8.9 9.0 7.5 9.0 7.7 

Temperature (degrees Celsius) ----------- 8.0 7.0 16.3 12.3 21.0 14.7 14.0 13.8 19.6 10.5 21.4 10.4 

Transparency, Secchi-disk (ft) ----------- 9.8 16 18 9.8 12 17 

Dissolved oxygen (DO) ------------------ 10.5 9.6 9.6 4.1 9.0 .1 7.0 6.6 9.6 .2 9.4 .2 

Hardness, as CaCOa (Ca,Mg) ------------ 100 -- -- -- -- -- 96 -- 95 100 97 110 

Noncarbonate hardness ------------------ -- -- -- -- -- -- 0 -- 0 0 0 0 

Calcium, dissolved ( Ca) ----------------- 22 -- -- -- -- 17 -- 20 22 19 24 

Magnesium, dissolved (Mg) -------------- 12 -- -- -- 13 -- 11 12 12 12 

C'.:l Sodium, dissolved ( N a) ------------------ 16 -- -- -- -- -- 18 -- 15 15 16 15 ~ Potassium, dissolved (K) ---------------- 8.3 -- -- -- -- -- 8.4 -- 8.0 7.9 8.1 8.4 ~ Bicarbonate (HCOa) -------------------- 158 160 162 161 147 166 163 163 

Alkalinity, total, as CaCOa --------------- 130 131 133 132 132 136 134 134 130 130 110 140 

Carbon dioxide ( C02) 

Sulfate, dissolved ( S04) ----------------- 6.1 -- -- -- -- -- 4.7 -- 11 13 5.7 2.1 

Chloride, dissolved ( Cl) ------------------ 5.1 -- -- -- -- -- 4.9 -- 2.9 2.6 6.6 5.8 

Silica, dissolved ( Si02) ------------------ 1.2 1.3 2.0 4.0 2.6 9.6 8.6 9.1 .1 4.1 .4 3.9 

Dissolved solids, calculated, sum of 

constituents --------------------------- -- -- -- -- -- 155 -- 146 156 134 158 

Nitrate plus nitrite, total as N ----------- .02 .02 .04 .02 .02 .02 .02 .02 .00 .00 .00 .00 

Nitrogen, ammonia, total as N ----------- .09 .11 .05 .14 .10 .11 .16 .18 .00 .33 .00 1.2 

Nitrogen, total organic, as N ------------- .22 .22 .66 .57 3.9 .10 .74 .78 .78 .87 1.0 .80 

Nitrogen, total, as N -------------------- .33 .35 .75 .73 4.0 .23 .92 .98 .78 1.2 1.0 2.0 

Phosphorus, total, as P ------------------- .03 .03 .02 .06 .03 .05 .04 .04 .04 .05 .02 .12 

Phosphate, ortho, dissolved (P04) -------- .01 .00 .01 .01 .01 .06 .04 .03 .00 .03 .03 .18 

Iron, dissolved, as Fe (,ug/L) ------------ 40 50 40 60 30 150 60 70 <10 190 30 980 

Manganese, dissolved, as Mn ( ,ug/L) ____ 10 30 10 60 20 340 60 50 <3 660 0 1,200 

Carbon, organic, total, as C -------------- 8.0 -- 8.0 -- 11 -- 9.5 

Chlorophyll a (,ug/L) ------------------- 2.0 1.3 7.9 6.6 2.8 8.2 
concentrations and caused falsely high readings. Sed ell and others ( 1980) reported that the 

biological productivity of Spirit Lake has never 

been higher, but that it has thus far been limited primarily to greatly expanded populations 

of bacteria. No biological data are available 

for Venus Lake. 

The high temperatures and low DO concentrations observed in Spirit Lake after the 

eruption most likely killed all fish in the lake. 

Fish conditions in other blast-zone lakes have 

been described by B. A. Crawford of the Washington Department of Game (oral commun., 

November 24, 1980). In September 1980, according to Crawford, gill nets were set in three 

blast zone lakes not studied as part of this 

investigation. Live fish were found in all three 

lakes. The fish were fat and in good condition, but most had been feeding on terrestrial, 

as opposed to aquatic, insects. Crawford believes the long-term implications of this diet 

are significant. The fish will most likely survive the winter season by becoming semidormant beneath the ice cover of the lake and by 

utilizing stored fat reserves. However, the 

spring season will be especially critical for the 

fish, until such time as the terrestrial and (or) 

aquatic insect populations become large enough 

to support the fishery. Crawford thinks all fish 

in St. Helens Lake were killed by the high 

turbidity, although gill nets have not been set 

in that lake. 

The study lakes of eastern Washington 

(Warden, Sprague, and Amber) are considerably more alkaline and productive than the 

lakes discussed above. A comparison of chlorophyll a concentrations before and after the 

eruption indicated that the concentrations generally have not changed. An algal bloom observed in Sprague Lake on August 13, 1980, 

resulted in a chlorophyll a concentration of 133 

p.g/L. Sprague Lake has a history of summer 

blooms, and there is no evidence to indicate 

that the bloom observed on that particular date 

was a result of ash deposited in the lake. 

The speed and extent of biological recovery 

of lakes in the blast zone of the volcano will 

depend in large measure on the specific biological effects of the physical and chemical 

changes observed in this study. It is likely that 

the lakes will not recover to their exact preeruption biological levels, but rather to new 

levels of productivity that are determined by 

prevailing physical and chemical eonditions. 

Because algae are at the base of the aquatic 

food chain, and because they produce organic 

tissue from inorganic substances dissolved in 

water, the recovery and well-being of the algal 

population is of prime concern in discussions 

of lake recovery in general. 

A prediction of the likely biological effects 

of the observed changes is difficult; not all the 

changes affect algal growth in the same manner. Some of the changes, such as increased 

concentrations of nutrients, dissolved solids, 

silica, alkalinity, and hardness, would tend to 

encourage algal growth. Other changes, such 

as reduced transparency and the presence of 

potentially toxic trace metals (cadmium, copper, and zinc) might discourage growth. The 

effects of still other changes, such as increased 

temperature and increased concentrations of 

organic substances, iron, manganese, sulfate, 

and chloride, are more difficult to assess. Further complications arise from the fact that 

some elements, such as copper, are considered 

vital for algal growth, yet the same elements 

in excessive concentrations act as deterrents 

to growth. 

Recent experiments by D. M. McKnight, G. 

L. Feder, and E. A. Stiles (U.S. Geological 

Survey, written commun., September 20, 

1980) investigated the possible toxicity of 

leachate from volcanic ash collected in eastern 

Washington. The investigators determined 

that, although the leachate from ash collected 

near Richland was toxic to cultures of the bluegreen alga Anabaena fios-aquae in dilutions up 

to 1 to 250, the leachate from ash collected 

near Moses Lake had no effects, either stimulatory or inhibitory, on the same organism. 

The investigators concluded that the toxic substance is an organic compound that is not 

uniformly distributed in the ash fall, and that 

the ash fall had no effect on the chemistry or 

biology of four lakes studied, which included 

W alupt and Warden Lakes. 

SUMMARY AND CONCLUSIONS 

The preliminary findings of a study designed 

to determine the effects of the Mount St. 

Helens eruption of May 18, 1980, on the physical, chemical, and biological characteristics of 

selected lakes in Washington indicate that the 

lakes closest to the volcano were the most 

G23 
TABLE 10.-Generalized water-quality conditions in lakes at various distances from the volcano 

[Milligrams per liter unless otherwise indicated] 

Lake --------------------------------------- Distance (miles) and direction from volcano ___ _ 

Spirit 

4(NE) 

Fawn Walupt 

9(NNW) 37 (NE) 

Before 

Specific conductance (p,mhos at 25 o C) __________ 27 

Temperature (°C) --------------------------- 10 

Transparency (ft) --------------------------- 23 

Dissolved oxygen, top water __________________ 10.4 

llardness ----------------------------------- 12 

Alkalinity ---------------------------------- 11 

Silica --------------------------------------- 12 

Dissolved solids ----------------------------- 30 

Total nitrogen ------------------------------- .04 

Total phosphorus ---------------------------- .01 

Dissolved iron (p,g/L) ----------------------- 20 

Dissolved manganese (p,g/L) _________________ 0 

Chlorophyll a (p,g/L) ------------------------ .7 

affected. These findings are supported by the 

data in table 10, which summarizes waterquality conditions in lakes at various distances 

from the volcano. 

Spirit Lake, at the base of the volcano, was 

affected to the extent that it must now be considered a completely different lake. It has increased in area, decreased in depth, and risen 

about 240 ft in altitude as a result of the eruption. The surface of the lake is covered with 

logs, and the outlet to the North Fork Toutle 

River has been blocked. 

The water of Spirit Lake is dark in color, 

contains large quantities of dissolved organic 

material, and emits foul-smelling gases. The 

water temperature rose to at least 32.8°C immediately following the eruption, and most of 

the dissolved oxygen was depleted. The concentrat!ons of several chemical constituents, 

including iron and maganese, increased 

sharply. 

The biological productivity of Spirit Lake is 

high but, so far, has been limited to bacteria. 

The fish population, once composed chiefly of 

cold-water species, has undoubtedly been decimated or destroyed. 

Other lakes in the blast zone were similarly 

affected, but not to such an extent. Chemical 

constituents in St. Helens, Fawn, and Venus 

Lakes have probably increased, and water 

transparency has decreased. Biological conditions in these lakes are largely unknown, and 

the speed of biological recovery cannot be predicted with certainty at this time. 

After 

844 

26.1 

2.5 

0.8 

240 

110 

46 

574 

1.8 

1.8 

8,800 

5,000 

Before 

30 

15 

21 

8.8 

.13 

.00 

After 

666 

15.6 

7.0 

9.2 

200 

19 

8.1 

392 

.58 

.02 

40 

1,000 

3.6 

Before After 

27 38 

17.8 16.7 

26 24 

8.8 8.6 

12 14 

14 8 

8.0 6.4 

23 23 

.19 

.00 .02 

10 20 

0 0 

2.5 

Lakes outside the blast zone of the volcano 

appear to have been unaffected by the eruption, 

despite the deposition of up to 3 inches of ash 

in some lakes. 

REFERENCES CITED 

Bartleson, G. C., Dion, N. P., McConnell, J. B., and 

Nelson, L. M., 1976, Reconnaissance data on lakes 

in Washington, volume 4: Washington Dept. Ecology Water-Supply Bulletin 43, vol. 4, 197 p. 

Bartleson, G. C., lliggins, G. T., and llill, G. W., 1974, 

Data on selected lakes in Washington, part 2: 

Washington Dept. Ecology Water-Supply Bulletin 

42, part 2, 145 p. 

Dethier, D. P., lleller, P. L., and Safioles, S. A., 1979, 

Reconnaissance data on lakes in the Alpine Lakes 

Wilderness Area, Washington: U.S. Geological 

Survey Open-File Report 79-1465, 186 p. 

Dion, N. P., Bartleson, G. C., and Innes, J. K., 1980, 

Data on selected lakes in Washington, part 6: 

Washington Dept. Ecology Water-Supply Bulletin 

42, part 6, 125 p. 

Dion, N. P., Bartleson, G. C., McConnell, J. B., and 

Innes, J. K., 1976, Data on selected lakes in Washington, part 5: Washington Dept. Ecology WaterSupply Bulletin 42, part 5, 125 p. 

Korosec, M. A., Rigby, J. G., and Stoffel, K. L., 1980, 

The 1980 eruption of Mount St. llelens, Washington, Part 1: March 20-May 19, 1980: Washington 

Department of Natural Resources Information 

Circular 71, 27 p. 

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Sedell, J. R., Franklin, J. F., and Swanson, F. J., 1980, 

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Taylor, H. E., and Lichte, F. E., 1980, Chemical composition of Mount St. Helens ash: Geophysical 

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1:< U.S. GOVERNMENT PRINTING OFFICE: 1981- 341-614 1151 

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