42° 

METRIC CONVERSION FACTORS 

Multiply 

foot (ft) 

cubic yard (yd3 ) 

mile (mi) 

square mile (mi 2 ) 

cubic foot per second (ft 3 /sec) 

By 

0.3048 

0.7646 

1.609 

2.590 

.02832 

To obtain 

meter (m) 

cubic meter ( m 3 ) 

kilometer (km) 

square kilometer (km 2 ) 

Cubic meter per sec;ond (m3 /s) 

105' 

490 J2QO 1150 1100 --- _____, 

~ ~~-------------IT_____________________ \ , _ _) ' ' 

I \ 

Seattle Spokane co \ I ~ ' \ MONTANA \ 

,"'~ I 

Olymp1a WASHINGTON 

\ • Mount St Helens 

I .--------------1_ { Helena I 

I 

l,'\ 1 

\ ------------------

...__.,.- ... _--~- ... 

Portland J c 

Salem 

-----

OREGON 

( 

/ 

., 

I 

I 

I 

' I 

., ___ {\j ,r- I 

I 

I 

I 

I 

I IDAHO 

' I ------------~---------------~ 

0 100 200 300 MILES 

0 100 200 300 KILOMETERS 

COVER: North Fork Toutle River, June 30, 1980. Volcanic mud flow breccia 

and debris from the May 18, 1980 eruption of Mount St. Helens (in upper 

right) are as much as several hundred feet thick in the reach shown. 

Photograph by Austin Post, U.S. Geological Survey. 
Some Chemical Effects of the 

Mount St. Helens Eruption on 

Selected Streams in the 

State of Washington 

By John M. Klein 

Hydrologic Effects of the Eruptions 

of Mount St. He•ens, Washington, 1980 

GEOlOGICAl SURVEY CIRCUlAR850-E 

1984 
United States Department of the Interior 

JAMES G. WA TI, Secretary 

Geological Survey 

Dallas L. Peck, Director 

Free on application to Branch of Distribution, 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 Fork 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 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 findngs 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 

comparisions of pre- and 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. 

III 

Dallas L. Peck 

Director 

Abstract ... 

Introduction . 

Data collection 

Ash composition 

Results and discussion 

CONTENTS 

Effects of ash on river water quality 

Klickitat River . 

Ahtanum Creek 

Yakima River . 

Spokane River . 

Effects of volcanic debris and mudflows on river water quality 

Occurrence of trace metals 

Summary 

Selected references . . . . . . . 

ILLUSTRATIONS 

Page 

1 

1 

1 

3 

4 

4 

4 

10 

11 

14 

18 

21 

25 

26 

Page 

FIGURE 1. Map showing location of Mount St. Helens in Washington, and location of water-quality sampling sites . 2 

2. Diagram showing percentage composition of water in the Klickitat River near Glenwood . . . . . 5 

3. Diagram showing percentage composition of water in the Klickitat River near Pitt . . . . . . . . 6 

4-10. Graphs showing variation of selected chemical and physical characteristics with time for water samples 

from the Klickitat River near Pitt: 

4. Sulfate . . . . . . . . . . . . . 7 

5. Chloride . . . . . . . . . . . . 7 

6. Dissolved-solids concentration 8 

7. Total and organic nitrogen . 8 

8. Turbidity . . . . . . . 9 

9. Specific conductan('e . . . . 9 

10. pH . . . . . . . . . . . . . . 10 

11. Diagram showing percentage composition of water from the NOrth Fork of Ahtanum Creek 11 

12-16. Graphs showing variation of selected chemical and physical characteristics with time for water samples 

from the Yakima River at Union Gap: 

12. Sulfate . . . . . . . . . . . . . 12 

13. Chloride . . . . . . . . . . . . 12 

14. Dissolved solids concentration 13 

15. Total and organic nitrogen . . 13 

16. Turbidity . . . . . . . . . . . . 14 

17-21. Graphs showing variation of selected chemical and physical characteristics with time for water samples 

from the Yakima River at Kiona: 

17. Sulfate . . . . . . . . . . . . . 14 

18. Chloride . . . . . . . . . . . . 15 

19. Dissolved-solids concentration 15 

20. Total and organic nitrogen . 16 

21. Turbidity . . . . . . . . . . . . 16 

v 
FIGURES 22-26. Graphs showing variation of selected chemical and physical characteristics with time ior water samples 

from the Spokane River at Riverside State Park: 

22. Sulfate . . . . . . . . . . . . . 

23. Chloride . . . . . . . . . . . . 

24. Dissolved-solids concentration 

25. Total and organic nitrogen . . 

26. Turbidity . . . . . . . . . . . . 

27. Diagram showing percentage composition of water from the Toutle River near Castle Rock 

28-32. Graphs showing variation of selected chemical and physical characteristics with time for water samples 

from the Cowlitz River at Kelso: 

28. Sulfate . . . . . . . . . . . . . 

29. Chloride . . . . . . . . . . . . 

30. Dissolved-solids concentration 

31. Total and organic nitrogen . . 

32. Turbidity . . . . . . . . . . . . 

33. Diagram showing percentage composition of water from selected sampling sites near Mount St. Helens . 

TABLES 

TABLE 1. List of characteristics determined for water from streams and rivers to document the impact of Mount St. 

Page 

17 

17 

18 

19 

20 

21 

22 

22 

23 

23 

24 

25 

Page 

Helens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

2. Major, minor, and trace constituents in volcanic ash . . . . . . . . . . . 4 

3. Variation in trace elements (micrograms per liter at selected stations) 24 

VI 
HYDROLOGIC EFFECTS OF THE ERUPTIONS OF 

MOUNT ST. HELENS, WASHINGTON, 1980 

SOME CHEMICAL EFFECTS OF THE MOUNT ST. HELENS 

ERUPTION ON SELECTED STREAMS IN THE 

STATE OF WASHINGTON 

By JOHN M. KLEIN 

ABSTRACT 

The eruption of Mount St. Helens in southwestern 

Washington had a pronounced effect on the chemistry of water 

in rivers draining these areas affected by the debris deposits, 

pyroclastic flows, mudflows, and airborne ash. Comparison of 

pre-eruption and post-eruption data show that there were 

marked increases in selected rivers of the levels of sulfate, 

chloride, turbidity, total nitrogen, total organic nitrogen, and 

total iron, manganese, and aluminum. In streams affected solely by ash, the changes were shortlived and the intensity of 

change decreased with distance downwind from Mount St. Helens. Streams in the blast and mudflow-affected areas showed 

more persistent effects. 

INTRODUCTION 

After 100 years of dormancy, Mount St. Helens, 

in southwestern Washington (fig. 1), erupted with 

moderate intensity on March 27, 1980. Ash and 

steam were emitted, and a crater opened on the 

flank of the cone. Eruptions of ash and steam continued for several weeks, the crater enlarged 

daily, and continual seismic activity was recorded. 

On April 23, a bulge was detected on the north 

flank overlooking Spirit Lake. The bulge continued to grow outward at the rate of about 5 feet 

per day. 

On May 18 at 8:32 a.m., Mount St. Helens 

erupted violently. After an explosive north-trending lateral blast, ash and steam were shot vertically to about 50,000 feet. In the immediate vicinity north of the volcano, a once-productive forest 

was completely pyrolyzed or burned; with increasing distance from the mountain, trees were uprooted and stripped of bark, branches, and needles 

1 

or leaves. Ash was carried easterly by the prevailing winds and deposited to depths of up to 5 inches 

over much of the agricultural lands of eastern 

Washington. Watersheds immediately east of the 

volcano received heavy ash fall, and streams 

draining to the south, tributary to the Columbia 

River, received only traces of ash. 

At the onset of the eruptive activity, the major 

part of the north flank of the volcano collapsed, 

depositing a massive plug of debris, including 

rock, ash, pumice, and ice in the upper 17 miles 

of the North Fork Toutle River valley. Following 

the initial blast, a mudflow quickly developed in 

the South Fork Toutle River, and several hours 

later a much larger mudflow originated from the 

massive debris avalanche deposit in the North 

Fork Toutle valley. This mudflow caused widespread destruction as it moved downstream 

through the lower Toutle and Cowlitz Rivers, and 

a considerable part of the sediment was conveyed 

through the Cowlitz into the Columbia River. 

The massive physical alterations caused by the 

eruption could be expected to have marked effects 

on river water quality. This paper describes some 

of the effects caused by (1) ash deposition in rivers 

east of the volcano, and (2) the massive debris 

deposit and mudflows in rivers draining to the 

west and south. 

DATA COLLECTION 

Following the initial eruption on March 27, 1980, 

a program for the collection of water-quality data 
.,. 

-~~- ----- 1r 120' 118' - _________ __j__·---~.!;D_A ___ L_ __ 

, TACOMA 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

.0

1 50 1 00 MILES 

r--.~~~----r~l---,1---~---~1 

0 50 100 KILOMETERS 

EXPLANATION 

e long-term monitoring with pre-eruption 

water-quality data; additional sampling 

after March 27, 1980 

~ National Stream Ac;:ounting Quality Networt 

station 

0 little or no pre-eruption data; sampling 

began after May 18, 1980 

FIGURE 1.-Location of Mount St. Helens in Washington, and location of water-quality sampling sites. 

(water chemistry, sediment, and biology) was initiated at selected stream sites surrounding Mount 

St. Helens (fig. 1) to document the effects of the 

initial eruption and resultant ash fallout on the 

physical and chemical character of the water and 

to collect background data at unaffected sites. 

These measurements supplement data collected 

monthly at 3 U.S. Geological Survey National 

Stream Quality Accounting Network Stations1 and 

at 22 other sites sampled periodically in cooperation with the Washington State Department of 

Ecology, the Tacoma City Light, and the Confederated Tribes and Bands of the Yakima Indian N ation. 

Following the May 18 eruption, additional sites 

1

The U.S. Geological Survey National Stream Quality Accounting Network is 

a series of surface-water monitoring sites at which systematic and continuing measurements are made to detennine the quality of the nation's stream!-l.. 

2 

(fig. 1) were chosen for an intensive sampling program. The frequency of collection at these sites 

decreased with time to daily at some of the heavily 

impacted but accessible sites until several days 

after the eruption, then weekly until the end of 

June, and monthly thereafter. 

All samples for chemical analysis were collected 

along the stream cross section using depth-integrating samplers and methods (Guy and Norman, 

1970). These sample-collection techniques assure 

a sample that is representative of the average 

chemical conditions in the cross section of the 

stream at the time of sampling. Water samples 

for dissolved trace elements and selected major 

chemical-constituent determinations were filtered 

through a 0.45-J..Lm (micrometer) pore-size membrane filter, placed in an acid-washed polyethylene 

bottle, and acidified with double-distilled, analyti-
TABLE 1.-List of characteristics de~ermined for water from streams and rivers used to document the impact of 

Mount St. Helens 

Alkalinity, total (CaCOJ) 

Arsenic, dissolved 

Arsenic, to ta 1 

Barium, dissolved 

Barium, suspended 

Barium, total 

Cadmium, dissolved 

Cadmium, suspended 

Cadmi urn, to ta 1 

Calcium, dissolved 

Carbon, organic dissolved 

Carbon, organic suspended 

Chloride, dissolved 

Chromium, dissolved 

Chromium, suspended 

Chromi urn, to ta 1 

Cobalt, dissolved 

Cobalt, suspended Cobalt, total 

Copper, dissolved 

Copper, suspended Copper, tota 1 

Fluoride, dissolved 

Hardness, noncarbonate 

Hardness, to ta 1 

I ron , d i s so 1 v ed 

I ron, suspended 

Iron, total 

Lead, dissolved 

Lead, suspended Lead, total 

Magnesium, dissolved 

Manganese, dissolved 

Manganese, suspended 

Manganese, to ta 1 

Mercury, dissolved 

Mercury, suspended 

Mercury, total 

Nitrogen, dissolved 

(N02+N03 as N) 

Nitrogen, dissolved 

(NH4 as N} 

Nitrogen, dissolved 

(NH4 + organic as N) 

Nitrogen, dissolved 

(organic as N) 

mg/L 

1-Lg/L 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

mg/L 

Do. 

Do. 

Do. 

1-Lg/L 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

mg/L 

Do. 

Do. 

~J.g/L 

Do. 

Do. 

Do. 

Do. 

Do. 

mg/L 

1-Lg/L 

Do. 

Do. 

Do. 

Do. 

Do. 

mg/L 

Do. 

Do. 

Do. 

cal-grade nitric acid to prevent adsorption and 

chemical precipitation. Unfiltered samples were 

analyzed for total element concentrations. Samples 

for nutrient analysis were chilled at the time of 

collection and during shipment to the Geological 

Survey National Water Quality Laboratory, Arvada, Colo. A list of the chemical constituents determined is shown in table 1. Constituents were 

analyzed by methods outlined by Skougstad and 

others (1979). The chemical data collected since 

the March 27 eruption have been released in a 

data report (Turney and Klein, 1982). 

Nitrogen, dissolved (as N) mg/L 

Nitrogen, suspended (NH4 +organic as N) Do. 

Nitrogen, total 

(N02 + N03 as N} Do. 

Nitrogen, total 

(NH4 as N) Do. 

Nitrogen, to ta 1 

(NH4 +organic as N) Do. 

Nitrogen, total (organic as N) Do. 

Nitrogen, total (as N) Do. 

pH field 

pH lab 

Phosphorus, dissolved (as P) Do. 

Phosphorus, total (as P) Do. 

Phosphorus, total (P04} Do. 

Potassium, dissolved Do. 

Potassium 40, D.PCI/L 

Residue dis calc sum Do. 

Residue dis ton/aft 

Residue dis 1800C Do. 

SAR 

Selenium, dissolved 

Selenium, supended 

Selenium, to ta 1 

Silica, dissolved 

Silver, dissolved 

Silver, suspended 

Silver, total 

Sodium + potassium 

Sodium, dissolved 

Sodium, percent Specific conductance field 

Specific conductance lab 

Sulfate, dissolved 

1-LQ/L 

Do. 

Do. 

mg/L 

~J-9/L 

Do. 

Do. 

mg/L 

Do. 

1-Lmho/cm at 25DC 

Do. 

Turbidity (NTU} EPA 

Water temperature (degrees C) 

Zinc, dis so 1 v ed 

mg/L 

NTU 

oc 

1-Lg/L 

Zinc, suspended IX>. 

IX>. 

Do. 

Do. 

Do. 

IX>. 

Do. 

Do. 

Zinc, to ta 1 

Lithium, dissolved 

Lithium, total 

Aluminum, dissolved 

A 1 umi num, to ta 1 

Boron, dissolved 

Boron, to ta 1 

3 

ASH COMPOSITION 

Fruchter and others (1980) have reported some 

general ash composition trends with increasing 

distance from the volcano. Silica increased with 

distance, whereas iron, magnesium, calcium, and 

manganese decreased. Potassium and sodium 

showed little variability. Taylor and Lichte (1980) 

have also analyzed volcanic ash samples for major, 

minor, and trace constituent composition. They 

also observed a change in chemical composition of 

the ash as a function of distance from Mount St. 
TABLE 2.-Major, minor, and trace soluble constituents in volcanic ash 

Constituent* Tam~ico 1 Wash. Ft. Sim~co 2 Wash. Moses Lake 2 Wash. Potlach 2 Idaho 

Calcium 89 190 151 190 

Magnesium 13 42 27 30 

Sodium 87 209 143 164 

Potassium 1.7 41 20 23 

Anmonium 0.07 0.9 1.2 0.75 

Chloride 134 319 178 369 

Fluoride 0.81 2.4 1.3 3.7 

Sulfate 297 744 534 524 

Silica 8.1 16 19 13 

Nitrate 1.8 7.0 2.8 1.0 

Boron 0.28 0.74 0.58 0. 47 

Iron 0.013 0.013 0.024 0.013 

Manganese 2.0 7.3 2.0 5.8 

Zinc 0.024 0.062 0.012 0.240 

*Concentrations in microgram per gram of dry ash {from Taylor and Lichte, 

1980). 

Helens and related these changes to changes in 

the physical characteristics of the ash. In addition, 

Taylor and Lichte have reported water-soluble 

components after column-leaching the ash with 

known volumes of distilled water. Table 2 is a 

summary of some of the major, minor, and trace 

soluble-constituent concentrations of the ash at 

specified locations. 

From these analyses alone, one might expect 

that a major impact on river water quality would 

be an increase, from pre-eruption levels, in the 

concentrations of certain soluble constituents, 

especially chloride and sulfate. The timing of such 

compositional and concentration changes in the 

surface-water chemistry, with respect to the eruption, would depend on whether the ash fell on land 

or water, and the occurrence and intensity of precipitation on land-deposited ash. If ash did fall directly on water, the soluble constituents would 

dissolve rapidly and be observed in analyses of 

samples collected soon after deposition. Heavy 

precipitation on top of land-deposited ash would 

wash large quantities of soluble constituents into 

streams; whereas light precipitation would leach 

those constituents into the soil, where they would 

probably react with soil materials. In the latter 

case, changes in the stream water composition 

might not be measurable. Moreover, any changes 

would occur at some later date, after sufficient 

water had leached through the soil and eventually 

entered a water course. 

Calcium and bicarbonate are normally the predominant dissolved constituents in streams of the 

4 

northwest. Variations in concentrations ·are small, 

occur slowly, and are correlated with stream discharge. A major geologic event, such as the eruption and subsequent ashfall, might be expected to 

produce noticable changes in the chemical composition of waters. 

RESULTS AND DISCUSSION 

EFFECTS OF ASH ON RIVER WATER QUALITY 

As expected, based on the distribution of ashfall 

(fig. 1), streams to the south of the volcano, tributary to the Columbia River (stas 4 and 5), were 

unaffected. A small tributary to the Klickitat 

River (sta 1) was also unaffected. 

East of Mount St. Helens, the magnitude of the 

observed effects of ash deposition was a function 

of the pattern of ash depths, and the relative volumes of water draining from heavily and slightly 

affected areas down to the sampled sites. In general, the magnitude of the observed effects ranged 

from pronounced in streams close to the volcano 

to slight in streams in eastern Washington. In the 

following sections, the effects are described for 

streams located progressively eastward. 

KLICKITAT RIVER 

Samples from the Klickitat River near Glenwood (sta 2) and near Pitt (sta 3) showed that 

ash deposition had a pronounced effect on water 

composition. The changes at the downstream Pitt 

station were not as pronounced as those near the 

headwaters Glenwood station owing to dilution 
EXPLANATION 

• Pre-May 18, 1980 eruption 

+ Post-May 18, 1980 eruption and date 

Calcium 

~ -~ Chloride 

CATIONS ANIONS 

PERCENTAGE COMPOSITION 

FIGURE 2.-Percentage composition of water in the Klickitat River near Glenwood. 

from tributary drainages that received light 

ashfall. 

Variation in chemical composition is shown by 

both trilinear diagrams (see figs. 2, 3) and in timeseries plots (for example, figs. 4-10). Within each 

triangle and the center quadrangle of the trilinear 

diagrams, the milliequivalent percentages of the 

major cations (calcium, magnesium, sodium, and 

potassium) total 100, as they also do of the major 

anions (bicarbonate, carbonate, chloride, and sulfate); thus, changes in the relative concentrations 

of these constituents are shown concisely. In each 

trilinear diagram, dates are included with the plot5 

ted data points for the anions (lower right 

triangle) and for the center quadrangle portion of 

the diagram to illustrate the degree and rate of 

compositional changes. Variation in cation composition (lower left triangle) was relatively minor, 

precluding the need for accompanying dates. V ariation in the concentrations of sulfate, chloride, 

total nitrogen, total organic nitrogen, and turbidity2 are shown in time series plots for selected 

sites. For each characteristic, the same scale is 

2

Turbidity, an optical phenomenon, was determined as the nephelometric turbid· 

ity unit, NTU, which refers to the amount of light scattered at 90" when the tur· 

bidimeter is calibrated with formazin. 
EXPLANATION 

• Pre-May 18, 1980 eruption 

+ Post-May 18, 1980 eruption and date 

PERCENTAGE COMPOSITION 

FIGURE 3.-Percentage composition of water in the Klickitat River near Pitt. 

used for all sites to permit easy comparison of the 

relative magnitudes of change. 

Figure 2 shows the changes in the relative concentrations for the Klickitat River near Glenwood 

before and after the eruption. Following the eruption there was change in the composition, particularly noticeable for the anions; however, by May 

29, the anion composition had returned to preeruption conditions. 

A similar shift in chemical composition in the 

Klickitat River near Pitt from May 19 until several 

days afterwards is illustrated in another trilinear 

6 

diagram (fig. 3). The sample taken on May 18 

failed to show any effects of ashfall, but the sample collected the following day showed a strong 

shift in the anion composition toward higher percentages of chloride and sulfate, suggesting additions of soluble chloride and sulfate compounds 

from the ash. By May 20, the anion composition 

had shifted back toward the normal pre-eruption 

percentages, and subsequent samples confirmed 

that the composition returned to the normal 

ranges. The cation composition failed to vary to 

any measurable extent, probably because the per-
15 

a: 

w 

1-

:::::i 

a: 

w 

a.. 

Cl) 

:E 

<C 

a: 10 c::J 

:::::i 

....I 

:E 

~ 

z 

0 

i= 

<C 

a: 

1-

z 

w 

~ 5 z 

0 

~ 

w 

1-

<C 

..... 

....I 

::::::1 

Cl) 

0

J FMAMJJASONDJ FMAMJJASONDJ FMAMJJASO 

1978 1979 1980 

FIGURE 4.-Variation with time of sulfate for water samples from the Klickitat River near Pitt. 

o~~~~~-L~~~~~~~~~~-L-L-L-L~~~~L-~kU~~-L~ 

J FMAMJJASONDJ FMAMJJASONDJ FMAMJ JASO 

1978 1979 1980 

FIGURE 5.-Variation with time of chloride for water samples from the Klickitat River near Pitt. 

centage composition of soluble cations in the ash 

(table 1) was not substantially different from that 

of the native waters. 

Changes in the anion concentrations in the Klickitat River at Pitt were extremely short lived, 

as illustrated by the time series of sulfate, 

chloride, and dissolved solids (figs. 4, 5, 6). Samples collected just after May 18 showed increases 

in the concentration of these constituents. The increase in sulfate, while significant, did not exceed 

previous high concentrations. The chloride in7 

crease noted in the May 19 sample was notably 

greater than other pre- and post-eruption samples. 

By the end of June, the concentrations of both 

sulfate and chloride had returned to within the 

pre-eruption ranges. 

The most dramatic effects of the ashfall on 

water quality in the Klickitat is illustrated in the 

time series of total nitrogen, total organic nitrogen, turbidity, and specific conductance (figs. 7, 

8, 9). Samples collected just after May 18 contained concentrations of these characteristics well 
Cl) 

0 

:z:: 

:IE 

0 

a: 

!: 80 :IE 

i!E 

z 

0 

i= 

~ 70 ..... 

ifi 

(.) 

z 

0 

(.) 

~ 60 .... 

0 

Cl) 

6 

LU 

::; 

0 

Cl) 

Cl) 

i5 

KLICKITAT RIVER NEAR PITT 

~JFMAMJJASONDJFMAMJJASONDJFMAMJJAS 1978 1979 1980 

FIGURE 6.-Variation with time of dissolved-solids concentration for water samples from the Klickitat River near Pitt. 

D:: S --TotaiN 

~ ·----Organic N 

I 3 

<-' ::::i 

..J 

~ 

~ 

z 2 

~ 

z 

~ ~ c 

~ 1 

z 

0 

0 

~ 0 J FMAMJJASONDJ FMAMJJASONDJ FMAMJ JASO 

1978 1979 1980 

FIGURE 7.-Variation with time of total and organic nitrogen for water samples from the Klickitat River near Pitt. 

8 
0

J FMAMJ J ASONDJ FMAMJ J ASONDJ FMAMJ J ASO 

1978 1979 1980 

FIGURE 8.-Variation with time of turbidity for water samples from the Klickitat River near Pitt. 

KLICKITAT RIVER NEAR PITT 

FIGURE 9.-Variation with time of specific conductance for water samples from the Klickitat River near Pitt. 

above the highest observed during the previous 

2 years. Because the nitrogen analyses were made 

on unfiltered samples, the correspondence between the peaks in nitrogen and turbidity suggest 

that the nitrogen was closely associated with the 

particulate material. The peaks observed in June 

were probably related to ashfall from the minor 

eruption of June 12-13. 

The high nitrogen concentrations cannot be as 

easily correlated with the ash as were the high 

9 

sulfate and chloride concentrations because, unfortunately, the ash was not analyzed for organic nitrogen. However, the increase in nitrogen corresponding to the time of ash deposition is not surprising. The major blast on May 18 denuded the 

nearby environment including the lush forest, vegetation, and soils. It is thought that pyrolysis (a 

major chemical change due to intense heat) of the 

forest resulted in vaporization of much of the 

forest organic material, including a large quantity 
:c 

Q. 

8 

KLICKITAT RIVER NEAR PITT 

1978 1979 1980 

FIGURE 10.-Variation with time of pH for water samples from the Klickitat River near Pitt. 

of nitrogen. The vaporized organics probably condensed, attached to the ash particles, and were 

transported in the ash plume. Organic carbon concentrations in ash samples collected elsewhere 

tend to confirm this. For the short term, organic 

nitrogen conveyed by ash into water would stay 

attached to the ash particles. With time, dissolution, mineralization, and nitrification of this nitrogen would shift the nitrogen species dominance toward dissolved nitrate. 

The effects of ashfall on the nitrogen concentrations and turbidity were shortlived. By July, variations had returned to within the normal range. 

Figure 10 shows variations in pH. Historically, pH 

has ranged from 6.5 to 8.3 at this site. The 6.5 

reading was obtained following the March 27 eruption, when a light dusting of ash occurred in the 

Klickitat drainage. A peak on June 17 on the 

graphs of chloride, sulfate, nitrogen, and turbidity 

probably represents ash deposited by the June 12-

13 eruption or eroded into the river by precipitation in the upstream basin. 

10 

AHTANUM CREEK 

In streams farther east of the volcano, such as 

the North and South Forks of Ahtanum Creek 

(stas 6 and 7), variations were similar to those 

in the Klickitat River. The North Fork Ahtanum 

Creek site near Tampico (sta 6) is used here to 

illustrate the similarity (fig. 11). 

The shift in anion composition toward higher 

percentages of sulfate and chloride was observed 

in the sample taken May 18, the day of the eruption, rather than May 19, when the shift was seen 

in the Klickitat. The time difference is probably 

due to closer proximity of Ahtanum Creek to the 

heaviest ashfall area (fig. 1) and to a shorter time 

of travel of water from within the watershed to 

the sampling site. The degree of change in composition over normal values was also greater because 

the entire drainage received substantial ash. A 

small shift toward higher percentages of sulfate 

and chloride can be seen on June 24 and 28, possibly the remnant effect of the ashfall from the 

minor eruption of June 17. 
EXPLANATION 

• Pre-May 18, 1980 eruption 

+ Post·May 18, 1980 eruption and date 

~ c~~ 

ANIONS 

PERCENTAGE COMPOSITION 

FIGURE H.-Percentage composition of water from the North Fork of Ahtanum Creek. 

YAKIMA RIVER 

In streams and rivers still farther east of the 

volcano, the effects of ashfall on water quality 

were much less apparent than in the Klickitat 

River and Ahtanum Creek. The Yakima River is 

the major river draining central Washington, and 

much of the land it drains received significant 

ashfall. Two sites for which historical water-quality data were available, the Yakima River at 

Union Gap (site 8, fig. 3) and near Kiona (site 

9, fig. 3), were chosen for intensive sampling to 

document water-quality changes caused by volcanic activity. The changes in water chemistry during 

the May 18 ashfall for the Yakima River at Union 

Gap were not as dramatic as seen in the North 

Fork Ahtanum Creek because of dilution by water 

draining areas unaffected by ash fall. The sulfate, 

chloride, and dissolved-solids concentrations varied sharply over a short period of time, and the 

changes were small when compared with seasonal 

variations; however, they are detectable in figures 

11 
15 

a: 

w 

t-

::::; 

a: 

w 

a.. 

Cf.) 

::E 

cc 10 a: 

C!::J 

::::; 

..... 

:i 

ill: 

z 

c 

t= 

cc 

a: 

tz 

w 

(.) 5 z 

c 

(.) 

w 

tcc 

u.. 

..... 

:::;) 

Cf.) 

0 JFMAMJJASONDJ FMAMJ JASONDJ FMAMJJASO 

1978 1979 1980 

FIGURE 12.-Variation with time of sulfate for water samples from the Yakima River at Union Gap. 

0 J FMAMJJASONDJ FMAMJJASONDJ 

1978 1979 

FIGURE 13.-Variation with time of chloride for water samples from the Yakima River at Union Gap. 

12-16. The greatly reduced effects in the Yakima 

River as compared with those in the Klickitat 

River and Ahtanum Creek probably can be 

explained by dilution; water from highly ash-affected tributaries is diluted by waters from 

tributaries that received little or no ash. 

By contrast, the total nitrogen and organic nitrogen concentrations and turbidity values (figs. 

15, 16) increased dramatically. Of further interest, 

immediately after the eruption the total nitrogen 

concentration was primarily organic nitrogen, 

12 

which in preceding years had made up only about 

50 percent of the total nitrogen concentrations. 

Figures 17-21 show the water-chemistry data 

for the Yakima River at Kiona site from April 

1978 to August 1980. At the Kiona site, as with 

the other sites, changes in the major chemical constituents are apparent, but delayed and of short 

duration. Total-nitrogen concentration and turbidity changed dramatically, and dissolved chloride 

concentration increased significantly. Dissolved 

sulfate and dissolved-solids concentration also in-
YAKIMA RIVER NEAR UNION GAP 

1980 

FIGURE 14.-Variation with time of dissolved solids concentration for water samples from the Yakima River at Union Gap. 

--TotaiN 

------Orpnic N 

1 

o~~~~~~~-L~~~~~~L-~~~~~~~~~~~~~~~~ 

J FMAMJJASONDJFMAMJ JASONDJ FMAMJJASO 

1978 1979 1980 

FIGURE 15.-Variation with time of total and organic nitrogen for water samples from the Yakima River at Union Gap. 

creased with ash deposition, but the effects were 

small when compared with the peaks of past 

periods. Although total nitrogen showed a large 

increase, the organic nitrogen component was not 

13 

as large as at several of the other sites, possibly 

because of alteration of the organic nitrogen to 

inorganic forms such as ammonium or nitrate. Additionally, the nitrogen, which began to increase 
300 (,.) 

a: 

.... 

L&.l 

:E(I) 

9!:: 

wz 200 ~:;) 

LLI>-

z .... zc -c:c >§ IS .... 100 

cc 

a: 

:;) 

.... 0 

J FMAMJ JASON DJ FMAMJ J ASONDJ FMAMJ J ASO 

1978 1979 1980 

FIGURE 16.-Variation with time of turbidity for water samples from the Yakima River at Union Gap. 

501 I I I I I I I I I I I I I I I I I I I I I I I I I I -

a: 

w 

t-

::::i 

a: 

w 

0... 

(I) 

::::E 

<C 

a: 

C!:l 

::::i 

__. 

:E 

~ 

z 

0 

i= 

<C 

a: 

tz 

w 

(,.) 

z 

0 

(..) 

w 

!;;( 

LL-

....1 

:::::1 

Cf.) 

YAKIMA RIVER AT KIONA 

1978 

FIGURE 17.-Variation with time of sulfate for water samples from the Yakima River at Kiona. 

on May 6, before the May 18 eruption, did not 

peak until June 25, probably because this component may have a lag time in this river system. 

The turbidity extreme that occurred on June 19 

was also accompanied by a dissolved-solids decrease, indicating the possibility of dilution by precipitation and erosion of ash from the land surface 

to the river. 

SPOKANE RIVER 

Farther to the east, the effects of ashfall on 

water quality were much less apparent than noted 

14 

in the previous sections. Samples were collected 

from the Spokane River near Riverside State Park 

(site 10, fig. 1) and from Hangman Creek (site 

11, fig. 1). The Spokane River drains an area of 

northwestern Idaho and eastern Washington that 

received substantial ash and is below the mouth 

of Hangman Creek, which drains the area south 

of Spokane. Figures 22-26 show the chemical variations observed in water from the Spokane River 

site. As with the Yakima River sites, changes in 

the water chemistry caused by ash fall are similar. 

The peaks observed in the data in figures 22-26 
25 

a: 

u.t 

1-

::::; 

a: 

u.t 

~ 

Cl) 

~ 

<C 

a: 

c:J 

::::; 

..... 

:i 

~ 

2 

0 

i= 

<C 

a: 

1-

z 

u.t 

(..) 

z 

0 

(..) 

u.t 

c 

a: 

c 

..... 

:z: 

(..) 

1979 

FIGURE 18.-Variation with time of chloride for water samples from the Yakima River at Kiona. 

Cl) 

0 

:z: 

~ 

0 

a: 

(..) 

:i 

~ 

YAKIMA RIVER AT KIONA 

~ 220 

i= 

<C 

a: 

1-

z 

u.t 

(..) 

z 

0 

(..) 

Cl) 

c 

::::; 

0 

Cl) 

6 

u.t 

> 

..... 

0 

Cl) 

Cl) 

a 

80 J F M A M J J A S 0 N D J 

1978 

FIGURE 19.-Variation with time of dissolved-solids concentration for water samples from the Yakima River at Kiona. 

15 
a: 

LLI 

1-

~ 

a: 

LLI 

a.. 

Cl) 

:::E 

c:c 

a: 

t::l 

~ ...... 

:i 

~ 

z 

Cl) 

c:c 

z 

...... 

c:c 

to 

1-

c 

:z 

c:c 

z 

YAKIMA RIVER AT KIONA 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

'---1 

FMAMJJASONDJFMAMJJASONDJ 

1978 1979 

FIGURE 20.-Variation with time of total and organic nitrogen for water samples from the Yakima River at Kiona. 

Cl) 

1-

z 

::;) 

> li5 

as 

a: 

::» 

1-

~ 

ii: 

1-

LLI 

:::E 

0 

...... 

LLI 

:::c: 

a.. 

LLI 

:z 

~ 

> li5 

as 

a: 

::» 

1-

YAKIMA RIVER AT KIONA 

0 JFMAMJJASONDJFMAMJJASONDJ 

1978 1979 

FMAMJJAS 

1980 

FIGURE 21.-Variation with time of turbidity for water samples from the Yakima River at Kiona. 

16 
50 

SPOKANE RIVER AT RIVERSIDE 

a: 

LLI 

.... 

::::::i 

a: 

LLI 

a.. 

Cl.) 

::&: 

<C 

a: 

c::J 

::::::i 

...... 

:i 

iE 

z 

0 

i= 

<C 

a: 

.... 

z 

LLI 

(.) 

z 

0 

(.) 

LLI 

.... 

<C 

u.. 

...... 

:::;) 

Cl.) 

1978 

FIGURE 22.-Variation with time of sulfate for water samples from the Spokane River at Riverside State Park. 

FIGURE 23.-Variation with time of chloride for water samples from the Spokane River at Riverside State Park. 

17 
120 

a: 

w 

1-- 110 

::::::i 

a: 

w 

ca.. 

(/) 

:E 

c::c 

a: 

(!] 

::::::i 

-1 

:i 

~ 

2 

0 

i= 

c::c 

a: 

1--

z 

w 

u 

z 

0 

u 

(/) 

c 

::::::i 

0 

(/) 

c 

w 

> -1 

0 

(/) 

(/) 

c 

1979 

FIGURE 24.-Variation with time of dissolved-solids concentration for water samples from the Spokane River at Riverside 

State Park. 

do not necessarily coincide with the days of 

maximum ash deposition in the Spokane area. 

Rather, the peaks for chloride (fig. 23), total and 

organic nitrogen (fig. 25), and turbidity (fig. 26) 

are 1 week later (May 27), during and following 

rains that washed large quantities of ash into the 

river system. Additionally, large quantities of ash 

in the Spokane area were reportedly dumped into 

the Spokane River for disposal. 

At the Spokane River sampling site, the organic 

nitrogen component of the total nitrogen predominated and, on the days preceding the eruption, 

made up almost the entire total-nitrogen concentration. 

EFFECTS OF VOLCANIC DEBRIS AND 

MUDFLOWS ON RIVER WATER QUALITY 

The headwaters of the Toutle River drainage 

were altered beyond recognition by volcanic debris 

deposits and pyroclastic flows from the May 18 

eruption. The downstream reaches of the Toutle 

and of the lower Cowlitz below its confluence with 

the Toutle River were devastated by massive 

18 

flooding and mudflows. Water samples from the 

Toutle and Cowlitz Rivers at sites 12, 13, and 14 

(fig. 1) collected on a regular basis since the May 

18 eruption show that these events have had a 

pronounced and persistent effect on the surfacewater chemistry. 

Water samples collected on March 29, 1980, at 

the Toutle River near Castle Rock (site 12, fig. 

1) before the major eruption indicate that calcium 

and bicarbonate were the principal dissolved 

chemical constituents. Water samples collected on 

May 20 indicate an entirely different chemical 

composition (fig. 27), with dissolved sulfate and 

chloride abruptly becoming the dominant anions. 

The June 24 sample suggested a trend of the river 

back to its pre-eruption composition; however, the 

July 22 sample showed another large increase in 

the chloride concentration, indicating that some 

upstream activity is continuing to alter the 

chemistry of the river water, such as dredging and 

continuing leaching of the ash, debris, and 

mudflow deposits. 

The mudflows that occurred on the evening of 

May 18 in the Toutle River prohibited collection 
a: 

LU 

1-

:::; 

a: 

LU 

a.. 

~3 < a: 

t::l 

:::; 

...... 

:E 

~ 

z 2 en 

< 

z 

...... 

~ 0 

1-

c 

z 

< 

z 

SPOKANE RIVER AT RIVERSIDE 

FIGURE 25.-Variation with time of total and organic nitrogen for water samples from the Spokane River at Riverside State 

Park. 

of satisfactory water-quality samples. The specific 

conductance of the mudflows on May 19 was 1,200 

micromhos per centimeter at 25°C, as compared 

with normal water values of about 90 JJ.mho, decreasing to 560 JJ.mho on May 20 when the first 

water samples could be obtained. 

Following the major eruption, the sampling frequency at Cowlitz River at Castle Rock (site 13, 

fig. 1) was increased to determine the effects 

caused by inflow from the Toutle drainage. Starting on May 30, 1980, sample intensity was also 

increased downstream from the Cowlitz River at 

Kelso (site 14, fig. 1) to monitor changes in chemical composition between the two sites and to document the chemistry of the water flowing into the 

Columbia River. 

The compositional variations in the Cowlitz 

River at Castle Rock were similar to those observed in the Toutle. The overall effect, however, 

was reduced because of dilution of the flow in the 

Cowlitz. The variability of the composition at the 

Castle Rock site was and is being determined by 

the nature and magnitude of the effects of flow 

from the devistated Toutle system, dredging activities upstream in the Toutle and Cowlitz, and 

by dilution affects of water from the upper Cowlitz. 

Long-term data from the Cowlitz River at Kelso 

can be examined to determine the degree of impact of volcanic activity on river-water chemistry 

at this point. Figures 28-32 show data for selected 

characteristics from April1978 to the present (August 1980). The largest variations occurred in the 

concentrations of sulfate, dissolved solids, total 

and organic nitrogen, and turbidity. High concentrations of sulfate and chloride were observed in 

late May and June, although maximum values for 

both ions were below those in samples collected 

monthly during the previous 2 years. However, 

the mudflows had a drastic effect on the levels 

of total organic nitrogen, total nitrogen, and turbidity (figs. 31 and 32). Samples collected in late 

May and early June showed turbidity values well 

above the normal values observed at this station, 

and, as before, these increases were accompanied 

by major increases in total nitrogen concentration, 

19 
Ci') 

.... 

z 

::::::1 

E; 250 c 

i 

::::::1 

.... 

~ 200 cc: 

.... 

LLI 

:::&: 

c 

..... 

LLI 

:::c 

C1.. 

LLI 

z 

~ 

> 

.... 

s 

iii 

cc: 

::::::1 

.... 

FIGURE 26.-Variation with time of turbidity for water samples from the Spokane River at Riverside State Park. 

with most of the increase due to total organic nitrogen. 

When and where possible, streams draining the 

slopes of Mount St. Helens have been sampled to 

determine the effects of the volcanic eruption on 

water chemistry and to determine chemical 

changes with time. The debris pile, covering the 

North Fork of the Toutle and several pre-existing 

data sites, the mudflows, and the flooding severely 

altered the conditions of most of the sites close 

to Mount St. Helens. Following the May 18 eruption, miscellaneous sampling sites were established at the locations shown in figure 33. 

Background data were collected at several of these 

sites beginning on March 28 and 29, and these data 

can be compared with those collected since the 

eruption to assess chemical changes. 

At the South Fork Toutle River (site 15, fig. 

33) there was a major increase in chloride composition and sulfate increases were negligible. Only 

minor cation changes were observed. Similar 

changes were observed in Pine Creek at its mouth 

near Cougar (site 16, fig. 33). Samples collected 

20 

before the major eruption indicated that the water 

was characterized by sodium and bicarbonate, but 

post-eruption changes resulting from the 

mudflows in Pine Creek showed a shift toward 

higher chloride concentration (fig. 33). 

The Kalama River at site 17 (fig. 33) was relatively unaffected by the May 18 eruption, but received ash deposits from the May 25 event. Few 

overall concentration and compositional changes in 

water chemistry were apparent, except for a 

minor increase in the sulfate and chloride components. 

Post-eruption water-chemistry data from the 

North Fork (mainstem) of Coldwater Creek (site 

18) and the Toutle River near Kid Valley (site 19) 

showed nearly equal percentages of the major dissolved-chemical constituents (fig. 33). Both stations had uniquely greater percentages of sulfate 

and chloride in comparison with all other sites, 

indicating a greater chemical effect of the eruption 

on streams whose headwaters are within or very 

near the blast area and the debris avalanche deposit. 
EXPLANATION 

• Pre-May 18, 1980 eruption 

+ Post-May 18, 1980 eruption and date 

PERCENTAGE COMPOSITION 

FIGURE 27.-Percentage composition of water from the Toutle River near Castle Rock. 

OCCURRENCE OF TRACE METALS 

Analysis of the ash (table 2) showed the presence of iron, manganese, and several other metals 

which, in the investigated streams and rivers, normally occur in very low concentrations. To determine the effects of ashfall on concentrations of 

these trace metals, both filtered and unfiltered 

samples were analyzed to measure the dissolvedand total metal concentrations. The difference between the two values represents the concentration 

in the suspended sediments. 

Suspended-sediment concentrations were high 

in most of the samples, and most of the trace metals determined were associated with these sediments. The dissolved-metal concentrations (table 

3) were generally much lower than the suspendedsediment metal concentrations and only slightly 

elevated above pre-eruption levels in those 

streams affected solely by ash deposition. In the 

Toutle and Cowlitz Rivers, post-eruption concentrations of dissolved iron, manganese, and aluminum increased and the increases persisted owing 

21 
a: 

w 

...... 

::::; 

a: 

w 

CL.. 

Cl) 

:::IE 

cc 10 a: 

(!) 

::::; 

..... 

:i 

~ 

z 

0 

i= 

cc 

a: 

...... 

z 

w 

(.) 5 z 

0 

(.) 

w 

...... 

cc 

u.. 

..... 

~ 

Cl) 

o~~~~~~~~~~~~~~-L-L~~~~~~~-L-L~U-~L-~w 

J FMAMJJASONDJ FMAMJJASONDJ FMAMJJASO 

1978 1979 1980 

FIGURE 28.-Variation with time of sulfate for water samples from the Cowlitz River at Kelso. 

25 

a: 

w 

...... 

::::; 

a: 

w 

CL.. 

Cl) 

:::IE 

cc 

a: 

(!) 

::::; 

..... 

:i 

~ 

z 

0 

i= 

cc 

a: 

...... 

z 

w 

(.) 

z 

0 

(.) 

w 

c 

a: 

c 

..... 

:::t: 

(.) 

QL-~~~~~~~~_L_L_L_L_L~_L_LJ_J_~~~~~~~L-~~~~~ 

J FMAMJ J ASONDJ FMAMJ J A SONDJ FMAMJ J ASO 

1978 1979 1980 

FIGURE 29.-Variation with time of chloride for water samples from the Cowlitz River at Kelso. 

22 
a: 

LLI 

...... 

::; 

a: 

LLI 

a.. 

Cll 

::::IE 

c:c 

a: 

t::l 

::; 

...... 

~ 

i!!: 

z 

0 

i= 

c:c 

a: 

...... 

z 

LLI 

u 

z 

0 

u 

Cll 

0 

::; 

0 

Cll 

ffi 40 

::::; 

0 

Cll 

Cll 

c 

FIGURE 30.-Variation with time of dissolved-solids concentration for water samples from the Cowlitz River at Kelso. 

---TotaiN 

------Organic N 

0

J FMAMJJASONDJ FMAMJJ ASONDJ FMAMJJASO 

1978 1979 1980 

FIGURE 31.-Variation with time of total and organic nitrogen for water samples from the Cowlitz River at Kelso. 

to continued leaching from the debris and mudflow 

deposits. 

Total concentrations of iron, manganese, and 

aluminum increased greatly over pre-eruption 

23 

levels (table 3). Total concentrations of these metals at the Toutle and Cowlitz stations increased 

100 to 500 times over pre-eruption values, 

whereas the concentrations increased only about 
c:n 

1-

z 

:;:) 

>- 1-

c 

as 

a: 

:;:) 

1-

c..:J 

iS2 

1-

L&J 

::E 

0 

..... 

L&J 

:::c 

c.. 

L&J 

z 

~ 

> 1-

c 

as 

a: 

:;:) 

1-

OJ FMAMJJASONDJFMAMJJASONDJFMAMJ 

1978 1979 1980 

FIGURE 32.-Variation with time of turbidity for water samples from the Cowlitz River at Kelso. 

TABLE 3.-Variation in trace elements, in micrograms per liter, at selected stations 

Station Date Iron Manganese Aluminum 

(1980) Dissolved Total Dissolved Total Dissolved Total 

Klickitat River 5/13 60 850 3 20 40 620 

near Pitt 5/18 80 680 20 40 40 500 

(station 3) 5/19 70 4,200 10 90 70 3,100 

5/20 60 1,100 7 30 40 820 

5/29 47 500 3 3 30 640 

North Fork 3!30 170 600 7 20 140 470 

Ahtanum Creek 5/18 50 17,000 70 360 60 16,000 

near Tampico 5/19 60 4,600 10 80 110 2,200 

(stat ion 6) 5/28 85 920 10 20 50 400 

Toutle River 3/29 70 230 20 20 40 200 

near Castle Rock 5/20 95 22,000 1,000 1,300 310 20,000 

(station 12) 5/22 21 76,000 1,200. 2,200 700 55,000 

5/25 160 50,000 350 1,400 540 33,000 

5/27 110 78,000 490 2,000 250 5,700 

5/29 65 41,000 400 1,300 270 34,000 

6/ 5 110 32,000 380 1 '100 110 65,000 

6/10 140 40,000 320 1,100 100 85,000 

6/19 240 33,000 290 290 40 20,000 

6/24 210 19,000 290 680 140 100,000 

Cowlitz River 4/16 50 1100 5 10 

at Kelso 5/30 24 12,000 110 350 120 29,000 

(station 14) 6/12 90 10,000 90 290 80 10,000 

6/17 70 45,000 110 900 20 39,000 

6/25 80 8,000 70 230 60 10,000 

24 
EXPLANATION 

SITES STATION NAME DATE SYMBOL 

15 South Fork Toutle River 3/30 • below Disappointment Creek 6/6 A 

16 Kalama River below falls 3130 c 

5/21 • 

6/6 0 

17 Pine Creek at mouth 3130 X 

6/6 + 

18 North Fork Coldwater Cnlek 6/6 v 

near Spirit Lake 

North Fork Toutle River 6/6 • at Kid Valley 

PERCENTAGE COMPOSITION 

FIGURE 33.-Percentage composition of water from selected sampling sites near Mount St. Helens. 

5 to 50 times at the ash-affected stations on the 

Klickitat River and the North Fork Ahtanum 

Creek. There was also a marked difference between the mudflow- and ash-affected stations in 

the duration of total-metal-concentration increases. At the Klickitat and North Fork 

Ahtanum stations, the increases in total metal concentrations were short lived. In contrast, increases at the Toutle and Cowlitz River stations 

persisted at least through June, owing to the continuing influx of suspended sediment. 

Concentrations of other trace metals of interest-arsenic, cadmium, chromium, and cobaltwere not noticeably elevated over pre-ashfall 

levels in either the filtered or unfiltered samples. 

SUMMARY 

The May 18 eruption of Mount St. Helens in 

southwestern Washington had a pronounced effect 

on river water quality. The effects were greatest 

in the Toutle River system, which was devastated 

by the blast, a massive debris deposit, and 

25 

mudflows. The Cowlitz River, into which the Toutle drains, was similarly affected. Relatively smaller but still marked changes in water quality were 

observed in volcanic-ash-affected drainage basins 

east of the volcano. 

The major changes in water quality associated 

with the eruptive events included increases in the 

levels of sulfate, chloride, total nitrogen, total organic nitrogen, turbidity, iron, manganese, and 

aluminum. In the ash-affected basins east of 

Mount St. Helens, the observed river quality 

changes were short lived and, in general, decreased in magnitude with distance from the volcano. Changes in quality in the Toutle and Cowlitz 

Rivers have tended to persist owing to continuing 

im1uxes and leaching of sediment from the devastated headwater areas. 

Total concentrations of iron, manganese, and 

aluminum increased greatly over pre-eruption 

levels, up to 100 to 500 times in the Toutle and 

Cowlitz Rivers compared with 5 to 50 times at 

the reported sites east of the mountain. The ele-
vated total concentrations of these metals have 

tended to persist in the Toutle and Cowlitz Rivers; 

whereas, those in the ash-affected streams quickly 

returned to pre-eruption levels. At all sampled 

sites, the dissolved-metal concentrations were 

generally much lower than the suspended-metal 

concentrations. 

High concentrations of total nitrogen and total 

organic nitrogen were observed in post-eruption 

water samples. In all cases, the high nitrogen concentrations were associated with high levels of 

turbidity, and the greater proportion of the nitrogen was organic. The high concentrations of organic nitrogen probably resulted from pyrolysis of 

the forest within the blast zone. It is envisioned 

that the vaporized organic products immediately 

attached to volcanic ash particles and were then 

transported to points of deposition. 

*U.S. GOVERNMENT PRINTING OFFICE:1984-n6-041 I 4014 26 

SELECTED REFERENCES 

Fruchter, J. S., and others, 1980, Mount St. Helens ash from 

the 18 May 1980 eruption: chemical, physical, mineralogical, and biological properties: Science v. 209, no. 4461, p. 

111&-1125. 

Guy, H. P., and Norman, V. W., 1970, Field methods for measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, Book 3, 

Chapter C2, 59 p. 

Skougstad, M. W., Fishman, J. J., Friedman, L. C., Erdmann, 

D. E., and Duncan, S. S., eds., 1979, Methods for determination of inorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water- Resources Investigations, Book 5, Chapter A1, 626 p. 

Taylor, H. E., and Lichte, F. G., 1980, Chemical composition 

of Mount St. Helens volcanic ash: Geophysical Research 

Letters v. 7, no. 11, p. 944-953. 

Turney, G. L., and Klein, J. M., 1982, Surface-water-quality 

data from selected sites in Washington affected by Mount 

St. Helens eruptions: March '!.7- September 30, 1980: U.S. 

Geological Survey Open-File Report 81-1007, 153 p.