Total Alkalinity of Surface Waters
A Map of the Western Region
&EPA
ENVIRONMENTAL RESEARCH LABORATORY
U.S. Environmental Protection Agency
Corvallis, Oregon 97333
-------
PAGE NOT
AVAILABLE
DIGITALLY
-------
EPA-600/D-85-219
February 1986
TOTAL ALKALINITY OF SURFACE WATERS:
A MAP OF THE WESTERN REGION
by
James M. Omernik
Environmental Research Laboratory Corvallis
U.S. Environmental Protection Agency
200 S.W. 35th Street
Corvallis, Oregon 97333
and
Glenn E. Griffith
Northrop Services, Inc.
200 S.W. 35th Street
Corvallis, Oregon 97333
-------
Abstract
This map illustrates the regional patterns of mean annual alkalinity of
surface water in the western portion of the conterminous United States. As
such, it provides a qualitative graphic overview of the relative potential
sensitivity of surface waters to acidic inputs. The map is based on data from
approximately 3400 lakes and streams and apparent spatial associations between
these data and macro-scale watershed characterisecs that are thought to affect
alkalinity.
DISCLAIMER
The information in this document has been funded by the United States
Environmental Protection Agency. It has been subjected to Agency
review and approved for publication.
-------
A major goal specified in the National Acid Precipitation Assessment Plan
(Interagency Task,Force on Acid Precipitation, 1982) is the quantification of
the extent of sensitivity of the nation's lakes and streams to acidification^
Most earlier efforts to determine patterns of surface water sensitivity to
acidic deposition have relied on interpretations of. bedrock distribution and
chemistry (Galloway and Cowling, 1978; Likens et al., 1979; Hendrey et al.,
1980; National Atmospheric Deposition'Program, 1982). One effort was based on
soil sensitivity. (McFee, 1980) .and another on surficial geology (Shilts, 1981).
Although each of these contributed to the general knowledge of the extent of
surface water sensitivity, they are in sharp disagreement for many portions of
the country. More importantly, there is a lack2 of spatial correlation' between
the patterns drawn by these efforts and the observed patterns of surface water
alkalinity. Alkalinity is commonly used as an index of potential sensitivity
because it expresses, in part, the acid-neutralizing capacity of water bodies
and thus their relative tolerance or potential sensitivity to acidic inputs.
Although there is general agreement that surface water alkalinity is
directly related to mineral,availability, it is apparent that maps of rock type
or soil.type alone are inadequate to express patterns of mineral availability
that are meaningful in terms of surface water sensitivity. For instance,
results from several recent studies of patternsof surface water sensitivity in
different regions of the United States (Eilers et al., 1983; Haines and
Akielaszek, 1983; Twaroskl et al., 1984). indicate that no single factor (e.g.,
bedrock geology) can explain observed patterns of surface water alkali'nity.
Rather, these studies indicate that.one must consider a variety of causal or
integrating spatial factors that affecttalkalinity such as land use, physio-
graphy, and soil type (as well as geology), and that the relative Importance of
any one, or a particular combination of those .factors, may vary within or among
regions.
A recent report of the National Acadeniy of Sciences (Environmental Studies
Board, 1984) defined several important geochemi'cal and hydrological processes
of watersheds that determine whether waters will acidify and the rates at which
acidification might proceed, these processes are not*yet defined on a regional
scale and, therefore, cannot presently be used in a definition of relative
sensitivity of regions to. acidic deposition..
In light of the above, it is clear that caution must be used 1n any effort
to use a_single measure such as alkalinity to assess the sensitivity of surface
waters to acidic deposition. Alkalinity is certainly the most readily avail-
able measure of the acid-neutralizing capacity of surface waters; however, the
actual response of a given lake or stream to acidic input is determined by
numerous biogeochemical and hydrological factors of the watershed plus chemical
processes within water bodies. Total alkalinity includes the sum of the
bicarbonate, carbonate, and hydroxide alkalinity and is often expressed as:
[Alk] = [H.C03-] + 2[C03-2] + [0H-] - [H+].
In most surface waters, alkalinity is largely a function of the carbonate-
bicarbonate system. In low alkalinity waters, however, where total inorganic
carbon.concentrations are low, other substances such as organic acids, sili-
cates, ammonia, or aluminum-hydroxy compounds may also contribute to the
acid-neutralizing capacity. Alkalinity is also only a static measure of the
1
-------
capacity of a water body to neutralize incoming acids. These measurements
ignore processes that control the rate of alkalinity generation in the water-
shed or aquatic system and, thus, do not adequately reflect the long-term
ability to assimilate acids. Although alkalinity values do not completely
incorporate the influences of all factors into a definition of surface water
sensitivity, they do provide a reasonable basis for determining spatial
patterns of relative potential sensitivity.
With this rationale, we approached the problem of depicting the likely
patterns of surface water sensitivity in the conterminous United States by
analyzing spatial patterns of surface water alkalinity as an integrator of the
various factors that determine sensitivity. We accomplished this by: (1)
assembling available alkalinity data on as many surface waters as necessary
and/or possible; (2) plotting these data on relatively large-scale maps; and
(3) analyzing the patterns of the values of the plotted data for spatial
correlations with other characteristics such as land use, geology, and physio-
graphy.
A national map compiled earlier (Omernik and Powers, 1983) described the
general patterns of surface water alkalinity in the conterminous United
States. By comparison, the regional map presented here is based on an order of
magnitude more data (for the Western portion of the national map) and depicts
the spatial patterns of surface water alkalinity in greater detail and at a
greater resolution than was possible in the national map.
We chose the alkalinity ranges of the five map units to reflect potential
sensitivity patterns on a regional scale, as compared with the broader ranges
used for the national map. Although it is not possible to define exact break
points between sensitive, moderately sensitive, and insensitive waters, it is
generally agreed that waters of total alkalinity > 200 ueq/1 are relatively
insensitive to acidic deposition (Blank et al., 1984).
As was the case with the national map, our purpose is to show what range
of alkalinity one might expect to find in most of the surface waters most of
the time. Relative to the national map, the regional map provides more
detailed ancillary information on ranges of conditions, significant apparent
regional and local relationships between alkalinity and macro-scale watershed
characteristics such as land use and physiography, seasonal variations, and
other factors. This information in turn provides a basis for understanding the
confidence with which predictions and estimations of potential surface water
sensitivity might be made for the region, or parts of the region. We emphasize,
however, that the map and the ancillary information are not intended for making
precise predictions of sensitivity for individual water bodies or specific
locations. Rather, this map and the other regional maps are intended to help
fill the urgent need to understand the relative potential sensitivity of
surface waters in different parts of the country in order to provide a national
perspective of the potential problem, provide rationale for selecting geo-
graphic areas for more detailed studies, and allow more accurate regional
assessments of effects of acidic deposition on aquatic resources.
2
-------
Map' Development
The methods used to develop this.map were similar to those used to prepare
the previous regional alkalinity maps (Omernik and Griffith, 1985; Omernik and
Kinney, 198b). The alkalinity data were .selected and mapped according to
several categories, with separate designations given for streams, lakes, and
reservoirs, as well as to sites associated with watersheds of less than 260 sq
km (100 sq mi_). Separate designations were also given to sites represented by
single samples or the mean of two samples only. . Each data point was scrutin-
ized for representativeness by keeping the watershed size consistent with the
relative homogeneity of major watershed features; thought to influence surface
water alkalinity such as physiography, vegetation type, and land use., In areas
of relative heterogeneity, most of the data were associated with small water-
sheds less than 130 sq km (50 sq mi). Representative data were imperative for
detection of spatial patterns of alkalinity, possible correlations with
patterns- of other characteristics and, ultimately, extrapolation of the data.
Inclusion of data from sites having large watersheds of widely differing
characteristics (e.g., the Willamette River at Salem, Oregon, »the watershed of
which includes vast contrasts in soils, geology, climate, and land use), or
data downstream from^ major industrial waste discharges, would mask'thiese
spatial patterns.
The map of the Western Region,.similar to the national map and the other
regional maps, was based on patterns of the actual alkalinity values and the
apparent spatial associations of these values with areal characteristics that
are believed to be causal or integrating factors affecting alkalinity,. Causal
factors, as used in this paper, refer to those that are generally believed to
directly affect alkalinity (e.g., geology and soils). Integrating factors, on
the other hand; are considered those that reflect combinations of causal
factors; for example, land use and potential natural vegetation reflect
regional combinations, or an integration, of causal factors such as soils, land
surface: form, climatej and geology^ We believe that the importance of each of
these factors, and the hierarchy of importance relative to the combinations of
factors, varies from .one region to another and even within regions. Clarifying
these regional factors /is a major goal of .our. overa 11 synoptic analyses.
We acquired alkalinity data from a variety of sources. As expected,
uniformity of coverage and temporal consistency were lacking. In; general, the
amount of data we acquired was a function of its availability and, more-impor-
tantly, the apparent complexity of regional patterns of alkalinity. In some
areas, after gathering and plotting a certain number.of data^ the spatial
patterns became clear :enough so that the addition of more data merely verified
the patterns already identified. In other areas, more data, and/or analyses at
increasingly larger scales, were necessary to distinguish the alkalinity
patterns.
Approximately 31% of the data for the Western Region were obtained from
ST0RET, an EPA computer-based water quality data storage and retrieval system
that contains data from a variety of state and federal agencies. About 25% of
our data came from the U.S. Geological Survey, either from WATST0RE (the water
quality data system of the USGS), from USGS publications or papers authored by
USGS personnel, or from unpublished USGS data sets. Another 19% of the data
.originated from state agencies, and 16% came from other Federal agencies such
-------
as the U.S. Fish and Wildlife Service, the U.S. Forest Service, the Army Corps
of Engineers, the National Park Service, and the Environmental Protection
Agency. The final 10% of the data were obtained mostly from university-affili-
ated scientists. These combined sources yielded approximately 3360 values (52%
from lakes and 48% from streams). We plotted these data on 1:250,000 or
1:500,000-scale topographic maps, with each site represented by a small circle
color-coded to an alkalinity class value. The exact value and the water body
type were noted beside the circle. Of these values, 52% represented single
samples only, 9% were the mean of two samples, 18% were the mean of three to
six samples, and 22% were the mean of seven or more samples. Approximately 87%
of the data were from alkalinity samples obtained between 1979 and 1983.
Another 12% of the data were from 1970 to 1978, and approximately 1% were from
samples collected before 1970.
Although the spatial patterns of the alkalinity values were the most
important factor for determining the class areas, other characteristics that
may have spatial associations with the alkalinity patterns were assessed in
order to extrapolate into areas that lacked alkalinity data. These character-
istics and associations were the fine tuning mechanisms for guiding the final
map unit delineations. The maps with the plotted alkalinity data were either
overlaid onto or compared with a variety of maps showing geology (King and
Beikman, 1974; Loy et al., 1976; Donley et al., 1979; Greer et a 1., 1981),
major land uses (Anderson, 1967; Colorado Land Use Commission, 1974; Loy et
al., 1976; Pacific Northwest Regional Commission, date unknown), soils (Soil
Conservation Service, 1967; Loy et al., 1976; Greer et al., 1981), forest types
(U.S. Forest Service, 1967), and potential natural vegetation (Kuchler, 1966;
Loy et al., 1976; Donley et al., 1979).
The strongest associations that we observed were those between alkalinity
and land use. Low alkalinity waters are generally found only in areas of
ungrazed forest, alpine meadows, or mountain peaks above timberline, while high
alkalinity is found where agricultural land uses predominate. Intermediate
types of land use generally reflected alkalinity values that corresponded to
the degree of agricultural use (including grazing). Wherever agriculture
occurs, even as a fairly small portion of the land use mosaic, mean annual
alkalinity values are usually over 400 ueq/1.
Where alkalinity values varied within an area categorized entirely by
ungrazed forest, physiographic characteristics such as elevation or land
surface form could, in some cases, be used as guides in the interpolation or
extension of mapped alkalinity values. Geology maps were also used to focus
our attention and data collection efforts on areas of suspected sensitive rock
types. If the rock type for an area of low alkalinity values was granite or
gneiss, it was likely that nearby mountains of approximately the same elevation
and rock type would have similar low alkalinity surface waters. Thus, the
final map unit alignments were based primarily on the patterns of alkalinity
values, physiographic features, land use, and geology.
Data Assessment
The alkalinity data used to compile this map were obtained from a variety
of sources and, consequently, they differ in their analytical methodologies and
time periods of sampling. Alkalinity values for approximately 43% of the sites
4
-------
were determined by potentiometric titration to a single endpoint, 16% were
determined by colorimetric titration to a single endpoint, 14% were determined
by the titration method of Gran (1952), 3% were determined by potentiometric
titration to a double endpoint (American Public Health Association, 1980), 1%
were determined by conductometric titration (Golterman, 1970), and approxi-
mately 22% were of unknown methodology. California waters had the greatest
percent of analyses (34%) by Gran titration, while Montana lakes and streams
had the greatest percentage of analyses (41%) by colorimetric methods.
For low alkalinity waters, the most commonly used fixed endpoint proce-
dures (either potentiometric or colorimetric) often yield overestimates of
alkalinity (Dillon et al., 1978; Zimmerman and Harvey 1979-1980; Jeffries and
Zimmerman, 1980; National Research Council of Canada, 1981; Henriksen, 1982;
Kramer and Tessier, 1982; Church, 1984). Precision may also be significantly
less with colorimetric procedures because of uncertainty as to the exact
endpoint (Kramer and Tessier, 1982; Church, 1984). In contrast, the double
endpoint procedure and the procedure of Gran are unbiased and more precise for
low alkalinity waters (Gran, 1952; American Public Health Association 1980;
Church, 1984).
When making our final interpretations of spatial patterns of the data and
subsequent map unit delineations, we attempted to compensate for the probable
bias introduced by selected analytical procedures. If actual endpoint pH
values of all the titrations had been known, then quantitative procedures might
have been applied to correct for bias (National Research Council of Canada,
1981; Henriksen, 1982; Kramer and Tessier, 1982; Church, 1984), but because of
the lack of such information, adjustments were not possible. However, from our
experience in comparing alkalinity values determined by Gran's method to those
of colorimetric methods (Omernik and Griffith, 1985), and from the comparative
work of others (Haines and Akielaszek, 1983), we estimated approximate correc-
tion factors for the plotted data. For areas where representative sites had
borderline or slightly above borderline values between alkalinity classes
(e.g., 50, 100, 200, and 400 ueq/1) and where the analytical methods had been
other than double endpoint or Gran titration, we assigned the respective areas
to the lower alkalinity class and drew the map units accordingly. In some
cases, however, the compensation may not have been enough to account for the
bias due to methodology as suggested in the sources cited above. Hence, some
areas shown to be in the lower alkalinity classes may actually be slightly
larger than is shown; e.g., the areas shown as map unit #1 (< 50 ueq/1) may
include some of the adjacent areas shown as map unit #2 (50 to 100 ueq/1), the
areas shown as map unit #2 may include some of the adjacent areas shown as map
unit #3, etc.
Another area of concern is the use of single sample values as representa-
tive data points. The alkalinity of surface waters can fluctuate on a daily,
weekly, monthly, and annual basis, and a single sample from a water body may
not always be representative of that lake or stream's mean annual alkalinity.
We believe, however, that for the purposes of this map, one-sample data points
are sufficiently representative to be used in this macro-scale assessment of
the spatial patterns of surface water alkalinity. Our experience in mapping
the Western Region was very similar to what we found in mapping the Upper
Midwest Region (Omernik and Griffith, 1985): that is, the more data we
plotted, no matter what the sample month or number of samples, the better we
5
-------
were able to extrapolate and draw the class boundaries. If a single sample
appeared to be anomalous, more scrutiny was given to the data source, method-
ology, sample month and year, and location.
Seasonal Variation
Surface water alkalinity of lakes and streams is subject to seasonal and
annual fluctuations due partially to climatic, meteorologic, and related
hydrologic events. Recent data showing complete month by month and seasonal
trends of alkalinity concentrations are scarce for the high elevation lakes and
streams in the Western Region. These waters of lowest alkalinity, generally
located along crests of mountain ranges, appear, however, to have distinct
seasonal patterns of alkalinity concentrations. As in other regions, alkalin-
ity in the West tends to decrease in water bodies during spring snowmelt. In
northern California, water samples collected from mountain lakes following
snowmelt generally represent minimum values, whereas samples in the fall prior
to snowfall appear to approach maximum values for the year (Wilson and Wood,
1984). In the lower alkalinity areas of the mountainous West, most of the
precipitation accumulates as snow and enters lakes and streams rapidly during
snowmelt in a diluting manner. Especially on steep slopes, this runoff has
little opportunity for neutralization or buffering by alkalinity in the soil or
groundwater. According to Tonnessen and Harte (1982), in the Sierra Nevada
some lakes may gradually lose the ability to buffer acid because the buffering
capacity may be partially used up during the successive snowmelt acid pulses.
In other areas, such as the Wasatch Mountains of Utah, alkaline snow can
concentrate alkalinity, rather than acidity, in the initial melt fractions
(Messer et a 1., 1982). In these areas, however, the bulk snow will be of a
lower pH and water bodies would also show a spring decline in alkalinity due to
dilution.
The data are too limited to adequately assess seasonal fluctuations and
trends for low alkalinity water bodies in small watersheds. Most of the low
alkalinity lakes are represented by only one or, at most, a few alkalinity
samples per year. One example of a stream draining a larger low alkalinity
area, however, provides some illustration of the seasonal variations. The
Merced River in Yosemite National Park, California, drains an area of map units
#1, 2, and 3 (alkalinity classes < 50, 50 to 100, and 100 to 200 ueq/1), and
from the sample point ranges in elevation from 1224 m to approximately 4000 m
(4016 ft - 13,000 ft). The forty-three values collected from 1979 to 1983 show
a 55% difference between the mean low value month and the mean annual value of
the period (Figure 1). The two other examples in Figure 1 are for rivers with
very large drainage basins, and they also show a spring depression in alkalin-
ity with highest values in the fall. The Kings River drains most of Kings
Canyon National Park, California, with waters from map units #1, 2, 3, and 4
(alkalinity classes < 50, 50 to 100, 100 to 200, and 200 to 400 ueq/1), from an
elevation of 287 m to more than 4300 m (942 ft - 14,000 ft). The difference
between the mean low value month and the mean annual value of the 1979-1983
period is 51%. The Coeur D'Alene River of Idaho also has a very large drainage
basin, consisting of map units #3, 4, and 5 (alkalinity classes 100 to 200, 200
to 400, and > 400 ueq/1), at generally a lower elevation, and has only a 20%
difference between the mean low value month and the mean annual value for the
time period.
6
-------
JFMAMJ J ASCND
1979 - 1983
Merced River at Happy Isles Bridge
near Yosemite, CA.
N = 43
mean = 111
median = 120
range = 20 - 180
stand, dev = 47
Drainage basin = 469km^ (181 mi2)
Elevation range = 1224m - 3997m
(4016tt - 13.114ft)
lr~
¦
,!¦
JFMAMJJASOND
1979 - 1983
Kings River below North Fork
near Trimmer, CA.
n = 38
mean = 307
median = 340
range = 100 • 560
stand, dev. = 1 19
Drainage basin = 3476km2 (i342mi2)
Elevation range = 287m - 434 1m
(942ft - 14.242M)
100
J FMAMJ JASOND
1979 - 1983
Coeur D* Alene River
at Enaville, ID.
N = 32
mean = 39 1
median = 400
range = 240 - 560
stand, dev. = 86
Drainage basin = 232Okm2(095m|2)
Elevation range = 640m - 2077m
(210011 - 681511)
Figure 1. Seasonal variations in alkalinity at three stream sites in the
Western Region. Source: STORET 1979-1983. Methodology: Single
endpoint potentiometric titration (USGS).
Regional Patterns
In the Western Region, spatial patterns of surface water alkalinity are as
varied as those of physiography. The surface waters most likely to be affected
by acidic deposition are primarily the alpine and subalpine glacial lakes and
streams. Most of the low alkalinity waters are found in areas that have been
glaciated (Figure 2). In general, surface water alkalinity is inversely
related to watershed elevation. Higher alkalinity values predominate at lower
elevations and lower alkalinity values are most often found at higher eleva-
tions. Abrupt differences from low to high alkalinity are common at the forest/
rangeland interface, the base of mountains, and/or breaks in some rock types as
shown on the USGS 1:2,500,000-scale geologic map. The association with eleva-
tion is common throughout the high mountainous West, but varies in significance
from one place to another.
The general altitudinal zonation of alkalinity in some parts of the
mountainous West may then have some correspondence with other characteristics.
For example, the floristic gradients noted on Kuchler's potential natural
vegetation map (Kuchler, 1966) have some general correlation with alkalinity,
i.e., the lowest alkalinity is found in the higher elevation zones: the alpine
meadows and barren land, the spruce-fir forest of the Rockies, the fir-hemlock
forest of the Cascades, and the lodgepole pine-subalpine forest of the Sierra
7
-------
Figure 2. Glaciated areas of the western United States. Source: Denny
(1965).
Nevada. At lower elevations, but with higher surface water alkalinity, are the
Douglas fir and pine-Douglas fir forests of the Rockies, the silver fir-Douglas
fir of the Cascades, and the red fir and mixed conifer forest of the Sierra
Nevada. For certain areas of Colorado, Turk and Adams (1983) and Turk and
Campbell (1984) proposed that, for predictive purposes, lake elevation can be
used as a surrogate variable for the mechanisms actually controlling lake
alkalinity. In other areas of the West, however, there is no apparent associa-
tion between alkalinity and elevation. For example, in Glacier National Park,
Montana, the surface water alkalinity appears to be relatively high even at
higher elevations. This is probably due to the types of sedimentary formations
that are found in this area.
We divided the Western Region into five subregions, based loosely on
patterns of homogeneity of general characteristics and spatial associations in
the areas of low alkalinity that are important in understanding the potential
sensitivity of these surface waters to acidification (Figure 3). These sub-
regions are delineated mainly for descriptive purposes, and, although the
individual subregions are not closed entities of uniform characteristics, they
provide some basis for analyzing and comparing the differences and similarities
between areas of low alkalinity. The subregions include: (a) the Sierra
Nevada and Klamath Mountains of California; (b) the Cascade Range of northern
California, Oregon, and Washington; (c) the northern Rocky Mountains of
Montana, Idaho, and northeast Oregon; (d) the central Rocky Mountains in
southern Montana, Wyoming, and northeast Utah; and (e) the southern Rocky
Mountains of southern Wyoming, Colorado, and northern New Mexico.
8
-------
A. Sierra Nevada Range
B. Cascade Range
C. Northern Rocky Mountains
D. Central Rocky Mountains
E. Southern Rocky Mountains
Figure 3. Western subregions.
Sierra Nevada Range
This subregion includes the Sierra Nevada Range of California, and several
mountain groups in the Klamath area of northwestern California, including the
Siskiyou Mountains, Salmon Mountains, Marble Mountains, Trinity Alps, and Scott
Mountains. The Sierra Nevada Range contains the largest area of map unit #1
alkalinity (< 50 ueq/1) in all of the Western Region. The alpine and subaipine
lakes and streams of this area share many of the physical and chemical charac-
teristics common to systems considered sensitive to acid deposition: low
alkalinity waters, small watersheds, granitic basins, and thin acidic soils
(Tonne'ssen, 1984). Loadings of acidic'materials have been measured in the High
Sierra, and some believe that if the acidity of precipitation increases, the pH
of the lakes will decrease rapidly because of their extremely low buffering
capacity (Melack et al., 1982). Many of these waters are at elevations over
3000 meters (9800 feet'-), and some mountain peaks reach elevations of over 4300
meters (14,000 feet). Our analysis leads us to believe that most of the lakes
in the Sierra Nevada above the timberline have average annual alkalinity
concentrations of less than 50 ueq/1.
The Sierra Nevada Range is a massive tilted fault block, and most of the
streams in the rangie flow down the more gently sloping western side. The range
contains large amounts of embedded acidic plutonic rocks with remnants*of
Paleozoic sediments and metamorphic rocks. Low alkalinity surface waters are
located primarily on^the granitic rocks of the Cretaceous period. Areas of
Triassic and Jurassic eugebsynclinal deposits alsooccur at some of the higher
elevations, but the lakes located on these rock types often do not appear to be
significantly higher or lower in alkalinity than those on nearby granite areas.
In other'small areas, however, particularly east of the crest where eugeo-
9
-------
synclinal deposits of the Lower Paleozoic to Lower Mesozoic Eras can be found,
several lakes have alkalinity concentrations greater than 400 ueq/1, even at
elevations above 2200 meters (7200 feet).
The map unit #1 areas (< 50 ueq/1) of the Sierra Nevada extend from Ebbets
Pass in Alpine County in the north, to the southern tip of Sequoia National
Park in Tulare County in the south. The alkalinity of surface waters in these
areas can be extremely low. Areas delineated as map unit #1 contain ninety-
five alkalinity data points (four streams and ninety-one lakes), with mean and
median values of 28 ueq/1 and 27 ueq/1 respectively. The map unit #2 areas
(50-100 ueq/1) in the Sierra Nevada contain thirty-five alkalinity data points
(fourteen streams and twenty-one lakes), with a mean value of 82 ueq/1 and a
median value of 68 ueq/1 (Figure 4).
100
80
60
40
20
Map Unit #1
N = 9 5
mean = 28
m e d i a n = 27
range = I - 7 7
stand, dev. =16
to 100
Sing
0 50 100 200 400
Alkalinity jjeq/l
Method: Gran (85);
le endpoint potentiometric (10).
•o
-------
watersheds, may help to explain why some lakes with greater alkalinity are
found near low alkalinity lakes at high elevations. Many low alkalinity lakes
are located in the Trinity Alps in the Caribou Lake/Thompson Peak area. Wilson
and Wood (1984) found that, based on alkalinity, calcium ion, and conductance,
lakes in the Trinity Alps were more "sensitive" to acidification than those in
other nearby mountain areas they sampled. We have classified this area in map
unit #2 (50-100 ueq/1), although more than a half dozen lakes in the unit have
alkalinity concentrations of less than 50 ueq/1. We have delineated two other
areas as map unit #2: along the Trinity Divide or The Eddys west of the Castle
Crags Wilderness, and in the Salmon Mountains centered on Russian Peak.
Although the frequency distribution of the lake values in these combined map
unit #2 areas (Figure 5) reveals that a majority of the sampled lakes have
alkalinity levels less than 50 ueq/1, the spatial distribution of these lakes
and their grouping with lakes of higher alkalinity resulted in a classification
of 50-100 ueq/1.
CO
o
o
©
CO
00
o
T3
O
60'
a
E
40-
CO
V)
—
?0'
o
Map Unit #2
N = 1 7
mean = 59
medians 4 4
range =20 • 144
stand, dev. = 3 1
0 50 100 200 400
Alkalinity M e q / I
Method: Single endpoinl potentiometric.
Figure 5. Frequency distribution of lake alkalinity values in areas shown by
map unit #2 (50-100 ueq/1) in the Klamath Mountains, California.
Source: Wilson and Wood (1984).
Cascade Range
This subregion comprises the Cascade Range, which extends from northern
California through Oregon and Washington, the Coast Ranges of Oregon and south-
west Washington, and the Olympic Mountains of' northwest Washington. Here,
alkalinity iis generally inversely related to elevation, although there is more
variability at the higher elevations than in the Sierra Nevada subregion, and
there are some lakes and streams of low alkalinity along the coastal margins.
Volcanic activity hais shaped much of the landscape of this subregion, but
sedimentary and metamorphic rocks that affiect the alkalinity patterns are found
in several areas.
11
-------
The Coast Range is a long narrow belt of hills and low mountains extending
north from near the Coquille River in southwestern Oregon, into the southwest
corner of Washington. The geology of these mountains is primarily of Eocene
sedimentary and volcanic (pillow basalt) rocks, and the elevations of the main
ridge summits range from 450 meters to 750 meters (1500 to 2500 feet). The
Eocene-age rocks are overlain in some places by younger Tertiary igneous rocks
that form some of the higher peaks, reaching 800 meters to over 1000 meters
(2600 to 3300 feet) in elevation. These scattered Oligocene age intrusive
rocks, largely gabbro, cap some of the prominent peaks such as Marys Peak, the
highest point in the Coast Range at 1249 meters (4097 feet). The steep-sloped
hills and ridges receive heavy rainfall and are characterized by dense forests
and numerous perennial streams. We have classified most of the surface water
in this area as map unit #4 (200-400 ueq/1). Some surface waters (mostly
colored-water lakes) with alkalinities of between 100 and 200 ueq/1 occur along
the coast, particularly in the dune area of the central Oregon coast. These
lower alkalinity waters are scattered and in close proximity to higher alkalin-
ity streams, however, not allowing us to draw lower alkalinity map units at the
scale of this regional map.
North of the Coast Range in Washington, the Olympic Mountains are com-
prised of rugged, steep-sloped ridges and relatively high elevation peaks, 2100
to 2428 meters (6900 to 7965 feet). Glaciation has strongly influenced the
landforms here, and the major peaks of Olympic National Park are ringed with
cirques and cirque glaciers. This area is composed largely of Tertiary sedi-
mentary rocks (mostly Eocene and Oligocene eugeosynclinal deposits), with some
bands of marine pillow basalt at the lower elevations on the north, east, and
south. Although some lakes and streams have greater than 400 ueq/1 of alkalin-
ity, mean annual alkalinity values of most of the surface waters are in the
200-400 ueq/1 range. Within Olympic National Park, lake sampling by Welch and
Chamberlain (1981) showed that at least five lakes had alkalinity concentra-
tions less than 200 ueq/1, one of which was less than 50 ueq/1.
The Cascade Range has a variety of geologic and physiographic character-
istics along its length, and this great north-south trending volcanic belt
contains the lowest alkalinity waters in this subregion. The northern
Washington Cascades, north of Snoqualmie Pass, are unlike the Cascade Mountains
to the south. These deeply dissected northern mountains are, to a large
extent, comprised of Paleozoic sedimentary rocks, most of which were later
folded and at least partially metamorphosed. In these metamorphic complexes
are found an abundance of schist, phy1 lite, and felsic paragneiss. Continental
sedimentary formations were also laid down during the late Cretaceous and early
Paleocene epochs. Cretaceous granitic rocks are also found in the area. In
Tertiary times, there was further intrusion by granitic rocks, and granite,
granodiorite, and quartz diorite can be found in several areas near the crest
of these northern Cascades. The two dominant peaks of the northern Cascades of
Washington, Mt. Baker (3285 meters [10,778 feet]) and Glacier Peak (3213 meters
[10,541 feet]), were built up during the Pleistocene epoch and are mainly of
andesite flows. This mix of geology contributes to the wide range of surface
water alkalinity found in the northern Washington Cascades.
By contrast, the southern Washington Cascades, which extend from
Snoqualmie Pass south to the Columbia River, contain very little sedimentary
and metamorphic rocks and only minor amounts of igneous intrusive rocks. In
12
-------
this area, the Cascades are made up mainly of Eocene to Recent andesite and
basalt flows with their associated breccias and tuffs. These mountains are
generally heavily forested with pass elevations averaging 1500-1600 meters
(4900-5200 feet). The Quaternary deposits include the Pleistocene to Recent
andesite flows and pyroclastics, which comprise the slopes of Mt. Rainier (4392
meters [14,410 feetj), Mt. Adams (3751 meters [12,307 feet]), and the active
Mt. St. Helens (previously 2949 meters [9677 feet]).
The areas of low alkalinity surface water in the Washington Cascades
contain a variety of rock types; however, the lowest alkalinity waters (map
unit #1) appear to be associated mostly with Cretaceous and Tertiary Intrusive
and granitic rocks. Surface waters in map unit #2 (50-100 ueq/1) are also <¦
found on these types of rocks, as well as on some of the metamorphlc rocks such
as the gneisses arid schists, and on the Quaternary volcanic rocks. Surface
waters on the various sedimentary rock types are generally of higher alkalinity.
For our largest map unit #1 area, in the Alpine Lakes Wilderness, we
obtained values for eighteen lakes. All of these values are less than 50 ueq/1
alkalinity. Welch and Chamberlain (1981) concluded that this general area
contained the lowest alkalinity lakes in their sampling 1n Washington. They
characterized the watersheds as being sparsely vegetated, steep-sided,
granitic, with little or no soil to buffer acidic precipitation. The largest
map unit #2 area is centered on therGlac1er Peaf Wilderness area and Includes a
mix of metamorphlc, Cretaceous granitic, Tertiary intrusive, and Quaternary
volcanic rocks. Approximately 72% of the lakes sampled 1n this unit have
alkalinity between 50 and 100 ueq/1. (The mean of the eighteen lakes sampled
here was 76 ueq/1 and the median, 72 ueq/1). Farther to the south, the map
unit #2 area around Mt. Rainier is characterized mainly by Quaternary volcanic
rocks with lesser amounts of Tertiary Intrusives^and Tertiary andesite. Only
32% of the lakes sampled here have ^lkal.lnity between 50 and 100 ueq/1, while
36% are less than 50 ueq/1. Another 32% of the lakes in .this unit have alka-
linity greater than 100 ueq/1. (The mean of twenty-two lakes was 88 ueq/1, and
the median, 77 ueq/1.) For the Washington Cascades as a whole, frequency
distributions of lake values for all map unit #1 and map unit #2 areas show the
proportion of lakes in .each alkalinity interval, and provide some Idea, of the
central tendency of our data sets in these low alkalinity areas (Figure 6).
The Oregon Cascades can also be divided Into two distinct physiographic
areas: the High Cascades on the east and the dissected Western Cascades. The
Western Cascades are made up of older deposits of basalt, andesite, and pyro-
clastic rocks laid down during the Ollgocepe and Miocene. The relief 1s
generally rugged with steep-sided, heavily-forested slopes, with peak eleva-
tions ranging from 1500 to !800 meters (4900 to ^5900 feet). Although at the
higher elevations there are some areas'of map.unit."#3 (100-200 ueq/1), most of
the surface water in the Western Cascades, .including the major reservoirs of
.the Willamette basin, are 1n map unit #4 (200-400 ueq/1).
In the late Tertiary, the lava, outlets shifted to the east, producing the
higher elevation eastern margin of the Oregon Cascades. These High Cascades
have broad, gently sloping .areas of 1500 to 1800 metiers in elevation and are
dotted with geologically young (Pliocene, Pleistocene and Recent) volcanic
peaks and cones, with some flows of basalt lava only several hundred years old.
The major peaks located on this rolling terrain reach elevations between 3000
13
-------
w 100
™ 80
T3
® 60
a
E
03
o
05
TD
0)
a
E
CO
CO
100
80
60
40 i
1 20
Map Unit * 2
N = 87
mean = 87
median — 80
range =1 " 370
stand, dev. = 59
0 50 100 200 400
Alkalinity jjeq/l
Method: Gran [56);
conductometric (16);
'lorimetric (5); unknown (10).
Figure 6. Frequency distributions of lake alkalinity values in areas shown by
map unit #1 (< 50 ueq/1) and map unit #2 (50-100 ueq/1) in the
Washington Cascades. Sources: Logan et al. (1983); Welch and
Chamberlain (1981); Dr. David Brakke, Western Washington University,
unpublished data; USGS, unpublished data.
to 3424 meters (9800 to 11,235 feet). Andesite and basalt are the dominant
rock types, and these may be covered in places by pumice, ash, or glacial till.
Almost all of the naturally occurring lakes in this range are the result of
glaciation or of lava flows damming streams. Two areas with an abundance of
very low alkalinity lakes (< 50 ueq/1) are found north of Mt. Jefferson and in
the vicinity of Waldo Lake near Willamette Pass. Although these are the only
map unit #1 areas that we have delineated in the Oregon Cascades, there are a
number of other lakes with less than 50 ueq/1 of alkalinity that are scattered
along the crest of the range. These are generally found in areas designated as
map unit #2 (50-100 ueq/1) and are usually surrounded by surface waters of
slightly higher alkalinity. As can be seen from the frequency distribution of
alkalinity values in the map unit #2 areas (Figure 7), there are many lakes
with alkalinity less than 50 ueq/1 in these areas of the Cascade Range.
In California, much of the Cascade Range is relatively unabrupt compared
to the surrounding terrain, although a few distinctive volcanic peaks and cones
rise prominently above the general surface. Most all of this part of the
Cascade Range is composed of Quaternary volcanic rocks, with lesser areas of
upper Tertiary andesite. Mt. Shasta, a stratovolcano rising to 4316 meters
(14,161 feet), is the second highest peak in the entire Cascade chain. Many of
the streams running off this peak are of low alkalinity, and, although we have
delineated this area as map unit #2 (50-100 ueq/1), several streams probably
have seasonal alkalinity concentrations of less than 50 ueq/1. To the south-
east, Lassen Peak (3187 meters [10,457 feet]) is surrounded by streams and
lakes with a broad range of alkalinity concentrations. Although stream alka-
14
-------
w 100
0)
co 80'
¦o
® 60
a
I 40
CO
r 20
Map Unit -01
N = 30
mean = 36
median - 40
range = 3 - 100
stand dev. = 23
0 50 100 200 400
Alkalinity e q /1
Method: Gran (19);
single e n d p o i n t poientiomeiric (11)
¦u
CD
a
E
<0
CO
O
se
100'
80
60
40
20
Map Unit # 2
N = 4 8
mean =88
median = 60
r a n g e = 1 2 - 304
stand, dev. -75
0 50 100 200 400
Alkalinity /jeq/l
Method: Gran (12); single
endpoint potentiometric (27),
unknown (9).
Figure 7. Frequency distributions of surface water alkalinity values in areas
shown by map unit #1 (<50 ueq/1) and map unit #2 (50-100 ueq/1) in
the California and Oregon Cascades. Sources: Nelson and Delwiche
(1983); Rinella (1979); Oregon Department of Environmental Quality,
unpublished data; U.S. Environmental Protection Agency, unpublished
data; STORET 1979, 1981.
linities appear to be very high directly north of the peak, there are streams
of lower alkalinity to the west, while east of the national park are several
lakes with alkalinity concentrations near or below 100 ueq/1.
Northern Rocky Mountains
A diverse collection of mountain ranges of different rock types and
surface water alkalinity is contained in this subregion. The subregion is
centered on Idaho and western Montana and includes low alkalinity waters in the
Bitterroot Range, the Selkirk Mountains, the Cabinet Mountains, the Sawtooth
Range, and the Wallowa Mountains of Oregon, to name the most important. Most
of the high-elevation mountain ranges are composed of either Precambrian
sedimentary rocks or granitic rocks of the Cretaceous period. Although there
is an apparent association between alkalinity and geologic rock type in certain
areas as shown on the USGS 1:2,500,000-scale geologic map (King and Beikman,
1974), in other areas, high and low alkalinity waters may be found on a similar
formation. Where there are large areas of granite, we generally found alka-
linity values that are less than 400 ueq/1, with much lower alkalinity at the
higher elevations. Along the Idaho/Montana border in the Bitterroot Mountains,
for example, we found surface water alkalinity to be less than 50 ueq/1. Much
of northern Idaho and western Montana contain Precambrian sedimentary forma-
tions, and here we found alkalinity of surface waters to vary from low to high.
A number of streams in this area may be affected by mining activities, compli-
cating the accurate assessment of alkalinity patterns.
15
-------
The lowest surface water alkalinity in this subregion is in the Bitterroot
Mountains along the divide between Idaho County, Idaho, and Ravalli County,
Montana. These glaciated mountains are comprised of the Cretaceous granitic
rocks of the Idaho batholith, with peaks ranging from about 2500 to over 3100
meters (8200 to 10,200 feet) in elevation. Our map units are based on data for
lakes and streams primarily on the Montana side of the divide, with the area of
low alkalinity stretching approximately from Nez Perce Pass to Lolo Pass. Most
of this area is within the Selway-Bitterroot Wilderness. Although the map unit
#1 area includes alkalinity values for only seven high-elevation lakes, these
lakes are well distributed along the crest of this part of the range. These
values are complemented by stream values in adjacent basins at lower elevations
which help define the map unit §2 area (Figure 8). The alkalinity values for
the adjacent map unit HZ area (50-100 ueq/1) are at the high end of the class
range, but are taken near the mountain/valley break in slope and help to
determine the low elevation boundary of the unit.
100
80
60
40
20
o
Mao U n i 1 #1
N - 7
mean = 2 1
median - 18
r a nge = 10 - 35
stand, dev. = 9
0 50 100 200 400
Alkalinity peq/l
Method: Gran
"O
CD
c.
E
o
M e
00
30
60
40
20
Map Unn #2
N = 6
mean =106
median = 95
range* 93 - J 5 1
stand, dev. = 23
0 50 100 200 400
Alkalinity jjeq/l
Ihofl: Unknown (5); Gran ( 1 ) .
Figure 8. Frequency distributions of surface water alkalinity values in areas
shown by map unit #1 (< 50 ueq/1) and map unit #2 (50-100 ueq/1) in
the Bitterroot Mountains, Idaho and Montana. Sources: Dr. Gordon
Pagenkopf, Montana State University, unpublished data; Bitterroot
National Forest, unpublished data.
In other mountains of the Bitterroot Range, the alkalinity is generally
higher in lakes and streams, most likely a result of the different geology.
The Beaverhead Mountains east of Salmon, Idaho, along the Continental Divide,
have several peaks over 3000 meters (9800 feet) in elevation, with numerous
lakes set in a glaciated landscape. The dominant rock type is Precambrian
sedimentary, and the surface water alkalinity is generally higher than in the
granitic areas of the Bitterroot Range to the north. Many of the high-eleva-
tion lakes on the east side have been sampled by the Montana Department of
Fish, Wildlife and Parks. Although there are a few lakes with alkalinity
concentrations less than 100 ueq/1, most of the area containing these waters is
classified in our map unit #3 (100-200 ueq/1).
16
-------
The other area of map unit #1 alkalinity (< 50 ueq/1) in this subregion
occurs in the Wallowa Mountains of northeastern Oregon. These rugged mountains
have several peaks over 2900 meters (9500 feet) in elevation, and a Pleistocene
ice cap and valley glaciers left numerous cirques, glacial lakes, and morainal
deposits. The map unit #1 and #2 areas are centered on Eagle Cap and the Eagle
Cap Wilderness, and much of this area is intruded by Cretaceous granitic rocks
similar to the Idaho batholith. For the area shown by map unit #1, we obtained
alkalinity values from three of the relatively large high-elevation alpine
lakes in the area. Mi nam and Mirror lakes, at elevations between 2230 and 2300
meters (7300 and 7500 feet), both had September 1982 alkalinity values of 40
ueq/1; Glacier Lake, at about 2460 meters (8100 feet) in elevation, had an
alkalinity concentration of 20 ueq/1 (single endpoint potentiometric titra-
tion). Although these lakes are in mostly granitic basins and are low in
buffering capacity, there are other rock layers in these mountains that may
contribute higher alkalinity levels to some lakes and streams. In some areas
the granite is overlain by limestone, and near the crests are argillaceous beds
containing hornfels, shales, slates, sandstones, quartzites, and some limestone
(Baldwin, 1976).
In northern Idaho, two areas of map unit #2 (50-100 ueq/1) surface waters
are found in the Selkirk Mountains and in the Cabinet Mountains. These two
areas are particularly interesting because the alkalinity of the lakes is
roughly similar, but the geology of the mountains is different. The Selkirk
Mountains on the west are composed primarily of Cretaceous granite, whereas the
Cabinet Mountains to the east contain Precambrian sedimentary material. The
general elevations, land use, and forest cover are similar (Figure 9).
» 100
©
JC
« 80'
Mao Unit #2
N = 1 1
mean— 73
median = 80
"O
® 60/
a
range = 40 - 140
I 40'
stand, dev. = 27
in
- 20'
o
<*
1
0 50 100 200 400
Alkalinity jjeq/l
Method: Unknown
Figure 9. Frequency distribution of lake alkalinity values in areas shown by
map unit #2 (50-100 ueq/1) in the Selkirk Mountains, Idaho, and
Cabinet Mountains, Idaho and Montana. Source: STORET 1979.
In southern Idaho, we delineated the Sawtooth Mountains within the
Sawtooth Wilderness as another map unit #2 area. This glaciated area has
several mountain peaks over 3000 meters (9800 feet) in elevation, with numerous
lakes at or above timberline. Much of this area is composed of Tertiary
17
-------
intrusive rock, surrounded by the Cretaceous granite of the Idaho batholith.
Near the Snowyside Peak/Parks Peak area, alkalinity levels for three high-
elevation lakes, Hell Roaring Lake, Toxaway Lake, and Twin Lake, were measured
to be 80 ueq/1 (methodology unknown).
Central Rocky Mountains
The central Rocky Mountain subregion contains areas of low alkalinity
(< 200 ueq/1) in the Uinta Mountains of Utah; the Wind River Range, Bighorn
Mountains, Absaroka Range, and Yellowstone area of Wyoming; and the Madison
Range, Gallatin Range, Beartooth Mountains, and Crazy Mountains of Montana.
These specific areas contain some of the oldest Precambrian granitic rocks, as
well as relatively recent Tertiary and Quaternary volcanic rocks.
The largest area of the lowest surface water alkalinity in this subregion
is in the Wind River Range of Wyoming, This range is composed of Precambrian
crystalline igneous rocks (granite) and metamorphic rocks (orthogneiss and
paragneiss), with younger beds of sedimentary material at the lower elevations.
The range contains a large number of alpine lakes and includes Gannet Peak, at
4202 meters (13,786 feet) in elevation, the highest point in Wyoming. The
Bn'dger and Fitzpatrick Wilderness areas border each other along the Contin-
ental Divide and contain over 2000 lakes. Pleistocene glaciation left its
landmarks of cirques, aretes, U-shaped valleys, scoured bedrock, and glacial
debris. Several large glaciers still exist along the Continental Divide,
primarily on the east side. On the west side, at lower elevations, several
major lakes are impounded behind terminal moraines. The Precambrian rocks are
very low in calcium and magnesium, and the soils have been reported as having
even less calcium than the crystalline rocks (Worl et al., 1984). Calcium is
usually associated with buffering materials. Low alkalinity waters are found
on both the felsic igneous rocks and metamorphic rocks. The lakes of lowest
alkalinity (< 50 ueq/I) are generally found above elevations of 3200 meters
(10,500 feet) and are located primarily from the forty-third parallel north to
Whiskey Mountain. South of the forty-third parallel to Atlantic Peak, surface
waters within map unit #2 (50-100 ueq/1) predominate, even near the crest of
the divide. In each of these map units, the small standard deviations of the
alkalinity values indicate a high degree of similarity in alkalinity from one
lake to another (Figure 10).
The only other map unit #1 area that we have classified in this subregion
is in the Beartooth Mountains of Montana. The Absaroka-Beartooth Mountain area
of Montana, much of it designated as wilderness, contains nearly one thousand
lakes. More than 80% of these are situated at elevations over 2743 meters
(9000 feet), primarily in the alpine and subalpine zones. The small map unit
#1 area, located immediately north of the Wyoming border along the Carbon
County-Park County line, is based on colorimetric (methyl orange) alkalinity
values for twelve lakes, all of which were listed as having "zero" alkalinity
(Marcuson, 1980). These are, however, the least reliable data for any of our
map unit #1 areas in the Western Region, and these lakes possibly have some
levels of alkalinity. There were a large number of colorimetric data for the
Absaroka-Beartooth Wilderness, and although not highly accurate, after plotting
it on a 1:250,000-scale topographic map, some general patterns became evident.
We believe there are numerous lakes in the Absaroka-Beartooth area potentially
susceptible to acidic deposition (alkalinity < 200 ueq/1). Most of this area
18
-------
CO
0)
JL
100 j
Map Unit #
1
V)
0>
2L
100-
M a o Unit *2
03
SO-
N = 23
(C
80
N =
4 4
¦o
mean = 32
"D
mean =82
a>
SO-
median = 33
a>
60'
median = 84
a
range =10 •
53
a
range -57 - 128
E
CD
40-
stand, dev.
= 1 3
E
ra
40'
stand, dev. =16
C/>
U>
Q
20-
o
20'
I
0 50 100 200 400
Alkalinity ueq/l
Method: Gran
0 50 100 200 400
Alkalinity ueq/l
Method: Gran
Figure 10. Frequency distributions of lake alkalinity values in areas shown by
map unit H (< 50 ueq/l) and map unit #2 (50-100 ueq/l) in the Wind
River Range, Wyoming. Source: Bridger-Teton National Forest,
unpublished data.
is characterized by Precambrian orthogneiss and paragneiss metamorphic rocks,
and there appears to be a wide variation in alkalinity values on these rock
types. There are also areas of Lower Tertiary volcanic rocks, Tertiary
intrusive rocks, and Paleozoic sedimentary layers that will also influence
alkalinity concentrations.
The Yellowstone area in northwest Wyoming is characterized by a wide
variability in geology, physiography, and surface water chemistry. Yellowstone
National Park is a high plateau surrounded on three sides by mountain ranges,
with geologic formations ranging from Precambrian metamorphic rocks to Mesozoic
sedimentary rocks to Tertiary and Quaternary volcanic rocks. A series of major
glaciations covered much of the park and, in some areas, left abundant till and
glaciofluvial deposits. Rhyolite is the dominant bedrock type and has chemical
and weatherability characteristics similar to granite (Gibson et al., ,1983).
Most of the low alkalinity lakes in Yellowstone occur on the large rhyolite
flow, although some higher alkalinity waters can be found there also. The
alkalinity of surface water in Yellowstone may especially be affected by
factors other than bedrock, because glacially transported rock material,
groundwater flows, or sulfate-bearing hydrothermals can influence the water
chemistry. In general, though, the lakes of lowest alkalinity are found on the
central rhyolite plateau, in the more basaltic Bechler River/Falls River area
in the southwest corner of the park, and in the Tertiary andesitic and basaltic
upper elevations of the Specimen Creek drainage in the northwest corner of the
park in Montana. The area shown by map unit #2 (50-100 ueq/l), immediately
north of Yellowstone Lake, includes alkalinity values from five lakes that have
a mean of 85 ueq/l, and range from 40 ueq/l to 146 ueq/l. Gibson et al. (1983)
state that this colorimetric methyl orange alkalinity data (titration endpoint
pH 4.6) overestimates alkalinity by 25 ueq/l for each sample. After correc-
tions are made, these lakes would still fall within map unit #2 with a 60 ueq/l
19
-------
mean, 55 ueq/1 median, and lb-121 ueq/1 range. Although these lakes are low in
alkalinity, the streams within this area are probably higher in alkalinity due
to their larger watersheds.
The last area of this subregion with a large extent of low alkalinity
surface water is found in the Uinta Mountains of northeastern Utah. Created by
anticlinal uplifting, this range is unlike other major ranges in the U.S. in
that it trends east and west rather than north and south. The High Uintas
include several peaks that exceed 400U meters (13,000 feet) in elevation, as
well as Kings Peak, at 4114 meters (13,478 feet), the highest point in Utah.
The core and crest of the Uinta Mountains consist of Precambrian sedimentary
and metamorphic rocks, mainly quartzites, whereas the lower elevations contain
Paleozoic and Mesozoic limestones, sandstones, and shales. This range also
experienced extensive glaciation during the Pleistocene, with glacial erosion
creating a landscape of horns, cirques, aretes, glacial troughs, and moraines,
as well as more than 1400 small lakes (Greer et a 1., 1981). A large portion of
this area is designated as wilderness. We have classified most of the highest
elevation area as map unit #2 (50-100 ueq/1), although there are probably a
number of scattered lakes with alkalinity concentrations less than 50 ueq/1.
Data are lacking, however, for many high-elevation lakes in the central part of
the range. For the two map unit ft2 areas, ten lake alkalinity values and one
stream value gave a mean of 76 ueq/'l, a median of 74 ueq/1, and a ranga from
40-100 ueq/1 (Figure 11). Surface water alkalinity increases greatly at lower
elevations as contact is made with the Paleozoic and Mesozoic sedimentary
materials containing more buffering agents.
"O
CD
a
E
ro
100
80'
60
40
20
Map Unit #2
N = 1 1
moan =76
median = 74
range = 40 - 100
stand, dev. = 20
0 50 100 200 400
Alkalinity e q / I
Method: Unknown
Figure 11. Frequency distribution of surface water alkalinity values in areas
shown by map unit #2 (50-100 ueq/1) in the Uinta Mountains, Utah.
Source: STORET 1979-1981; Utah Department of Health (1982).
20
-------
Southern Rocky Mountains
Centered on Colorado, this subregion extends from the Medicine Bow
Mountains of southern Wyoming to the Sangre de Crlsto Mountains of northern New
Mexico. Similar to other mountainous regions in the West, surface water
alkalinity in the southern Rocky Mountains varies greatly from place to place
-- from the low alkalinity lakes in parts of Rocky Mountain National Park and
the Mt. Zirkel Wilderness, to the very high alkalinity (>2000 ueq/1) waters in
the intermontane valleys, basins, and plateau areas of these three states.
Here also, there is generally an inverse relationship between elevation and
alkalinity.-: The mountains with low alkalinity waters have some variation in
rock types,I ranging from Precambrian granite and gneiss to Tertiary volcanics.
The areas of lowest surface water alkalinity (< 50 ueq/1) are found
primarily in northern Colorado. The Rocky Mountain National Park in particular
has several watersheds with potentially sensitive lakes and streams. Located
along the Continental Divide, this area has numerous peaks over 3500 meters
(11,500 feet) in elevation, including Longs Peak at 4345 meters (14,255 feet).
Similar to other parts of the Rockies, most of this area consists of Pre-
cambrian granites and metamorphic rocks and has undergone extensive Pleistocene
glaciation that left hundreds of tarns, steep slopes, and areas of moraihal
material. At the highest elevations, surface water alkalinity is especially
affected by the exposed scoured bedrock and rock talus, with very little or no
soil development to influence the runoff. Descending in elevation, the thick-
ness of glacial deposits and soil often increases, and, with a decrease in
slope, the flow path and contact time of water with the surficial material
increase, resulting in potentially more buffering capacity. The soils of the
Rocky Mountain National Park, however, are coarse, high in sand, low in clay,
low in basic cations, relatively acid, and relatively steep-sloping (Gibson et
al., 1983). These properties provide little opportunity for neutralizing
acidic Inputs or adding alkalinity to water bodies. The two map unit #1 areas
in the park are at higher elevations of mainly Precambrian granite and gneiss,
generally above 3050 meters (10,000 feet). The northern-most area encompasses
Hagues Peak and Ypsilon Mountain in the Mummy Range, while the southern one
straddles the Continental Divide around Hal let Peak and Longs Peak. The map
unit #2 areas surrounding these low alkalinity units may also have at the
highest elevations some lakes with alkalinity concentrations of less than 50
ueq/1. Chemistry data was lacking for many of these waters; however, based on
the data we were able to obtain for this area and adjacent areas, and the
apparent associations of alkalinity to elevation and geology, we estimated that
the mean annual alkalinity of most of the surface waters in the area would be
in the 50 to 100 ueq/1 range (Figure 12).
The other map unit #1 area in this subregion is in northwest Colorado in
the Mt. Zirkel Wilderness area along the Continental Divide. Similar to areas
in Rocky Mountain National Park, this glaciated range has Precambrian granitic
and gneissic bedrock, thin soils, and sparse vegetative development at the
higher elevations, providing the surface water with very little buffering
capacity. Although variations in surficial geology and surface water alkalin-
ity are common in this area, most surface waters have alkalinity concentrations
of less than 200 ueq/1. Using more detailed and larger-scale geologic maps,
Turk and Campbell (1984) found that rock type (exclusive of altitude) is very
significant in predicting alkalinity in the Mt. Zirkel area, accounting for 70%
21
-------
100
80-
60'
40'
20'
Map Unit #1
N - 4 7
mean = 42
median = 42
range =10 - 98
stand, dev. = 18
0 50 100 200 400
Alkalinity jjeq/l
Method: Gran
®
a
E
to
tn
O
3?
100
80
60
40
20
Map Unit #2
N = 2 8
m e a n = 8 1
median = 82
range = 5 7 - 136
stand, dev. =17
0 50 100 200 400
Alkalinity jjeq/l
Method: Gran
Figure 12. Frequency distributions of surface water alkalinity values in areas
shown by map unit #1 (<50 ueq/1) and map unit #2 (50-100 ueq/1) in
the vicinity of Rocky Mountain National Park, Colorado. Sources:
Gibson et al. (1983); Baron (1983).
of the alkalinity variance. They found that areas of Quaternary till and
terrace gravel deposits had lakes with relatively higher alkalinity values,
whereas the low alkalinity lakes were associated with large areas of Pre-
cambrian crystalline rocks such as felsic gneiss or quartz monzonites. Our map
unit #1 area (< 50 ueq/1) is located on the east side of the Continental
Divide, north and east of Mt. Ethel (3634 meters [11,924 feet]). This map unit
is based on nine lake alkalinity values with a mean of 35 ueq/1 (Figure 13).
Several other lakes with alkalinity concentrations less than 50 ueq/1 are
scattered along this part of the Park Range.
In other mountainous areas of this subregion, we believe that most of the
surface waters have mean alkalinity values greater than 100 ueq/1. Many of
these ranges are covered by Tertiary volcanic rocks which generally have more
buffering capacity than the granitic and gneissic areas due to their mineralogy
and more rapid weathering. The San Juan Mountains in southwest Colorado have a
geology approximately analogous to that of the volcanic western portions of
Rocky Mountain National Park in the upper Colorado River basin (Gibson et al.,
1983). In this part of the park, in the Never Summer Mountains, alkalinity
values are generally greater than 200 ueq/1.
Recent water chemistry data do not exist for several high-elevation areas
in this subregion. In some alpine areas that we have classified as map unit #3
(100-200 ueq/1), there may be several lakes or streams with alkalinity concen-
trations less than 100 ueq/1. This is true in the Flat Tops Wilderness area,
an area primarily of volcanic bedrock, where both high and low alkalinity
waters can be found. Tertiary basalt covers much of this area; however, minor
amounts of Precambrian granite, as well as layers of limestone and dolomite are
also found here (Turk and Adams, 1983), which can greatly affect the range of
alkalinity values. Other map unit #3 and #4 areas in the southern Rockies that
22
-------
(/>
a>
100-
Map Unit #1
•
o
GO
N = 9
"O
uean:3 5
a
60-
median^ 3 1
a
range=28 - 80
E
ca
40-
stand, dev. = 20
l/l
o
20-
ae
0 50 100 200 400
Alkalinity /j e q / I
Method: Gran
Figure 13. Frequency distributions of 1
map unit #1 (< 50 ueq/1) and
Zirkel Wilderness, Colorado.
o
o
s
Map Unit #2
©
f 80"
2
II
mean -76
"O
® 60-
median = 78
Q
range = 42 - 92
^ 40'
CO ^
stand, dev. =14
CO
- 20-
o
*
0 50 100 200 400
Alkalinity ^eq/l
Method: Gran
ike alkalinity values in areas shown by
map unit #2 (50-100 ueq/1) in the Mt.
Source: USGS, unpublished data.
most likely contain some waters with alkalinity levels less than 100 ueq/1 are
primarily found on granite, gneiss, or other crystalline rock types. These
areas would include the Snowy Range in Wyoming; the Medicine Bow Mountains in
the Ramah Wilderness, Colorado; the Mt. Evans/Grays Peak area east of Loveland
Pass, Colorado; and possibly in the Sawatch Range of Colorado, north of Monarch
Pass to the Mt. Harvard area. In addition, low alkalinity values (< 100 ueq/1)
have been recorded in the Mexican Cut area in the Elk Mountains of Gunnison
County, Colorado (Oodson, 1982; Harte et al., 1985), as well as in several
other high-altitude lakes in Colorado (Nelson, 1985).
Summary
Our map of total alkalinity of surface waters 1n the Western Region of the
United States illustrates the general patterns of the relative potential
sensitivity of surface waters to addle deposition. The map was developed
through analysis of the spatial patterns of alkalinity values from approxi-
mately 3400 lakes and streams, as well as through determination of apparent
spatial associations between these data and various watershed characteristics
believed to be causal. As with geology and physiography, surface water alka-
linity in the Western Region is extremely varied. Most all of the low alka-
linity lakes and streams are found in the glaciated high-elevation alpine and
sub-alp1ne zones of the numerous mountain ranges. In these areas, watersheds
are small, with steep slopes and thin acidic soils. The lowest alkalinity
waters are most often associated with granitic and gneissic rock types, but may
also be found 1n volcanic areas, and even certain sedimentary areas. Alkalinity
concentrations are generally greater 1n surface waters at lower elevations, and
are often extremely high in the intermontane valleys, basins, and plateau areas
of the Western Region.
23
-------
References
American Public Health Association. 1980. Standard methods for the examina-
tion of water and wastewater. Fifteenth Edition. Washington, D.C.
Anderson, J. R. 1967. Major land uses. Scale 1:7,500,000. In: The National
Atlas of the United States of America. U.S. Dept. of the Interior --
Geological Survey. 1970. Washington, D.C.
Baldwin, E. M. 1976. Geology of Oregon. Kenda11/Hunt, Dubuque, Iowa.
Baron, J. 1983. Comparative water chemistry of four lakes in Rocky Mountain
National Park. Wat. Res. Bull. 19(6):897-902.
Blank, G. B., P. J. Dillon, and J. D. Gregory. 1984. Alkalinity as an indi-
cator of sensitivity. In: The acidic deposition phenomenon and its
effects: Critical assessment review papers, Volume II. Effects Sciences,
Chapter 4 — Effects on Aquatic Chemistry. EPA-600/8-83-016BF.
Church, M. R. 1984. Analysis of trends based on historic measurements of
surface water quality. In: The acidic deposition phenomenon and its
effects: Critical assessment review papers, Volume II. Effects Sciences,
Chapter 4 -- Effects on Aquatic Chemistry. EPA-600/8-83-016BF.
Colorado Land Use Commission. 1974. Existing land use, Colorado, 1973. Scale
1:500,00U. Denver, Colorado.
Denny, C. S. 196b. Glacial geology of conterminous United States. Scale
1:20,000,000. In: The National Atlas of the United States of America.
U.S. Dept. of Interior, Geological Survey. 1970. Washington, D.C.
Dillon, P. J., D. S. Jeffries, W. Snyder, R. Reid, N. D. Yan, D. Evans, J.
Moss, and W. A. Scheider. 1978. Acid precipitation in south-central
Ontario: recent observations. J. Fish. Res. Board Can. 35:809-815.
Dodson, S. I. 1982. Chemical and biological limnology of six west-central
Colorado mountain ponds and their susceptibility to acid rain. Am. Midi.
Nat. 107(1):173-179.
Donley, M. W., S. Allen, P. Caro, and C. P. Patton. 1979. Atlas of
California. Pacific Book Center, Culver City, California.
Eilers, J. M., G. E. Glass, K. E. Webster, and J. A. Rogalla. 1983. Hydro-
logic control of lake susceptibility to acidification. Can. J. Fish.
Aquat. Sci. 40:1896-1904.
24
-------
Environmental Studies Boar;d, National Research Council. 1984. Acid deposi-
tion: process of lake acidification. National Academy Press, Washington,
D.C.
Galloway, J. N., and E. B. Cowling. 1978. The effects of precipitation on
aquatic and terrestrial ecosystems: a proposed precipitation chemistry
network. J. Air Pollut. Control Assoc. 28(3):229-235.
Gibson, J. H., J. N. Galloway, C. Schofield, W. McFee, R. Johnson, S. McCarley,
N. Dise, and D. Herzog. 1983. Rocky Mountain acidification study. U.S.
Fish and Wildlife Service, Division of Biological Services, Eastern Energy
and Land Use Team, FWS/0BS-80/40.17.
Golterman, H. L. 1970. Methods for chemical analysis of fresh waters. IBP
Handbook No. 8. Blackwell Scientific Publ., Oxford and Edinburgh.
Gran, G. 1952. Determination of the equivalence point in potentiometric
titrations. Part II. Analyst 77:661-671.
Greer, D. C., K. D. Gurgel, W. L. Wahlquist, H. A. Christy, and G. B. Peterson.
1981. Atlas of Utah. Brigham Young University, Provo, Utah.
Haines, T. A., and J. J. Akielaszek. 1983. A regional survey of chemistry of
headwater lakes and streams in New England: Vulnerability to acidifica-
tion. U.S. Fish and Wildlife Service, Eastern Energy and Land Use Team,
Kearneysvi1le, West Virginia. FWS/0BS-80/40.15.
Harte, J., G. P. Lockett, R. A. Schneider, H. Michaels, and C. Blanchard.
1985. Acid precipitation and surface water vulnerability on the western
slope of the high Colorado Rockies. Water, Air, and Soil Pollut. 25(3):
313-320.
Hendrey, G. R., J. N. Galloway, S. A. Norton, C. L. Schofield, P. W. Shaffer,
and D. A. Burns. 1980. Geological and hydrochemical sensitivity of the
eastern United States to acid precipitation. EPA-600/3-80-024. Corvallis
Environmental Research Laboratory. U.S. Environmental Protection Agency,
Corvallis, Oregon.
Henriksen, A. 1982. Alkalinity and acid precipitation research. Vatten.
38:83-85.
Interagency Task Force on Acid Precipitation. 1982. National acid precipita-
tion assessment plan. Washington, D.C.
Jeffries, D. S., and A. P. Zimmerman. 1980. Comments on the analysis and
sampling of low conductivity natural waters for alkalinity. Can. J. Fish.
Aquatic. Sci. 37:901-902.
King, P. B., and H. M. Beikman. 1974. Geologic map of the United States.
Scale 1:2,500,000. U.S. Dept. of the Interior -- Geological Survey.
Reston, Virginia.
25
-------
Kramer, J. F., and A. Tessier. 1982. Acidification of aquatic systems: a
critique of chemical approaches. Environ. Sci. Technol. 16:606A-615A.
Kuchler, A. W. 1966. Potential natural vegetation. Scale 1:7,500,000. In:
The National Atlas of the United States. U.S. Dept. of the Interior,
Geological Survey. 1970. Washington, D.C.
Likens, G. E., R. G. Wright, J. N. Galloway, and T. J. Butler. 1979. Acid
rain. Sci. Am. 241(4):43-51.
Logan, R. M., J. C. Derby, and L. C. Duncan. 1982. Acid precipitation and
lake susceptibility in the central Washington Cascades. Environ. Sci.
Technol. 16(11):771-775.
Loy, W. G., S. Allen, C. P. Patton, and R. D. Plank. 1976. Atlas of Oregon.
University of Oregon. Eugene, Oregon.
Marcuson, P. E. 1980. Fisheries management plan for mountain lakes in the
Clarks Fork of Yellowstone River drainage, Montana. Montana Dept. of
Fish, Wildlife, and Parks.
McFee, W. W. 1980. Sensitivity of soil regions to acid precipitation. EPA-
600/3-80-013. Corvallis Environmental Research Laboratory, U.S. Environ-
mental Protection Agency, Corvallis, Oregon.
Melack, J. M., J. L. Stoddard, and D. R. Dawson. 1982. Acid precipitation and
buffer capacity of lakes in the Sierra Nevada, California. In: Proceed-
ings of the International Symposium on Hydrometeorology, Denver, Colorado
(June 13-17, 1982), American Water Resources Association, pp. 35-41.
Messer, J. J., L. Slezak, and C. I. Liff. 1982. Potential for acid snowmelt
in the Wasatch Mountains. Utah Water Research Laboratory. Utah State
University. Logan, Utah.
National Atmospheric Deposition Program. 1982. Distribution of surface waters
sensitive to acid precipitation: a state level atlas. NADP Tech. Rept.
No. IV, S. A. Norton, editor. Department of Geological Sciences, Uni-
versity of Maine, Orono, Maine.
National Research Council of Canada. 1981. Acidification in the Canadian
aquatic environment: Scientific criteria for assessing the effects of
acidic deposition on aquatic ecosystems. NRCC Publication No. 18475.
Ottawa, Canada.
Nelson, P. 0., and G. K. Delwiche. 1983. Sensitivity of Oregon's Cascade
lakes to acid precipitation. Water Resources Research Institute, Oregon
State University, Corvallis, Oregon.
Nelson, W. C. 1985. Alkalinities of high altitude lakes in Colorado. Aquatic
Wildlife Section, Colorado Division of Wildlife, Ft. Collins, Colorado.
26
-------
Omernik, J. M., and G. E. Griffith. 1985. Total alkalinity of surface waters:
a map of the Upper Midwest region. Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, Corvallis, Oregon.
EPA-600/D-85-043.
Omernik, J. M., and A. J. Kinney. 1985. Total alkalinity of surface waters:
a map of the New England and New York region. Corvallis Environmental
Research Laboratory, U.S. Environmental Protection Agency, Corvallis,
Oregon. EPA-600/D-84-216.
Omernik, J. M., and C. F. Powers. 1983. Total alkalinity of surface waters: a
national map. Ann. Assoc. Am. Geog. 73(1):133-136.
Pacific Northwest Regional Commission. Date unknown. Land use of Idaho.
Scale 1:500,000. University of Oregon, Department of Geography, Eugene,
Oregon.
Rinella, J. F. 1977. Lakes of Oregon, Vol. 5, Marion County. U.S. Dept. of
the Interior, Geological Survey. Portland, Oregon.
Rinella, J. F. 1979. Lakes of Oregon, Vol. 6, Douglas County. U.S. Dept. of
the Interior, Geological Survey. Portland, Oregon.
Shilts, W. W. 1981. Sensitivity of bedrock to acid precipitation: modifica-
tion by glacial process. Geol. Surv. Can. Paper 81-14.
Soil Conservation Service. 1967. Distribution of principal kinds of soils:
orders, suborders, and great groups. Scale 1:7,500,000. In: The
National Atlas of the United States of America. U.S. Dept. of the
Interior, Geological Survey. 1970. Washington, D.C.
Tonnessen, K., and J. Harte. 1982. Acid rain and ecological damage: implica-
tions of Sierra Nevada lake studies. Public Affairs Report 23 (6):1-9.
Tonnessen, K. 1984. Potential for aquatic ecosystem acidification in the
Sierra Nevada, California. In: Early Biotic Responses to Advancing Lake
Acidification. G. Hendrey (ed.), Acid Precipitation Series, Vol. 6.
Butterworth Publishers, Boston, Massachusetts, pp. 147-169.
Turk, J. T., and D. B. Adams. 1983. Sensitivity to acidification of lakes in
the Flat Tops Wilderness area, Colorado. Wat. Resour. Res. 19(2):346-350.
Turk, J. T., and D. H. Campbell. 1984. Prediction of lake alkalinity in the
Rocky Mountains, western United States. In: Air Quality and Acid Depo-
sition Potential in the Bridger and Fitzpatrick Wildernesses. Workshop
Proceedings. U.S. Dept. of Agric., Forest Service, Intermountain Region,
Ogden, Utah. pp. 268-274.
Twaroski, C. J., J. D. Thornton, S. A. Heiskary, and D. Anderson. 1984.
Aquatic, terrestrial, and peatland ecosystems in Minnesota considered
sensitive or potentially sensitive to acid deposition. Minnesota Pollu-
tion Control Agency. Roseville, Minnesota.
27
-------
United States Forest Service. 1967. Major forest types. Scale 1:7,500,000.
In: The National Atlas of the United States of America. U.S. Dept. of
the Interior, Geological Survey. 1970. Washington, D.C.
Utah Department of Health. 1982. State of Utah clean lakes inventory and
classification (draft). Salt Lake City, Utah.
Welch, E. B., and W. H. Chamberlain. 1981. Initial detection of acid lakes in
Washington state. University of Washington, Department of Civil Engineer-
ing. Seattle, Washington.
Wilson, D., and R. Wood. 1984. Mountain lake water quality survey -- 1983.
Region 1 Data Report. State of California. Department of Fish and Game.
Redding, California.
Worl, R. G., J. C. Antweiler, T. P. Hulsebosch, M. E. Koesterer, and G. K. Lee.
1984. Geology and geochemistry of the Bridger Wilderness and Green-
Sweetwater roadless area, Wyoming; background data for an acid deposition
monitoring plan. In: Air Quality and Acid Deposition Potential in the
Bridger and Fitzpatrick Wildernesses. Workshop Proceedings. U.S. Dept.
of Agric., Forest Service, Intermountain Region, Ogden, Utah. pp. 47-66.
Zimmerman, A. P., and H. H. Harvey. 1979-1980. Sensitivity to acidification
of waters of Ontario and neighboring states. Final Report for Ontario
Hydro. University of Toronto.
28
------- |