ASSIMILATIVE CAPACITY OF ARCTIC RIVERS
FEDERAL WATER QUALITY ADMINISTRATION
NORTHWEST REGION
ALASKA WATER LABORATORY
College, Alaska
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ASSIMILATIVE CAPACITY OF ARCTIC RIVERS
Prepared by
Eldor W. Schallock
Ernst W. Mueller
Ronald C. Gordon
United States Department of the Interior
Federal Water Quality Administration, Northwest Region
Alaska Water Laboratory, College, Alaska
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A Working Paper presents results of investigations
which are to some extent limited or incomplete.
Therefore, conclusions or recommendations—expressed
or implied—are tentative.
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"";:..-: ASSIMILATIVE CAPACITY OF ARCTIC RIVERS
Introduction
Waters of the arctic and sub-arctic rivers are presently being utilized
as receiving waters for wastes of many types. However, little information
is available on the condition of arctic and sub-arctic waters or how man's
manipulations affect the stream ecosystem. A paucity of information causes,
in part, a lack of understanding of the principles governing these eco-
systems.
Assimilative capacity is one parameter of a stream that may be defined
differently by various disciplines. As a result, it is necessary to define
the term as it will be used in this discussion. An early definition stress-
ing the dilution concept states'that the assimilative capacity is the abil-
ity of a stream to accept waste material without detrimental effects to the
stream. Because this concept stresses a physical rather than a dynamic bio-
logical process, in this discussion the assimilative capacity will be the
ability of a stream ecosystem to convert transported nutrients into proto-
plasm without significantly altering the ecosystem. The assimilative capac-
ity of a stream depends upon three general categories which may be neatly,
if not precisely, separated in this manner:
(1) the geographical, geological and meteorological features of the area,
(2) the related physical, chemical characteristics of the water and stream,
(3) the resultant biota of the stream.
Basically, these are the complex interrelationships of an ecosystem. Al-
though the components of the ecosystem have been placed in three groups,
,the elements of each group affect the others. In each ecosystem, at least
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'one factor limits the biological populations.
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Objectives
""'
"--—The objectives of this paper are to document some of the physical,
chemical and biological characteristics of arctic and sub-arctic rivers
and to discuss how these characteristics of a stream will be affected by
pollution. Although pollution may have several effects, dissolved oxygen
will be the primary concern.
Discussion
It is currently accepted that dissolved oxygen is probably one of
the critical limiting factors affecting benthic (bottom) and piscine pop-
ulations of the aquatic environment. The dissolved oxygen concentration
of any water at a particular time is dependent on several factors. Ini-
tially, this concentration is dependent on the source of the water and the
geological characteristics of the area. , Once the water has entered the
river system, the concentration is reduced by the oxygen demand and in-
creased by physical reaeration and the photosynthetic activity of aquatic
organisms.
During the critical winter period, meteorological conditions reduce
water temperature, stream discharge, photosynthetic activity and river
surface area exposed to the atmosphere. In the resultant fragile system,
the dissolved oxygen concentration can be easily affected.. The dissolved
oxygen concentration in samples obtained from several Alaskan rivers under
virtual total ice cover are shown in Table 1. It should be noted that the
rivers in which the dissolved oxygen concentration falls below 50% satura-
tion include many of economic importance in Alaska. The drainages of the
Colvilie, Tanana, and Copper rivers are among the largest in Alaska. The
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concentratio/i may fall below 10% saturation in some cases. Among these
are the Sagavanirktok River which drains an area of rapid development on
Alaska's Arctic Slope and the Chena River in the Interior.
The annual dissolved oxygen variation of the Chena River is presented
in Figure 1 (Frey 1969). This data shows that the dissolved oxygen concen-
tration is directly related to meterological conditions and for this dis-
cussion is correlated with water temperature. The May through September
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summer period has dissolved oxygen levels ranging from approximately 9 to
13 mg/1. However, in October, when the river water temperature approaches
,0°C, the dissolved oxygen concentration decreases appreciably. With some
variation, the reduction continues into February and March after which time
the concentration begins to return to the summer high level. Numerous fac- .
tors may contribute to this observed phenomenon. Meteorological conditions
and geological features account- for physical characteristics such as dis-
charge, velocity, water temperature, and affect many of the chemical char-
acteristics such as discharge, velocity, water temperature, and affect many
of the chemical characteristics such as pH, alkalinity, and dissolved cations
and anions. Isaac (1962) stated that stream bottom muds and sludge exert
considerable oxygen demand. However, he did not distinguish between biolog-
ical and chemical oxygen demands. Bacteria, insect larvae, other inverte-
brates, and fish populations have significant effect on the dissolved oxygen
concentration. Gordon (1970) has shown that indigenous bacteria exert a
demand on the dissolved oxygen under laboratory conditions and that the
addition of organic and inorganic nutrients increases the rate of oxygen
utilization. Dissolved oxygen concentration may be affected by stream
velocity. Data gathered by a joint U.S. Geological Survey and Alaska Water
Laboratory study indicated that stream velocity in the Sagavanirktok River
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WINTER DISSOLVED OXYGEN CONCENTRATION FROM VARIOUS RIVERS IN ALASKA
STREAM •'" D.O. in PERCENT
mg/1 SATURATION
Chena River 1.1 7
Sagavanirktok River (1969) 1.1 7
Sagavanirktok River (1970) 1.2 9
Shaw Creek 1.1 7
Colville River 3.4 23
Colvilie River (Uniat) 7.5 51
Copper River (Copper Center) 4.6 31
Tanana River (Tanana) __ 5.1 35
Tanana River (below Nenana) 8.6 59
Tanana River (Tetlin Junction) 6.7 46
Gulkana River .7.7 53
Rivers virtually covered with ice.
TABLE 1
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during the winter was not measurable on a Gurley pygmy flow meter (U.S.
Geological Survey, 1970). As a result a particular water mass remains in
the river system for an extended period of time, allowing biological or
chemical processes to reduce the finite amount of oxygen present.
The previous discussion describes some of the factors affecting dis-
solved oxygen in the arctic and sub-arctic aquatic ecosystems. These fac-
tors, and others, are interrelated directly or indirectly and as a result
the effects cannot be attributed to one specific cause. In the following
discussion, data collected from arctic and sub-arctic rivers is interpreted.
The objective is to relate how changes in these factors affect dissolved
oxygen and, as a result, the assimilative capacity of these rivers.
The range of chemical and physical data collected from the Sagavan-
irktok River that were collected during the summer of 1969 and the winter
of 1970 is presented in Table 2-. Nineteen parameters were examined in June
(spring) and August (fall), 1969 and again in .May (winter), 1970. It is
important to note that concentrations of many of these parameters were
higher during the winter sampling period, particularly total alkalinity,
total hardness, conductivity, calcium, chloride, magnesium, sodium, po-
tassium, silica, and the nitrogen forms. Ammonia was present at concen-
trations approximately twenty times the highest summer value. Since ammonia
and nitrite can be oxidized to nitrate an oxygen demand is created. During
the winter, surface water runoff is minimal. Thus, the samples collected
during the winter period were essentially ground water.
Gordon (1970) investigated the effects of various organic and inorganic
nutrients on the rate of oxygen reduction in polluted and unpolluted sub-
arctic river water containing indigenous bacteria. The polluted water was
found to contain both organic and inorganic nutrients from the sewage
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RANGE OF CHEMICAL AND PHYSICAL PARAMETERS IN THE
SAGAVANIRKTOK RIVER DRAINAGE
During June and August 1969 and May 1970
Dissolved Oxygen
PH
HO Temperature C°
Total Alkal. CaC03.
Total Hardness
Conductivity
Calcium
Chloride
Magnesium
Iron
Sodium
Potassium
Nitrogen-Ammonia
Nitrate
Nitrite
Phosphate, Total
Phosphate, Ortho
Silica (SiOo)
Turbidity JTV
Unless otherwise noted, all parameters in mg/1
. TABLE 2
June
9.9-12.6
7.60-8.22
3.9-12.0
36.2-88.6
40.0-87.0
85-178
11.4-32.4
0.30-2.33
2.9-4.0
0.40-1.12
0.18-0.73
0.02-0.09
0.05-0.11
<0.01
0.010-0.036
0.003-0.016
0.07-2.7
35-62
August
12.0-13.2
7.75-8.12
1.1-6.7
50.5-124
53.5-118
122-242
16.1-41.5
0.50-1.51
4.3-5.5
< 0.1-0. 7
0.37-1.41
0.19-0.43
0.02-0.07
0.07-0.15
<0.01
0.01-0.05
<0. 01-0. 02
1.2-2.5
4.3-21.5
May (Winter)
1.2-15.0
7.72-8.55
0.0-1.0
54.0-875.2
54.9-952.0
125-1700
16.7-295
0.30-1.66
4.1-48.0
<0.5-0.94
0.62-90.0
0.32-1.97
0.01-0.18
0.02-0.76
0.003-0.015
0.01-0.02
0.01-0.02
1.1-12.5
12-120
f
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effluents and other sources. There was also.evidence that bacteria, capable
"of metabolic activity at low temperatures, were added with the sewage ef-
fluents. Studies on the effect of added nutrients were conducted at incu-
bation temperatures between 0° and 20°C using both polluted and unpolluted
water samples. Since the only effect of incubation temperature appeared to
be on the rate of dissolved oxygen reduction, 10°C was arbitrarily selected
as the incubation temperature for intensive study. Selected results from
these studies are shown in Figure 2. From the 10.5 mg/1 level, the unpol-
luted control (curve A) exhibited less than 0.5 mg/1 dissolved oxygen re-
duction to 10 mg/1 in 200 hours, while the level in the polluted control
was reduced approximately 1.5 mg/1 to 9 mg/1 in 90-100 hours (curve-D).
Addition of glucose to unpolluted and polluted water caused increased dis-
solved oxygen utilization. The concentration of oxygen was reduced in both
samples with that in the unpolluted water being reduced to about 6 mg/1 in
180 hours (curve B), while the dissolved oxygen level in the polluted water
was reduced to less than 0.5 mg/1 in 95 hours (curve E).
Experiments using casamino acids.as the added substrate resulted in
even faster reduction. . The dissolved oxygen in both polluted and unpolluted
samples (curves C and F) was reduced to virtually 0 mg/1 at the same rate
although the lag phase in the unpolluted water was nearly 50 hours longer
than in the polluted water.
The conclusion drawn from these data is that the rate' and extent of
dissolved oxygen reduction in river water is increased by the addition of
both nutrient material and bacteria.
Another source of oxygen demand in any aquatic system is through res-
piration by organisms other than bacteria. McDonnell (1969), in a study on
benthic organisms in England, attributed 52-55% of the benthic oxygen
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A UNPOLLUTED BLANK
B UNPOLLUTED GLUCOSE
C UNPOLLUTED CASAMINO
D POLLUTED BLANK
E POLLUTED GLUCOSE
F POLLUTED CASAMINO
20
60
80
100
120
140
160
180
200
TIME (HOURS)
F5GURE 2. EFFECTS OF NUTRIENT ADDITION ON DISSOLVED OXYGEN
CONCENTRATION IN POLLUTED AMD UNPOLLUTED CHENA RIVER WATER
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utilization to invertebrates. In Alaska, these organisms have not been
extensively investigated but the role of this group in dissolved oxygen
reduction cannot be denied. Table 3 illustrates the number of organisms
per square foot of stream bottom in several Alaskan rivers. These range
from 30-100 organisms per square foot in the Sagavanirktok River (Schallock
ejt jil_, 1970) to nearly 500 organisms per square foot in the Chena River
(Frey erb jil_, 1970). Schallock (1970) sampled other interior Alaska waters
where more than 3,000 organisms were collected in one foot square benthic
sample. In addition to the benthic organisms, respiration by large numbers
of eggs deposited in the stream bottom by spawning fish exert considerable
oxygen demand.
The data presented in this paper documents that in the natural state,
Alaskan rivers may have low dissolved oxygen levels, high nutrient levels
and significant biological activity during the winter. Gordon (1970)
pointed out that the addition of nutrient material and/or indigenous bac-
teria drastically increase the rate of dissolved oxygen utilization in arc-
tic and sub-arctic river water. Isaac (1962) showed that river bottom muds
can exert strong oxygen demand when deposits of mud and/or sludge are al-
lowed to accumulate. Considering the oxygen demand being exerted by bio-
logical systems and low dissolved oxygen levels in the rivers during the
winter, little additional demand can be placed upon the already stressed
ecosystem without significant alteration.
Conceivably the streams could receive heavy organic loading in the
summer and low organic loading in the winter. It should be noted, however,
that heavy loading with nutrients under summer conditions can result in
luxurient algal growth that will die, decay, and exert a supplemental oxy-
gen demand in winter.
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NUMBER OF BENTHIC ORGANISMS FOUND IN ALASKAN STREAM BOTTOMS
(Sample Size - 1 Foot Square)
RIVER
1. Sagavanirktok River
2. Shaviovik River
3. Koyukuk River
4. Dietrick River
5. Chena River
6. Clear Creek
7. Forty Mile River
AREA
North Slope Brooks Range
North Slope Brooks Range
South Slope Brooks Range
South Slope Brooks Range
Interior Alaska
Interior Alaska
Interior Alaska
NUMBER OF ORGANISMS
0-100 101-500 >500
X
X
X
X
TABLE 3
7-3
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Some physical, chemical, and biological characteristics of arctic and
v-sub-arctic rivers have been listed .and the importance of selected factors
on the dissolved oxygen concentrations of the water has been developed.
Significant dissolved oxygen utilization at low temperatures by naturally
occuring microbial populations has been demonstrated. Because of these
characteristics and factors, the problems of waste disposal must be ap-
proached with greater caution than in the more temperate regions. Even
though little is known about the role of aquatic populations in causing dis-
solved oxygen reduction and the effects of extremely low levels of dissolved
oxygen on these organisms, dissolved oxygen concentrations do reach low
levels in natural ecosystems and the discharge of inadequately treated
wastes can seriously alter these naturally occurring systems.
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References
Frey, Paul J., 1969. Ecological Changes in the Chena River. U.S. Dept. of
the Interior, Federal Water Pollution Control Administration.
Frey, Paul J., Ernst W. Mueller, Edward C. Berry, 1970. Chena River Study.
(In print.) U.S. Dept. of the Interior, Federal Water Quality Admin-
istration, College, Alaska.
Gordon, Ronald C., 1970. Depletion of Oxygen by Microorganisms in Alaskan
Rivers at Low Temperatures. International Symposium on Water Pollution
Control in Cold Climates, University of Alaska, College, Alaska.
Isaac, Peter C.G., 1962. "The Contribution of Bottom Muds to the Depletion
of Oxygen in Rivers." Biological^Problems in Water Pollution, 3rd
Seminar, pp. 346-354. U.S. Dept. of Health, Education, and Welfare.
McDonnell, A.J., and S.E. Hall, 1969. "Effect of Environmental Factors on •
Benthic Oxygen Uptake." Journal of Water Pollution Control, Federal
Research Supplement 41, pp. 353-363.
Schallock, Eldor W., 197.D. Unpublished data from Alaska Water Laboratory
data files. U.S. Dept. of the Interior, Federal Water Quality Admin-
istration, College, Alaska.
Schallock, Eldor W., Ernst W. Mueller, and Ronald C. Gordon, 1970.
Saqavam'rktok River Study. Manuscript in preparation. U.S. Dept.
of the Interior, Federal Water Quality Administration.
U.S. Geological Survey, 1970. Water Quality Data for Alaska. U.S. Dept.
of the Interior.
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