WSP10787

• File Number: 8170
• Description: Arkansas Basin Water Quality Issues
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 9/1/1981
• Author: Bureau of Reclamati
• Title: Heavy Metals Pollution of the Upper Arkansas River - Colorado - and its Effects on the Distribution of the Aquatic Macrofauna
• Water Supply Pro - Doc Type: Report/Study

The world's largest molybdenum mine. located
at Climax, Colorado. just north of the head-
waters of the East Fork, produces 60 percent of
the total mined in the United States and 40 per-
cent of that mined in the western world.
Molybdenum is essential for plant growth, but at
times may accumulate in concentrations high
enough to be toxic to livestock (Chappell, 1975
124)). Voegeli and King (1969) 11561 reported
that most surface waters in the mountainous
areas of Colorado contain less than
0.005 mg/L of molybdenum, but according to
Chappell (19751 1241 levels of 9 mg/L have
been detected in Ten-Mile Creek, which drains
the Climax mine. These high levels were found
during the spring runoff.

Cadmium

Cadmium is often found in nature as an impurity
in zinc-lead ores. There is no evidence that cad-
mium is an essential micronutrient and once it
enters the body it is likely to remain in animal
and human tissue (McKee and Wolf. 1963
[1051 ). Cadmium is extremely toxic and often
acts synergistically with other elements (Hublou
et aI., 1954 [79] ). Clubb et al. (19751 [27]
measured cadmium uptake and elimination in
two stoneflies, Pteronarce/la badia and Pteronar-
cys california, exposed to subacute levels of
cadmium followed by return to cadmium-free
water. Uptake was curvilinear in both species
while elimination was rapid and linear. The latter
result suggests that these insects may be
capable of recovering from intermittently high
exposures to cadmium.

Cadmium is usually found in fresh waters of the
United States in concentrations of less than
1.0 /lg/L, but it was not found to be toxic to
embryos and larvae of freshwater fish in some
waters until levels of 4.0 /lg/L were reached
(Eaton et aI., 1978143] I. McKim et al. (19751
[107] found cadmium to be acutely toxic to
rainbow trout at 7.0 /lg/L. Mount and Stephan
(19671 [115] have shown that fish liver ac.
cumulated high concentrations of cadmium
during chronic exposure, but accumulated very
little following acute exposure; it was suggested
that fish liver concentrations exceeding 300 /lg
Cd/g dry weight indicate a previous history of
chronically damaging cadmium exposure.

Davies and Goettl (19761 [341 suggest that
levels of cadmium not exceed 0.4 /lg/L in waters

of less than 100 mg/L hardness (as CaCa,).
and not exceed 1.0 /lg/L in waters of less than
200 mg/L hardness. The Environmental Protec-
tion Agency (19801 [52] recommends that
average concentrations of cadmium over a
24-hour period should not exceed 0.012,
0.025. and 0.051 /lg/L in waters at hardnesses
of 50, 100, and 200 mg/L (as CaCa,). respec-
tive/y.

METHODS AND MATERIALS

Description of the Area

The study area lies east of the north-south trend-
ing Sawatch Range, whose crest forms the Con-
tinental Divide. Colorado's highest peak, MI..
Elbert, with an elevation of 4398 m above m.s.1.
(mean sea level), is located in this range. The
Mosquito Range lies immediately to the east and
is generally parallel to the Sawatch Range. The
area is characterized as a high mountain basin
with a natural dendritic drainage pattern opened
to the south.

The Arkansas River in the study area flows in a
broad valley which has been subjected to re-
peated glaciation. Main uses of the valley today
are mining on the upper slopes and grazing in the
bottom lands. Some of the Arkansas River tribu-
taries originate from small alpine lakes while
others, like the river itself, begin on mountain
slopes. Flow is characterized by high late-spring
and early-summer flows which recede to more
stabilized flows for the remainder of the year, al-
though diversions from the western slope aug-
ment the river's flow considerably below Tur-
quoise and Twin Lakes. Many of the natural
gulches dry up during the summer and fall,
although some are known to carry seepage to
creek channels and thus to the Arkansas River
(LaBounty et al.. 19751941 ).

The 1979 stream and lake evaluation map of the
State of Colorado classifies river drainages
according to the existing fishery resources. The
upper Arkansas River is given a I rating. which
designates it a highest-valued fishery resource.
Lake Fork and Halfmoon Creek are given a II
rating which designate them high-priority fishery
resources. The remaining tributaries to the upper
Arkansas River are less important for fish pro-
duction.

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