WSP10317

• File Number: 8200.760
• Description: Yampa River General
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 12/5/1976
• Author: USGS
• Title: Surface-Water Quality in the Yampa River Basin - Colorado and Wyoming - An Area of Accelerated Coal Development
• Water Supply Pro - Doc Type: Report/Study

002850

from the entire Yampa River basin was estimated at nearly 406,000 tons
(368,000 t) per year. Recent calculations by the authors indicate that the
historical long-term load during the 1951-74 water years was approximately
450,000 tons (404,000 t) annually, or perhaps 10 percent higher than the esti-
mates of Iorns, Hembree, and Oakland (1965). In either case, about 5 percent
of the dissolved-solids load of the upper Colorado River basin is contributed
by the Yampa River basin (Iorns and others, 1965, fig. 8).

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TRACE ELEMENTS AND PH

During the August-September 1975 reconnaissance, water samples were col-
lected at all sites for determination of selected trace elements in dissolved
and total phases (Steele and others, 1976a, p.13). Bottom-sediment samples
for trace-element determinations were obtained at only 48 of the 82 sites,
because bed materials were prohibitively large at the remaining sites. Se-
lected results of trace-element and pH determinations are discussed in this
paper; a more detailed discussion is given in the expanded technical report.

Frequency distributions of dissolved and total trace elements in streams
of the Yampa River basin were typically positively skewed as shown by the to-
tal Se example in figure 9A. This is the case for all except dissolved Cu
and total Zn, which are more symmetrical (see, for example, fig. 9B).

Stream sites with one or more anomalous water-quality characteristics were
determined by analyzing the various frequency distributions and separating the
outliers (indicating perturbed areas) from the distributions representative of
ambient or unperturbed conditions. For example, the concentrations of 71 ~g/L
total Se in figure 9A and 550 ~g/L dissolved Cu in figure 9B were found by
this analysis to be outliers.

Using the above techniques, four sites were found to have anomalously
high total or dissolved trace-element concentrations. These sites are Y-26
(5 outliers), Y-46 (4 outliers), Y-54 (2 outliers), and Y-68 (7 outliers)
(see fig. 1). If Fe and Mn are deleted from the outlier analysis, three
sites remain; these are Y-26 (5 outliers), Y-46 (4 outliers), and Y-68 (3 out-
liers). The rationale for deleting Fe and Mn is discussed in the expanded
technical report.

Site Y-68 (known also as the Oak Creek Drain) appears to be an abandoned
drainage tunnel and is the only known site in Colorado affected by the oxida-
tion of pyritic materials associated with coal (Wentz, 1974a). Water issuing
from the drain deposits a bright-orange coating of ferric hydroxide (yellow
boy) on the channel bottom between the tunnel and Oak Creek. In addition to
total and dissolved Fe and Mn, total Cd and dissolved Co and Ni were found to
be present at anomalously high concentrations in August-September 1975.
There appears to have been enough dilution from Oak Creek so that the latter
three constituents are not a problem at Y-67, the next site downstream on Oak
Creek. Previous chemical data reported by Wentz (1974a) and Moran and Wentz
(1974) indicate that Cu, Pb, and V also may occur at relatively high concen-
trations in the drain at certain times of the year, but that downstream
effects on Oak Creek are minima~.

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