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<br />o [11 7:. 9
<br />
<br />in the synoptic data-collection program. The criterion for selecting a stream
<br />for sampling was that the stream be flowing in April 1981.
<br />
<br />In this study, 18 sites were chosen from the original 26 to colle~t
<br />trace-element data. The reduced number of sites results from an additional
<br />criterion that a site must have a large concentration of suspended material.
<br />In addition to these 18 sites sampled during the study period, 18 established
<br />surface-water gaging stations were selected that had similar trace-element
<br />data available. Locations of these established surface-water gaging stations
<br />and additional surface-water sampling sites are shown in figure 1.
<br />
<br />The area of data collection was the southern part of. the Yampa River
<br />basin between the confluence with Oak Creek upstream .from .steamboat Springs,
<br />downstream to the surface-water gaging station, 09251000 Yampa River near
<br />Maybel!. This downstream station was chosen as the western limit of the study
<br />area because it is included in the National Stream Quality Accounting Network
<br />(NASQAN), and it is a station for which a large number of water-quality
<br />analyses are available.
<br />
<br />DESCRIPTION OF DATA
<br />
<br />At each .study site, water samples were collected as discharge decreased
<br />through the season. As flow decreased, suspended-sediment concentration
<br />generally decreased: When the sediment concentration was less than 100 mg/L,
<br />data collection was discontinued at the site.
<br />
<br />The instantaneous discharge of the stream was measured at the time of each
<br />sample collection, and the onsite.measurements of water temperature, pH, and
<br />specific conductance were recorded. Analyses of the water-quality samples
<br />were performed at the Denver Central Laboratory of the U.S..Geological Survey,
<br />Arvada, Colo.
<br />
<br />The individual trace elements and suspended sediment properties analyzed,
<br />with units of measurement, are listed below:
<br />
<br />Phosphorus, total (mg/L as P)
<br />Aluminum, (~g/L as AI)
<br />Arsenic, (~g/L as As)
<br />Cadmium, (~g/L as Cd)
<br />Chromium, (ug/L as Cr)
<br />Cobalt, (~g/L as Co)
<br />Copper, (~g/L as Cu)
<br />Iron, (~g/L as Fe)
<br />Lead, (~g/L as Pb)
<br />Manganese, (~g/L as Mn)
<br />Mercury, (~g/L as Hg)
<br />Selenium, (~g/L as Se)
<br />Zinc, (~g/L as Zn) .
<br />Sediment, suspended (mg/L)
<br />Sediment, discharge, suspended (ton/d)
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