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<br />I <br /> <br />I <br /> <br />I' <br /> <br />1794 <br /> <br />Figure 8 near bere. Median seasonal dissolved and total-recoverable copper concentrations <br />in the upper Arkansas River, Aprill990-Marcb 1993 <br /> <br />Figure 9 near bere. Median percentage of dissolved copper in the upper Arkansas River, <br />April1990-Marcb 1993 <br /> <br />The seasonal patterns in total-recoverable copper concentrations were dominated by the snowmelt-runoff <br /> <br />period (fig. 8). During the other three seasonal s:re:unfiow regimes, there was little difference between the median <br /> <br />total-recoverable copper concentrations and they typically ranged from Ito 5 !!g!L (fig. 8). During snowmelt run- <br /> <br />off, the median total-recoverable copper concentration increased from a minimum of 4 !!g/L at Leadville to a max- <br /> <br />imum of 12.5!!g!L at Parkdale and Portland (fig. 8). Although most of the measured copper load in most of the <br /> <br />main-stem reaches was accounted for by measured tnourary and main-stem loads, this was not the case in reach 4 <br /> <br />from Buena Vista to Nmhrop (table 7). Only 51 to 78 percent of the measured copper load at Nathrop was <br /> <br />accounted for by mainstem loading at Buena Vista or by measured tributary loading in the reach. The unaccounted <br /> <br />copper load may be from suspension or nonpoint sources within the reach. Downstream from Buena Vista, copper <br /> <br />loading from the tnoutaries was relatively small (< 10 percent) compared to main-stem load contn'butions (table <br /> <br />7). The copper load estimates (table 7) are believed to be very reasonable, because of the relatively small number <br /> <br />of samples that had total-recoverable copper concentrations that were less than the detection limit. <br /> <br />Table 7 near bere. Average percentage of seasonal instantaneous streamflow and instantaneous <br />total-recoverable copper load contributed to tbe downstream main-stem site in a reacb <br />by the upstream main-stem site and tbe intervening tributaries in the same reacb, <br />April 1990-March 1993 <br /> <br />.'. ~-ll!'-'''jiJ <br />...~:i~t:.!:r.;.: ~J~fj n"'l'-':~',,; <br />.~ -....~ V..-.w ~..Jtl~ U!!lt'i~r n <br />Subject to Ravision <br />pO ~OT QUOTE OR RELcAS2 <br />~'$dlng Approval by Directcr, <br />U.S. G~c!o!2:!:al Survey <br /> <br />24 <br />