Laserfiche WebLink
<br />, <br /> <br />. <br />. <br /> <br />I <br /> <br />1'796 <br /> <br />Iron <br /> <br />The spatial and temporal variability in iron concentrations (fig. 10) was largely a function of the ubiquitous <br /> <br />nature of iron throughout the basin, the degree of partitioning between the dissolved and particulate iron phases, <br /> <br />and deposition and resuspension of fluvial sediments. The median dissolved-iron concentrations were largest dur- <br /> <br />ing pre-snowmelt runoff; the maximum median concentration (330 Ilg/L) occurred at Leadville (fig. 10). Dis- <br /> <br />solved-iron concentrations were much smaller during the other three seasonal flow regimes than during pre- <br /> <br />snowmelt runoff and they were not substantially different from one another (fig. 10). Concentrations of dissolved- <br /> <br />iron decreased in the downstream direction largely because of the increased partitioning of iron to the particulate <br /> <br />phase (fig. 11). The median percentage of iron in the dissolved phase decreased from a ma'Cimum of 42 percent at <br /> <br />Leadville to a minimum of three percent at Portland (fig. 11). The median total-recoverable iron concentrations <br /> <br />were largest during snowmelt runoff and increased from 665 IlgIL at Leadville to 4,600 IlgIL at Portland, an <br /> <br />increase of almost 600 percent (fig. 10). Total-recoverable iron concentrations were much smaller during the other <br /> <br />three seasonal flow regimes than during snowmelt runoff and they were not substantially different from one <br /> <br />another (fig. 10). The downstream increase in total-recoverable iron concentrations was caused by the resuspension <br /> <br />and downstream transport of iron-enriched fluvial sediment. The elevated streamflow during snowmelt runoff has <br /> <br />the largest potential impact on the resuspension and downstream transport of sediment. An analysis oftotal-recov- <br /> <br />erable iron load contributions indicates that tributary contributions of iron were typically small (< 10 percent) com- <br /> <br />pared to the main-stem loads (table 10) with the exception of California Gulch. Lake Fork above Halfmoon. and <br />Lake Creek below Twin Lakes Reservoir. <br /> <br />;;::;-?~~'-~:'~:~-i:- r~!~),.~ Ol.! :;po, .._., ...~_ <br />'!'h ~ 'il ",..:-:,!!." IS.,,,, .~'!..~ lrfo ..~j ',.'" ". ..." <br />-....- ........~ut,;ll'.I~~ Un::N3t' ~ <br />Subject to Rsvision . <br />DC; NOT QUOTE OR RCP=.'1c.-; <br />:"'~... ,. .._~.. ~... :.. <br />~-.::;nti,"g AnDrovol by Df"re.-"~ .. <br />., ......e-..;rl' <br />U.S. G~O!09ic{'j! S(Jrv€'y <br />, <br /> <br />26 <br />