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. . . 1774 Figure 1 near here. Map showing the location of the study area. Table 1 near here. Selected water-quality sites and analytical groups sampled in tbe Arkansas River Basin, April 1990-March 1993 Water-quality sample collection in this study was designed to provide data that represented water-quality conditions for a variety offlowregimes (fig. 2); these included low flow, early spring runoff, snowmelt runoff, POSI- snowmelt runoff, and reservoir releases. A few rainfall runoff samples were collecled when possible. Sites on lhe Arkansas River were sampled 8 to 9 times per year. Tributaries that contributed at least 5 percent of the annual streamflow to the Arkansas River were sampled 4 to 8 rimes depending on their pOlential impact on the Water qual- ity and flow contribution within a particular stream reach; the two mine drainage sites were sampled 6 to 8 times per year. Water-qu.ality samples were collected in a downstream order ~ough~~t the basin.In addition, samples co!, lected in the upper basin during May through mid-August, when there were large daily variations in streamiiow, were collected in a downstream order that reflected the travel time of the water parcel. Multiple in situ dye studies were performed to verifY the travel-time estimations. During the other times of the year, when smaIl daily varia- tions in streamflow were observed, an assumption was made that steady-St:lte conditions existed and less emphasis was given to sampling the same water parcel. This sampling approach minimized water-quality variations that occurred betWeen sites as a result of non-steady state conditions and allowed for a more "process orientated" anal- ysis of the data. In the lower basin, long travel times made it unpractical to sample a parcel but sampling did occur in a downstream order. ~~;:-~~~~J~~~~~Q~~J~i. fJ~lTi~;~B-- S:Jbjsct to Ravisicn \>~ NOT QUOTE OR RE!.CASE P$!v:Hng Approval by Direc~cr, U.S. Gso!o9icol Survey 4