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• <br />Gain-Loss/Conductivity Surveys. Tro gain-lose/conductivity studies rare performed on <br />Dry Creek 7/19/93 and 11/4/93. Figure 7-7 shows the five locations along Dry Creek at <br />which the floc and rater quality measurements ware taken.' The summer gain-lose study <br />(July 1993) showed floc losses between Stations 1 and 2, 3 and 4, and 4 and 5 with the <br />greataet floc loos (14 gpm) occurring between 9tationa 4 and 5. The channel flow stayed <br />constant batxean Stations 2 and 3. During the fall survey (October 1993), Ploxe rare <br />lover overall, but two of the reaches showed increasing floc rates in the downstream <br />direction. Between Stations 1 and 2 there was a 6.7 qpm increase in flow and betraen <br />Stations 3 and 4 there roe a 1.7 gpm floc increase. The fall evidence of gaining <br />reaches due to ground rater inflow is moat probably due to the fact ET rates rare at a <br />minimum and the effects on bank storage (there had been several storms prior to the fall <br />survey) were also negligible. Conductivity values ranged from 4510 to 4770 mhos/® in <br />the summer survey to 3630 to 5970 umhos/® in the fall survey. Conductivity levels <br />consistently increased in the downstream direction during both surveys, excepting <br />batxean 9tatione 4 and 5 in the summer survey Thera there was a 190 mhos/® drop. The <br />greataet increaea in flow batxean stations shoxad a conductivity increaea o£ 40 <br />mhos/cm, while the greatest decrease in floc showed a conductivity increase of 1580 <br />mhos/cm. Conductivity values rare higher in the summer (except between Stations 4 and <br />5), while flows rare also higher and ground rater contributions were not measurable. <br />Reaches showing ground rater inflow do not appear to cause any greater increases in <br />conductivity than losing reaches. Conductivity increases appear to be slightly <br />correlated to flow rates and reductions in Plows. Tha greataet increase in conductivity <br />occurred in the reach rich the greataet drop in flox rate and the lowest downstream <br />flow. Tha gain-loss and conductivity survey data are summarized in Table 7-8. During <br />the surveys, there was no rater being diverted from Dry Creek Por irrigation purposes <br />and there Tee no irrigation tailratar flowing into Dry Creak. Also, there Tae no flow <br />from Stokae Gulch during either survey. Thus, the results o£ the surveys are reflective <br />of naturnl conditions unaffected by irrigation withdrawals or discharges. <br />Seasonal Variability and Trends. Tables 7-5, 7-6, and 7-7 present the stream xater <br />chemistry dnta for monitoring Sites HGSD1, HGSD2, and HGSD3. The analytical results <br />presented in Table 7-5 and Table 7-6 indicate same seasonal variability in concentration <br />far several constituents at both the up-stream (HGSD1) and downstream (HGSD2) sites. <br />Major ions concentrations of bicarbonate (HC03) sulfate (SO.), calcium (Ce), magnesium <br />(Mg) and sodium (Na), generally increased slightly batxean the spring anowmalt period <br />and the baeeflow-dominated months (August-November), although no discernible change in <br />water type occurs. TDS also increases in concentration at both sites after anoxmelt <br />ends and lover <br />,Qnr , vi <br />19 Revised 2/98 <br />