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<br />a: <br />W <br />f- <br /><( <br />~f- 0.6 <br />Ow <br />ZW <br /><(LL <br />oo~ <br />W . / <br />f-oo h <br /><(0 <br />~<( 1,\ <br />wO <br />uoo Henderson 1A <br /><(0 <br />LLZ 0.5 <br />00<( <br />::lz <br />enO <br />Zen <br />Woo <br />Ww <br />~~ <br />Ww <br />"'I Road 8 1A 1\ <br />Wf- 0.4 \ <br />0<( <br />::len <br />C...J <br />f-...J <br />...JW <br /><(~ <br />~<( <br />en~ <br />WW <br />UI <br />zf- 0.3 <br />wz <br />00- <br />W <br />LL <br />LL <br />15 <br /> <br />0.7 <br /> <br /> <br />0.2 <br /> <br />OCTOBER <br /> <br />NOVEMBER <br /> <br /> <br /> <br /> <br />DECEMBER <br /> <br />JANUARY <br /> <br />1992 1993 <br /> <br />Figure 3. Difference in altitude between surface water and water in the 1 A wells at Henderson and <br />Road 8. Positive values indicate that the water level in the well was higher than the stage in the <br />adjacent river. <br /> <br />The transient nature of instantaneous ground- <br />water discharge rates in the small-area flow system <br />were analyzed in a series of hourly measurements <br />of discharge at the McKay Road, Henderson, and <br />Road 8 sites (fig. 5). At each site, low-flow conditions <br />existed during the measurement periods; therefore, the <br />obselVed changes in river ~tage were related to varia- <br />tions in the MWRD effluent-discharge rates (fig. 2). <br />Instantaneous ground-water discharge rates varied dur- <br />ing the measurement period. The rate and direction of <br />water movement from the small-area flow system at the <br />McKay Road and Road 8 sites were related to changes <br />in river stage. At both of those sites, the highest rates <br />of ground-water discharge corresponded to the lowest <br />river stages, whereas the lowest rates of discharge gen- <br />erally occurred at higher river stages. Ground-water <br /> <br />discharge data from the Henderson site were quite dif- <br />ferent from data from the other two sites in that values <br />of discharge at the Henderson site were negative during <br />the entire period of record, and the least negative dis- <br />charge rates generally corresponded to the highest river <br />stages. The overlap between high river stage and the <br />high (relative) discharge rate at the Henderson site may <br />indicate a delayed response by hydraulic heads in the <br />bed sediments to changes in river stage, causing a for- <br />tuitous overlap of the peaks; however, the data are <br />insufficient to fully assess this possibility. The contin- <br />uously negative rates of ground-water discharge at <br />Henderson may indicate induced infiltration of surface <br />water by gravel-mine dewatering operations on the <br />west side of the river. <br /> <br />14 Quontity ond Quollty of Ground-Wotor Dlschorgo to tho South Plotts Rlvor, Donvor to Fort Lupton, Colorodo, <br />August 1992 Through July 1993 <br />