WSP08349

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 12/6/1995
• Author: USGS
• Title: Quantity and Quality of Ground-Water Discharge to the South Platte River - Denver to Ft Lupton - Colorado - August 1992 through July 1993
• Water Supply Pro - Doc Type: Report/Study

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Figure 9. Concentrations of dissolved nitrite plus nitrate in water from wells at McKay Road, Henderson, and Road 8.

Small-Area Flow System

Values of pH in water from the piezometers
screened I It below the sediment/water interface
ranged from 6.71 to 8.64, with a median value of
7.33 (fig. 12 and table 9). As with values of pH in
ground water from the monitoring wells, values of
pH in ground water from the small-area flow system
generally were lower than values in the river (fig. 12).
Measurements of pH indicate that values of pH at
depths ofless than 84 in. below the sediment/water
interface were less than values in the surface water
(table 10 and fig. 13). These data indicate that water
discharging from the small-area flow system had the
potential to lower pH values in the river.

Concentrations of DO in water from the piezom-
eters ranged from less than 0.1 to 1.7 mg/L, with a
median value of 0.2 mg/L (fig. 14 and table 9). The
median concentration of DO in ground water from
below the sediment/water interface varied in different
reaches of the river from between 0.2 and 0.3 mg/L;
however, the median concentration in each reach was
substantially lower than the median DO concentration
(2.5 mg/L) in ground water from the lA/IB wells at
Henderson and Road 8. DO concentrations in ground
water from the INIB wells at Henderson and Road 8
are considered to be representative of the DO concen-
trations in the large-area flow system in the agricultural
area. Concentrations of DO in ground water from the
small-area flow system were substantially lower than

QUALITY OF GROUND-WATER DISCHARGE 23