Dames & Moore, 1999 - USDA Forest Service

streamflow measurement, the absolute magnitude of the inflow components cannot be evaluated from the
water balance results. The conclusions presented herein were developed based on field measurements
with inherent variability. The variability in field measurements result in a potential error in water balance
values, depending on the methods utilized to analyze the data. Potential error is assumed randomly
distributed about the mean such that mean values can be compared directly. The accuracy of the water
balance inputs, therefore, is subject to the assumptions made in the analysis and the observations made in
the field. Given these constraints, the water balance analysis generally indicates that there are no
significant missing inflow components. This conclusion is supported by the chemical loading analysis
presented in Section 6 and, therefore, provides substantiation of the above conclusion as well as the
general magnitude of the estimated inflows to Railroad Creek.
Reacb 1 - RC-1 to RC-4 (Table 4.4-9, and Figures 4.4-20 and 4.421)
The water balance results for Reach 1 generally indicates that too much water has been accounted for,
although the error relative to the flow at RC-4 is low, ranging less than -1 to -2 percent for the spring
water balance and 0.3 percent to -1.7 percent for the fall (Table 4.4-9). The water balance equation for
Reach 1 is expressed as:
where:
where:
Qrc4=Qrc1 +Qa+Qb+Qsr (Reference ~~uation 4- 13)
Qrc4 = 460 cfs (spring) 125 cfs (fall)
Qrcl = 460 to 465 cfs (spring) 125 to 126 cfs (fall
Qa = ' 1.5
to 0 3 cfs (spring) 0.5 to -0.5 cfs (fall)
Qb= 1.3,cfs(spring) 0.15 cfs (fall)
Qor = 2.3 cfs (spring) .0.02 cfs (fall)
Qr = Qrc4 - (Qrcl + Qa + Qb + Qsr) (4- 1 5)
Qr = -4.1 to - 10.1 cfs (spring) 0.3 to - 1.7 cfs (fall)
The inflow estimates for this reach are within the measurement error for streamflow and the estimates
appear to be biased toward too much inflow. Thus, it is likely that inflow components large enough to
impact the water balance have not been overlooked. Additionally, the water balance components as
estimated can adequately account for chemical inputs observed within Railroad Creek (see Section 6.0).
The water balance results also show that direct seep flow, measured as surface flow, is only a small
component of baseflow inputs from the alluvial aquifer. The contribution of water flow from the bedrock
aquifer (Qb) as measured'at the 1500-level main portal drainage station P-1 (Qpl) was estimated to be
relatively low for the MayIJune time period (0.3%) and negligible for the September time period. Flow
from the portal drainage, even considering losses from the drainage as it flows from P-1 to P-5, is
sufficient to account for inflow from the bedrock aquifer during both periods. Recharge to the alluvial
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17693-00S-019Uuly 19. 1999;4:51 PM;DRAFT FINAL RI REPORT