2010-12-17_REVISION - C1981019 ‎(140)‎

• Permit No: C1981019
• IBM Index Class Name: REVISION
• Doc Date: 12/17/2010
• Doc Name: Exhibit 7 Item 22 Collom Pit Regional Hydrogeologic Model
• Type & Sequence: PR3
• Email Name: JRS
• Media Type: D
• Archive: No

Model calibration DRAFT 19
*A-
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The steady-state calibration also considered Collom area water balance estimates. The
average recharge rate to the groundwater system for the entire model area was
0.53 inches per year based on model calibration. This average recharge rate falls within
the range of recharge rates of 0.17 to 0.72 inches per year from the water balance
described in Section 2.4 for the major stream valley water sheds. Model areas with
ground elevation above 7500 ft receive between 0.53 and 1.1 inches of recharge per
year with the higher rate applied to bedrock outcrop areas for the units above the KM
bed, and the lower rate applied to the units below the KM to the Trout Creek Sandstone
(Figure 3.11). Based on model calibration, 0.11 inches of recharge per year were
applied to the model area below elevation 7500 ft.
In the steady-state numerical model, recharge to and discharge from the model area are
equivalent. As described above, recharge to the model is from infiltration of
precipitation, estimated to be 0.53 inches per year over the entire model area based on
calibration. Discharge from the model occurs as stream base flow and valley fill
groundwater outflow along the major drainages. Since ET is not specifically included in
the model, the total discharge calculated by the model also includes water that is
estimated as ET losses in the Collom area water balance. Table 4.1 provides a
comparison of estimated recharge/discharge amounts from both the Collom area water
balance and the regional model. The table indicates that he overall water balance in the
numerical model is a good match to the Collom area water balance.
Table 4.1 Groundwater recharge/discharge summary from water balance
and regional model
Drainage Collom area water Collom area water Numerical model
balance estimated balance estimated predicted
•
recharge/discharge recharge/discharge recharge/discharge
- (ft3ld) (gpm) (gpm)
Morgan / Straight Gulch 118,790 617 616
Collom Gulch 25,886 134 134
Jubb Creek 14,764 77 62
Wilson Creek 76,956 400 377
Taylor Creek 8,259 62 44
Good Spring Creek 186,986 971 938
Milk Creek --- --- 524
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