2009-05-19_REVISION - M1977416 ‎(29)‎

• Permit No: M1977416
• IBM Index Class Name: REVISION
• Doc Date: 5/19/2009
• Doc Name: EPP‎(AM-01)‎ Att 4: Bioavailability; Att 5: Water Bal; Att 6: Percolation; Att 7: Lab Rpts. ‎(part 4)‎
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM1
• Email Name: RCO
• Media Type: D
• Archive: No

J
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Job #: 68838.64986.03.3.14 Calc By: N. Anton; M. Nelson
Client: Denison Mines CHK By: G. Hazen Date: 1/27/2009
Project: Hydrogeology Report Date: 2/3/2009 Calc #: 1
Detail: Water Balance Estimation of Percolation
PETcalculation results for all months according to a water year is shown below in Table A:
8560. The
water balance calculation was completed using precipitation data for two cases: 1) using the
average monthly precipitation for the period of record (1962 through 2007); and 2) the total
monthly precipitation for the wettest water year on record (1997).
AA Runoff Calculation
Runoff was assumed to be 10 percent of the precipitation (Guyman 1994).
B. Water Balance Model Calculations
For the purposes of performing the water balance calculation, Equation 2 can be simplified
further. The water balance is started for the first month of the water year (October), where
percolation (Po) is assumed to be zero. Equation 2 then simplifies to the following:
Sm = Pi- R.- ET Equation 3
In addition, ET is replaced by the actual amount of evapotranspiration that takes place every
month, or AET, and the relationship of Pi - R. is replaced by a new term called infiltration (10). to
is the amount of moisture from precipitation that infiltrates into the soil. Equation 3 then
simplifies to the following:
Sm= Io- AET Equation 4
Since AET is defined as the actual amount of evapotranspiration that occurs, its value is
dependent on the actual amount of available moisture in the soil column for each month to
evaporate. For any given month, the actual amount of available moisture (MA) is represented as
the sum of infiltration for the current month and storage from the previous month (where "1"
represents current month and "0" represents previous month):
MAl = Iol + Smo Equation 5
Calculation of MA represents a metric to determine if moisture will be stored in the soil or lost
from the soil by evaporation. If the MA is greater than the PET (maximum amount that can
evaporate), then AET actually equals PET. The current monthly Sm is then calculated according
to Equation 4, and the total accumulated Sm is the summation of the current monthly Sm and the
MathCAD V14
N:\64986-Denison Mines\Task Order 3 - DMO
Tabl e A - PET Calculat ions
Va
r. Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Ph 7.75 6.72 .52
6 .76
6 6.72 8.33 8
.95 10
.02 10
.08 10.22 9.54 8.39
Tf 54.23 40.73 30.61 28.97 36.09 43.94 51.66 61.55 70.93 77.50 75.24 66.00
F 4.20 2.74 2.00 1.96 2.42 3.66 4.62 6.17 7.15 7.92 7.18 .54
5
PET 3.36 2.19 1.60 1.57 1.94 2.93 3.70 4.93 5.72 6.34 5 .74 4.43
PETS 3.36 2.19 0.48 0.47 1.94 2.93 3.70 4.93 5.72 6.34 5.74 4.43
ations
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Saved 2/17/20095:15 PM
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