How to Calculate Dilution Attenuation Factor

The dilution attenuation factor, or DAF, measures how the concentration of soil water contaminants drops when they reach the water table. To calculate it, you need a number of data points concerning the area's water flow.

Things You'll Need

• Scientific calculator or computer

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Instructions

• 1

  Multiply the aquifer's thickness, in meters, by the gradient, in meters/meters. If the thickness is 10.7 m and the gradient is 0.00015 m/m:

  10.7 * 0.00015 = 0.0016

• 2

  Multiply your answer by aquifer hydraulic conductivity, or the rate at which water moves through the soil, in meters per year. If hydraulic conductivity is 391:

  0.0016 * 391 = 0.626

• 3

  Multiply the infiltration rate in meters per year by the length of area parallel to ground flow, in meters. For instance, if the infiltration rate is 0.3 meters per year and the length of area is 30 m:

  0.3 * 30 = 0.9

• 4

  Multiply your answer by -1.

  0.0351 * -1 = -0.9

• 5

  Divide the answer to Step 4 by the answer to Step 2.

  -0.9 / 0.626 = -1.43769968

• 6

  Find the exponent of your answer.

  exp(-1.43769968) = 0.237473396

• 7

  Subtract your answer from 1.

  1 - 0.237473396 = 0.76253

• 8

  Multiply your answer by the aquifer thickness.

  0.76253 * 10.7 = 8.159

• 9

  Square the length of area parallel to ground flow.

  30 * 30 = 900

• 10

  Multiply your answer by 0.0112

  900 * 0.0112 = 10.08

• 11

  Find the square root of your answer.

  Sqr(10.08) = 3.174

• 12

  Multiply answers of step 11 and step 8

  3.174 * 8.159 = 25.897

• 13

  Multiply your answer by the gradient, in m / m.

  25.897 * 0.00015 = 0.00388455

• 14

  Multiply your answer by aquifer hydraulic conductivity in meters per year:

  0.00388455 * 391 = 1.51886

• 15

  Divide your answer by the answer to Step 3.

  1.51886 / 0.9 = 1.68762

• 16

  Add 1 to your answer.

  1.68762 + 1 = 2.68762

  This is the dilution attenuation factor.