Enter the thickness, hydraulic conductivity, and the recharge into the calculator to determine the radius of influence.

Radius of Influence Formula

The following formula is used to calculate a radius of influence.

RoI = b*SQRT(K/(2*N))

  • Where RoI is the radius of influence
  • b is the thickness (m)
  • K is the hydraulic conductivity (m/s)
  • N is the recharge (m/yr)

To calculate the radius of influence, multiply the thickness by the square root of the hydraulic conductivity divided by 2 times the recharge rate.

What is radius of influence?


A radius of influence is defined as the maximum distance at which drawdowns can be detected with usual measures.

How to calculate radius of influence?

Example Problem:

The following example outlines how to calculate a radius of influence.

First, determine the thickness. For this example, the thickness is 100m.

Next, determine the hydraulic conductivity. In this problem, the hydraulic conductivity is .000005 (m/s)

Next, determine the recharge rate. In this case, this is measured to be .00000002378 m/s.

Finally, calculate the radius of influence using the formula above;

RoI = b*SQRT(K/(2*N))

RoI = 100*SQRT(.000005/(2*.00000002378))

RoI = 1025.33 m