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 two times the recharge rate.

What is radius of influence?

Definition:

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

FAQ

What factors can affect the hydraulic conductivity in a radius of influence calculation?

Hydraulic conductivity can be influenced by several factors including the porosity and permeability of the soil or rock, the presence of fractures or voids, the saturation level of the material, and the temperature and viscosity of the fluid. Changes in any of these factors can lead to variations in hydraulic conductivity, thereby affecting the calculation of the radius of influence.

How does the thickness of the aquifer layer impact the radius of influence?

The thickness of the aquifer layer directly impacts the radius of influence as it is a multiplier in the formula. A thicker aquifer can potentially extend the radius of influence since it allows for a greater volume of water to be stored and transmitted, assuming other factors such as hydraulic conductivity and recharge rate remain constant.

Can the radius of influence change over time?

Yes, the radius of influence can change over time due to variations in recharge rates, changes in hydraulic conductivity due to sediment deposition or erosion, alterations in groundwater extraction rates, or shifts in the hydrological characteristics of the area. Monitoring and recalculating the radius of influence periodically can help in understanding and managing the effects of these changes.