ISKRIT / Site investigation & geotechnics / Permeability from a pumping test
Site investigation & geotechnics
Permeability coefficient from a pumping test
Enter the well discharge, the drawdown and the aquifer geometry, and get the coefficient of permeability by the Dupuit steady-state formulas for a fully penetrating well. Unconfined and confined aquifers are two different formulas, so the tool asks which one you tested and the aquifer thickness term is not mixed up. The result comes out in metres per day.
Data current as of 2026-09-26
Standards
Dupuit steady-state formulas for a fully penetrating well: unconfined kf = Q·ln(R/r)/(π·(H² − h²)), where h = H − s; confined kf = Q·ln(R/r)/(2π·m·s). The well is assumed fully penetrating and the flow steady.
Input
Aquifer type, discharge Q in cubic metres per day, drawdown s, radius of influence R, well radius r, and the thickness: H of the unconfined aquifer or m of the confined one.
Output
Coefficient of permeability kf in metres per day and the logarithmic term ln(R/r) of the formula applied.
What it does
- Both aquifer types by the Dupuit formulas
- Result and the values substituted into the formula on screen
- Load field tests from Excel, export the schedule to XLSX
- Calculations are stored on the server and reopen next time, company letterhead with signatures
Price
Free in full, no sign-up and no payment.
Open the calculator →Questions
Does this cover falling head and constant head laboratory tests?
No. This works up a field pumping test from a well. A falling head or constant head permeameter test on a specimen is a laboratory procedure with its own formula and it is not covered here.
Which formula is used for an unconfined aquifer?
The Dupuit formula kf = Q·ln(R/r)/(π·(H² − h²)), where H is the initial saturated thickness and h = H − s is the thickness at the well after the drawdown. The confined case uses kf = Q·ln(R/r)/(2π·m·s) with m the thickness of the confined aquifer.
Where does the radius of influence come from?
It is your input. It is taken from observation wells around the pumped well, or estimated by an empirical relation such as the Sichardt formula. The result is only weakly sensitive to it, because it enters as a logarithm.
What are the assumptions?
Steady-state flow, a fully penetrating well, a homogeneous aquifer of constant thickness, and horizontal flow. A partially penetrating well or an unsteady test needs a different work-up.