How to use the well drawdown calculator
Estimate how far the water level drops around a pumping well in a confined aquifer. Enter pumping rate, transmissivity, radius of influence, distance from well in the fields above; the drawdown at distance r are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “well drawdown”, “Thiem equation”, “pumping well water level drop”, “calculate well drawdown”, “find drawdown at distance r”.
Formula
Variables
- Q — Pumping rate (m³/s)
- T — Transmissivity (m²/s)
- R — Radius of influence (m)
- r — Distance from well (m)
Worked example
With pumping rate = 0.01 m³/s, transmissivity = 0.001 m²/s, radius of influence = 300 m, distance from well = 0.1 m, the calculator gives drawdown at distance r ≈ 12.74253 m; drawdown at distance r ≈ 41.8062 ft.
Frequently asked questions
What is the well drawdown calculator used for?
Estimate how far the water level drops around a pumping well in a confined aquifer. It helps with questions such as “well drawdown”, “Thiem equation”, “pumping well water level drop”.
What is the formula for the well drawdown calculation?
Drawdown at distance r (m) = Q / (2 × π × T) × ln(R / r). Drawdown at distance r (ft) = [Drawdown at distance r] × 3.28084. Here Q is pumping rate (m³/s), T is transmissivity (m²/s), R is radius of influence (m), r is distance from well (m).
What inputs do I need for the well drawdown (thiem equation) calculator?
You need pumping rate in m³/s, transmissivity in m²/s, radius of influence in m, distance from well in m. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the well drawdown calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the well drawdown result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.