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Dewatering Well Yield Calculator (Dupuit-Forchheimer)

Estimate the steady-state pumping rate a dewatering well can sustain in an unconfined aquifer, using the Dupuit-Forchheimer equation.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax
328 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Estimated well yield

2.76 L/s

Check your inputs

This is a steady-state estimate assuming a fully penetrating well in a homogeneous, isotropic unconfined aquifer — real dewatering systems are affected by partial penetration, aquifer boundaries, and non-steady flow, and should be verified with an actual pump test.

Equivalent in m³/day
238.3 m³/day
Equivalent in US gallons per minute
43.72 gpm

Running these inputs gives 2.76 L/s as the estimated well yield. Note that hydraulic conductivity (k, m/s) and outer radius (r1) sit at the edge of the range this calculator was checked against, so treat the output as indicative rather than settled. Expect some drift against the real job; the calculation is solid but conditions on site are not. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Add the equipment this sizes

This result is a specification — 2.758 L/s — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Dupuit-Forchheimer equation for steady radial flow to a well in an unconfined aquifer: Q = pi x K x (h1² − h2²) / ln(r1/r2)

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Frequently asked questions

What is the Dupuit-Forchheimer equation used for?
It's a classic well hydraulics formula for estimating steady-state groundwater flow to a pumping well in an unconfined aquifer, widely used for early dewatering and water supply well planning.
Why does the answer depend on ln(r1/r2) rather than a simple ratio?
Radial groundwater flow toward a well isn't uniform — flow lines converge, and the logarithmic term correctly captures how the hydraulic gradient increases as flow approaches the well, a signature feature of radial flow problems.
How accurate is this compared to real dewatering performance?
It's a reasonable planning-level estimate for a single well in ideal conditions — real systems (especially well fields with multiple wells) benefit from an actual pump test and, for complex sites, numerical groundwater modeling.