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The aquifer's hydraulic conductivity.
From a pump test or published typical soil values.
The undisturbed saturated aquifer thickness far from the well.
Measured at the radius of influence, where drawdown is negligible.
The remaining saturated thickness right at the pumping well, after drawdown.
Must be less than h1 — the difference reflects the target drawdown at the well.
The radius at which h1 is measured (often the radius of influence).
See the Wellpoint Dewatering Radius of Influence Calculator.
The radius of the pumping well itself.
The well, not the borehole — though the effective radius is closer to the outside of the filter pack than to the screen, because the pack is permeable and behaves as part of the well. Yield depends on this only logarithmically, which is the practical point: doubling a well's radius buys very little extra flow, so where more water is needed the answer is more wells rather than bigger ones.
Estimated well yield
44.7 gal/min
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
- 243.51 m³/day
- Equivalent in US gallons per minute
- 44.67 gpm
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Dewatering Well Yield Calculator (Dupuit-Forchheimer): 44.67 gal/min — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Dupuit-Forchheimer equation for steady radial flow to a well in an unconfined aquifer: Q = pi x K x (h1² − h2²) / ln(r1/r2)
Inputs used
- Hydraulic Conductivity (K, m/s)
- 0
- Saturated Thickness at Outer Radius (h1)
- 33 ft
- Saturated Thickness at the Well (h2)
- 23 ft
- Outer Radius (r1)
- 165 ft
- Well Radius (r2)
- 6 in
Intermediate steps
- Equivalent in m³/day
- 243.51 m³/day
- Equivalent in US gallons per minute
- 44.67 gpm
Confidence note: 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.
What this calculation does not cover
- The equation covers one fully penetrating well pumping on its own. It does not add the drawdown cones of neighbouring wells or wellpoints, so it cannot tell you how many wells an excavation needs or how far apart to set them — in a ring or a line each well delivers less than this figure.
- Steady state only, in a homogeneous, isotropic, unconfined aquifer. There is no time in the arithmetic, so the higher rate while the cone is still developing and the total volume pumped over the job both sit outside it, as do partial penetration, layered or anisotropic ground, confined and leaky aquifers, and any recharge or no-flow boundary such as a river, a cut-off wall or bedrock.
- This is a planning-level flow estimate, not a dewatering design and not a pump specification. Screen entrance velocity, filter pack capacity, drawdown available to the pump, suction lift limits, friction losses in the header and discharge run, and standby capacity are all separate calculations, and the yield itself should be confirmed by a pump test before plant is ordered.
- Nothing here covers the consequences of lowering the water table: settlement of shallow-founded structures and services inside the drawdown cone, migration of fines and piping into the well, or the discharge consent and abstraction licensing the pumped water needs. Where drawdown reaches a neighbour's property, an abstraction, or compressible ground, that is a geotechnical engineer's assessment, not a page of arithmetic.
- Yield is directly proportional to the hydraulic conductivity you type, and K in natural ground varies by orders of magnitude over short distances and directions. The result carries no uncertainty band around that, and the K box is read as metres per second whichever measurement system the page is set to.
Add the equipment this sizes
This result is a specification — 44.7 gal/min — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- 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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