Dewatering Pump Calculator

Because Water Head — the driving force behind seepage — is Excavation Depth minus Water Table Depth, clamped so it can't go negative. If the excavation floor stays above the water table, there's no head to push groundwater in, so Seepage Inflow and every output that depends on it come back as zero.

No — Discharge Distance has no effect on Seepage Inflow or Required Pump Capacity at all; those are set entirely by the excavation geometry, soil permeability, and water table depth. Discharge Distance only affects Pump Horsepower, through the added friction loss of pushing water through more pipe.

Depth has the more direct effect, since it sets the water head that drives inflow in a straight line — though not in exact proportion, since Water Head is Excavation Depth minus Water Table Depth, so it's offset rather than purely scaling with Depth (at the default 4-ft water table, going from 10 ft to 20 ft of depth moves head from 6 ft to 16 ft, a roughly 2.7x change, not exactly double). Area affects inflow too, but only through an assumed seepage perimeter that scales with the square root of area, so doubling the area moves the perimeter — and inflow — by far less than doubling the depth moves the head.

It's a simplified single-well Dupuit-style approximation meant for preliminary sizing, not a substitute for a geotechnical dewatering study. It doesn't account for soil layering, recharge from nearby water bodies, or interference from adjacent excavations — all of which can meaningfully change real-world pumping requirements.