Work out groundwater flow (darcy) instantly with clear inputs, formula shown and shareable results.
Darcy's law makes groundwater discharge proportional to hydraulic conductivity, gradient and area: Q = KiA. A 3.5 m head drop over 250 m gives a gradient of 0.014, so with K = 2e-4 m/s across 400 m2 the flow is 1.12e-3 m3/s, about 97 m3 a day. The Darcy velocity is a flux, not the actual pore water speed.
Darcy's law
Q = K x i x A, with i = head difference / path length
Darcy velocity
v = K x i
Because water only moves through the pores. Dividing by porosity gives the higher seepage velocity that a tracer would actually show.
Gravel 1e-2 to 1 m/s, sand 1e-5 to 1e-2, silt 1e-8 to 1e-5, and clay below 1e-9 m/s.