Water Resources and Environmental Engineering

Drawdown

The lowering of the water table or piezometric surface around a pumping well.

Pumping a well lowers the hydraulic head around it in a cone of depression; the drawdown at any distance is how far the head has fallen from its original level. It is largest at the well and dies away with distance, roughly with the logarithm of the radius.

At steady state the Thiem equation relates the pumping rate to the heads at two observation wells. In an unconfined aquifer the heads enter squared, πK(h₂² − h₁²)/ln(r₂/r₁); in a confined aquifer the aquifer thickness multiplies the head difference instead, 2πKb(h₂ − h₁)/ln(r₂/r₁).

How much of the FE Civil exam is Water Resources and Environmental Engineering?