A pumping test pumps a well at a controlled rate while water levels are recorded, to find aquifer properties and how much the well can yield.
A pumping test, or aquifer test, measures how an aquifer and a well respond to controlled pumping. Water levels are recorded in the pumped well and, ideally, in one or more observation wells at known distances. There are three common stages. A step-drawdown test raises the pumping rate in stages to show well performance and well losses. A constant-rate test runs at a steady rate, often for 24 to 72 hours, to measure aquifer properties. A recovery test records the rise in water level after the pump stops. The results are analysed with models chosen to suit the aquifer: Theis or Cooper-Jacob for confined aquifers, Hantush for leaky aquifers and Neuman for unconfined aquifers. The Cooper-Jacob form gives transmissivity from Δs, the drawdown per log cycle of time. Good practice includes measuring levels before the test to catch existing trends, keeping the rate steady, recording levels often in the early minutes and piping the discharge far enough away that it cannot return to the aquifer. Nearby pumping, rainfall and boundaries such as rivers can all distort the curve, so they should be noted.