A measurement of how a particular water level is affected by the withdrawal of groundwater. It is made by establishing the vertical distance at a given point between the original water level and the pumping water level. The water table of an unconfined aquifer or the potentiometric surface of a confined aquifer is lowered when a well is pumped, and an inverted cone of depressions develops around the pumping well.

Changes of drawdown at different distances from the well are shown with a drawdown curve. Specific capacity is the rate of discharge of water from the well divided by the drawdown within the well. The drawdown within a well divided by the discharge rate of water from the well—inverse of specific capacity—is called specific drawdown.