This Demonstration represents the response (in terms of the well function ) of a confined aquifer subject to pumpage from a fully penetrating well. If there is no leakage from an adjacent hydrogeologic unit to the main aquifer, the response is the red curve, widely known as the Theis-type solution. When an adjacent aquifer is hydraulically connected to the main unit, the latter becomes a leaky confined aquifer, leading under this condition to the cyan curve, known as a Hantush–Jacob-type solution. The well function has a single argument for the Theis (or nonleaky) case named , whereas for the Hantush (or leaky) case, there are two arguments, and . Notice how the Hantush–Jacob solution deviates from the Theis curve as the ratio increases.