Fig. 20.4 shows an equivalent hydraulic system in an aquifer of infinite areal extend. For the equivalent hydraulic system, the time drawdown relationship for the pumping well and also for the imagery recharge well can be obtained separately. The actual drawdown can be obtained using the principle of superposition.

• Fig. 21.4 Equivalent hydraulic system in a aquifer of infinite areal extend

Consider the Fig. 21.5 below. The pumping well is at a distance of x from the stream boundary. In order to calculate the actual drawdown at the observation location, an image well is

• 
• Fig. 21.5 Pumping well, Observation well and Image well