•                        
• a) Drawdown of first well                                       (b) Drawdown of second well

                                          

•                   (c) Combine drawdown
•                   Fig. 21.2 Cone of depression of multiple wells system

Wells near aquifer boundaries

The assumption of infinite horizontal extend is no longer valid when water is pumped from a well near the aquifer boundary. Method of superposition can be used to implement the effect of aquifer boundary by adding a well at different location. The well that creates the same effect as boundary is called image well.

Well near a stream

Fig. 21.3 shows a well near a stream. In this case, the actual drawdown at the stream boundary will be zero as stream is considered as an infinite source. In order to maintain zero drawdown, an imaginary recharge well is considered at a distance equal to the distance between the pumping well and the stream boundary.

• Fig. 21.3 Well near a stream