8.3.3 Group wells
No simple and reliable equations to compute the total quantity of water to be pumped for the multiple wells in the nonequilibrium state or in confined aquifers are available so far.
Pumping with multiple wells at the same time will encounter problems of intervention.Figure 8.15（a）diagrams the multiple wells in a free aquifer.Assuming only well＃1 is used in pumping，in the equilibrium state，the required quantity of water to be pumped for well＃1 can be computed according to Eq.8.20：
Figure 8.15 Group wells
Similarly，if well＃2 is used exclusively，the required quantity of water to be pumped can also be computed using the same equation.Assuming there exist n wells，pumping can also be computed using the same equation.Assuming there exist n wells，pumping would be（Forchheimer，1930）
where
Qtot＝total quantity of water to be pumped；
n＝number of wells；
h＝groundwater level at point P；
r1，r2，…，rn＝distances from well＃1，＃2，…to point P.
When the group is arranged in a circle［see Figure 8.15（b）］，the above equation can be simplified.The total quantity of water to be pumped at the center P is
However，no simple and reliable equations to compute the total quantity of water to be pumped for the multiple wells in the nonequilibrium state or in confined aquifers are available so far.