The influential radius is a controversial conception. For different aquifer conditions and concept models
there are distinct methods to calculate the influential radius. The empirical formulas
which lack of strict theoretical basis
are more popular in practice. The routine method to ascertain the influential radius in leaky confined aquifer is stretching the s-log(r) line through three or more observation holes in steady flow to find the zero-drawdown distance. The method may bring misunderstanding to engineers; the misreading has been pointed out and the routine method has been revised.