English Abstract This report describes the program FLOP3N, the
mathematical background, the implementation and guidelines for running the
program together with some results. FLOP3N is a particle tracking program
for a system of homogeneous anisotropic layers, in which partially
penetrating wells are active. Besides the wells, the user can specify a
natural groundwater flow. The program calculates pathlines and travel times
of water particles under steady state flow conditions, and so, the capture
zones around groundwater abstraction sites. The calculations are based on
an exact analytical solution for the corresponding three-dimensional
problem. FLOP3N is specifically useful for all those cases where more
simple approximations are not valid, because the standard assumptions that
the vertical gradient is small or that the filters of the wells extend over
the full height of the aquifer, are not applicable. Normally, for such
cases one has to take one's resort e.g. to the class of finite-element
methods, which are very demanding in general with respect to the input and
are also time-consuming.
