Niektóre nieprawidłowości w obliczeniach czasu przesączania wody podziemnej przez pakiet warstw w strefie saturacji

Legal permits concerning water usage often contain improperly calculated time of vertical seepage through a pack of homogeneous layers in the saturated zone.. Usually the following mistakes against the rules of hydraulics are made: (1) it is assumed that hydraulic gradient in each layer of the package is equal to the gradient corresponding to the package as a whole; (2)the formula used is wrong because it is based on inadequate assumption, (3) the formula is right but is not used in correct way, (4) time duration of flow through the layer of high permeability is neglected, (5) too high value of the active porosity is assumed. An example is shown comparing the incorrect calculations with the ones consistent with the hydraulics laws. Some of the above mistakes result in significant underestimation of the seepage time (up to 60 % in the example used), some others overestimate the time, hence they affect the correctness of implementation of Polish Water Law concerning protection zones of water intakes and lead to improper administrative decisions.