This code implements the Clarke model for the evaluation of the discharge at the output cross section of a river basin. The advantage to have a GIS based tool is given by the possibilit to represent each variable as spatially distributed (as it is). This allows to obtain more precise measures than the ones obtained by qualitative or syntetic estimation of spatial dipersion of parameters. A paper (in Italian language) accompanying the code is published at the following link: https://doi.org/10.5281/zenodo.3234835