For two-dimensional groundwater flow in an isotropic confined aquifer, it has been shown elsewhere that two independent steady state sets of data, i.e., piezometric heads and source terms corresponding to different steady state flow conditions, and the value of transmissivity at one point suffice to determine transmissivity uniquely in a connected domain. The data are independent if the hydraulic gradients are not parallel anywhere over the domain. Here transmissivity is numerically determined by integration of suitably approximated functions of the data along polygonal lines connecting the nodes of a lattice; integration stars from the node where transmissivity is given. The choice of the integration path is based on the results of the stability analysis and allows us to minimize the effects of the approximations on the data. Since the approximated solution is computed along internode segments, the internode transmissivities are immediately calculated without introducing arbitrary averages of the node transmissivities. The internode transmissivities are the quantities necessary to set up a management model within a conservative finite differences scheme. The applicability of this technique to real cases is tested with two synthetic examples. The first one was set up by ourselves, whereas the second one has been taken from the literature. The internode transmissivities identified with our procedure are compared with the synthetic reference ones. The ultimate check is performed of evaluating new head fields on the basis of the identified and reference internode transmissivities. The fit is good. The relative error for the identified internode transmissivities is very low when error-free data are used, and it varies by an amount approximately constant over the entire aquifer when an error on the initial value of transmissivity is introduced. The errors on the piezometric heads bear more relevance, but nonetheless, the affected results are still good. ¿ American Geophysical Union 1995