In 2010-2012, scientists of Riga Technical University (RTU) have developed the hydrogeological model (HM) of Latvia (LAMO). LAMO represents the active groundwater zone of Latvia, as the source for providing drinking water. LAMO covers the area of 475km300km and includes 27 geological layers; the plane approximation step is 500 meters. In 2013, the first practically important results have been provided by LAMO. The set of hydrogeological maps has been prepared to update the current water management plans for Latvia. For aquifers, maps of groundwater head and infiltration flow distributions have been prepared. Numerous maps for geological profiles have been obtained, because they are the most informative ones. To obtain correct maps for the profiles, it was necessary to develop a new interpolation method accounting for different comportment of the isolines within aquifers and aquitards of LAMO. Customary methods of making the isoline distributions for profiles result in wrong designs due to ignorance of this unlikeness. Theory of the proposed interpolation method is considered and results of its practical appliance are reviewed.