This research is a part of the Project of the European Regional Development Fund and the Riga Technical University entitled “Creating of hydrogeological model of Latvia to be used for management of groundwater resources and for evaluation of their recovery measures”. The regional hydrogeological model (HM) for Latvia will be created. Important task is data preparation for the hydrographical network (HN) that will be incorporated into the ground surface relief. The relief will be used as the boundary condition in HM. In this article, problems and their solutions are described for getting and exporting ESRI shapefile data into the GDI BLN format. The ESRI shapefile is a format, which stores geometries and attributes in separate binary files. The program ESRI ArcGIS is the main software for working with data of this format. The GDI BLN format is the Golden Software BLN format extended version for obtaining X, Y and Z data for isolines, elevation marks, lakes and rivers that are needed for making of HN.