The map application displays hydrogeological maps that were processed during the solution of various types of projects in the CGS. The extent of hydrogeological units is derived from the geological map on a scale of 1: 50,000 and the HydroGEOČR50 layer, which was created within the R&D project of the Ministry of the Environment of the Czech Republic SP/2e1/153/07. Within the individual regions, the values of the transmissivity of the hydrogeological units, the type of the hydrogeological environment and the sequence of collectors and aquicludes in the Czech Cretaceous basin are shown in the hydrogeological maps. Data on the chemical composition of groundwater and hydraulic properties of rocks are presented for selected archival wells. Descriptions, results of field measurements and photo documentation are available for individual hydrogeological objects documented in the field (eg springs).