An analysis was made of cartographic works appearing from the mid-18th to the 19th centuries with inland waters of Poland as the principal element of their content. Maps of inland waters and general-purpose maps were discussed, including the scale criterion and cartometric reliability, as basic cartographic sources presenting and interpreting hydrographic elements. The problem of the use of cartographic material which is not fully cartometric in a spatial reconstruction of river systems was presented on the example of the lower Warta River near its junction with the Oder River in the Kostrzyn area. Two manuscript maps from the 18th century (1773 and 1786) were analysed to compare their ways of presenting basic elements of a river system and to assess their reliability when reconstructing the directions and scope of change in water conditions resulting from the human impact. Additionally, the content of the two maps was compared with the picture of the lower Warta reaches as presented on a map from 1928, which is a fully cartometric material. It was decided that manuscript maps, prepared before the times of field measurements, based on triangulation were a rich source of information about the state and degree of transformation of inland waters; however, their varying cartometric reliability and ways of presentation of the hydrographic content limit their usefulness in spatial analyses. Materials concerning water conditions that can be regarded as fully cartometric are only topographic maps constructed after triangulation had been introduced in the 19th century. In order to attempt a detailed reconstruction of water conditions in a given area, it is necessary to take into consideration not only cartographic works, but also historical source materials and the results of archeological and geological studies.