hydrological map

hydrological map, chart showing such hydrologic features as rivers and streams; the purpose and content of these maps vary according to the country of their origin. Some maps are used as supplements to a detailed written text, whereas others, such as the USGS Hydrologic Investigations Atlases series, provide only a brief and general discussion as the text. Since hydrology embraces the many subsystems relating to water, the maps may be constructed for each individually or may combine the features of more than one subsystem.