Fig. 1

Lake Lucerne at the northern margin of the Alps in Central Switzerland, with main rivers, neighbouring lakes and tectonic units. A rough bathymetry of the lake is given by contour lines (20 m interval, swisstopo DTM 25); the deepest points of the 7 main basins are marked with capital letters, and sills of presumed glacial origin are numbered I to IV. Areas with available high-resolution bathymetry data are shaded, with grey lines showing the individual survey lines for swath bathymetry. Inset Location of other figures. Shaded onshore relief swisstopo DTM25