hydrograph

n. [ Hydro-, 1 + -graphy: cf. F. hydrographie. ] 1. The art of measuring and describing the sea, lakes, rivers, and other waters, with their phenomena. [ 1913 Webster ]

2. That branch of surveying which embraces the determination of the contour of the bottom of a harbor or other sheet of water, the depth of soundings, the position of channels and shoals, with the construction of charts exhibiting these particulars. [ 1913 Webster ]