fluvial vs freshwater

fluvial

adj
  • Of, pertaining to, inhabiting, or produced by the action of a river or stream. 

freshwater

adj
  • Consisting of fresh water. 

  • neoclassical, in reference to U.S. macroeconomics and economics departments near the Great Lakes. 

  • Unskilled as a seaman. 

  • Living in fresh water. 

noun
  • A body of fresh water 

How often have the words fluvial and freshwater occurred in a corpus of books? (source: Google Ngram Viewer )