canal vs catchment area

canal

noun
  • An artificial waterway or artificially improved river used for travel, shipping, or irrigation. 

  • A tubular channel within the body. 

  • One of the faint, hazy markings resembling straight lines on early telescopic images of the surface of Mars. 

verb
  • To dig an artificial waterway in or to (a place), especially for drainage 

  • To travel along a canal by boat 

catchment area

noun
  • An area from which water drains into a particular lake, river, etc.; the catchment area of a large river includes its tributaries. 

  • The area served by a local institution, such as a hospital or school, or by extension, a railway station. 

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