groundwater level vs water table

groundwater level

noun
  • The level, at a particular site, below which the subsoil and rock masses of the earth are fully saturated with water. 

water table

noun
  • The level, underground, below which the ground is saturated with water. 

  • A molding or other projection in the wall of a building to throw off rainwater. 

How often have the words groundwater level and water table occurred in a corpus of books? (source: Google Ngram Viewer )