flowrate vs seepage

flowrate

noun
  • The rate of flow, usually of a fluid, measured in either volume or mass per unit time. 

seepage

noun
  • The process by which something, especially a liquid, leaks through a porous substance; the process of seeping. (Also used figuratively: the process of diffusing.) 

  • Water that has seeped or oozed through a porous soil. 

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