In karst geology, estavelle or inversac is a ground orifice which, depending on weather conditions and season, can serve either as a sink or as a source of fresh water. It is a type of ponor or sinkhole.[1][2]


  1. ^ "Karstgeology: Estavelle". Retrieved 24 April 2020.
  2. ^ Milanovic, Petar (2004). Water Resources Engineering in Karst. CRC Press. pp. 211–212. ISBN 978-0-203-49944-3. Retrieved 24 April 2020.