|Sinkhole through which water either emerges or disappears, depending on hydrological conditions|
|Used on these elements|
|Tools for this tag|
Anis a sinkhole, typically connected to a waterbody, which can act as a ponor or as a karst spring, depending on hydrological conditions:
- if the groundwater level inside the karst system rises, the estavelle acts as a discharge, allowing the karst water to flow out forming a surface waterway
- on the contrary, with falling water levels, the estavelle acts as a ponor, swallowing surface water and draining it to the karst groundwater system.
An estavelle may be on the path of a waterway, or connected to a main waterway by a small one, whose flow will change according to the respective water levels of the karst system and of the waterway; if in the second case, use flow_direction=both to highlight the flow variations of the connecting waterway.
The Trou des Glanes, an estavelle in France, would be tagged this way: