résurgence

A résurgence is a point where an underground stream or aquifer returns to the surface, often as a spring in karst and fractured-rock landscapes. The term is widely used in European hydrology and caving to describe locations where water that has entered the subsurface through sinkholes, ponors, or diffuse recharge re-emerges after flowing through caves, conduits, or porous rock.

Resurgences vary in size and behavior from small trickles to powerful, perennial outlets. Their flow regime is controlled by the geometry of the underground channels, the storage properties of the aquifer, and rainfall or snowmelt patterns; many show rapid response to storms and can flood nearby valleys. Because subsurface routes are often complex, dye tracing and flow monitoring are commonly used to map connections between sink points and resurgences.

Ecologically, resurgences create distinct habitats with stable temperatures and often high dissolved mineral content, supporting specialized aquatic communities. They have long been important for human use as reliable water sources, locations for mills, and, in some cases, sites for hydroelectric schemes. Cave diving and speleological exploration have revealed many resurgences to be entrances to extensive cave systems.

Famous examples include the Fontaine de Vaucluse and the Blautopf, both well-studied karst springs. The word derives from French résurgence and Latin resurgere, meaning “to rise again,” reflecting the reappearance of surface water after an underground passage.