An ancient river disappears in a Mediterranean karst land: the old history of Cana River (Apulia, Southern Italy)

Apulia is one of the most interesting karst lands in the Mediterranean area, hosting a variety of distinctive surficial and underground landforms. Among these, polje, a wide and flat depression of tectono-karstic origin, represents one of the most typical epigean landforms in karst. The “Canale di Pirro” polje, located in the central part of Apulia (SE Italy), is the largest in the region (Pisano et al., 2020), bounded on both sides by tectonically-controlled ridges, with an overall length of some 12km and a remarkable underground system of caves, among which there is the deepest of Apulia, where the water table is reached at -264 m from the ground (Parise & Benedetto, 2018). As a karst land, within the polje the water rapidly infiltrates into the ground, making difficult its accumulation at the surface, with the exception of the period of heavy rainfall, when wide sectors of Canale di Pirro become temporary lakes which require several hours to days to be absorbed underground. In ancient documents and maps, with particular regard to historical cartography, the Canale di Pirro polje was drawn as being crossed by a long river, nowadays missing, called Cana (from this river, it seems that the same toponym of the polje took its name). The first written testimonies concern in particular a parchment dating back from the twelfth century; the more recent document we found, still showing the presence of the river, instead, is an ancient map of the nineteenth century. Considering the time span in which Cana River is still represented in historical writings and maps, it is possible to identify its existence between 1195 and 1840, and to hypothesize a presumed coincidance with the Little Ice Age, a climate interval characterized by a long cooling period, especially in the northern hemisphere. In this work, we present a series of historical documents about the existence of the Cana River, collected through literature research, in order to evaluate all the possible causes that led to the river disappearance over the centuries.