L’acquedotto romano di Padova e l’Arzeron della Regina. Un unicum nel panorama dell’idraulica antica?

Abstract

In the area north of Patavium (Padova) an ancient rectilinear earthwork, the Arzeron della Regina (now dismantled), had a length of roughly 12 km and steadily rose above the surrounding plain to the site of Montà at an elevation of ca. 3 m. This monumental structure, recorded on historical maps and reported in the chronicles, has been almost completely eroded by centuries of human activity, but some remnants survive beneath the existing road. Previous studies and tradition interpreted this earthwork as a Roman construction, either as a raised road heading towards the Prealpine area or as a dyke to protect the territory from floods of the Brenta River. However, the Arzeron was actually built on stable ground unaffected by flooding since the last glaciation, suggesting that it was not used for protection. New archaeological and geoarchaeological investigations carried out along the Arzeron demonstrate that the structure is an earthen embankment whose inner core is characterized by the presence of masonry pillars spaced 16 Roman feet apart. The Arzeron likely started in Boschiera, near Piazzola sul Brenta. To the north, near Carturo, an underground Roman water conduit has been discovered maintaining the same westerly direction for over 7 km, to reach the area of Fontanon del Diavolo. This important spring is fed by groundwater seeping along
the so-called ‘line of springs’ with a nearly steady discharge throughout the year. Thus, the Arzeron is interpreted as a structure built to maintain the correct slope of the Padova aqueduct, probably in the second part of the 1st century B.C. The conduit, built of brick, was 60 cm wide with a maximum water level of about 75 cm, with the Arzeron, sustained by the pillars, running on top. Hydraulic calculations demonstrate that the average gradient of the earthwork was between 0.6-0.7 and in Montà, where the Arzeron ended, the base of the water flow attained an elevation of ca. 17 m asl, with an estimated discharge ranging from 70 to 200 m3/s and a velocity from 23 to 43 cm/s. From this point, about 3.5 km west of the city of Padova, the flow could easily arrive at the highest locations in the urban urban center which, at that time, reached a maximum elevation of about 14-14.5 m asl. Other Roman aqueducts with a channel running atop earthworks include those of Ulpia Noviomagus (Njimegen, The Netherlands) and the Atuatuca Tungrorum (Tongeren, Belgium), where the earthen dyke is ca. 5 km long and over 10 m high. This new discovery about the aqueduct of Padova sheds light on Roman hydraulic techniques and suggests that the so-called ‘Lagozzo’ earthwork arriving at Altinum from the area of the line of springs, and currently interpreted as a raised road, was also likely a structure to elevate a water conduit reaching the city along the Venice Lagoon.

KEYWORDS: Roman acqueduct, Padua, ancient hydraulics.