IWA Specialized Conference on Water&Wastewater 22-24 March 2012 Technologies in Ancient Civilizations Istanbul-Turkey 823 MN-122 A Contribution to the History of Water Management and Dams: The Roman and Medieval Hydraulic Structures on the Rio Grande Stream, Amelia (Umbria, Italy) W. Dragoni*, B. Giammartini* and D. Dragoni** * Perugia University, Perugia, Italy, ** Cassino University, Cassino, Italy (E-mail: dragoni@unipg.it) Abstract This paper describes some ancient hydraulic structures located along the Rio Grande stream (Amelia, Central Italy). The main structures are two large dams, not previously mentioned in the literature on dam’s history. One of two dams is an arch dam, already existing in 1427, while the other one is probably of Roman age. The main purpose of the two dams, both higher than 15 m, was to provide water to not less than three water-mills. Both reservoirs may possibly have also been used for irrigation and fishery. Keywords: Amelia; Arch Dam; Italy; History of Dams; Para Dam; Rio Grande Dam INTRODUCTION This paper presents the first results of an investigation regarding two little known ancient dams on the Rio Grande (or Fosso Grande) stream, tributary of Tiber River, in the territory of the town of Amelia (Central Italy, Figure 1). As far as we know, the two dams are not mentioned in any publications dealing with the history of dams (see for instance Smith, 1971; Schnitter, 1994) nor in an old but authoritative list of Italian dams (Ghetti and Tonini, 1960): indeed it is not even known when the dams were built. Figure 1 is a geological map of the area where the two dams are located; in the map the dams are identified by the numbers 1 and 2, in red. The present names of the dams are Para (n. 1) and Rio Grande Dam (n. 2). Figure 2 shows a general view of the site, looking from North-East towards South-West. It has to be noted that, from the engineering and geological modern point of view, both dams are located in an excellent position. THE PARA DAM The Para (Figure 3) is an arch dam. It is about 15 m high; at the top we measured a thickness of 1.8 m and an arch length of 51 m. We were not able to measure the thickness at the bottom, which seems to be 2-3 times larger than at the top. The dam, resting on a thick rectilinear basement, was built with small limestone blocks, typical of Middle Age; the reservoir is at present completely silted (Figure 4). The overflow spillway visible in Figure 3 is modern, as it was build at the end of 1950s (Manciola, 2000). The original spillway is a channel, at present in very poor conditions, located on the right hydrographic site of the river, slightly higher than the modern spillway (Figure 5). The original spillway was in part dug in the limestone and in part built with limestone blocks. On the upstream site of the old spillway, some remnants of a brick floor are still visible. There is evidence that a vault, now collapsed, covered the old spillway. The dam has a bottom discharge conduit (its exit can be seen on the right of the water fall in Figure 3), but the way it was operated is unclear. An obvious raison d'etre of the Para Dam was the water-mill located on the left side of the river (Figure 3); the other reason may possibly have been its use as a reservoir for irrigation and fishery. It is not known when the dam was build, but it is known that in 1427 A.D. the dam was under construction or reconstruction (Di Tommaso, 1931).