What may seem surprising, at least at first sight, is the presence of installations making use of channelled water, such as the above described bathing installation (ST 20). Further work indicates that ST 20 is not the only building on the summit of Umm al-Biyara that is supplied by channelled water. For instance, ST 7, built on a protruding rocky promontory on the southern part of the eastern ridge and offering again a splendid view over the city centre (fig. 20), was most probably also connected to a water channel.
Fig. 20: Overall view of ST 7 (photo: S. G. Schmid)
This is suggested by the presence of a fragment of a stone cut water channel (fig. 21). Although a surface find and not in situ, this item most likely was connected to ST 7. In the case of the above described ST 26, the supposed temple of Morton and Bennett, it is a rock-cut water channel (fig. 22) that brings water into the area, so that we can suppose a rather luxurious water supply for that building as well.
Fig. 21: Stone cut water channel from ST 7 (photo: S. G. Schmid)
All of these water channels, as well as others, are connected to the system of cisterns on top of Umm al-Biyara which give it its Arabic name. With the exception of one cistern, situated on a much lower terrace on which so far no structures have been identified, all other seven cisterns on the plateau are part of a thoroughly sophisticated water management system. Every cistern is supplied by at least two incoming channels, sometimes as many as six. From every cistern at least two channels bring the overflow either to another cistern or lead into rock-cut or built channels which take water to the above mentioned structures. This system of multiple connections clearly reminds one of the Nabataean water management attested all over the city of Petra. The cistern system and its close connection to the clearly Nabataean buildings on the eastern ridge of the plateau makes it very likely that it should be dated to the Nabataean period. Diodorus Siculus describes typical Nabataean cisterns as „(…) big holes with small mounds; in depth they enlarge the shaft continuously until it reaches one plethron at every side“Diod. 19, 94, 7. , a description that fits rather well the eight piriform cisterns of Umm al-Biyara. However, dating the eight cisterns exclusively to the Nabataean period creates problems in explaining where the Edomite settlement got its water from.
Fig. 22: Rock-cut water channel SW of ST 26 (photo: S. G. Schmid)
In the final report on the excavations of the Edomite settlement, Bienkowski (in press) admits that the cisterns cannot be convincingly dated to either the Edomite or Nabaatean period. In the current state of knowledge, it cannot be excluded that the cisterns are originally Edomite in date and reused during the Nabataean period. How efficient that ancient system of water collection still is could be observed during two days of rainfall during our 2010 spring campaign. After only five minutes of rain, water started gushing into the cisterns, although only a very small percentage of the water collecting system is still extant and it is working at a vastly reduced capacity.
