a survey of the function of tchoghazanbil water structure

doruntash ancient city )tchoghazanbil( was built about13 th century b.c and middle period of elam civilization. as a complex ,doruntash was protected by three concentrated walls which are named: inner wall, middle wall and outer wall .big ziggurat ,mausoleums and palaces are some of the must monuments of the ancient city .tchoghazanbil is also famous for its water technologies and water elements such as gutters ,sewage shafts and a brick water structure .the function of this structure ,located in the outer west wall of the site ,is the focus of present study. since its discovery ,three considerable hypotheses have been proposed about the function of tchoghazanbil water structure .roman ghrishman )1895-1979(, who first excavated the water structure ,believed that the brick structure functioned as a purification plant to which water was transferred with a channel from somewhere out of the ancient city .this hypothesis has been accepted as a principle and has occasionally been discussed and expanded in later studies. nevertheless ,further survey in recent years ,especially on the topography of tchoghazanbil shows that the ancient city has a higher altitude than the land of water structure and the water channel .in fact, it can be assumed that the water structure had functioned either as a drainage element to repel water or as a cistern to save water behind the outer wall .due to the ruins in most parts of the water system and lack of historical records ,the diversity of the relevant hypotheses make it hard to determine the real function of the water structure. as a result ,distinguishing the actual function of the water structure is as an inevitable task which could be aided by new technologies. hence ,this study benefited from laser scanning system ,geophysics survey and hydrology prospection .finally ,as a complement to earlier theories ,the original plan of the water structure was modelled .accordingly ,the drainage element is an acceptable theory for the function of tchoghazanbil water structure ;although archaeological excavation is required for conclusive proof.