Investigation of the Arjan weir-bridge and analysis of its role in the prosperity of agricultural economy based on historical texts and archaeological studies.

Arjan weir-bridges in southwestern Iran from the Sassanid era to the rule of Muslim Arabs are among the irrigation and water supply structures that were considered by geographers and historians of the first to middle Islamic centuries. The upper weir-bridge of Arjan is a huge structure with different uses that some geographical and historical sources have described. After the destruction of the upper weir-bridge, a smaller sample was built downstream of the river. There are few traces of the structural buildings of Arjan double weir- bridges; The forthcoming research is based on such a necessity to document the impact of these weir-bridges on Arjan's economy. The purpose of the forthcoming research; Analysis of the existence of an upper weir-bridge in the prosperity of the agricultural economy of Arjan in the Sassanid era and the early Islamic centuries. This article seeks to answer these questions: What is the description of these bridges (mostly upper weir-bridge) in historical texts? And what is the position of double weir-bridges and especially upper weir-bridge in the prosperity of the agricultural economy of Arjan region during the Sassanid era and the first centuries of Islam? Historical texts provide a relatively confusing description of bridges, especially the upper weir-bridge. Answer to the second question by reviewing historical texts, analyzing the discharge and outlet of canals similar to Qanats with the help of studies from archaeological surveys and basic hydro-logical data of today's Maroon River route and calculating the amount of water in Arjan Weir-Bridge Basin under modern conditions and Its activation has come to an end. The result is that the amount of irrigation of Arjan weir-bridge caused relatively extensive artificial irrigation in the lands of the northern part of Arjan plain and the case of wheat as a product that the texts have repeatedly mentioned; Based on water needs and calculation of OPTIWAT software has been a significant success in this area.