Abstract
The Kur River basin, located in the Northwest of Fars province, is considered one of the main centers of the formation of the Achaemenid Empire. In terms of geographical landscape and climatic characteristics, the mentioned region includes vast intermountain plains (including Marvdasht and Korbal), rivers with deep beds (Kur and Sivand) and semi-arid climate. According to these conditions, the managers of Achaemenid economic-political institutions intelligently used the environmental capabilities of the region by building dams, weirs, Pool, reservoirs/catchments and canals to control surface waters and direct them to the ground. Agriculture and human settlements have paid. The dams and Weirs, while playing the aforementioned role, also prevented the damage to the agricultural lands located downstream by controlling the floods. The method of construction and selection of materials in the construction of structures has been different depending on the environment and their function. Dams and Weirs are mainly formed with an earthen core and a stone wall. The canals are also created in two ways: earthen and stone, or a combination of these two methods. The discussed structures have been attributed to the Achaemenid period, mainly based on their morphological features, type of materials, connection with the surrounding sites and comparative comparison with similar structures. The present study tries to introduce the Hydraulic Structures of the Kur River basin, its functional nature and morphological characteristics by using the descriptive-analytical method and by examining the evidences resulting from archaeological excavations and surveys. 
Keywords: Achaemenians, Kur River Basin, Hydraulic Structures, Canal, Agriculture.

Introduction
Central Fars region/Kur basin has a semi-arid climate with a Mediterranean rainfall pattern, most of which occurs in the winter season. New geological research and climate data show that during the Achaemenid period, the weather conditions of the Kur River basin were very similar to today (Djamali et al., 2009; Kehl et al., 2009; Rigot, 2010). Therefore, water control and management in a semi-arid environment with irregular rainfall patterns and rivers with deep beds has been vital and inevitable. According to these conditions, the managers of the political and economic institutions of the region have invested in the construction of structures such as dams, Weirs, reservoirs, and canals, whose works and evidence have been proven as a result of research and investigation. These Structures were built in different areas of the Kur River and with different purposes. The discussed structures in terms of dimensions and size, the amount of work and the materials used show the support and investment of the government. Therefore, the existence of various water structures, conducting targeted research in order to find out the functional nature of the structures, their physical structure and the reasons for assigning them to the Achaemenid period seems necessary. The main and important question of the current research is what was the function and performance of Hydraulic Structures in the Kur River basin during the Achaemenid period? What was the basis of the chronology and assignment of the studied water structures to the Achaemenid period? The structure, the environmental study and the geographical background of the formation of the structures have shown their various functions, such as supplying water to human settlements and agricultural lands, controlling and directing floods. Also, the discussed structures have been dated to the Achaemenid period, mainly based on their morphological features, type of materials, connection with the surrounding sites and comparative comparison with similar Structures.

Identified Traces 
As it was mentioned before, as a result of Archaeological investigations and researches, several important Hydraulic structures from the Achaemenid period have been identified and studied in the Kur river basin. In terms of morphological characteristics, the mentioned structures are divided into groups such as Dams, Weirs, Canals and Reservoirs. Among them, we can mention Band-e- Dokhtar, Bard Burideh II, Band-e- Bas II, Rahmat Mountain Canal, Asiyab Dam, Qondashloo Mountain Canal, etc. For the accurate dating of some of these structures (such as the band Dokhtar and the Bard Burideh), there is enough evidence, including the use of carved stone blocks and Dovetail Clamps. But some others can be attributed to the Achaemenid period based on possible evidence, including comparative comparison with similar structures and the connection with the surrounding sites. Band-e- Bas II and identified channels are included in this group. The precision and skill used in the construction of these structures indicate the existence of advanced engineering in the Achaemenid period. The chosen place for the implementation of Hydraulic projects reflects their functional nature. Therefore, it can be said that most of the Hydraulic Structures can be defined in connection with water supply and irrigation projects. The reason for the existence of Channels makes sense in this connection. Band-e- Dokhtar, Band-e- Bas and Asiyab Dam probably had a multifaceted function (irrigation, water supply and flood control). The Persepolis Tablets refer to a large amount of Agricultural and horticultural products in the Kur River basin. According to the texts of Persepolis, the diet of the people of this area in the Achaemenid period was mainly based on Agricultural products (barley and wine). Some of these crops can only be cultivated if irrigated. In addition, the implementation of irrigation projects has made it possible to plant nurseries and fruit gardens (mentioned in the Tablets).

Conclusion 
As the heart of the Achaemenid Empire, the Kur River basin has diverse environmental and geographical capabilities, including vast and fertile plains and permanent rivers. These natural characteristics have prompted the economic policy makers of the Achaemenid Empire to implement the economic programs of the Kur region according to its potential. The use and exploitation of surface water (rivers and springs) for the economic prosperity of the region by building structures such as dams, Weirs, canals and reservoirs is one of these measures. In this context, Band-e- Dokhtar and the canal branching from it, Bard Burideh II, Band-e- Bas II, Koh-e- Rahmat Canal, Koh-e- Qondashloo Canal, Koh-e- Ayyub Canal, Dezhabad-Amir Aqueduct are worth mentioning. The environmental study of the formation of structures and their placement in the landscape of the region shows that the main purpose of creating structures was to supply water to human settlements and Agricultural lands. The Persepolis Archive implicitly indicate the expansion and prosperity of agriculture/Gardening activities and diet based on agricultural products in the Kur river basin. Also, the reference of the Tablets to the cultivation of water crops (cotton, flax and rice) and various fruits can be considered as clear evidence of the role of water supply structures. The discussed structures have been attributed to the Achaemenid period, mainly based on their morphological features, type of materials, connection with the surrounding Sites and comparative comparison with similar structures. In terms of size and dimensions, the above structures show the amount of work and materials used for government support and investment.