Nahr-e Velash (Vologass creek); program for the Agricultural Development of the Zahab plain in the Sassanid period, Western foothills of Zagros Mountain, Iran

One of the infrastructure programs for the economic development of the plains located in the western slopes of the Zagros Mountains in the Sassanid period has been the establishment of water transmission systems and water supply canals. This article tries to introduce the Nahr-e Velash in the northeast of the SarPol-e Zahab area as one of these examples with a descriptive method and historical approach, which has transferred the water of Alvand River to Zahab plain. This canal is 30 km long, a little more than two meters wide and one meter deep, and with exact calculations, it passed through the northern margin of agricultural lands in the SarPol-e Zahab area and finally reached Zahab plain as the most important fertile plain on the western slopes of Zagros Mountains. The construction and maintenance of the canal, as a large project with about 51,000 of digging, was naturally beyond farmers and villagers reach in the region, and its creation and maintenance were possible only with government support. The nature, distribution, and location of historical monuments in the region show that this irrigation system was established to develop the agricultural economy of these regions, and it was probably established during the reign of the Sassanid king, Belash (Vologass), and by the governor/lord of Velashgerd . In recent years, two more irrigation canals have been created parallel to this canal. The choice of this route with modern knowledge shows that the engineers of the Sassanid period had high knowledge and exemplary skills to create this canal and were able with accurate scientific calculations in the construction and location of this canal. As the agricultural hub of the region to cultivate water. Although at present the patterns of operation and the method of water distribution of this canal are not clear to us, this carefully engineered project is an important infrastructure for the prosperity of the region's agricultural economy in the Sassanid period.