Nahrawan

The Nahrawan Canal (Arabic: قناة النهروان‎‎) was a major irrigation system of the Sassanid and early Islamic periods in central Iraq, along the eastern banks of the Tigris and the lower course of the Diyala River. Created in the 6th century, it reached its peak under the Abbasid Caliphate, when it served the main water supply for the Abbasid capital of Baghdad, while the regions irrigated by it served as the city's main breadbasket. Its destruction and progressive abandonment from the mid-10th century onwards mirror the Abbasid Caliphate's decline.

The first irrigation works along the Diyala River were undertaken in Parthian times. Indeed, it may be that the lower part of the Nahrawan Canal was originally the lower course of the Diyala. The large-scale canal system of early medieval times however was created in the reign of the Sassanid ruler Khosrau I (531–579), who also established it as a separate administrative district (Bazidjan Khusraw). A treasury and mint were possibly established there.

In early Islamic times, the town of Jisr al-Nahrawan in the middle of the canal was the site of a battle on 17 July 658 between Ali and the Kharijites under Abdallah ibn Wahb. Under the early Caliphates, and especially under the Abbasids who made nearby Baghdad their capital, the canal network was repaired and expanded, reaching its peak in the 9th and early 10th centuries. In Abbasid times, the region was divided into three tax districts, Upper, Middle and Lower Nahrawan.

The canal was breached in 937/8, during the revolt of Bajkam against Ibn Ra'iq; the latter tried to impede Bajkam's advance from Wasit to Baghdad by flooding the region in between. The move barely obstructed Bajkam, but succeeded in destroying the agriculture of the region, hitherto the breadbasket of the Abbasid capital. As Hugh N. Kennedy writes, "the breach of the Nahrawan canal was simply the most dramatic example of a widespread phenomenon of the time; and it was symbolic of the end of ‘Abbasid power just as the breach of the Marib Dam was of the end of the prosperity of pre-Islamic south Arabia". The lower and middle Nahrawan were entirely abandoned for almost 14 years, until the Buyids under Mu'izz al-Dawla restored the canal. Nevertheless, the canal network continued to decline thereafter. As late as 1140, the Seljuq governor Bihruz tried to restore it, but according to the 13th-century scholar Yaqut al-Hamawi, infighting among the Seljuqs once again meant the neglect of the canal, and its use as a road by their troops compounded the destruction of the network. By Yaqut's time, the canal network had largely silted up and the countryside along them was abandoned.

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