https://en.wikipedia.org/wiki/Arab_Agricultural_Revolution#I...
> "A 13th century observer claimed there were "5000" waterwheels along the Guadalquivir in Islamic Spain; even allowing for medieval exaggeration, irrigation systems were certainly extensive in the region at that time. The supply of water was sufficient for cities as well as agriculture: the Roman aqueduct network into the city of Cordoba was repaired in the Umayyad period, and extended."