Database: Baghdad's Canals
In Baghdad's dry climate, the city's water supply depended on a dense network of natural and artificial waterways starting, of course, with the Tigris and its tributary the Diyala river. Added to these was a system of canals whose construction could be traced over a millennia, and which was restored and expanded by the Umayyads and Abbasids. Around the city, this network was incredibly dense and went from large navigable canals to very narrow trenches. Some of the water was also provided by canals coming from the Euphrates to the west.
This massive system fulfilled multiple needs. It provided the city with the water necessary for daily consumption, hygiene, a sewer system, etc. It played a crucial role in irrigating the cultivated lands around Baghdad, turning them into the breadbasket of the city and its growing suburbs. Linked by canals, the Tigris and the Euphrates were also essential communication and trading routes of worldwide importance, used to bring goods and people from the Indian Ocean to the Mediterranean region. Finally, the water system could easily turn into a useful defensive feature when needed. Most of the bridges over Baghdad were in fact on wooden pontoons which could be disconnected or even destroyed in case of attacks.
This useful system came at a cost. Maintaining it was extremely labor-intensive, demanding ever-increasing efforts from a large number of free and enslaved workers.