Medieval Science, Technology, and Medicine by Medieval Science Technology & Medicine; an Encyclopedia (2005)

Author:Medieval Science, Technology & Medicine; an Encyclopedia (2005)
Language: eng
Format: epub
ISBN: 9781135459390
Publisher: Taylor and Francis
Published: 2014-01-27T05:00:00+00:00

Medieval Irrigation

Many medieval Italian towns (e.g., Salerno, Saluzzo, Viterbo) had irrigated market-garden districts on their peripheries. The Po valley was the site of large irrigation projects, always drawn from tributaries of the Po. In Milan, the Naviglio Grande was built in the late twelfth century, originally to supply water from the Ticino River to the city’s moat. It was then enlarged and used both for navigation and irrigation. In the later Middle Ages, outlets of fixed dimension supplied secondary canals, replacing haphazardly placed diversion dams that impeded navigation.

In Spain, although the Romans had irrigated there, the irrigation systems in place when the Christian forces conquered Islamic Spain, had generally been built and organized by tribal irrigators, either Arab or Berber. Place-name evidence slows this to be true both for the small mountain communities, as well as for the large, peri-urban huertas surrounding such cities as Valencia and Murcia. In Valencia, where the water table of the huerta is very high, Muslim tribal groups irrigated from springs. As settlement grew denser and the spaces in between settlements gradually were brought under irrigation, the water table was lowered at the same time as the system grew more and more integrated until, at some point before the Christian conquest of 1238, the canals were linked up and water diverted from the Guadalaviar (modern Turia) River, replacing the system of springs. The history of the Valencian huerta is further complicated by the fact that some decades before the Christian conquest, a huge flood carved out an entirely new river bed between the city and the sea, making the early Muslim-built system even harder to reconstruct. The division of water among the eight canals of the huerta, moreover, also seems to reflect a Muslim-inspired allocation principle: it replicates the allocation of water among the canals of the Ghuta or huerta of Damascus, where the water at each stage of the river is reckoned as holding twenty-four units (qirats, in Damascus, filas, or “threads” of water, in Valencia), apparently representing an original division by hours.

In the oases of the Islamic world, irrigation developed a distinctive cultural style. Date palms required irrigation and also a system of canals designed so that the parcels could be laid out regularly. Ibn Hawqal describes the palm grove of Basra (Iraq) and a complex network of channels drawn from the Obolla canal, as an integrated hydraulic system: “At high tide, water flows into each canal, irrigates the palm groves and, upon passing the walls surrounding them, it is distributed through the network of secondary canals without any need to measure it.” In the Saharan oases, some of which (like Gafsa) also had palm groves, water was typically distributed by time units measured with inflow or outflow clepsydras.

Medieval irrigation systems have been studied archeologically, especially small-scale, tribally based systems of Islamic Spain. One of the advantages of this kind of analysis is that it covers long extensions of time, across cultural frontiers (the Christian conquest and continuation of relict Muslim systems) and

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