|A Persian qanat was built by digging a serie of shafts and connect them at a certain subterranean level. It is in principle tapping an aquifer just above the bedrock. Note the distribution channels where the main channel comes to light.||A 'bucket chain' of which many can be found at the countryside of Spain, originaly as a donkey driven saqiya, later equipped with a diesel engine. Nowadays put out of use and replaced by diesel or electric water pumps.||The famous Lamasba inscription (Algeria) preserves a schedule for irrigation that used water from a perennial spring. Each entry in the schedule lists the name of the landowver to whom water is allocated, the amount, and the time of the day for channeling the water.|
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IrrigationWater was not only a necessity for private consumption but was also needed to grow crops. Most agricultural activities were done based on 'dry-farming': it is striking that ancient writers about agriculture like Cato did not mention mechanical irrigation at all. In arid areas streams were tapped, wells dug and aqueducts built. One of the forerunners of artificial catchment schemes were the qanats. In the early part of the first millennium bc Persians in present Iran started constructing elaborate tunnel systems for extracting ground water from an aquifer. Along the length of these subterranean qanats vertical shafts were sunk at regular intervals. The main outlet was near a village were the water by means of open channels was transported to farming areas for irrigation purposes.
When necessary water lifting devices were used like the noria's in Spain, the shaduf in the Near East and the screw of Archimedes, but these apparatus were expensive and limited in their capacity to transport water over substantial levels and in large water volumes.
Although there was a constant supply, the water had to be divided among the different farmers which was realized by a system of time-sharing. Known are several inscriptions and documents describing balanced schemes of water distribution in time.
Frontinus recalled the poor quality of the water of the Anio Vetus aqueduct so it was designated for irrigation (Frontinus 92). Talking about the bad quality of the Aqua Alsietina water, he also noted that the surplus of the Naumachia - the main purpose of the construction of this aqueduct - was granted to adjacent properties and for purpose of private irrigation (Frontinus 11.1). According to the same writer, the Aqua Crabra - of which is unknown whether it was an aqueduct or a local brook - watered all villa's in the neighborhood of Tusculum, "the apportionment (was) made by scheduled days in fixed quantities" (9.5), so again an example of time-sharing.
In extreme arid regions in the Near East there were special provisions made to cope with water shortage e.g. 'water harvest area's' near Roman desert forts in present Israel in combination with large cisterns, and dams crossing wadi's to trap soil and water in basins where it could be cultivated.