*Mesopotamia (*Babylonia) and *Egypt were the main areas of the ancient world where agriculture depended on irrigation from a river rather than rainfall, although irrigated pasture and fields were common alongside perennial rivers elsewhere, and many drainage schemes to reclaim land were carried out, e.g. in the Strymon delta and the Po valley. In Mesopotamia the powerful *Euphrates and *Tigris rivers permitted irrigation of extensive plains through a radial network of descending *canals. The gentle gradient of the Nile and its narrow valley meant that local basin irrigation was predominant in Egypt. Both these ‘natural’ systems required heavy communal work to clear canals and repair dykes, and careful drainage to avoid salination, but only the former, being an integrated system, needed centralized control. ‘Artificial’ irrigation was necessary for land which lay above the flood-level and for additional watering of other land outside the period of inundation. The pole-mounted scoop (Arabic shaduf) was the cheapest and commonest mechanical aid; the Persian to Hellenistic periods saw the appearance of the far more efficient and expensive man-powered compartmented waterwheel and Archimedean screw (see archimedes) and animal-powered wheel with pot-garland (Arabic saqiyah), but they were rare, only achieving significant diffusion on large private estates in later Roman Egypt and Syria, although treadmill-driven compartmented wheels were also used in Roman mines to extract water.Less