aqueducts

An aqueduct is a water supply system designed to convey water from a distant source to a city or agricultural area, using gravity to maintain flow. The word comes from Latin aqua "water" and ducere "to lead". Aqueducts may be above ground, carried on arches or piers, or underground as tunnels and channels, and frequently incorporate reservoirs, intakes, and distribution networks.

In ancient times, the Romans built extensive networks using precisely graded channels, usually lined with stone, brick, or concrete; they employed waterproof bedding, inverted siphons, and gravity-driven gradients to move water across long distances, often spanning valleys with substantial arcades.

Notable examples include the Pont du Gard in France, part of the Nîmes aqueduct; the Segovia Aqueduct in Spain; the Aqua Claudia and Aqua Anio Novus in the Roman region; the Valens Aqueduct in Istanbul. In many places, surviving segments continue to influence modern water supply systems.

Today, aqueducts remain part of urban water infrastructure, often integrated with modern pipelines, reservoirs, and treatment facilities; some serve as drainage or irrigation canals. Engineering challenges include maintaining gradient, preventing losses, and mitigating environmental impact.