Saint Remy, les Baux de Provence & Pont du Gard from Avignon

The Pont du Gard was constructed around the mid-1st century AD by the Roman Empire to transport water from springs near Uzès to the Roman colony of Nîmes. This magnificent engineering feat took approximately 15 years to complete, showcasing the Romans' exceptional engineering skills. It was used to supply daily water for the residents of Nîmes, as well as for public baths and fountains. The Pont du Gard is not just a functional aqueduct but also a symbol of the Roman Empire's influence in the Provence region.

The core operating principle of Roman aqueducts is gravity flow. Engineers meticulously measured the terrain, designing an extremely gentle slope to allow water to flow naturally from higher to lower elevations. For instance, the Pont du Gard descends only about 34 centimeters per kilometer, ensuring a stable water flow that wouldn't erode the channel. This design eliminated the need for complex pumping systems, efficiently and reliably transporting water sources to cities over long distances.

Common terms related to Roman aqueducts include 'Aqueduct,' referring to the entire water system; 'Arch,' its iconic supporting structure; 'Pier,' the vertical section supporting the arches; 'Specus,' the enclosed channel on the upper level that carries the water; and 'Settling Basin,' used to remove impurities from the water to maintain its quality.

The Pont du Gard played a crucial role in the Roman aqueduct system for Nîmes. It was the most spectacular and technically challenging section of this 50-kilometer-long aqueduct, responsible for crossing the Gardon River valley. This bridge ensured a stable and abundant supply of clean water reached the city of Nîmes, serving as a vital component for maintaining public health, agricultural irrigation, and the daily lives of its residents, reflecting the Roman Empire's emphasis on infrastructure development.

The Romans implemented several strategies to ensure the long-term, stable supply of water through the Pont du Gard aqueduct. They precisely calculated the gradient of the channel to utilize gravity for natural flow. They also coated the interior of the channel with waterproof mortar (opus signinum) to prevent leakage. Furthermore, maintenance passages and settling basins were established along the route for regular cleaning, upkeep, and sediment removal, ensuring water purity and allowing the aqueduct to function for centuries.

The construction of the Pont du Gard overcame numerous significant challenges. Firstly, the rugged terrain required precise measurement and control of the slight gradient over the 50-kilometer length of the aqueduct. Secondly, crossing the Gardon River valley necessitated the construction of a towering three-tiered bridge and the transportation of heavy stones, weighing several tons, to the site. Additionally, ancient Roman engineers had to solve technical difficulties in cutting, lifting, and positioning the stones to ensure the bridge's structural stability and durability.

The arch design of Roman aqueducts offers exceptional mechanical advantages. An arch effectively transforms the vertical weight and pressure from above into outward thrust, which is then transferred to the piers or ground on either side, thereby distributing the load. This allowed arch bridges to support immense weight and span wide distances while using less material than solid structures. It was an ingenious and robust construction method, especially in an era lacking steel reinforcement.

Roman aqueducts were primarily built using strong and durable local stone. For example, the Pont du Gard extensively used yellowish limestone. These stones were typically precisely cut into shape and assembled using dry-stone techniques or with minimal mortar. Additionally, to ensure the waterproof quality of the water channels, the interior was coated with a special waterproof mortar called 'opus signinum,' made from a mixture of lime, sand, and crushed brick, which provided excellent waterproofing.