Hydraulics
Canals, Locks, and the Engineering of Water
Water is the driving force of all nature.
— Leonardo da Vinci
Overview
If The Nature of Water is Leonardo's theoretical study of water's behavior, Hydraulics is where that knowledge meets practice. Leonardo was involved in some of the largest water engineering projects of his era — the canal systems of Milan and the Romagna, the proposed diversion of the Arno River around Pisa (for military purposes), and the design of improved canal locks.
His hydraulic work was grounded in direct observation. He studied how water moves through narrow channels, how erosion affects riverbanks, how to design gates that open and close efficiently, and how to calculate the volume of flow through locks of different sizes.
Canal Locks and Navigation
Practical water management
The lock must be as wide as the width of the boat, plus one third, and the length must be three times its width. I shall place at the entrance four wheels which by means of their counterweights will close the entrance after the boat has entered.
C.A.
All the water that is discharged from the mills and canals should be collected into a reservoir, and from this reservoir it should be let into the canals, because in this way there will always be sufficient water for the mills and for navigation.
The Arno Diversion
A river as a weapon of war
The Arno taken at Girone or at Arezzo would not require many locks, and at Girone it has enough water. The fall should be made at Arezzo so that it would flow through the Val di Chiana — that would irrigate the country and the canal from there would serve as port of Arezzo.
Madrid II
The plan was conceived during the war between Florence and Pisa (1503-1504). Machiavelli supported it. Leonardo designed it. The idea was to divert the Arno away from Pisa, cutting off the city's water supply and port access. The project was started but abandoned — the engineering was beyond what the available labor force could achieve. Still, Leonardo's maps and calculations for the project are among his finest technical drawings. -D
Leonardo's hydraulics work is where he most clearly operated as a professional engineer, not just a researcher. He was hired to solve actual problems — make this canal navigable, drain these marshes, figure out if we can reroute a river to cut off an enemy city. The Arno diversion ultimately failed (the trenches weren't deep enough), but his designs for canal locks and water management systems were genuinely practical. -D