In the Northern parts of today’s Iraq, for about 1900 years between 2500 BC and 600 BC, was a flourishing Mesopotamian empire known as the Assyrian Empire. Irrigation played a pivotal role in Neo-Assyrian civilisation (911–609 BC). King Sennacherib, ruler of the Assyrian Empire from 705 BC to 681 BC undertook one of the most ambitious canal networking projects of his time. It is believed that the canals had a dual purpose of irrigating the dry area for subsistence farming (growing crops and livestock for one’s consumption) and acting as a symbol of the power of the Assyrian elite. This is one of the earliest canal systems that has been discovered by archaeologists. They have identified and mapped over 60 km of canals across a wide swath of Assyria, many of which have never been recognised on the ground before.
Reposted from Terradininive Assyrian Project
Like everything else, the Chinese have marked their presence in the history of river navigation as well. Being one of the greatest early builders of canals, they undertook several major projects between the 3rd century BC to 13th century AD intending to combine the functions of irrigation and transport. The Grand Canal is one such project which began in the 5th century BC and had several extensions over centuries. The original canal followed the contour of the landscape, and this required boats to go up and down hills. Traversing the terrain was therefore quite problematic. The Chinese solved this problem with the help of water traps called Locks.
Reposted from CHINASAGE, EpicWorldHistory.
A lock is a device used for raising and lowering boats, ships and other vessels between stretches of water of different elevation on canals and rivers. The most primitive yet effective solution for traversing the elevation was to build a weir - a low dam built across a river to control its flow. This structure blocks the water on the higher elevation, with a gate in the middle to let a boat through. Opening the gates results in a sudden rush of water - a flash flood. This carries the boat across the gate. This primitive lock, for obvious reasons, is known as a Flash Lock. Although the locks had been used for a long time, it had its demerits - slow upstream assent and pretty rapid and dangerous downstream dissent.
Reposted from canalbookcollector blog, Wikimedia
With the increased damages to the boats, an improvement was made; something that we might think is pretty apparent today - adding a second gate. This gave birth to the Pound Locks. The term ‘pound’ refers to the stretch of water between two canal locks. The pound acts as a chamber whose water level can be varied to elevate or lower a vessel to meet the next water level. It is believed that the Chinese were the first to use this lock in the 10th Century, with the development of this slightly sophisticated lock credited to the Chinese engineer, Ch’iao Wei-Yo. The Europeans caught up much later at the 14th Century, with the Dutch and Belgians leading the way. Unlike its predecessor, it was entirely controllable and had none of the hazards and surges.
The working principle of the Pound Lock is reasonably simple to understand. It is demonstrated in the given image and the animation. The drain valve and filling valve are opened and closed in an appropriate sequence to alter the water level of the pound - water is filled from upstream and drained downstream. The gates are closed when the pound's water level is being adjusted. They are then opened to allow the boats to pass through.
Reposted from US Environmental Protection Agency Website
Reposted from Rideau Canal Webpage
Now that you have an idea about how a pound lock works try this simulation: https://www.pragmasoft.be/carnets/geo/ecluse/flash/ecluse_flash.html
In the late 15th Century, the Duke of Milan, Ludovico Maria Sforza had commissioned none other than the Italian polymath of the High Renaissance - Leonardo di ser Piero da Vinci to devise an improved form of pound lock. The two gates turned on hinges like doors and swung open in unison. When closed, they press up against each other at 45° forming a V-shape pointing upstream - thus giving rise to the name of Mitre Gates. This design ensured that the pressure of the water upstream closed them tighter, and they opened with ease only when the water level on either side were equal.
Reposted from leonardodavincisinventions.com, Daniel R.A. et al. 2013, Pinterest.
It is not always possible to achieve the elevation difference by just a single chamber. In such cases, a series of locks are employed - Lock Flights or Stair Locks. Like the 'Caen Hill Lock Flight', the series can have up to 30 locks. The whole series uses a single quantity of water for each trip with each lock using the water drained from the one above it. The pounds are also wide enough to allow climbing and descending at the same time. Stair Locks like 'Fonserannes Locks of Béziers' looks very similar to lock flights, with the difference that there is only one set of gates between each chamber. This means that the top gate of each lock functions as the bottom gate of the lock above.
Reposted from Alchetron, aeroengland, The Times.
As we have observed, the Canal Locks have a fixed chamber called pound in which the water level is varied. There are other machines like caisson lock, boat lift, and canal inclined plane where the chamber itself rises and drops. These machines will be described in the next part.
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