Since the ancient times people was trying to tame and use the powers of nature. Many of his efforts were related to water use.
A big achievement of 520 B.C. was a tunnel that was dug in Samos with simultaneous digging from both ends. Samos' tyrant governor Polycratis ordered it. This tunnel was used to carry fresh drinking water to the city. Water was conveyed through clay pipes laid in a trench on the floor. Designed by Eupalinus, son of Naustrophos, from the city of Megara. It is 1040 metres long with average 2.5 metre diameter and it was opened with simultaneous digging from both ends (!!!), it is a little difficult even for the modern average technician! It is located 55 m. above sea level and 180 m. below the top of the mountain. They had spent 10 years before they managed to finish the project. The deviation where the two teams connected the two parts of tunnel to one was very small! (530 B.C.) During the digging only 2 people in each part were digging. The German institute of ancient technology with the professor Hermann Kienast studying the tunnel, found many unknown but impressive details. The workers had some problem because of unstable soil and had to make a deviation, but they managed to find again the right way to the opposite working team. This deviation was 200 metres away from a straight line connecting the ends of the tunnel in the heart of the mountain! The workers used for digging were no less than 4 and no more than 15. Many of them were sport prisoners that the Samians used for the completion of the work.
When talking about Samos, we have of course to mention the breakwater that was constructed in the entrance of the seaport. It is 35 metres deep and 335 metres long. It is considered to be one of the most important ancient port structures.
The first known river deflection is found in Greek mythology when Hercules is changing the flow of a river to clean the stables of Aygeias.
Much later Herodotus reports the deflection of Alios river from Thalis from Melitus. At this very big scale soil movement work Thalis used mathematics to calculate the optimum use. This way the design passes from workers based to their experience to scientist engineers.
But we have something else even more impressive!
In 691 B.C., Sennacherib, king of Assyria, built a conduit to transport water from a river about 55 km (34 miles) distant to his fields and gardens in Nineveh. A gently sloping masonry channel was constructed, and where it passed over a valley, an arched bridge 9 m (30 ft) high was built to support it.
As I'm keep on searching, I've found something else much older and equally big! 3.500 years ago, close to 1500 B.C. at the area of Kopais (Greece), close to the city of Orchomenos, there was a lake that caused flood problems to the close areas. So, they opened a channel from there to the sea to let the water flow out. This way they had no flood problems any more but also got much more space for their agriculture!
The main channel was 43 Km long, 40m wide and 5 metres deep! A web of much smaller channels was leading the waters of the whole area to the main channel. This channel remained operational for many centuries, until some earthquakes destroyed big parts of it in 1100 B.C.
Much later, close to 330 B.C., another similar work was done in south Euboea at the lake of Dystos close to the city of Eretria. The most impressive thing about this work is not its difficulty but the contract that has been saved and includes many legal details. The work was subcontract from the township of Eretria to the engineer Herefanis. The work is described with many technical details (building of draining canals, sluices, building of cistern etc.) there is a - not exist anymore - line after four years, tax freedom to import materials for the work, and also many penalty clauses in the material and in the moral domain! This is the first known technical contract.
Romans also had managed to use the water easily in their cities. They had a good network of water supply and drainage but also they had network of hot water! Their capabilities on pumping water was so advanced that they could transform an arena of the
Coliseum to a little lake and making small sea fights in there, and these between other enjoyments in the Coliseum.
Other information says that the same way 'sea fights' was happening at the Dionysus theatre close to the acropolis of Athens, but it looks a small to me for such activities.