It is located about two hours away from Manhattan and is responsible for 40% of New York’s water supply; Ashokan Reservoir. It travels more than 100 miles of tunnels from this location to provide water to 8.4 million residents of the city. The Catskill Aqueduct that delivers water from Schoharie and Ashokan reservoirs is operational since 1915.
Recently, New York Public Library released about 200,000 digitized images and they also include the pictures of Catskill Aqueduct during the construction (1906-1915).
The NYC aqueduct system employs the use of a basic principle that was used by Romans to bring water to their capital city; gravity. You’d be surprised to know that only 5% of New York’s water requires to be pumped, the rest simply flows downhill. 
The New York engineers had access to something that Romans didn’t; dynamite. This allowed the construction workers to bury the tunnels underground rather than building aqueducts at an elevation. 
The Catskill Aqueduct tunnels sport a maximum width of 30’ and the tunnel show was 16ft and 7 inches. 
Workers dug a deep trench – same depth as that of the intended tunnel – by making use of steam shovels and dynamite.
The bottom of the trench was filled with concrete followed by concrete on sides. 
Then workers poured concrete on tunnel’s top and made use of steel forms to make it circular. The whole thing was then covered up using dirt.
The method employed required the removal of vegetation from top of the tunnel. The city compensated by planting 3 million trees around the two reservoirs that fed Catskill Aqueduct. 
Huge dams were constructed to condense the surrounding rivers and streams into a singular water supply. The Ashokan Reservoir, result, held 132 billion gallons of water. 
Workers had access to some electricity, however, still made use of horses for a number of projects.
This bucket pulley system was employed for the transport of dirt. 
After its completion, the Catskill Aqueduct was able to send 640 million gallons of water to New York City per day. 
As of today, it is capable of sending only 500 million because of the grime and bacteria that has built up on the tunnel during the course of years of service. 
The city is cleaning up the Catskill Aqueduct so that it is capable of providing fresh, clean water to New York City for another century. 
