Gravity-Fed Water Systems 102

As a continuation of Nick Rose’s post a couple weeks ago about gravity-fed water systems, we’re taking a cue from (and leaning heavily on) The New York Times to learn a little more about how this high-quality water is delivered to more than 8 million city residents every day of every month of every year in New York City.

As a nerd, one of the first things I tell people about living in New York is that the quality of the tapwater is absolutely fantastic. It’s crisp, clean, and free of any kind of “taste”; and isn’t that what we’re all looking for when we open the tap and grab one our eight 8-ounce glasses of water per day? We’ve all consumed tap water that has a “poolwater” taste (high residual chlorine), that stained our fixtures (due to organic “tannins”, originating in plant tissues), or that tasted or felt “minerally”, “slimy”, or “sulfurous”.  But, against all odds, our water here in NYC - at least typically - has none of those issues.

[The following content was inspired and informed by the New York Times article “How New York Gets Its Water”, originally published on March 24, 2016 and written by Emily S. Rueb - with illustration by Josh Cochran] :

Much like the water coming from Umani Springs to Usalama, the drinking water that arrives in New York City from reservoirs located upstate (as far north as the Catskills) is transported solely via gravity.  The city and state pay to protect the upstate Delaware/Catskill watersheds (which drain to the Ashokan Reservoir) and Croton watershed (which drains to the Kensico watershed) from contamination with sediment, agricultural runoff, and road salt.  By carefully controlling the land where our drinking water falls as rain, NYC avoids the need for filtration of the water derived from the Delaware/Catskill watersheds - which total over 1 million acres in area.


Josh Cochran - The New York Times

Gravity flow over such a long distance isn’t fast - but since it doesn’t stop, the roughly half-year travel time from the Catskills to NYC doesn’t hamper our ability to get consistent clean water in the city.  The water travels through subterranean aqueducts, which were constructed in an era of steam-powered machinery and conceived using hand-drawn engineering plans and calculations.  The Catskill Aqueduct in particular descends to a depth of more than 1,000 feet below the Hudson River, in order to avoid influence from the Hudson’s sedimented (and oft-contaminated) surface water.


Josh Cochran - The New York Times

The New York City Department of Environmental Protection (NYCDEP) is in charge of disinfecting the drinking water once it reaches Westchester County, and it does so by adding chlorine, phosphoric acid, and sodium hydroxide and by “zapping” the water with ultraviolet light to kill bacteria and other microorganisms that may have survived the trip.  The sheer difference in elevation as the disinfected water approaches NYC provides enough pressure for the water to shoot back up and reach the lower floors of most buildings in the city.  Additional pumping allows those of us in luxury penthouses to drink to our hearts’ content (raise your pinky to that).

To make sure everything is running smoothly and to check for the presence of harmful contaminants, such as heavy metals and persistent organic pollutants, the NYCDEP uses standpipe taps located on sidewalks throughout the city (they look like steel telephone booths) to collect regular water samples and test for compliance.


Josh Cochran - The New York Times


Though Usalama’s system is a microcosm of what enterprising New York State engineers have achieved in the construction and maintenance of one of the world’s largest drinking water distribution systems, it’s easy to draw a parallel between the DEP engineer opening a testing port on Fifth Avenue and an EWB-NY engineer turning on a kiosk to transfer untreated water into a petri dish for microbial analysis. Both systems utilize the free power of gravity to supply water to a community, with the help of engineers and legislators dedicated to making sure the water doesn’t stop flowing.

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