By Vanessa Murdock

GRAHAMSVILLE, N.Y. (CBSNewYork) – The source of New York City tap water is roughly two hours north of the Big Apple and beyond, nestled in the bucolic countryside of the Catskill mountains, sits the Catskill and Delaware Watersheds, the origin of the “the best water in the world.”

“I will not drink tap water anywhere else. Only in New York City,” said Upper West Side resident Maria Garcia.

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“New York City’s drinking water is certainly among the top tier of major cities in the United States and in fact the world,” said Eric Goldstein, New York City environment director for the Natural Resources Defense Council.

“Some folks say it’s more valuable in the 21st century than oil,” said Goldstein. “It’s a plentiful supply due to the vision of the people who built the system in the early 1800s.”

A large Manhattan fire revealed the necessity for a more substantial water source. Officials started looking north. The Croton Watershed in Westchester and Putnam counties came first. In the late 1800s, the Catskills entered the equation.

“Up here you can actually see water. You go down in the city, you just open up a tap, and the water’s always there,” said Paul Rush, deputy commissioner of the Bureau of Water Supply at New York City’s Department of Environmental Protection.

At the banks of the Neversink Reservoir, Rush explained it’s not the city producing high quality water.

“It’s the landscape, it’s the environment and it’s working with the people who actually live in the watershed,” Rush said.

Protecting the water from contamination is top priority. The DEP has spent more than $1 billion acquiring land and easements to limit encroachment. A dedicated police force patrols infrastructure from the air, on water, and the periphery. Swimming beneath the surface, fish – critical in detecting biological terrorism.

“Actual fish we’re talking about?” Murdock said.

“Actually fish, yes,” Rush said. “We monitor how it swims, if it coughs, changes in behavior, to pick up on possible contamination.”

DEP also works closely with farms in the watershed to reduce run-off. Thunderview Farms in Grahamsville is home to roughly 400 angus cattle. The Coombe family has partnered with the NYC DEP, along with the watershed agricultural council for decades to help ensure the quality of the water supply. Manager Ric Coombe shares his family’s land sits less than four miles from the Roundout Reservoir.

“Anything that happens on our farm could be in the New York City terminal reservoir in less than 24 hours, so it was very important for us to be an active participant,” he said.

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All cattle are fenced out of streams. Their water gets pumped in. The farm exercises rotational grazing. All manure gets captured in wintertime and is spread only when weather permits.

In addition, more than 1,000 DEP employees help ensure the safety and quality of the drinking water, from source to sink. One of them is Lori Emery, director of water quality and innovation.

“It’s pretty much just pure water from mountain streams and reservoirs,” she said.

Ninety percent unfiltered. What starts in the Catskills gets tested by scientists and robots. Floating on the Neversink is DEP’s continuous monitoring system. Sensors sit beneath the surface.

“We measure in real time turbidity, temperature, conductivity,” Emery said.

The data helps make a decision on not just which reservoir to ship water from, but also from what depth. From the watershed, water travels via aqueduct south.

“We disinfect the water with chlorine, but we also built the world’s largest ultraviolet disinfection facility,” Emery said.

That’s in Westchester County. Water passes under UV light, pathogens get washed away. Gravity then carries the water into heavily guarded Hillview Reservoir – the last place the H2O sees the light of the day before flowing hundreds of feet below the city and out through the spigot.

“My biggest concern long-term is climate change,” Rush said.

Rush says the system is sensitive to storms, and in the years to come stronger storms are expected with greater frequency.

“Those bigger storm events result in runoff that can cause turbidity, can cause fine materials, clays, to get suspended in the water,” he said.

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The New York City DEP is investing in research and modeling to understand all possibilities, so that 100 years from now, New York City tap water can still live up to being “the best water in the world.”

Vanessa Murdock