The suburban reservoirs that supply 10% of New York City’s vaunted drinking water are getting saltier due to decades of road salt being spread near the system — and they will eventually have to be abandoned if nothing is done to reverse the trend, city officials warn.

The plug wouldn’t have to be pulled until early next century, according to a new study. But the soaring saltiness could eventually affect the famous taste of the Big Apple’s water, which is sometimes called the champagne of tap water, and poses a challenge to managers of a system that serves more than 9 million people.

“The conclusion of this study is that if we don’t change our ways, in 2100 the Croton Water System becomes a nice recreational facility, but it ceases to be a water supply,” Rohit Aggarwala, the city’s environmental protection commissioner, said in an interview with The Associated Press. “And that will directly impact everybody who drinks New York City water.”

The Croton system dates back to 1842 — when the first Croton Aqueduct began delivering water to a reservoir in what is now Manhattan’s Central Park — and is now comprised of 12 reservoirs and three controlled lakes north of the city.

The report found the concentration of chlorides — an indicator of salinization — tripled from 1987 to 2019 in the system’s main reservoir, which is about 20 miles (32 kilometers) north of the city line. Concentrations are on track to exceed the state’s maximum contaminant level for chloride by 2108.

The report found salinity increases across the sprawling system of city reservoirs in upstate New York. However, the problem is far less of an issue in the Delaware and Catskill watersheds west of the Hudson River, which supply about 90% of the city’s water. That’s likely because there’s far less development in those watersheds.

Road salt is considered a main driver of the increase, along with sewage treatment plant discharges and water softeners. Millions of tons of rock salt is spread on U.S. roads each winter as a cheap and effective way to reduce accidents.

“It’s really a problem across the country in areas with a lot of snow,” said Shannon Roback, science director for the environmental group Riverkeeper. “We’ve seen rising levels of salt in water in the Northeast, in the Midwest and in most places that use road salt.”

Roback noted that high salt levels in drinking water pose a host of environmental concerns and can be harmful to people on low-sodium diets.

Aggarwala said the city has a few options.

Salt can be removed from water supplies through reverse osmosis systems, though the technology is expensive and requires a lot of energy. The city also could mix Croton water with less salty water from its other two watersheds. But the commissioner said that would not be a solution for the more than a dozen municipalities north of New York City that draw water from the Croton system.

City officials believe reducing the use of road salt locally is the most sensible option. That could involve persuading state and local road crews to use alternatives to salt, or sensors on plows to gauge road surface temperatures, or shutting off the applicators when plows make U-turns or K turns.

State Sen. Pete Harckham, who represents the area, called the new report alarming, but not surprising given a number of community wells taken offline due to high chloride levels. The Democrat is sponsoring bills that would address the road salt issue, including one that would study the issue in the Croton watershed.

“State agencies, local governments, everyone needs to come together on this,” he said, “because this is a real challenge.”