Drinking Water Is at Risk in Parts of Long Island, Study Finds

Drinking Water Is at Risk in Parts of Long Island, Study Finds - The New York Times

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Drinking Water Is at Risk in Parts of Long Island, Study Finds

Decades of pumping have allowed saltwater to threaten the aquifers that supply many communities, including Long Beach and Great Neck.

The supply of drinking water for parts of Long Island is under threat, according to a new federal report.

The report found that the groundwater in some coastal areas of Nassau County, a major suburb of New York City, is increasingly turning salty. That shift, called saltwater intrusion, is the result of decades of pumping fresh water out of wells for homes and irrigation, creating space for saltwater from the ocean to seep into the underground aquifers once filled with freshwater.

The change could take generations to reverse, even if pumping stopped altogether, according to the report. And it could force coastal areas — including Long Beach, Great Neck and Oyster Bay — to look for new supplies of drinking water, possibly by digging wells further inland, which could put new pressure on those places as well.

Those places “are at that point of the spear,” said Frederick Stumm, a research hydrologist at the U.S. Geological Survey and the report’s lead author. “They’re the most vulnerable communities right now to intrusion.”

The findings in Long Island come as the United States faces a groundwater crisis. In an investigation last year, The New York Times examined data for tens of thousands of wells around the country. In almost half those sites, the amount of groundwater had declined significantly over the past 40 years.

The growing stress on groundwater can be caused by population growth, as on Long Island. But climate change also plays a role. As temperatures rise, water demand increases. Warmer weather also means more water evaporates before seeping into the ground, reducing the rate at which water drawn from underground aquifers can be replaced.

One of many potentially dire consequences of overpumping groundwater is saltwater intrusion. Scientists refer to something called the saltwater interface, a sort of underground boundary with saltwater on one side and freshwater on the other. As fresh water is pumped out, that interface creeps inland. Once it reaches a drinking-water well, that well typically has to be shut down.

In a twist of history, western Long Island was the first place in America to experience that phenomenon. As Brooklyn and Queens boomed in the late 1800s and early 1900s, there were no major rivers to supply water for households or for factories. So people drilled wells. Those wells turned salty and had to be abandoned.

“That’s really how saltwater intrusion was first kind of learned,” Dr. Stumm said. “It was really the first concentrated area of coastal pumping that took place.”

Brooklyn and Queens were connected to the aqueduct that brings water to New York City from upstate. But Nassau County continues to rely on wells for its drinking water. And since 1940, the county’s population has almost quadrupled.

Yet despite that growth, officials had no way of knowing how far the saltwater interface was from their wells or how fast it was moving inland.

To find out, Dr. Stumm and his team drilled new monitoring wells, equipped with sensors that could detect the distance to saltwater. They could map, for the first time, the saltwater interface. They also compiled and analyzed decades’ worth of records from existing wells.

Their conclusion: The saltwater interface was much closer than people suspected. And it was moving inward.

In Great Neck, a wealthy peninsula on the north shore of Long Island where F. Scott Fitzgerald wrote part of “The Great Gatsby,” saltwater intrusion is getting worse, the report found. The same is true in nearby Manhasset Neck, the next peninsula to the east. One of the largest increases in saltwater intrusion was in Oyster Bay. Wells are also in danger in Long Beach, on the south shore.

In a news release, the New York State Department of Conservation, which regulates groundwater and funded the report, said it “provides valuable information.”

“Although saltwater intrusion remains a concern in certain localized areas of western Long Island, presently saltwater intrusion is not a significant concern for its overall water supply,” the statement said.

The department did not respond to questions about whether it would change its policies on groundwater following the report, or what would happen to communities facing threats to their water supplies.

Officials from Nassau County did not respond to a request for comment. A spokesman for Long Beach said the city needed time to digest the report.

Communities that lose their supply wells may be able to dig new wells further inland, Dr. Stumm said. But that’s no easy endeavor.

“It’s very expensive to move wells,” he said. “They’re significant depth. They’re significant width. They have to put very expensive types of pumps in them. There’s all this other infrastructure that goes with it.”

Upmanu Lall, director of the Columbia Water Center at Columbia University in New York, said that other options included conservation, harvesting rainwater, treating and reusing wastewater, and desalination. “Business as usual is unlikely to be successful,” said Dr. Lall, who wasn’t involved in the report. “One thing is sure, their costs are going to have to go up to deal with all this.”

Christopher Flavelle is a Times reporter who writes about how the United States is trying to adapt to the effects of climate change. More about Christopher Flavelle
U.S. Department of the Interior

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