The U.S. is facing a groundwater crisis and Long Island, where our sole source aquifer stores all our water needs in underground reserves, is no exception. 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.
Soon after the Land Alliance was founded in 2003, we found that the most important reason to protect land in western Long Island is to protect our water resources. Long Island’s drinking water comes from a sole source aquifer. We need open land for rain and snow to permeate the ground and replenish the aquifer. We need trees to absorb precipitation and increase the effectiveness of groundwater recharge. The deep-water recharge areas of the aquifer system are in the center of Long Island, just north of the Long Island Expressway. In the early 1980’s, as development increased and the natural areas needed for groundwater recharge decreased, New York State designated these areas as special groundwater protection areas (SGPAs) to protect the water supply for all Long Island.
The growing stress on groundwater can be caused by population growth, as on Long Island. Since 1950, the number of people living in Nassau County has more than doubled, and resource depletion has increased significantly as a result. According to the U.S. Geological Survey (USGS), every day around 400 million gallons of water are used on Long Island for household uses, with another 60 million daily gallons of usage coming from agriculture. For context, Long Islanders tend to use 70% more water than the national average.
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.
In recent years, the quality of our drinking water has been in question due to various forms of chemical pollution. Today, the quantity of our drinking water, which is much harder to measure, is also questionable.
In 2016, the USGS began an eight-year cooperative study with the New York State Department of Environmental Conservation (DEC) to evaluate the sustainability of Long Island’s sole-source aquifer system. The results, released in August 2024, found that the drinking water supply for parts of Long Island is under threat.
The study also found that the level of salt found in groundwater is increasing in some coastal areas of Nassau County. This change has been caused by decades of pumping fresh water out of wells for homes and irrigation. The removal of fresh water creates space for salt water from the ocean to seep into the underground aquifers.
One of the potentially dire consequences of over-pumping groundwater is saltwater intrusion. Picture a boundary located in the underground aquifer that has fresh water (from the aquifer) on one side and salt water (from the bay and other waterbodies) on the other. Scientists refer to this separation as the saltwater interface. As fresh water is pumped out of the aquifer, the interface moves farther inland until it eventually reaches a drinking well. Once this saltwater intrusion occurs, the well usually needs to be shut down.
Ironically, 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 abandonment led to establishing a connection from Brooklyn and Queens to the aqueduct that brings water to New York City from upstate. But Nassau County continues to rely on wells for its drinking water.
Due to the location of the aquifers deep below the surface, for many years officials had no way of knowing how far the saltwater interface was from their wells or how fast it was moving inland. Now they do!
The process for gathering the data was extensive. New monitoring wells equipped with sensors were dug. The sensors mapped the saltwater interface for the first time. Then, decades’ worth of data from existing wells was compiled and analyzed to establish a baseline.
The findings revealed that the saltwater interface was much closer than people suspected. And it was moving inward. One of the largest increases in saltwater intrusion was in Oyster Bay.
Further research suggests that saltwater intrusion could take generations to reverse, even if we stopped pumping altogether. And it could force coastal areas — including Long Beach, Great Neck and Oyster Bay — to look for new supplies of drinking water.
The cost to dig new wells in areas located more upland is very expensive, and not a long-term solution. So, what can we do to help save this vital water supply?
In a press release, the NYS DEC, which regulates groundwater and funded the report, said it was “reviewing the results and will review permits in the area of concern, require monitoring and work with the water suppliers to develop a plan for going forward.”
While we know and appreciate that our water providers will do their best, we too can help. The report emphasizes a need for preserving land located above the aquifer and conserving water resources through innovative methods.
Native Bee pollinating a flower
Native Plants
Here is a list of things you can do to help:
- Harvest rainwater and reuse it in your garden.
- Use smart sprinklers that turn off when it rains.
- Implement more sustainable farming practices like use of cover crops and no till that keep nutrients in the soil and allow roots to grow deeper.
- Plant more native species that require less water once established.
- Explore opportunities for graywater recycling. Graywater is defined as non-sewage wastewater from showers, washing machines and sinks which can be used for irrigation of lawns. Households can save up to half of their water costs by using this type of recycling and can even reduce nitrogen pollution when nutrients in the water are used by plants.
On a larger scale, there is a potential to use recycled water to irrigate golf courses, which are substantial contributors to water usage in the region. Indian Island Golf Course in Riverhead is an example of a pioneering course that uses reclaimed water from a nearby wastewater treatment plant to irrigate their land, saving up to 450,000 gallons of water a day that would otherwise be drawn from the aquifer.
Additionally, we can help save our water resources by preserving land on Long Island. Actions that we take on lands located above the aquifer affect both the quantity and quality of the water below. Undeveloped land can absorb stormwater runoff generated by impervious surfaces allowing it to slowly drain into the water table, replenishing the aquifer in a sustainable way. By prioritizing areas that have the greatest impact on water quality, like the SGPAs and wetlands, organizations like the Land Alliance will play a key role in protecting our water source.
While there is no current danger of Long Island’s aquifer running dry, it is important to understand that not all water is created equal. Land Alliance Advisory Board Member and Retired NYIT Professor Sarah Meyland puts it simply: “There will always be water in the aquifer system,” she said. “It’s just a question of, is it going to be potable freshwater or is it going to be saltwater?”
