Where does our water come from on Long Island?

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Every day, the average American uses about 80-100 gallons of water for various purposes. But do you know where it comes from? Here on Long Island, the water that flows from our faucets originates far below the earth’s surface, in deep, interconnected underground layers of sand, gravel and silt called aquifers. The water contained within consists entirely of what originated as rain that seeped slowly downward for hundreds—or even thousands—of years. The plentiful aquifers contain about 90 trillion gallons of water—enough to cover Long Island in a 300-foot flood—much more than is actually needed to meet our current demands. This unique system makes us less dependent on yearly rainfall as some other areas, such as New York City, which relies on reservoirs for its public water. Our water source, constantly replenished by precipitation, has many unique benefits. Starting as rainwater, it seeps through hundreds of feet of soil and closely-packed natural particles before reaching the aquifers. This procedure is actually a natural filtration process which cleanses the water of most impurities. The water is stored by nature, primarily in three underground layers.

The top one, called the glacial layer, contains water that fell somewhere between 10 and 50 years ago. It is the newest to the groundwater system. Under the glacial layer sits the Magothy aquifer, the largest of the aquifer formations. It holds the most water, much of which is hundreds of years old. Running as deep as 800 feet, this layer of sand, gravel and silt was deposited about 60 million years ago and is the region’s main source of drinking water. The deepest and oldest is called the Lloyd layer, starting approximately 1,100 feet below the surface. This aquifer is largely untapped. It holds the oldest water, some of which has been there for more than 5,000 years. Some 1,000 deep wells throughout Nassau and Suffolk pump about 125 billion gallons of water from our aquifer system each year for use by the area’s 2.7 million residents. Surprisingly, more water is replenished by rainfall than is actually pumped. Thankfully, we won’t run out of water anytime soon; however, we should make a conscious effort not to waste this precious natural resource. Although Long Island’s quantity of water is plentiful and its quality is among the best in the nation, always remember that the future of our supply will be determined by how well we treat our environment today. Paul Granger, P.E., is Vice President of H2M Water. He can be reached at pgranger@h2m.com.