Groundwater Vocabulary
Master the essential terms before diving into Long Island's aquifer system.
📚 Introductory Reading
Groundwater: Earth's Hidden Water Supply
Most of the fresh water available for human use is not found in rivers or lakes — it is found underground. When precipitation such as rain or melting snow falls on Earth's surface, some of it flows over the land as runoff into streams and rivers. However, a significant portion of this water seeps downward through soil and rock in a process called infiltration. This water eventually fills the tiny spaces, or pores, between underground rock particles and sediment. When these pore spaces become completely filled with water, the rock or sediment is said to be saturated. The underground layer of saturated, permeable rock or sediment that can store and transmit water is known as an aquifer.
The boundary between the saturated zone below and the unsaturated zone above is called the water table. The depth of the water table is not fixed — it rises during periods of heavy rainfall when recharge is high and drops during droughts or when too much water is pumped from wells. Two important properties determine how well an underground material can function as an aquifer. Porosity refers to the percentage of open pore space within the material, which controls how much water it can hold. Permeability refers to how easily water can flow through the connected pores of the material. A good aquifer, such as a layer of sand or gravel, has both high porosity and high permeability. Clay, on the other hand, may have high porosity but very low permeability because its tiny pores are not well connected, which is why clay layers often act as barriers that prevent water from moving between aquifer layers.
Aquifers are recharged when water from the surface slowly percolates downward through the unsaturated zone and reaches the water table. Areas where this recharge occurs are called recharge zones and must be protected from development and contamination. Once water enters an aquifer, it moves slowly through the pore spaces — sometimes traveling only a few centimeters per day. Because groundwater moves so slowly, contamination from surface sources such as chemical spills, fertilizers, or improperly maintained septic systems can persist in an aquifer for decades or even centuries. This is why understanding groundwater systems is critical to protecting public water supplies, especially in areas like Long Island, New York, where underground aquifers are the sole source of drinking water for millions of residents.
✏️ Check Your Understanding — Fill in the Blank
📖 Key Terms — Click to Study
🔗 Matching Activity
Terms
Definitions
📝 Part 1 Quiz
The Long Island Aquifer System
Explore the three-layer aquifer system that supplies drinking water to nearly 3 million people.
🗺️ Long Island's Three Aquifers
The Three Aquifer Layers
Upper Glacial Aquifer — The shallowest layer (0–120 ft deep), composed of sand and gravel deposited by glaciers. This aquifer is the most vulnerable to surface contamination because it has no protective clay layer above it. It is the first to receive recharging rainwater.
Magothy Aquifer — The primary drinking water source (200–1,000 ft deep), this massive layer of sand and gravel is separated from the Upper Glacial by the Gardiners Clay. It holds the majority of Long Island's fresh groundwater and takes decades to centuries to recharge.
Lloyd Aquifer — The deepest layer (1,000–1,500+ ft deep), resting on bedrock. Protected by the Raritan Clay above, this aquifer contains the oldest water on Long Island — some estimates suggest water in the Lloyd may be thousands of years old. It is used as a backup supply.
🌊 Interactive Digital Aquifer
👆 Click on a layer to learn more
Click anywhere on the aquifer diagram above to see detailed information about that layer.
📊 Water Table Facts
📡 Live Aquifer Data Monitor
🔬 Scenario Investigation
Scenario 1: Baseline Conditions
Turn everything off. This represents Long Island's aquifer in a normal state with average conditions.
Scenario 2: Heavy Rainfall / Recharge Period
Toggle rain on only. This simulates a wet spring season that recharges the aquifer system.
Scenario 3: Summer Drought + Heavy Pumping
Turn rain off, turn the well on. This simulates a dry summer with high water demand from residential and commercial use.
Scenario 4: Coastal Crisis — Over-Pumping + Saltwater Intrusion
Turn rain off, turn well on, and turn saltwater intrusion on. This is the worst-case scenario facing Long Island's coastal communities.
📋 Data Collection Table
| Scenario | Water Table Depth (ft) |
Upper Glacial Level (%) |
Magothy Level (%) |
Recharge (in/yr) |
Chloride (mg/L) |
Well Output (gal/min) |
|---|---|---|---|---|---|---|
| 1. Baseline | — | — | — | — | — | — |
| 2. Heavy Rain | — | — | — | — | — | — |
| 3. Drought + Pump | — | — | — | — | — | — |
| 4. Coastal Crisis | — | — | — | — | — | — |
📈 Graph Builder
🧠 Data Analysis Questions
📝 Part 2 Quiz
Pollution Pathways
Discover how contaminants infiltrate Long Island's aquifer system and threaten our drinking water.
⚠️ Sources of Contamination
🔬 How Pollutants Travel Underground
The Journey of a Contaminant
When a chemical is spilled on the surface or leaches from underground storage, it begins a slow but relentless journey downward through the soil. First, it passes through the unsaturated zone (vadose zone), where soil and air pockets exist between grains of sand. As it reaches the water table, it enters the saturated zone and begins spreading horizontally in the direction of groundwater flow.
On Long Island, groundwater generally flows from the central "spine" of the island outward toward the north and south shores. A contaminant spilled in central Nassau County could theoretically reach coastal waters — but it may take decades or even centuries to travel that far. Along the way, it forms a contaminant plume — an underground cloud of polluted water that can stretch for miles.
Clay layers like the Gardiners Clay act as barriers, slowing or preventing downward migration. However, if these layers have gaps or fractures, contaminants can reach deeper aquifers like the Magothy, which is the primary drinking water source.
🗺️ Contamination Plume Simulation
📝 Part 3 Quiz
Case Studies: Groundwater Pollution & Cancer Rates
Examine real-world connections between groundwater contamination and public health on Long Island and beyond.
📋 Case Study 1: Grumman/Bethpage Naval Facility
The Bethpage Community Park Plume
For decades, the Northrop Grumman (formerly Grumman Aerospace) facility and the U.S. Navy's Naval Weapons Industrial Reserve Plant in Bethpage manufactured aircraft components. Industrial solvents, including trichloroethylene (TCE) and tetrachloroethylene (PCE), were used for degreasing metal parts and then dumped or stored improperly.
This created one of the largest groundwater contamination plumes in the nation — stretching over 4 miles long and up to 2 miles wide, contaminating the Magothy Aquifer that serves as the drinking water source for surrounding communities. TCE levels in some monitoring wells were found to be hundreds of times above EPA safe drinking water standards.
Public water suppliers in Bethpage, South Farmingdale, and Massapequa had to install advanced carbon filtration systems, and some wells were shut down entirely. In 2019, the site was designated a federal Superfund site by the EPA, triggering large-scale cleanup efforts.
📝 Case Study 1 Questions
📋 Case Study 2: Camp Lejeune, North Carolina
Military Base Water Contamination & Cancer
From the 1950s to the 1980s, the drinking water at Camp Lejeune, a U.S. Marine Corps base, was contaminated with industrial solvents including TCE, PCE, benzene, and vinyl chloride. Sources included an off-base dry cleaning business, on-base industrial activities, and leaking underground storage tanks.
Studies by the Agency for Toxic Substances and Disease Registry (ATSDR) found that Marines, their families, and civilian workers exposed to the contaminated water had significantly elevated rates of several cancers, including kidney cancer, liver cancer, bladder cancer, and leukemia. Non-Hodgkin lymphoma and breast cancer rates were also elevated.
In 2012, Congress passed the Janey Ensminger Act, providing healthcare to affected veterans. In 2022, the PACT Act established a pathway for victims to seek compensation. An estimated 1 million people were potentially exposed during the contamination period.
📝 Case Study 2 Questions
📋 Case Study 3: Long Island Breast Cancer Study
The Long Island Breast Cancer Study Project (LIBCSP)
In the 1990s, researchers and community activists raised alarm about unusually high breast cancer rates on Long Island, particularly in Nassau and Suffolk counties. In 1993, Congress mandated the Long Island Breast Cancer Study Project to investigate potential environmental causes.
The study, conducted by Columbia University and other institutions, examined links between breast cancer and environmental exposures including organochlorine pesticides (like DDT), polycyclic aromatic hydrocarbons (PAHs) from vehicle exhaust and industrial emissions, and electromagnetic fields. These compounds can persist in soil and groundwater for decades.
While the study found that Long Island's breast cancer rates were approximately 15% higher than the national average, it did not identify a single environmental cause. However, researchers noted that individual PAH-DNA adducts (a biomarker of PAH exposure) were associated with increased risk. The study highlighted how multiple low-level environmental exposures could have cumulative effects on health, and led to increased monitoring of Long Island's groundwater quality.
📝 Case Study 3 Questions
📋 Case Study 4: PFAS — "Forever Chemicals" on Long Island
PFAS Contamination in Drinking Water Wells
Per- and polyfluoroalkyl substances (PFAS), known as "forever chemicals" because they do not break down in the environment, have been detected in numerous Long Island drinking water wells. These chemicals were used in firefighting foam (AFFF) at airports and military bases, as well as in consumer products like non-stick cookware and waterproof clothing.
Areas near Republic Airport in Farmingdale, Gabreski Airport in Westhampton Beach, and Francis S. Gabreski Air National Guard Base have shown elevated PFAS levels. Studies link PFAS exposure to kidney and testicular cancer, thyroid disease, immune system effects, and reproductive problems.
In 2020, New York State established some of the nation's strictest Maximum Contaminant Levels (MCLs) for PFOA and PFOS at 10 parts per trillion — far stricter than the previous EPA advisory of 70 ppt. Water districts across Long Island are now installing advanced granular activated carbon (GAC) filtration systems at a cost of hundreds of millions of dollars.