Approximately 30% of the world’s water is stored as groundwater. Groundwater moves very slowly, on the order of feet per day, however it is still part of the hydrologic cycle. Most of the water in the ground comes from precipitation that infiltrates downward from the land surface.
The upper layer of the soil is the unsaturated zone, where water is present in varying amounts that change over time, but does not saturate the soil. Below this layer is the saturated zone, where all of the pores, cracks, and spaces between rock particles are saturated with groundwater (figures 12A and 12B). Groundwater that is easily obtainable by wells occurs in aquifers, which are water-bearing formations capable of yielding enough water to supply peoples' uses. Aquifers are a huge storehouse of 30 percent of Earth’s water and people all over the world depend on groundwater in their daily lives.
Groundwater is the sole source of freshwater supply in Nassau and Suffolk Counties on Long Island. Long Island's aquifer system consists of a series of gently sloping Pleistocene glacial, glaciofluvial, and glaciolacustrine deposits and Cretaceous fluvial or deltaic deposits of unconsolidated sand, gravel, and clay. The upper surface of the groundwater system is the water table, which typically lies 0 to 190 ft beneath land surface; the lower limit is the Precambrian gneiss and schist bedrock that lies between 0 and 2,700 ft below land surface. The groundwater system is bounded laterally by saltwater. The saltwater interface (the diffuse boundary between fresh and salty water) has generally migrated landward in response to groundwater withdrawal in nearshore areas and the rise in sea level since Pleistocene time. The water table may rise or fall depending on several factors. Heavy rains or melting snow may increase recharge and cause the water table to rise. An extended period of dry weather may decrease recharge and cause the water table to fall (Clark and Briar, 1993).
Source: http://water.usgs.gov/edu/watercyclegwstorage.html
Source: http://pubs.usgs.gov/circ/circ1139/htdocs/boxa.htm
Source: http://pubs.usgs.gov/circ/circ1186/html/gen_facts.html
The USGS monitors groundwater levels in thousands of wells across the U.S. The measurements gathered across Long Island have been used to generate snapshots of the water table conditions since 1903 (Burr and others 1904; Veatch and others, 1906) as water-table maps. The water-table and potentiometric surfaces of Long Island’s aquifers have been mapped by the USGS through many investigations for over 100 years. The most recent 2016 hydrologic conditions maps from Como and others (2018) are available online.
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Table of Contents
State of the Aquifer, Long Island, New York - Introduction
- Precipitation
- NWIS - the USGS Data Archive
- Surface Water - Streamflow
- Groundwater Levels
- Water Table and Surface Maps
- Water Use
- Groundwater Budget
- Inflow to the Groundwater System
- Outflow from the Groundwater System
Below are other science projects associated with this project.
Hydrologic Cycle
Long Island Precipitation and Recharge
Long Island Surface Water
Long Island Hydrogeologic Units
Long Island Fresh and Saltwater Relations/Interactions
- Overview
Approximately 30% of the world’s water is stored as groundwater. Groundwater moves very slowly, on the order of feet per day, however it is still part of the hydrologic cycle. Most of the water in the ground comes from precipitation that infiltrates downward from the land surface.
The upper layer of the soil is the unsaturated zone, where water is present in varying amounts that change over time, but does not saturate the soil. Below this layer is the saturated zone, where all of the pores, cracks, and spaces between rock particles are saturated with groundwater (figures 12A and 12B). Groundwater that is easily obtainable by wells occurs in aquifers, which are water-bearing formations capable of yielding enough water to supply peoples' uses. Aquifers are a huge storehouse of 30 percent of Earth’s water and people all over the world depend on groundwater in their daily lives.
Sources/Usage: Public Domain.Figure 12. (A) Generalized precipitation entering the groundwater system as recharge (Winter and others, 1998; Cohen and others, 1968) (Public domain.)
Sources/Usage: Public Domain.Figure 12. (B) Cross section of Long Island showing zones of aeration and saturation within the pore spaces (Winter and others, 1998; Cohen and others, 1968) (Public domain.) Groundwater is the sole source of freshwater supply in Nassau and Suffolk Counties on Long Island. Long Island's aquifer system consists of a series of gently sloping Pleistocene glacial, glaciofluvial, and glaciolacustrine deposits and Cretaceous fluvial or deltaic deposits of unconsolidated sand, gravel, and clay. The upper surface of the groundwater system is the water table, which typically lies 0 to 190 ft beneath land surface; the lower limit is the Precambrian gneiss and schist bedrock that lies between 0 and 2,700 ft below land surface. The groundwater system is bounded laterally by saltwater. The saltwater interface (the diffuse boundary between fresh and salty water) has generally migrated landward in response to groundwater withdrawal in nearshore areas and the rise in sea level since Pleistocene time. The water table may rise or fall depending on several factors. Heavy rains or melting snow may increase recharge and cause the water table to rise. An extended period of dry weather may decrease recharge and cause the water table to fall (Clark and Briar, 1993).
Source: http://water.usgs.gov/edu/watercyclegwstorage.html
Source: http://pubs.usgs.gov/circ/circ1139/htdocs/boxa.htm
Source: http://pubs.usgs.gov/circ/circ1186/html/gen_facts.html
The USGS monitors groundwater levels in thousands of wells across the U.S. The measurements gathered across Long Island have been used to generate snapshots of the water table conditions since 1903 (Burr and others 1904; Veatch and others, 1906) as water-table maps. The water-table and potentiometric surfaces of Long Island’s aquifers have been mapped by the USGS through many investigations for over 100 years. The most recent 2016 hydrologic conditions maps from Como and others (2018) are available online.
_______________________________
Table of Contents
State of the Aquifer, Long Island, New York - Introduction
- Precipitation
- NWIS - the USGS Data Archive
- Surface Water - Streamflow
- Groundwater Levels
- Water Table and Surface Maps
- Water Use
- Groundwater Budget
- Inflow to the Groundwater System
- Outflow from the Groundwater System
- Science
Below are other science projects associated with this project.
Hydrologic Cycle
The water cycle has no starting point, but we'll begin in the oceans, since that is where most of Earth's water exists. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air; a relatively smaller amount of moisture is added as ice and snow sublimate directly from the solid state into vapor. Rising air currents take the vapor up into the...Long Island Precipitation and Recharge
Precipitation is water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. It is the primary connection in the water cycle that provides for the delivery of atmospheric water to the Earth. Most precipitation falls as rain. Water seeping down from the land surface and reaching the water table adds to the groundwater and is called groundwater recharge. Groundwater is...Long Island Surface Water
Streams either gain water from inflow of groundwater from the underlying aquifer or lose water by outflow to the underlying aquifer. Many streams do both, gaining in some reaches and losing in other reaches. Furthermore, the groundwater flow directions near any given stream can change seasonally as the altitude of the water table changes with respect to the stream-surface altitude or when rapid...Long Island Hydrogeologic Units
Long Island’s aquifer system consists of a seaward-dipping wedge of mostly unconsolidated stratified sediments comprised of sand, gravel, silt and clay.Long Island Fresh and Saltwater Relations/Interactions
Because saltwater has a greater density than freshwater, fresh groundwater in coastal aquifers will overlie any saltwater that is present in the aquifer at depth (Figure 14).