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 recharged from rain water and snowmelt. Groundwater also can be recharged from other sources such as, water-supply system (pipeline) leaks, on-site septic systems, and when crops are irrigated with more water than the plants can use (Clark and Briar, 1993).
Precipitation
The first comprehensive precipitation study covering Long Island was done by. On Long Island, average monthly precipitation throughout the year is fairly constant (about 3 to 4.5 inches per month), but on an annual basis can vary by location (see figure below) from around 40 inches per year in southern Nassau County to about 50 inches per year in west-central Suffolk County (figure 8) (Miller and Fredrick, 1969).
Recharge
In the report, precipitation on Long Island averaged about 43 inches for the analysis period. (Peterson (1987), compares precipitation values given by (Miller and Frederick (1969) with more recent and extended long-term averages and calculated the average Long Island precipitation to be 45.2 inches per year.
Much of the precipitation on Long Island never reaches the groundwater system because it is lost through evapotranspiration and as direct runoff. The remainder known as recharge, is the amount that infiltrates through the land surface and percolates downward to the water table, entering the groundwater-flow-system. Natural recharge can be calculated from the following equation:
Recharge = Precipitation - Evapotranspiration - Direct Runoff
Recharge investigations across Long Island estimate that the average annual recharge is approximately 50 percent of Long Island’s annual precipitation. USGS studies on Long Island have shown that the construction of catchment or “recharge” basins can enhance recharge to the aquifer system by intercepting street runoff. Conversely, large scale sewering can direct water that was formerly recharged to the aquifer from individual septic systems to a central water treatment facility, where it is directed to tidewater and thus removed from the aquifer system.
The rate at which precipitation replenishes the groundwater system may affect future water supplies in some areas. Annual precipitation on Long Island averages 45.2 inches per year, but less than 23 inches (or 50 percent), recharges the groundwater system (Peterson, 1987).
The rate of recharge varies locally and ranges from 29 to 57 percent of precipitation (figure 9) depending on land use, season, and amount of storm sewering in the area. Recharge was calculated by subtracting evapotranspiration and direct runoff values from known precipitation values. Evapotranspiration was calculated by the Thornthwaite and Mather method. Direct runoff rates to streams were calculated from streamflow records and size of known storm-sewer service areas (Peterson, 1987).
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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 Surface Water
Long Island Groundwater
Long Island Hydrogeologic Units
Long Island Fresh and Saltwater Relations/Interactions
- Overview
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 recharged from rain water and snowmelt. Groundwater also can be recharged from other sources such as, water-supply system (pipeline) leaks, on-site septic systems, and when crops are irrigated with more water than the plants can use (Clark and Briar, 1993).
Precipitation
The first comprehensive precipitation study covering Long Island was done by. On Long Island, average monthly precipitation throughout the year is fairly constant (about 3 to 4.5 inches per month), but on an annual basis can vary by location (see figure below) from around 40 inches per year in southern Nassau County to about 50 inches per year in west-central Suffolk County (figure 8) (Miller and Fredrick, 1969).
Sources/Usage: Public Domain.Figure 8. Mean precipitation on Long Island, N.Y. 1951-1965(Public domain.) Recharge
In the report, precipitation on Long Island averaged about 43 inches for the analysis period. (Peterson (1987), compares precipitation values given by (Miller and Frederick (1969) with more recent and extended long-term averages and calculated the average Long Island precipitation to be 45.2 inches per year.
Much of the precipitation on Long Island never reaches the groundwater system because it is lost through evapotranspiration and as direct runoff. The remainder known as recharge, is the amount that infiltrates through the land surface and percolates downward to the water table, entering the groundwater-flow-system. Natural recharge can be calculated from the following equation:
Recharge = Precipitation - Evapotranspiration - Direct Runoff
Recharge investigations across Long Island estimate that the average annual recharge is approximately 50 percent of Long Island’s annual precipitation. USGS studies on Long Island have shown that the construction of catchment or “recharge” basins can enhance recharge to the aquifer system by intercepting street runoff. Conversely, large scale sewering can direct water that was formerly recharged to the aquifer from individual septic systems to a central water treatment facility, where it is directed to tidewater and thus removed from the aquifer system.
The rate at which precipitation replenishes the groundwater system may affect future water supplies in some areas. Annual precipitation on Long Island averages 45.2 inches per year, but less than 23 inches (or 50 percent), recharges the groundwater system (Peterson, 1987).
Sources/Usage: Public Domain.Figure 9. Mean long-term annual recharge in Nassau and Suffolk Counties(Public domain.) The rate of recharge varies locally and ranges from 29 to 57 percent of precipitation (figure 9) depending on land use, season, and amount of storm sewering in the area. Recharge was calculated by subtracting evapotranspiration and direct runoff values from known precipitation values. Evapotranspiration was calculated by the Thornthwaite and Mather method. Direct runoff rates to streams were calculated from streamflow records and size of known storm-sewer service areas (Peterson, 1987).
_______________________________
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 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 Groundwater
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.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).