Summary of the 

Hydrologic Situation on

Long Island New York, 

as a Guide to 

Water-Management Alternatives

By O. L. FRANKE and N. E. McCLYMONDS

HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON 

LONG ISLAND, NEW YORK

GEOLOGICAL SURVEY PROFESSIONAL PAPER 627-F

Prepared in cooperation with the New York 

State Department of Conservation^ Division 

of Water Resources; the Nassau County 

Department of Public Works; the Suffolk 

County Board of Supervisors; and the 

Suffolk County Water Authority

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

W. A. Radlinski, Acting Driector

Library of Congress catalog-card No. 71-18O655

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 65 cents (paper cover) 

Stock Number 2401-1150
CONTENTS

Q Production,______________________________________

Background, purpose, and scope of the waterbudget study _______________________________

Purpose and scope of this report__________________

Location and general geographic features of the 

area_______________________________________

Location and extent of area._________________

Topographic and general physiographic features ____________________________________

Summary of climatic conditions._____________

Population and land use_____________________

Related investigations_________________________

Acknowledgments __ __________________________

hi natural hydrologic system.______________________

How and where the water occurs.________________

Bodies of surface water.,____________________

Zone of aeration__________________._________

Ground-water reservoir..____________________

Hydrogeologic features of the groundwater reservoir. ______________________

Boundaries of the fresh ground-water 

reservoir _ __________________________

Size of the fresh ground-water reservoir. 

Source of the water and inflow to the hydrologic 

system ______________________________________

Precipitation. _ _____________________________

Disposition of precipitation._________________

Direct runoff.__________________________

Evapotranspiration. ____________________

Infiltration to the zone of aeration________

Recharge to the ground-water reservoir_. 

Movement within the ground-water reservoir_____

Discharge from the ground-water reservoir.._______

Streamflow and springflow.__________________

Ground-water evapotranspiration..___________

Subsurface outflow of ground water.__________

Summary of relations between components of the 

hydrologic system.___________________________

Water quality._________________________________

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How man has modified the natural hydrologic system. _ _ 

History and present stage of development _____

Effects of man's activities on the movement and discharge of water __ ____________________-----.-

Disposal of direct runoff---_-___-_---_-------

Recharge basins... _-_-__ 

Streams...-.--....--..--------- -------

Pumping and distribution of ground water. _ _ _ _

Pumping of ground water ____.___._

Leaky water pipes_-______-_-_--_----__-

Exported water _____ __ __ 

Lawn sprinking and irrigation ___ 

Disposal of used water _________________

Recharge wells...... ____________ 

Cesspools and septic tanks. _______-_-_.--

Sanitary sewers ______________________

Summary of effects of man's activities on the movement and discharge of water___________________

Summary of artificial recharge _ ___--_-----

Loss of water from the hydrologic system as a 

result of man's activities..- _ .____--__-----_

Effects of man's activities on the quality of the water.

Water-management implications of the hydrologic

analysis. --____-_----------_---------------------

The present dilemma -..________-_-__---------

Some concepts related to water management- _.__-_ 

Principle of continuity..--------------------

Yield of the system. __._________-_----------

Conservation of ground water. ________-.----_

Water-management alternatives. __-_____-_-__---_

Increase inflow to the hydrologic system _ . .

Salvage outflow from the hydrologic system _

Permit a planned decrease of fresh ground water

in storage--.-.---------------------------

Maintain approximate balance between inflow

and outflow by means of artificial recharge. _.

Concluding comments on water-management

alternatives. _.____-__------_-----------------

Selected references---..-----------------------------

Tentative water budgets _____________-------------

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ILLUSTRATIONS

MJRES 1-4. Map showing 

1. Location and general geographic features of Long Island, N.Y_____. ______________-_____-------

2. Location of areas and subareas used in this report _ ____ ..______ _ ____-____-___----_------_

3. Landforms, location of major surface-water bodies, and location of start of flow in selected streams 

in June 1967 __ ..__ ___ __. _ _ ___ _ _. ___ __ _ __ __ _ _ ____ .. ___ .- --

4. Average population density in 1965 __ ______________.___________-_____---_-___-_---_-------

5. Graph showing land use in the early 1960's-__---------_____-____-__-___-_-__-------_--------------

in

Pfge
IV CONTENTS

Pa

FIGURE 6. Graph showing distribution of depths to the water table in the water-budget and adjacenl nearshore areas 

based on ground-water levels in September 1965__-_________-______-_.__________________________

7. Map showing depth to water table in southeastern Nassau County, in October 1961- _________________

8. Generalized section showing geologic features of ground-water reservoir. ____________________________

9. Estimated average position of the water table under natural conditions._______________________________

10. Geohydrologic section showing occurrence of salty ground water in southwestern Nassau County in 1961 __

11. Contour map of the bedrock surface____________________________________________________________

12. Map showing thickness of unconsolidated deposits saturated with fresh ground water in 19^5__________

13. Flow diagram of the hydrologic system under natural conditions____________________________________

14. Maps showing (A) average annual, (B) average cool-season, and (<7) average warm-season precipitation, 

water years 1951-65__________________------_____________________________

15. Graph showing composite average monthly precipitation for selected stations for the normal period 1931-60._

16. Graphs showing daily precipitation, average water content in the soil profile at one measuring site, and 

depth to water in an adjacent well, Brookhaven National Laboratory in 1966._____________________

.17. Idealized cross section showing potential and flow lines in part of a homogeneous ground-vater reservoir. _

18. Map showing water-table contours near Massapequa Creek in October 196l_______________.____________

19. Diagrammatic cross section of the southern half of the ground-water reservoir showing the part of the reservoir with primarily two-dimensional flow and the part of the reservoir with three-dinr^nsional flow to 

streams_____ ____________________ _____________________________________________________________

20. Geohydrologic section of the ground-water reservoir in northeastern Nassau County in March 1961_______

21. Geohydrologic section of the ground-water reservoir in southwestern Suffolk County in October 1960____

22. Profiles of the water table and piezometric surfaces at the base of the Magothy aquifer and in the Lloyd 

aquifer in 1963__-___________________________-__-_-__-__--__---__-________-__---____-_____

23. Graph of magnitude and frequency of annual average discharge of streams from the water-budget area____

24. Graph showing estimated duration curve of daily streamflow from the water-budget area._______________

25. Hydrographs of composite average monthly ground-water levels in selected wells and composite average 

monthly discharge of selected streams in Nassau County for the period 1940-50-____ ______________

26. Graph of average monthly discharge of selected streams and average monthly ground-water levels in selected 

wells in Nassau County for the period 1940-50----__--_____---_------__-___---___---_-___ ______

27. Graph of relation between average monthly discharge of selected streams and average r>onthly groundwater levels in selected wells in Nassau County for the period 1940-50-___________________________

28. Summer and winter recession curves for Carmans River.________-__----_-_____--__-____-_____-___-__

29. Maps showing estimated transmissivity of (A) upper glacial aquifer, (B) Magothy aquifer, and (O Lloyd 

aquifer..______________________________________________l-___-_______________________________

30. Graph of relation between a modified specific capacity factor (Q/sL) and the percentage of total number of 

wells for the principal aquifers__________--__--_----___---_-_-----_____---_---_-__---_--_-_--

31. Block diagram showing changes in the chemical quality of the water under natural conditions.___-____.__

32. Map showing status of water development in 1966--_-_-----_----_---------------_------_--------__-

33. Flow diagram of the hydrologic system in Nassau and Suffolk Counties in the 1960's____________________

34-36. Graph of 

34. Relation between rainfall and inflow to the Westbury recharge basin, Nassau County, 1966-67- __

35. Cumulative curves of annual direct runoff in East Meadow Brook and annual precipitation at 

Mineola__ ___________________________--_-__---_----_--------_--_----_--_-------_--_-_

36. Relation between rainfall and runoff for individual storms in the East Meadow Brock drainage area,

Nassau County, for urban (1964-66) and preurban (1934-43) periods________________________ '

37. Graph showing total treated sewage effluent discharged from Nassau and Suffolk Counties for the period 

1950-65- __________________________________-_-_-_-_.__--___________________________

38. Maps showing ground-water levels in Kings and Queens Counties in (A) 1903, (B), 1936, and (C) 1965__

39. Graph showing estimated discharge of water from Nassau and Suffolk Counties as a result of man's activities, 

1940-65 ________________________________________-_-_------___-_._________________

TABLES

P8|

TABLE 1. Population by county and total population of Long Island, N.Y., 1900-65._ _________________ .

2. Summary of the rock units and their water-bearing properties, Long Island, N.Y_ ______________--___-_-

3. Estimated volume of fresh ground water in storage beneath parts of Long Island, N.Y__________--_-_-_-

4. Average annual and average seasonal precipitation on Long Island, N.Y., and the water-budget area, water 

years 1951-65________________________________________________ 

5. Mean and extreme values of precipitation at Setauket, Long Island, N.Y., water years 188':'-1967 _-_

6. Annual direct runoff of selected streams on Long Island, N.Y., whose drainage areas closely approximate 

natural conditions, water years 1958 and 1964.________________________________________________
CONTENTS V

Page 

'A.BLE 7. Relation of depth to the water table and average time lag in response to recharge in till-covered areas of

northeastern Nassau County, Long Island, N.Y_ _____---_--__-------__-_-------------------_--- F22

8. Surface drainage areas and average flows of the 19 continuously gaged streams in the water-budget area of

Long Island, N.Y., water years 1940-65____________________________-__--__-___-_______-___..- 27

9. Average transmissivity of the principal aquifers for the water-budget area, Long Island, N.Y___________ 32

10. Estimated average subsurface outflow of ground water from the principal aquifers and total average subsurface outflow from the northern part, the southern part, and the entire water-budget area of Long 

Island, N.Y______,___._-_.________-________.___-__________--___-_---_--_-_-__---------_----_ 33

11. Water budgets of the northern and southern parts and the entire water-budget area of Long Island, N.Y.,

water years 1940-65._________________________________--______-..---------_--__-----_---- 33

12. Selected chemical analyses of natural water on Long Island, N. Y_ __________________-__--_---_---___-_ 36

13. Annual direct runoff of the 19 continuously gaged streams on Long Island, N.Y., for water years 1958 and

1964_______________________________________________________________________________________ 42

14. Gross ground-water pumpage in Nassau and Suffolk Counties, Long Island, N.Y., 1940-65-_____________ 42

15. Selected chemical analyses of water contaminated by man's activities on Long Island, N.Y_______--__-__ 50

16. Water budget of the northern part of the water-budget area within Nassau County, Long Island, N.Y.,

water years 1940-65__________________________________-.___..____----_----_-__---__---------- 59

17. Water budget of the northern part of the water-budget area within Suffolk County, Long Island, N.Y.,

water years 1940-65___________________________________________________________________ 59

18. Water budget of the southern part of the water-budget area within Nassau County, Long Island, N.Y.,

water years 1940-65-________________________________________________._____-___________ 59

19. Water budget of the southern part of the water-budget area within Suffolk County, Long Island, N.Y.,

water years 1940-65.__-_______________________________-__--_____-____----_---_-_-___------ 59

HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

SUMMARY OF THE HYDROLOGIC SITUATION ON LONG 

ISLAND, NEW YORK, AS A GUIDE TO WATERMANAGEMENT ALTERNATIVES

By O. L. FRANKE and N. E. MCCLYMONDS

ABSTRACT

Long Island has a total area of about 1,400 square miles 

and includes four counties Kings, Queens, Nassau and 

aid Suffolk. This report describes mainly the "water-budget 

a-ea," which includes about 760 square miles of Nassau and 

Suffolk Counties.

The ground-water reservoir of Long Island is a wedges' aped mass of saturated unconsolidated deposits that overlie 

n?arly impermeable consolidated bedrock and attain a 

maximum thickness of about 2,000 feet The boundaries of 

fie fresh ground-water reservoir are the water table, the 

f'esh-salt water interfaces, the bedrock surface, and the 

streams. The estimated volume of material saturated with 

f~esh ground water in the water-budget area is about 180 

c Tbic miles, and an estimated 10-20 trillion gallons of fresh 

viter would drain from these deposits if they could be 

r^watered.

Under natural conditions, precipitation was the ultimate 

source of virtually all the fresh water on Long Island. The 

£ verage annual precipitation on the island is about 44 inches, 

vhich averages about 1,600 mgd (million gallons per day) 

f » the water-budget area. About 5 percent of the streamflow 

('roughly 20 mgd) that discharges into the sea is direct 

runoff. Bvapotranspiration of precipitation, which averages 

rbout half the average annual precipitation, represents the 

largest element of fresh-water discharge from the hydrologic 

gvstem of the wateMmdget area. Evaporation from open 

liodies of water is negligible in terms of the overall water 

budget.

The principal elements of discharge from the ground-water 

r<*servoir are base flow of streams, subsurface outflow of 

ground water, and evapotranspiration of ground water; these 

< 'ements are estimated to average about 320, 450, and 15 mgd, 

r-^spectively, in the water-budget area. One of 'the most significant features of the fresh water on Long Island is its very 

low dissolved-solids content less than 50 milligrams per liter 

under natural conditions.

At present, more than 2,000 recharge basins in Nassau and 

!" -iffoik Counties recharge the ground-water reservoir with 

substantial quantities of direct runoff. The estimated average 

rnnual inflow to these basins is about 80 mgd. An estimated 

fdditional 60 mgd of direct runoff from urban areas discharges on the average to streams or directly to salty water 

J" Nassau and Suffolk Counties.

Gross ground-water pumpage in the two counties increased 

: -cm about 100 mgd in 1940 to about 330 mgd in 1965. The 

1->tal treated sewage effluent discharged from Nassau and 

Puffolk Counties increased from about 15 mgd in 1950 to

about 75 mgd in 1965. Most of this increased sewage effluent 

was derived from the ground-water reservoir in the southwestern part of Nassau County, and has caused a lowering 

of ground-water levels in that area. Much of 'the shallow 

ground water is contaminated with domestic wastes that wore 

discharged into the ground through cesspools and septic tanks. 

The hydrologic system of Long Island must respond to any 

water-management program in a way that is consistent with 

the water-budget equation. The amount of fresh ground water 

in storage ultimately will be depleted if total outflow j«rpetually exceeds total inflow. The safe yield of the groundwater reservoir of Long Island the amount of water which 

can be withdrawn from it annually without producing an 

undesired result can range between wide limits depend'ug 

upon (1) future management decisions, (2) the amount of 

natural discharge that is salvaged, and (3) the amount of 

additional ground-water recharge that is induced. Proposals 

to manage the water resources of Long Island include barrier 

injection wells, shallow skimming wells, recharge of treated 

sewage effluent through wells or shallow basins, and planned 

encroachment of salty ground water.

INTRODUCTION

BACKGROUND, PURPOSE, AND SCOPE OF THE WATTRBUDGET STUDY

Long Island, which extends from the southeastern 

part of the mainland of New York State eastward 

about 120 miles into the Atlantic Ocean, has a total 

area of about 1,400 square miles (fig. 1). Kings and 

Queens Counties, which are part of New York City, 

occupy slightly less than 200 square miles of the western part of the island, and have a combined population of more than 4.5 million people. Nassau and 

Suffolk Counties have areas of about 290 and 920 

square miles, respectively, and had a combined population of about 2.3 million people in 1965.

Although the New York City part of Long Island 

derives most of its water supply from surface-water 

sources in central New York State, the people of 

Nassau and Suffolk Counties derive their entire water 

supply from wells tapping the underlying groundwater reservoir. Because of present large demands on 

the local ground-water system, particularly in Nassau 

and Suffolk Counties, and because of the prospect of

Fl
F2 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

FIGURE 1. Location and general geographic feature® of Long Island, N.Y.

increased demands as Long Island continues to rapidly 

develop, knowledge about the hydrologic system with 

special emphasis on water conservation and management is a matter of vital concern to the present 

population and to the millions of people who will 

depend on the ground water in the future.

Considerable information is available about the 

water resources of Long Island as a result of studies 

made during more than 30 years by the U.S. Geological Survey in cooperation with New York State and 

county agencies. Although those studies meet many 

of the needs for information on specific problems and 

areas of Long Island, better quantitative information 

about the islandwide hydrologic system, and the relations between the various components of the system, 

is needed for water-management purposes. To provide 

that water information, a comprehensive water-budget 

study presently is being made by the U.S. Geological 

Survey in cooperation with the New York State 

Department of Conservation, Division of Water Resources; Nassau County Department of Public Works; 

Suffolk County Board of Supervisors; and Suffolk 

County Water Authority.

The major objectives of the water-budget study are 

(1) to summarize and interpret pertinent existing 

information about the hydrologic system of Long 

Island and (2) to fill several gaps in the knowledge 

of the hydrologic system. The results of these studies 

are being published in a series of coordinated reports. 

In some of the reports, information is developed for

all of Long Island; in others, however, the primary 

area of concern is limited to mosf of Nassau and 

Suffolk Counties.

PURPOSE AND SCOPE OF THFS REPORT

The present report, which is the summary report 

of the series, describes and discusses (1) how the 

hydrologic system of Long Island functioned under 

natural conditions, (2) how man has modified the 

natural hydrologic system, and (3) the water-management implications of this hydrologic analysis with particular reference to the concept of "yHd" of the system 

and long-term responses of the system to various watermanagement alternatives.

LOCATION AND GENERAL GEOGRAPHIC FEATURES 

OF THE AREA

LOCATION AND EXTENT O* AREA

Long Island is bounded on the nor*:h by Long Island 

Sound, on the east and south by th<\ Atlantic Ocean, 

and on the west by New York Bay and the East 

River (fig. 1). Several smaller islr.nds are included 

in the political boundaries of Long Island; the better 

known of these are Fire, Shelter, Gardiners, Fishers, 

and Plum Islands. The total area of Long Island 

(including the smaller islands within the political 

boundaries of the island, but excluding the bordering 

bays) is about 1,400 square miles; its maximum width 

is about 23 miles.

Fire Island is the longest of several barrier beaches
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F3

",t parallel the south shore of Long Island. It ranges

m about a quarter of a mile to a mile in width, 

 i is separated from the main island by Great

nth Bay, a shallow body of salty water that has 

maximum width of about 5 miles. The other barrier 

rches along the south shore are also separated from 

r, main island by salty bays, the best known of 

lich is Jamaica Bay along the south shore of Kings 

d Queens Counties.

The northern and eastern coast lines of Long Island 

r, indented by deep bays that form excellent harbors. 

i ?onic Bay, which is about 30 miles long, divides the 

rtern end of the island into two long, narrow peninns that are locally referred to as the North and 

nth Forks.

?ome of the succeeding hydrologic information pren ted in this report relates to all of Long Island. 

rst of the information, however, relates primarily

the "water-budget area." The various areas and 

bareas of Long Island (fig. 2), which are defined

this report to facilitate the hydrologic analyses, 

c, as follows: (1) The water-budget area subdivided 

to a northern part and a southern part; (2) the 

j .rshore area also subdivided into northern and 

rtherii parts; (3) the North and South Forks; and 

: the New York City part of Long Island. 

r-nhe water-budget area, which includes about 760 

rare miles, is bounded on the west by the border 

^iween Nassau and Queens Counties; the eastern 

rmdary is long 72°40' W., which is near the streamLqring station on the Peconic River; the northern 

nndary generally follows the northern shoreline; 

id the southern boundary is a curved line that joins 

\.f., streamflow-measuring stations on the major streams

that drain into the bays along the south shore. Th<> 

northern and southern parts of the water-budget are^ 

are separated by the ground-water divide on the watertable contour map for September 1965 (Cohen and 

others, 1968, p. 23), and have areas of about 310 and 

450 square miles, respectively.

The nearshore areas are located just north and south 

of the water-budget area and comprise those parts 

of the mainland of Long Island lying between th°- 

northern and southern boundaries of the water-budget 

area and the adjacent salty water of Long Island 

Sound and the bays adjacent to the south shore. Th°. 

areas of the northern and southern nearshore areas 

are about 15 and 80 square miles, respectively.

The North and South Forks, as here designated, 

include all the parts of the main island areas east of 

long 72°40' W., which total about 240 square miles. Th«, 

New York City part of Long Island (Kings and 

Queens Counties) has an area of slightly less than 200 

square miles.

The water-budget area comprises the bulk of that 

part of Long Island where public-supply water i^ 

derived from the underlying ground-water reservoir. 

Furthermore, most of the fresh ground-water reservoir 

of Long Island is located beneath the water-budge* 

area, and therefore, most of the subsequent development of the local water resources will take plac? 

within this area. The Forks have been designated as 

a separate area because, hydrologically, they are virtually independent of the main part of Long Island. 

Finally, the New York City part of Long Island is 

a logical area for separate discussion because most of 

its water supply is imported from upstate surfacewater sources.

73"00' 30' 7l°45'

^

EXPLANATION

Ground-water divide; 

>tember 1965 water levels

^Southern part of t^^j

water-budget area i\\\v-N

£[ Water-budget area

0 C

25 MILES

^^Southern

nearshore area , r 

A 1

D'30'

FIGURE 2. Location of areas and subareas used in this report.

 27-144 O - 71 - 2
F4 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

TOPOGRAPHIC AND GENERAL PHYSIOGRAPHIC 

FEATURES

Most of the major features of the present-day topography of Long Island (fig. 3) are related to the last 

ice age, which ended about 10 thousand years ago. 

The most prominent physiographic features are (1) 

the east-trending hills in the northern and central parts 

of the island, and their eastward extensions which 

form the "Forks," (2) the gently sloping plain that 

extends southward from the hills, (3) the deeply 

eroded headlands along the north shore, and (4) the 

barrier beaches along the south shore.

The two lines of hills, which are terminal moraines 

and which reach a maximum altitude of about 400 

feet, are separate and distinct in the central and eastern parts of the island, but they converge in the 

western part. The southernmost line of hills, the Ronkonkoma moraine, extends eastward to form the South 

Fork. The northern line of hills, the Harbor Hill 

moraine, extends eastward to form the North Fork.

The moderately flat surface that extends southward 

from the Ronkonkoma moraine to the south-shore bays 

is a glacial-outwash plain. It generally heads at an 

altitude of about 100-150 feet, and slopes southward 

at about 20 feet per mile until it merges with Holocene 

lagoonal deposits along the coast.

The eroded headlands along the north shore are 

composed mainly of various types of glacial deposits. 

After the ice sheets melted, the land surface of Long 

Island rose slightly with respect to sea level, the headlands were deeply eroded, and the many wide and 

deep harbors along the north shore were carved by 

northward-flowing streams. Wave erosion has steepened the northern slopes of the headlands into nearly 

vertical bluffs that, in places, are about 100 feet high.

Along the south shore, waves and ocean currents 

have formed offshore bars, or "barrier beaches." In 

terms of geologic time, these bars are ephemeral features that are gradually being eroded by wave action. 

Sand and silt deposited by the wind, streams, and 

tidal currents, as well as organic deposits, have partially filled and are continuing to fill the shallow bays 

behind the barrier beaches.

SUMMARY OF CLIMATIC CONDITIONS 

Long Island is located between 40° and 42° north 

latitude in a temperate-climate belt. The mean annual 

temperature on the island, about 51°F (11°C), is several degrees higher than the average for all of New 

York State because of the modifying influence of the 

bordering Atlantic Ocean and Long Island Sound. 

Minimum average monthly temperatures on Long Island occur in February and range from about 28° to

32°F (-2°-0°C); maximum average monthly tempe 

atures occur in July and range from about 69° to 75 c 

(21°-24°C). In general, average temperatures decrea 

from west to east, and south-shore temperatures a 

slightly less than north-shore temperatures at t 

same longitude, Maximum and minimum temper 

tures of record on Long Island are 103°F and -14C 

(39° and -26°C), respectively.

Precipitation averages about 44 inches per year aj 

is fairly evenly distributed thoughout the year 

Long Island.

The prevailing wind direction on Long Island 

northwest during most of the year, except during t 

summer months when south and southwest win 

prevail.

POPULATION AND LA1TD USE

Population figures for Kings, Queens, Nassau, ai 

Suffolk Counties and totals for all of Long Islai 

are given in table 1 for the period from 1900 to 19( 

During the first three decades of the century, bo 

magnitude of population and rate of population grow 

on Long Island were greatest in Kings County, whic 

at that time, was moderately industrialized and w 

characterized mainly by multiple-family dwelling 

Queens County was largely suburban, and Nassau a] 

Suffolk Counties were rural. In the next decade (t' 

1930's), the largest increase in population occurred 

Queens County, mainly as a result of the rapid i 

crease in construction of multiple-family dwellin 

and the growth of industry in that county.

Beginning soon after the end of World War 

and extending into the late 194 O's and the 1950 

marked suburban expansion into Nassau Coun 

caused a dramatic increase in the population of th 

county. The wave of suburban expansion, charactc 

ized mainly by large-scale developments of sing 

family homes, has been moving eastward with tir 

As a result, the population of central and easte

TABLE 1. Population by county and total population of L 

Island, N.Y., 1900-65 l

[In thousands of people]

Year

County

Kings Queens Nassau Suffolk

Tota

1900.--.-------- 1,167 153

1910_-_---_-_--- 1,634 288

1920___-------._ 2,018 469

1930-__--------_ 2,560 1,079

1940-__._------- 2,698 1,298

1950------------ 2,738 1,551

1960--_-----.__- 2,627 1,810

55

84

126

303

407

673

1,300

1965-___________________________ 1,418

78

96

110

161

197

276

667

893

1 Data from U.S. Census Bureau.
fl

w
F6 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

Nassau County increased rapidly in the mid-1950's. 

The population of western Suffolk began to increase 

markedly in the late 1950's, and has been increasing 

more rapidly than the population of any other area 

on Long Island during the past few years.

The present (1968) population density on Long 

Island ranges from very dense in the western part 

to sparse in the eastern part. The pattern of population 

density (fig. 4) mainly reflects the gradual eastward 

transition from highly urban communities characterized by high-rise apartment buildings in Kings County, 

to suburban communities in Nassau and western Suffolk Counties, and finally to the rural areas in eastern 

Suffolk County. In addition to the general pattern of 

progressive eastward decrease in population density, 

there has been a trend of preferential urban development along the north and south shores.

A summary of land use for each county on Long 

Island is shown in figure 5. This information was

74°

EXPLANATION

Average population density, in persons 

per square mile

0-999

1,000-1,999

2,000-4,999

5,000-9,999

10,000-24,999

25,000-50,000

FIGXJBE 4. Average population density in 1966. After Cohen, 

Franke, and Foxworthy (1968, pi. 1C).

compiled from reports prepared by the Nassau Count 

Planning Commission (1959), tin Suffolk Count 

Planning Commission (1962), and the New York Cit 

Department of Planning (1962), and the data ai 

not for exactly the same time. Furthermore, the thr< 

agencies did not use precisely the same land classiJ 

cations nor the same methods of obtaining and evali 

ating the data. Despite these inconsistencies, the dal 

shown in figure 5 are reasonably representative f< 

the early 1960's, and provide considerable insight 1 

the general characteristics of land use on Long Islar 

at present (1968).

The percentage of land occupied by streets ar 

parkways, which is a reasonably accurate measure < 

the intensity of urban development, is greatest 

Kings County (about 30 percent), decreases progre 

sively to the east, and is least in Suffolk County (le 

than 10 percent). Conversely, the percentage of vacai 

land and land that is classified a^ "open" increas 

toward the east from less than 10 percent in Kin/ 

County to nearly 75 percent in Suffolk County. Tl 

highly suburban character of Nassau County is ind 

cated by the fact that nearly 50 percent of the lar 

is classified as residential, and thr.t land is occupit 

mainly by single-family homes.

At present (1968), very little land is devoted 

agriculture in Nassau County; in Suffolk County 

1966 slightly less than 65,000 acres, or about 101 squa 

miles, was classified as agricultural land by the Suffo 

County Planning Commission. Much of this farr 

land is in the northeastern part of Suffolk Coum 

and on the adjacent North Fork.

The major industries of Nassau and Suffolk Counti 

are aviation, instruments, electronics, and fabricatic 

of metals; smaller industries include furniture, prin 

ing and publishing, textiles, and apparel. Most co: 

cerns are small, employing fewer than 100 peopl 

several aviation plants, however, employ several tho 

sands of persons.

RELATED INVESTIGATIONS

Considerable information in this report was derive 

from previously published reports of the U.S. Ge 

logical Survey, as well as from published reports 1 

other agencies and individuals. Many of these repoi 

are referred to in the text, and major sources of adc 

tional information are listed amorg the references.

The water-budget area was first defined and studi< 

in moderate detail in, "An Atlar of Long Islam 

Water Resources," by Cohen, Franke, and Foxwortl 

(1968). The present report contains much informati< 

that is not available in the atlas r.nd evaluates ma]
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F7

RESIDENTIAL

(T'VIMERCIAL AND 

INDUSTRIAL

RECREATIONAL

INSTITUTIONAL

STREETS AND 

PARKWAYS

OPEN USES1 

Al D VACANT LAND

KINGS COUNTY QUEENS COUNTY NASSAU COUNTY

20 40 60 25

LAND AREA, IN SQUARE MILES

75 100 0 50 100 150 200 250 0

SUFFOLK COUNTY

200 400 600 800

25 50 25 50 75 0 25 50 

LAND AREA, IN PERCENTAGE OF TOTAL AREA

75 25 50 75 100

s, nurseries, junk yards, and parking lots

FIGTJBE 5. Land use in the early 1960's. Aflter Cohen, Franke, and Foxworthy (1968, pi. ID).

sheets of the hydrology of Long Island in considerlly more detail than was possible in the atlas.

ACKNOWLEDGMENTS

The authors wish to express their appreciation for 

T-> generous assistance and the data received from 

ir,ny individuals and public agencies. Unpublished 

ata not contained in the files of the U.S. Geological 

T'rvey were obtained primarily from the New York 

t^te Water Resources Commission, Nassau County 

Apartment of Public Works, Nassau County Planrig Commission, Suffolk County Planning Commis- 

' n, and the Brookhaven National Laboratory.

The report was prepared under the immediate superL-Aon of Bruce L. Foxworthy, former Hydrologist-in- 

^ arge, and Philip Cohen, Hydrologist-in-Charge of 

T°> Long Island subdistrict, and under the general 

ruction of Ralph C. Heath and Garald G. Parker, 

T-merly District Chiefs, and Robert J. Dingman, 

Strict Chief, New York District of the U.S. Geo- 

^ical Survey. Special thanks is due to our colleague 

^ Hip Cohen, who played an important role in initiating, and gave invaluable assistance in, the course 

of this study.

THE NATURAL HYDROLOGIC SYSTEM

The following section of the report briefly summarizes how the hydrologic system of Long Island 

functioned under natural conditions. The discussion 

relates primarily, but not exclusively, to the previously 

defined water-budget area of central Long Island. 

Man's activities have markedly altered the hydrologic 

system in some parts of the water-budget area during 

the past 50 years, and have affected the hydrologic 

system in virtually the entire water-budget area. However, the effects of man's activities on most of th«, 

data presented in the following discussion are small cr 

negligible, unless otherwise noted.

Those aspects of the hydrologic system which ar% 

particularly important from the point of view of water 

management are emphasized in the following discursion, and the information presented in some sections c f 

the report is directed primarily to the information 

needs of the water manager.
F8 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

In this section of the report the basic time unit for 

presenting hydrologic information is the water year, 

which is the 12-month period beginning on October 1 

and ending on September 30; it is designated by the 

calendar year in which it ends.

HOW AND WHERE THE WATER OCCURS

On Long Island and its environs, water occurs as 

vapor, as a liquid, and at times during the winter as 

a solid in the form of ice or snow. The water vapor 

occurs primarily in the atmosphere and in the zone 

of aeration. In this study the water vapor of the 

atmosphere is not of concern until it condenses and 

reaches the land surface as precipitation.

Liquid water occurs mainly in bodies of surface 

water and as ground water. Fresh surface-water bodies 

include lakes and streams. In addition, Long Island is 

surrounded by the salty water of Long Island Sound 

and the Atlantic Ocean. Brackish surface water occurs 

in the estuaries and bays between the fresh-watet 

streams and ocean water.

Most of the fresh ground water occurs from the 

bedrock surface to the water table beneath the entire 

mainland of Long Island, except for the Forks where 

only the upper layers contain fresh ground water. 

Locally, small, and probably insignificant, amounts of 

fresh ground water occur in fractures and in the 

upper part of the bedrock where it is highly weathered. 

The occurrence of fresh ground water beneath the 

adjacent bays and barrier beaches varies with depth 

and specific location, and salty ground water occurs 

seaward of fresh ground water around the entire 

perimeter of Long Island.

BODIES OF SURFACE WATER

Several lakes and most of the principal streams on 

Long Island are shown in figure 3. Lake Ronkonkoma, 

with an area of about 0.35 square mile, is the largest 

lake on Long Island. The northward-flowing Nissequogue Eiver has the greatest average discharge about 

42 cfs (cubic feet per second) for the period 1940-65 

of any stream on Long Island. The eastward-flowing 

Peconic Eiver is the longest stream, having a main 

wet-channel length of about 9-10 miles upstream from 

the gaging station. The remaining larger streams flow 

southward into Great 'South Bay. Relative to the southward-flowing streams except for the Nissequogue 

River the northward-flowing streams are short, few 

in number, and discharge relatively small amounts of 

water.

ZONE OF AERATION

The zone of aeration is that part of the solid earth 

lying above the water table. The interstices in this

zone are largely filled with atmospheric gases (inclu 

ing water vapor) and liquid water. The extreme 

significant process of evapotranspiration occurs pi 

marily on and within several feet cf the upper surf a 

of the zone of aeration (land surface), and most 

the water that recharges the ground-water reserve 

passes through the zone of aeraticn.

The volumes of the zone of aeration for all 

Long Island and for the water-budget area we 

about 11 and 10 cubic miles, respectively, in Septet 

ber 1965. If the specific retention of the deposits 

the zone of aeration is assumed to be 10-15 perce 

(see section on "Infiltration to the Zone of Aeratioi 

p. F20), an average of about 1 cubic mile of water w 

stored in this zone on Long Island at that time. Ho^ 

ever, this water cannot move into a well and, therefoi 

is not available for direct use by man.

The distribution of areas with various depths 

the water table in the water-budget area and t] 

immediately adjacent near-shore are^s is shown in figu 

6. The data show that the depth to the water tab 

is less than 10 feet for about 14 percent, or for abo 

120 square miles of this area. Within the water-budg 

area, however, the depth to the water table is less ths 

10 feet in only about 50 square miles.

Figure 7 shows the depth to tl °- water table in 

typical area in the southern part of Long Islan 

based on water levels in October 1961. An appreciab 

area near the south shore is characterized by deptl 

to the water table that are less than 10 feet; the depl 

to the water table generally increases gradually nort] 

ward to the terminal moraine. In most of the are;

-

-

Oto 

10

10 to 

20

: - -. :

*:|||||1

-

If" -;;:' " -

i®::;l: .-, -::e~? 

20 to 40 to 1 80 to 120 to 160 to >200 

40 80 120 160 200 

DEPTH TO WATER, IN FEET

FIGUEE 6. Distribution of depths to t^e water table in th 

water-budget and adjacent nearsbore r re&s, based on grount 

water levels in September 1965.
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES

73°37'30" 35' 40 °47'30"

P9

32'30" 30'

Line of equal depth to 

October 1961

SOUTH OYSTER BAY

3 MILES

FIGURE 7. Depth to the waiter table in southeastern Nassau County in October 1961.
F10 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW TTORK

underlain by terminal-moraine deposits, the depth to 

the water table is more than 50 feet, and in small 

areas the depth to the water table is more than 200 

feet. Depths to the water table near the northern 

coast of the island generally are more than 20 feet, 

except adjacent to stream channels or in narrow bands 

near the shoreline.

GROUND-WATER RESERVOIR

HYDROLOGIC FEATURES OF THE GROUND-WATER RESERVOIR

The overall hydrogeologic setting of Long Island 

was described in considerable detail by Veatch (1906), 

Fuller (1914), and Suter, De Laguna, and Perlmutter 

(1949). The geology and related hydrology of several 

smaller areas of Long Island have been studied in 

greater detail by others, including De Laguna (1963),

NORTH

Isbister (1966), Lubke (1964), Lusozynski and Swai 

zenski (1966), Perlmutter and Geraghty (1963) 

Pluhowski and Kantrowitz (1964), and Swarzensl 

(1963).

Long Island is underlain by consolidated bedrocl 

which, in turn, is overlain by a wedge-shaped mass o 

unconsolidated rock materials (fig. 8).1 These mate 

rials, which constitute Long Island's ground-wate 

reservoir, consist primarily of a series of Pleistocen 

glacial deposits and Cretaceous fluvial or deltaic depos 

its composed of gravel, sand, silt, clay, and mixture 

thereof. The Cretaceous deposits were eroded b;

1 The actual dip of the upper bedrock surface is slightly less than 1 

to the southeast. The much greater inclination of the bedrock surfac 

and the Magothy aquifer shown in figure 8 is d ^e to the large vertical 

scale exaggeration of this cross section.

SOUTh

ATLANTIC 

OCEAN Mi5^

Uppe 

and undifferentiat 

deposits

EXPLANATION

Clay Sandy clay, clayey sand, and silt

o

o

o

\ *

0

*

o

6

Gravel 

FIGUBE 8. Geologic features of the ground-water reservoir.

Consolidated rock
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES

streams and glaciers so that the Pleistocene deposits 

lie on an irregular Cretaceous surface, and in places 

the Pleistocene deposits fill valleys cut by preglacial 

and glacial streams. These valleys have been fairly 

well defined in Kings and Queens Counties and along 

the northern margin of the island eastward to the 

middle of Suffolk County. In eastern Suffolk County, 

however, data on the contact between the Pleistocene 

and the Cretaceous are very sparse.

The upper surface of the Cretaceous deposits is 

above sea level in a large area in northern Nassau and 

western Suffolk Counties, and in all but a few small 

areas, the Pleistocene deposits cover the Cretaceous 

deposits throughout Long Island. Pertinent information concerning the principal hydrogeologic units 

within the ground-water reservoir are briefly summarized in table 2.

Ground water in the uppermost part of the zone 

of saturation on Long Island (mainly in the upper 

glacial aquifer, but locally also in the Magothy 

aquifer) is generally under water-table conditions. 

Artesian conditions predominate in most of the other 

parts of the ground-water reservoir of Long Island, 

where the saturated deposits are overlain and confined 

by silty and clayey layers of low hydraulic conductivity. The hydraulic head in the confined aquifers 

ranges from several feet below the water table to 

nearly 20 feet above it. At places along the north and 

south shores and on the barrier beaches, the head in 

the Lloyd aquifer is high enough to cause some wells 

which penetrate this aquifer to flow.

In addition to the Raritan clay, which confines water 

in the Lloyd aquifer, the other major well-defined 

confining layer in the ground-water reservoir is the 

Gardiners Clay. This unit locally confines water in 

the Jameco and Magothy aquifers. Numerous clayey 

and silty layers in the Magothy aquifer and clay 

beds in the glacial deposits also are significant confining layers. Normally, the degree of confinement in 

the Magothy aquifer increases with depth as more 

and more clayey layers intervene between the deep 

zone and the water table.

BOUNDARIES OF THE FRESH GROUND-WATER RESERVOIR

The boundaries of the fresh ground-water reservoir 

are the water table, the fresh-salt water interface, and 

the bedrock surface. The estimated average position 

of the water table under natural conditions is shown 

in figure 9. The position of the contours is based on 

a map of the water table in Kings, Queens, and 

Nassau Counties in 1903 (prepared by Veatch in 1906), 

and on later water-table maps of Suffolk County.

Major features of this map are the two ares^ of 

highest ground-water altitude (represented by c^sed 

80-ft and 60-ft contours) which extend approximately 

westward in the north-central parts of Nassau and 

Suffolk Counties. Also noteworthy are the steep waterlevel gradients near the north shore of Long Island 

compared to the gradients near the south shore.

The water table, which is the upper boundary of 

the ground-water reservoir, is a dynamic (moverble) 

feature. Present information indicates that recharge to 

the water table occurs throughout virtually all of 

Long Island. Therefore, the water table is not, from 

the point of view of potential theory, a stream surface. It is instead a surface characterized by a constantly varying potential which is equal to the altitude 

of the water table at any point. Because the vater 

table on Long Island is largely a recharging potential 

boundary of the ground-water reservior, streamlines 

flow perpendicularly from the water table into the 

ground-water reservoir. Locally, as near the shore1 ines 

where ground water is lost by evapotranspiration, the 

water table is a discharging potential boundary.

The ground-water reservoir is bordered laterally by 

a second moveable boundary the fresh-salt water interface. The position of this interface (or these interfaces) 

is fairly accurately known only in southwestern Nassau 

and southeastern Queens Counties as a result of an 

intensive investigation by Lusczynski and Swarzenski 

(1966). A north-south cross section through the groundwater reservoir in this area (fig. 10) shows three separate salt-water wedges a shallow wedge in the glacial 

aquifer and intermediate and deep wedges in the 

Magothy aquifer. Furthermore, a fourth wedge exists 

in the Lloyd aquifer somewhere seaward of the barrier 

beaches.

The occurrence of fresh ground water in the Lloyd 

aquifer below salty ground water in the lower part 

of the Magothy aquifer has never been adequately 

explained. However, this occurrence must be related 

in some way to the relatively impermeable Raritan 

clay overlying the Lloyd aquifer. At least four separate wedges of salty ground water with relative 

positions approximately as indicated in figure 10 probably occur for a considerable distance eastward from 

western Nassau County (on the order of ten? of 

miles) along the south shore of Long Island.

Very scanty information indicates that the L?oyd 

aquifer and the deep Magothy aquifer contain s«lty 

ground water beneath the Forks of Long Island. The 

fresh ground water beneath the Forks occurs in a 

lens ranging in thickness from a few feet to several 

hundred feet.

427-144 O - 71 - 3
F12 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

TABLE 2. Summary of the rock units and their water-bearing properties, Long Island, N.Y.

[After McClymonds and Franke, 1971]

System

Quaternary

Tertiary(?)

Cretaceous

Series

Holocene

Pleistocene

Pliocene(?)

Geologic unit

Artificial fill, salt 

marsh deposits,

stream alluvium,

and shoreline

deposits.

Upper Pleistocene 

deposits

 Unconformity? 

Oardiners Clay

 Unconformity? 

Jameco Gravel

 Unconformity 

Mannetto Gravel

 Unconformity 

Magothy Formation

Hydrogeologic

unit

Holocene 

deposits

Upper glacial 

aquifer

Gardiners

Clay

Jameco

aquifer

(Commonly

included 

with upper

glacial

aquifer.)

Magothy 

aquifer

Approximate

maximum

thickness

(feet)

BO

600

300

300

300

1.100

Depth

from

land

surface

to top

(feet)

0

0-50

60400

50-550

0-120

0-600

Character of deposits

Sand, gravel, clay, silt, organic mud, 

peat, loam, and shells.

Colors are gray, brown, green, black,

and yellow.

Holocene artificial-fill deposits of

gravel, sand, clay, and rubbish.

Till (mostly along north shore and in

moraines) composed of clay, sand,

gravel, and boulders. Forms Harbor

Hill and Ronkonkoma terminal

moraines.

Outwash deposits (mostly between

and south of terminal moraines,

but also interlayered with till)

consist of quartzose sand, fine to

very coarse, and gravel, pebble to

boulder sized.

Glaciolacus trine deposits (mostly in 

central and eastern Long Island)

and marine clay (locally along south 

shore) consist of silt, clay, and some

sand and gravel layers; includes "20-

foot clay" in southern Nassau 

County and Queens County.

Colors are mainly gray, brown, and

yellow; silt and clay locally are

grayish green.

Contains shells and plant remains,

generally in finer grained beds; also

contains Foraminifera.

Contains chlorite, biotite, muscovite,

hornblende, olivine, and feldspar as

accessory minerals; "20-foot clay"

commonly contains glauconite.

Clay, silt, and few layers of sand and 

gravel.

Colors are grayish green and brown.

Contains marine shells, Foraminifera,

and lignite; also glauconite, locally.

Altitude of top generally is 60-80 ft

below mean sea level.

Occurs in Kings and Queens Counties,

southern Nassau County, and

Suffolk County; similar clay occurs

in buried valleys near north shore.

Sand, fine to very coarse, and gravel

to large-pebble size; few layers of

clay and silt. Gravel is composed of

crystalline and sedimentary rocks. 

Color is mostly dark brown.

Contains chlorite, biotite, muscovite.

hornblende, and feldspar as accessory minerals. 

Occurs in Kings and Queens Counties, 

and southern Nassau County;

similar deposits occur in buried

valleys near north shore.

Gravel, fine to coarse, and lenses of

sand; scattered clay lenses. 

Colors are white, yellow, and brown.

Occurs only near Nassau-Suffolk

County border near center of island.

Sand, fine to medium, clayey in part;

interbedded with lenses and layers 

of coarse sand and sandy and solid 

clay. Gravel is common in basal 

60-200 ft. Sand and gravel are

quartzose. Lignite, pyrite, and iron

oxide concretions are common;

muscovite, magnetite, rutile, and 

garnet are accessory minerals. 

Colors are gray, white, red, brown,

and yellow.

Water-l taring properties

Permeable sandy beds beneath barrier 

beaches yield fresh water at shallow

depths, brackish to salty water at

greater depth. Clay and silt beneath

bays retard salt-water encroachment

and confim underlying aquifers.

Stream-flood-plain and marsh deposits may yield small quantities of

water, but are generally clayey or

silty and nrich less permeable than

underlying upper glacial aquifer.

Till is poorly permeable; commonly

causes perohed-water bodies and

impedes downward percolation of

water to underlying beds.

Outwash depots are moderately to

highly penreable; specific capacities

of wells tapping them range from

about 10 to more than 200 gpm per

foot of drawdown. Good to excellent

infiltration characteristics.

Glaciolacustrine and marine clay

deposits are mostly poorly permeable, 

but locally have thin moderately

permeable foyers of sand and gravel; 

generally re*ard downward percolation of grourd water.

Contains frest water, except near the 

shorelines. 7M11 and marine deposits

locally retaM salt-water encroachment.

Poorly permeable; constitutes confining 

layer for underlying Jameco aquifer.

Locally, sand layers yield small

quantities of water.

Moderately to highly permeable;

contains mostly fresh water, but 

brackish water and water with high

iron content locally in southeastern

Nassau County and southern Queens

County. Spvjjfic capacities of wells 

in the Jameco range from about 20 to 

ISO gpm per foot of drawdown.

Highly permeable, but occurs mostly 

above water table. Excellent infiltration characteristics.

Most layers are poorly to moderately

permeable; some are highly permeable locally. S -wific capacities of wells 

in the Magof.hy generally range from 

1 to about 31 gpm per foot of drawdown, rarelj* are as much as 80 gpm

per ft. Water is unconfined in uppermost parts, elsewhere is confined. 

Water is generally of excellent quality 

but has hiph iron content locally

along north and south shores.

Constitutes principal aquifer for

pubUc-suppl wells in western Long

island, except Kings County where 

it is mostly absent. Has been invaded

by salty-grmnd water locally in

southwestern Nassau County and

southern Queens County, and in

small areas along north shore.
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F13 

TABLE 2. Summary of the rock units and their water-bearing properties, Long Island, N.Y. Continued

S ^tem

rrtaceous

vmbrian

Series

Upper 

Cretaceous

Geologic unit

 Unc(

Raritan Formation

 Unco 

B

nformity 

Clay member

Lloyd Sand 

Member

sdrock

Hydrogeologic 

unit

Raritan clay

Lloyd aquifer

Bedrock

Approximate 

maximum 

thickness 

(feet)

300

600

Depth 

from 

land 

surface 

to top 

(feet)

70-1,600

200-1,800

0-2,700

Character of deposits

Clay, solid and silty; few lenses and 

layers of sand; little gravel. Lignite 

and pyrite are common. 

Colors are gray, red, and white, 

commonly variegated.

Sand, fine to coarse, and gravel, 

commonly with clayey matrix; some 

lenses and layers of solid and silty 

clay; contains thin lignite layers and 

iron concretions locally. Locally, has 

gradational contact with overlying 

Raritan clay. Sand and most of 

gravel are quartzose. 

Colors are yellow, gray, and white; 

clay is red locally.

Crystalline metamorphic and igneous 

rocks; muscovite-biotite schist, 

gneiss, and granite. A soft clayey 

zone of weathered bedrock locally is 

more than 100 ft thick.

Water-bearing properties

Poorly to very poorly permeab'e; 

constitutes confining layer for underlying Lloyd aquifer. Very few we'Js 

produce appreciable water from these 

deposits.

Poorly to moderately permeab'e. 

Specific capacities of wells in fie 

Lloyd generally range from 1 to abo it 

26 gpm per foot of drawdown, rarely 

are as much as 60 gpm per ft. Water is 

confined under artesian pressure by 

overlying Raritan clay; generally of 

excellent quality but has high iron 

content locally. Has been invaded by 

salty ground water locally in nec^s 

near north shore, where aquifer is 

mostly shallow and overlying clay 

discontinuous. Called deep confined 

aquifer in some earlier reports.

Poorly permeable to virtually impermeable; constitutes virtually fie 

lower boundary of ground-wat«r 

reservoir. Some hard, fresh water is 

contained in Joints and fractures, b'lt 

is impracticable to develop at mcst 

places; however, a few wells near the 

western edges of Qneens and Kin-*s 

Counties obtain water from the 

bedrock.

""he fresh-salt water interface is not a sharp 

Tindary. The horizontal distance over which the 

irsolved-solids content of ground water changes 

~Y>m completely fresh to completely salty is genT.lly on the order of 2-3 thousand feet near the 

r^th shore of Long Island. Over this distance, 

n dissolved-solids content of the ground water 

i ceases at first gradually in the direction of the 

> ty ground water and then more rapidly.

The fresh-salt water interface is a complex streamline surface, and fresh ground water discharging into 

the ocean and bays moves parallel to the interface 

and not across it. The hydrodynamics of a stable 

interface and, to an even greater degree, an unstable 

interface that changes position in response to changes 

in head within the ground-water reservoir, is complicated and beyond the scope of this report. (Se«. 

Lusczynski, 1961; Cooper, 1964; and Kohout, 1964.)

74«00 73'00' 72'00' 71'45'

EXPLANATION

Water-table contour

Shows estimated altitude of the water table 

under natural conditions. Contour intervals 

5, 10, and 20 feet. Datum is mean sea level

C"30'

FIGURE 9. Estimated average position of the water-table under natural conditions.
F14 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

73

QUEENS 

COUNTY

74

Intermediate

salty-water

wedge

-Deep salty-water wedge- "~-^_-i^^r^_~i_~-r-_r^_~_r^_~_'

900'-

1200'-

1 MILE 

I

FIGTJBE 10. Occurrence of salty ground water in southwestern Nassau County, In 1961. Adapted from Lusczynski and

Swarzen&ki (1966, pi. 3).

The top of the bedrock surface, which outcrops in 

western Queens County, dips southeast on the average 

about 65 feet per mile, or slightly less than 1°, to an 

estimated depth of about 2,000 feet in south-central 

Suffolk County (fig. 11). The number of control points 

on the bedrock surface, particularly in Suffolk County, 

is small; therefore, the surface undoubtedly is more 

irregular than is indicated in figure 11.

For practical purposes the bedrock surface is the 

impervious bottom of the ground-water reservoir. 

Hydraulically, therefore, the top of the bedrock is a 

stream surface; ground water flows parallel to the 

bedrock and not across it, and equipotential lines or 

surfaces intersect the bedrock at right angles.

Generally, the flowing parts of tH streams on Lon 

Island are ground-water drains, and the ground wate 

continually discharges into these p<\rts under natura 

conditions. Therefore, in relation to the ground-wate 

reservoir, the streams are discharging potential boun/7 

aries. The potential at a given point on the strear 

is equal to the altitude of the stream at that poin 

Thus, the potential along the stream channel varic 

continuously from the altitude of rtart of flow of th 

stream to the altitude of the surrounding bay c 

ocean.

The approximate location and altitude of the poiv 

of start of flow for several stream^ in June 1967 a T 

shown in figure 3. Because ground-water levels an
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F15

74-15' 74-00' 45' 30" 15' 73'0ty 45' 30' 15' 72*00- 71'45'

h NEW 

JERSEY

Bedrock contour

Shows altitude of bedrock surface, infett. 

Contour interval 200 feet. Datum is me<m,

5 0 5 10 15 20 25 MILES

I' "'I I I I I I

40-30' -1 / / I/

FIGURE 11. Contour map of the bedrock surfaice. Modified from Suter, De Laguira, and Perlmutter (1949, pis. 8-10).

streamflow were below average for this month, these 

altitudes are slightly lower than (on the order of 

5 ft) and the points of start of flow are slightly seaward (on the order of several hundred feet) of their 

average positions. The points of start of flow of the 

streams are points on the water table, and the locations of these points reflect local conditions relating 

to topography and position of the water table.

SIZE OF THE FRESH GROUND-WATER RESERVOIR

The volumes of various parts of the fresh groundwater reservoir are given in table 3. The estimates of 

the volumes of unconsolidated deposits saturated with 

fresh ground water (col. 2) were derived mainly

from a map showing the saturated thickness of the 

ground-water reservoir in 1965 (fig. 12). The water 

table at this time, particularly in Kings, Queens and 

western Nassau Counties, was considerably lower than 

the water table under natural conditions. However, the 

difference in the total volume of fresh ground water 

in the ground-water reservoir in 1965 compared to 

the volume under natural conditions is negligible compared to the total volume of fresh ground water in 

the ground-water reservoir.

The values in column 2 of table 3 are probably 

accurate to within about 10 percent, except for one 

entry the volume of deposits "beneath areas adjacent 

to the water-budget area" (item c). The magnitude

72"00' 71-45'

41°00

74-15' 74-00

I- NEW

JERSEY EXPLANATION

Water-budget area 

200

Line of equal thickness of

saturated material in 19(55

Interval 200 feet

5 0 5 10 15 20 25 MILES

III ii I I I I I __.. I

FIGURE 12. Thickness of unconsolidated deposits saturated with fresh ground water in 1965. After Cohen, Franke, and

Foxworthy (1968, pi. 2#).
F16 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

TABLE 3. Estimated volume of fresh ground water beneath parts 

of Long Island, N.Y.

Volume of

deposits satu- Total volume Range In estimated

Volume designation rated with of fresh storage capacity 

fresh ground ground water (gallons) 

water (cubic (gallons) 

miles)

Item (1) (2) (3) (4)

(a) 

(b)

(c)

(d)

(e)

(0

Above sea level in 

water-budget area. . . 

Beneath entire waterBeneath areas adjacent to waterSums of items b and c

Beneath mainland 

Kings and Queens

Sums of items d and e

5 

180

100

280

10

290

1,600,000 

59,000,000

33,000,000

92,000,000

3,300,000

95,000,000

280,000-560,000 

10,000,000-20,000,000

5, 500, 000-11, 000, 000

15,000,000-31,000,000

550,000-1,100,000

16,000,000-32,000,000

i Includes volume beneath the nearshore areas and the adjacent bays.

of this entry depends on the location of the fresh-salt 

water interface which is not known along much of the 

perimeter of Long Island.

To obtain the values of "total volume of fresh 

ground water" in column 3, the entries in column 2 

were multiplied by 0.30 (the estimated average porosity), and the result was converted to millions of 

gallons. This estimate probably is conservative because 

many of the finer deposits (clays) within the groundwater reservoir probably have a higher porosity.

The storage capacity of the ground-water reservoir 

is the total volume of water in the ground-water reservoir minus the volume of water that would be 

retained against the force of gravity if the reservoir 

were drained that is, the average porosity minus the 

average specific retention times the total volume of 

deposits saturated with water. The average porosity 

minus the average specific retention is equal to the 

average specific yield. Previous investigators estimated 

the average specific yield of deposits in the Long 

Island ground-water reservoir to be about 5-10 percent (Cohen and others, 1968, p. 26). The specific 

yield for individual layers in the ground-water reservoir probably ranges fom less than 1 to 25-30 percent. 

The values in column 4 of table 3 were obtained by 

multiplying the values in column 2 by 0.05-0.10 (or 

5-10 percent) and converting the result to millions of 

gallons.

As a result of the assumptions that were made, the 

values of storage capacity in column 4 are probably 

conservative. However, because of uncertainty about 

the process of salt-water encroachment and the large 

volume of fine-grained deposits (silt and clay) in the 

ground-water reservoir, such conservative estimates are 

necessary to ensure dependable figures for watermanagement purposes.

SOURCE OF THE WATER AND INFLOW TO THE 

HYDROLOGIC SYSTEM

Reference to the accompanying flow diagram (fig. 

13) facilitates the following discussion of the hydrologic system under natural conditions. Only flow 

paths that represent large quantities of water or those 

that are of special interest or significance are shown. 

Many other flow paths that commonly represent negligible quantities of water on Long Island, such as 

infiltration from bodies of surface water to the zone 

of aeration or direct runoff from the land surface 

to the ocean, are not discussed in this report.

PRECIPITATION

Under natural conditions, precipitation is the source 

of all the fresh water on Long Island that is, it is 

the total input to the fresh-water hydrologic system. 

The aspects of the precipitation reg:men on Long 

Island which are especially pertinent to this study are 

the areal distribution, averages, and ranges of annual, 

seasonal, and monthly precipitation. Mc^t of the information regarding precipitation considered in the present report is derived from a detailed report that was 

prepared as part of the present water-budget study 

of Long Island (Miller and Frederic!-, 1969).

Information on the distribution by month of the 

number of days in which specified amounts of precipitation fell and on intensity and frequency of precipitation on Long Island, which was developed in the 

report by Miller and Frederick, is not considered here. 

In addition, the drought, which occurred in the Northeastern United States in 1962-66, and its hydrologic 

consequences on Long Island are evaluated in a separate report (Cohen and others, 1969).

Maps showing average annual, average warm-season 

(April-September), and average cool-season (OctoberMarch) precipitation for water years 1951-65 are 

shown in figure 14. The period 1951-65 was chosen 

for these maps because (1) complete or almost complete records were available for that period for the 

largest number of stations, and (2) data from stations 

with sufficiently long records showed that averages for 

the period 1951-65 were close to averages for the socalled normal period, 1931-60.

A significant feature in figure 14J. is the area of 

high precipitation in north-central Suffolk County. 

Miller and Frederick (1969) state that this feature is 

probably largely related to two factors: (1) The 

greater distance of the area from the Atlantic Ocean 

and Long Island Sound and (2) its slightly higher 

altitude. The map for the average cool-season precipitation (fig. 142?) also shows an area of high precipitation in north-central Suffolk County. However, this
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES H7

ATMOSPHERE

PRECIPITATION EVAPOTRANSPI RATION

A

V I

EVAPOTRANSPI RATION ,

^^ >^_ i -^

 ^ \ ^. -1 

1 I

J « n^

v /f v IEVAPORATION j

1 AND °IIRFAPF DIRECT pnr>irro nr 01 ipr

V 

INFILTRATION ..INFILTRATION

ZONE OF r

AERATION ^ L

V

CAPILLARY RISE DOWNWARD LAHLLAKY Klbt PERCOLATION

SEEPAGE

' >r >

ACE

i *

' )

I

ZONE OF SATURATION

VV/A i t.r\ j ^

\ 1

1 

1

t

± J

J ^1

EVAPOTRANSPI RATION

SEEPAGE 

AND 

SPRING 

FLOW

1

i

^

SURFACE-WATER 

OUTFLOW v

SUBSURFACE 

GROUND-WATER 

OUTFLOW \

0

c

E 

A 

N

EXPLANATION

Heavy lines represent major flow paths; thin lines, minor flow paths; 

solid lines, flow of liquid water; dashed lines, flow of gaseous water

FIGURE 13. Flow diagram of the hydrologic system under natural conditions. After Cohen, Franke, and Foxworthy (1968,

pi. 6A).

feature is less evident in the warm season (fig. 146"), 

presumably because precipitation is more evenly distributed in the warm season than in the cool season.

Mean values of precipitation (derived from fig. 14) 

for all of Long Island (including the Forks) and for 

the water-budget area, and ranges in average precipitation are given in table 4. These values show that 

average warm-season precipitation and cool-season precipitation are almost equal on Long Island.

Composite average monthly precipitation for selected 

stations for the normal period 1931-60 (fig. 15) indicate that precipitation is distributed fairly evenly 

throughout the year, and that average monthly precipitation ranges from about 3 to more than 4 inches. 

During the winter, most of the precipitation on Long 

Island is derived from regional storms. In the summer, however, most of the precipitation is associated 

with local thunderstorms. On the average, the lowest

monthly precipitation occurs in June a montl of 

transition between the period when regional storms 

predominate and the period when local thunderstorms 

supply most of the precipitation.

Precipitation data from Setauket, the station with 

the longest period of record (table 5), indicate that 

precipitation on Long Island ranges widely from month 

to month and from year to year. For example, although 

average annual precipitation at Setauket is about 44.5 

inches, observed annual precipitation ranged from a 

low of about 31 inches in 1966 to a high of about 56 

inches in 1898.

The values of precipitation described in the previous text are total values that is, they include snow, 

snow mixed with rain, and rain alone. The average 

annual snowfall on Long Island is about 25-30 inches, 

or about 10-15 percent of the water equivalent of the 

cool-season precipitation. A tabulation of the number
F18 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

72-00' 71M5'

40°30'

I- NEW 

JERSEY

74-15' 74-00' 72-00' 71-45

h- NEW 

JERSEY

72-00' 71-45

EXPLANATION 

40

Line of equal average precipitatior, 1951-65

Interval 1 and 2 inches with supplementary

0.5-inch litres (dashed)

5 0 5 10 15 20 25 MILES

I i i i i I I I I I I

FIGURE 14. Average annual (A), average, cool-season (B), and average warm-season precipitation (C), water years 1951-65.

After Miller and Frederick (I960).
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F19

OCT NOV DEC JAN FEB MAR APR JUNE JULY AUG SEPT

"IGTJRE 15. Composite average monthly precipitation for selected stations for the normal period 1931-60.

\ABLE 4. Average annual and average seasonal precipitation 

on Long Island, N.Y., and the water-budget area, water years 

1951-65

[In inches]

:f snowstorms greater than 6 inches for the New 

Tork Weather Bureau Office in Manhattan County 

'or the period 1884^1960 (Miller and Frederick, 1969) 

iHowed that most of the large snowstorms were fairly 

rrenly distributed between the first of December and 

,' e middle of March. The greatest number of large 

i'lowstonns occurred during the first half of February.

DISPOSITION OF PRECIPTATION

Precipitation on the land surface follows three main 

)aths (fig. 13) direct runoff to bodies of surface 

vater (primarily streams), return to the atmosphere

TABLE 5. Mean and extreme values of precipitation at Setauket, 

Long Island, N.Y., water years 1888-1967

[In inches]

Precipitation

Area

11 of Long Island (including

1 'ater-budget area. .............

Annual Cool season

Mean Range Mean Range

AA Q dft-*\A 91 (\ 91 97

.. 44.8 41-50 23.8 21-27

Warm season

Mean Range

20. 7 19-23 

21. 0 20-23

by evapotranspiration, and infiltration into the zone 

of aeration. Precipitation that infiltrates into the zone 

of aeration is either transpired by plants or percolates downward to the ground-water reservoir (zine 

of satuation).

DIRECT RUNOFF

Values of direct runoff to selected streams, whose 

drainage areas have remained virtually unaffected by 

man, are given in table 6. Data for water years 1958 

and 1964 were chosen for comparison because th?,se 

were years of exceptionally high and low annual precipitation, respectively. On the basis of meager dtf.ta, 

it appears that the amount of annual precipitation 

did not materially affect the percentage of total streamflow that was derived from direct runoff under natural 

conditions. Furthermore, the figures indicate that the 

percentage of direct runoff in the discharge of the 

two northward-flowing streams (Mill Neck Creek and 

Nissequogue Kiver) was slightly greater than the 

percentage of direct runoff in the discharge of Germans Kiver, a southward flowing stream. Two factors 

probably accounted, at least in part, for this difference: 

(1) Slightly less permeable soils in areas underlain by 

glacial till near the north shore as compared to the 

highly permeable glacial outwash deposits near the 

south shore and (2) steeper land-surface gradients 

adjacent to the north-shore streams compared to the 

south-shore streams.

Because southward flowing streams include most of 

the streamflow on Long Island (about 75 percent), 

the data in table 6 suggest that under natural conditions an average of less than 5 percent of total measured streamflow is direct runoff. This quantity of water 

represents less than 1 percent of the precipitation 

that fell on the drainage areas of the streams in the 

water-budget area.

EVAPOTRANSPIRATION

Total evapotranspiration from the hydrologic system of Long Island includes evaporation from the land 

surface and surface-water bodies, evapotranspiration

TABLE 6. Annual direct runoff of selected streams on Long Island, 

N.Y., whose drainage areas closely approximate natural conditions, water years 1958 and 1964

Precipitation

d'ean. ._ _______

?i me of occurrence. _ 

4 ;nimum _ _______

'i *ne of occurrence. _

Annual

44. 5

56.4 

1898

30. 8 

1966

Warm season

21.7

35.4 

1938

11.0 

1965

Cool season

22.8

34. 1 

1899

12.0 

1947

Monthly

3.7

13 2 

Sept. 1938

0. 1 

June 1949

Water year 1968

Stream

Mill Neck Creek.. 

Nissequogue

Carmans River. __

Average discharge (cubic 

feet per 

second)

10.7

47. 3 

30. 6

Water year 1964

Direct runoff Average dis- 

(percentage of charge (cubic 

total dis- feet per 

charge) second)

10

7 

3

7.2

37. 7 

20.9

Direct runoff 

(percentage of 

total discharge)

10

r 

3

427-144 O - 71 - 4
F20 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

from the zone of aeration, and evapotranspiration 

directly from the ground-water reservoir (fig. 13). 

Total evapotranspiration excluding evapotranspiration 

of ground water is briefly discussed in this section 

of the report. Evapotranspiration of ground water is 

discussed in the section on "Discharge from the 

Ground-Water Reservoir."

Annual evapotranspiration constitutes the greatest 

unknown in the disposition of precipitation on Long 

Island. Previous investigators estimated average annual evapotranspiration by difference from other 

quantities in a hydrologic budget. Thus, any errors 

in the estimates of these other quantities were incorporated in the estimate of evapotranspiration. This 

procedure resulted in estimates of average annual 

evapotranspiration that were about one-half of average annual precipitation, or between about 20 and 25 

inches. Information is not available to improve upon 

these estimates in the present investigation.

Average annual values of "potential" evapotranspiration derived by the application of methods developed by Thornthwaite and Mather (1955, 1957) and 

Meyer (1928) are about 29 and 32 inches, respectively. 

Thus, the upper limit of annual "potential" evapotranspiration for a specific year is probably on the 

order of 30-35 inches. Minimum warm-season precipitation for the months April to September for most 

stations ranges from about 12 to 15 inches. If it is 

assumed that most of this precipitation is discharged 

to the atmosphere and that some additional evapotranspiration occurs during the winter months, the 

minimum values of annual evapotranspiration are 

probably on the order of 10-15 inches.

Mean annual evaporation from a land pan in central 

Nassau County for the period 1949-60 was about 48 

inches (Pluhowski and Kantrowitz, 1964), of which 

an average of about 36 inches, or about 75 percent evaporated during the summer months (AprilSeptember) . This same seasonal distribution of average 

annual evapotranspiration was indicated by the 

monthly values of potential evapotranspiration derived 

from the methods of Thornthwaite and Mather and 

Meyer.

INFILTRATION TO THE ZONE OF AERATION

No data are presently available to estimate directly 

the quantity of water that infiltrates into the zone of 

aeration. However, systematic measurements of soil 

moisture provide an estimate of evapotranspiration 

from the zone of aeration and recharge to the water 

table through the zone of aeration. In addition, such 

measurements provide valuable information on the 

storage characteristics of the deposits in the zone

of aeration and in the upper part of the zone o 

saturation.

Studies of soil moisture in glacial outwash deposit 

using a neutron meter have been underway for severa 

years at the Brookhaven National Laboratory unde 

the direction of G. M. Woodwell. The results of thes 

studies are included in a report by P^iners and Wood 

well (1966). Their report included a water budge 

based on soil moisture measurements for the summe 

and fall of 1963. Unpublished data from these studie 

for most of 1966, which include daily precipitation 

average water content of the upper 6 feet of the soi 

profile, and the depth to the water table in a shallow 

nearby well, are shown in figure 16. The following 

observations can be made from this figure: (1) Wliei 

the average water content of the 6-foot soil profil 

was between about 10 and 11 inche?, as in April am 

late September, ground-water levels slowly declined 

(2) when the average water content of the soil pro 

file was greater than about 11 inches as during mos 

of May, ground-water levels rose; and (3) in thi 

extremely dry period of late July and early August 

the average water content of the soil was betweei 

5 and 6 inches and ground-water levels declined.

These data and data from Reirer and Woodwel 

(1966) suggest the following tentative conclusions con 

cerning the soils and uppermost deposits in the Brook 

haven area: (1) Field capacity of these soils is aboul 

10-15 percent; and (2) if the total porosity is assumec 

to be about 30-35 percent, which is indicated by soil 

moisture measurements in the capillary fringe, the 

specific yield of these materials if on the order oi 

15-25 percent. Although these con?lusions are basec 

on very sparse data, they are comparable to con 

elusions concerning similar deposits elsewhere, anc 

may, therefore, be reasonably representative of tht 

glacial-outwash deposits of Long Island.

Additional observations by Reirer and Woodwel 

(1966) indicate that the effect of vegetation on soi 

moisture must occur primarily in the upper 3 fee 

on Long Island, because the root systems of mos 

indigenous vegetation do not extenc1 below this depth 

Probably only the largest trees have any appreciab1 

effect on soil moisture below 'a depth of 10 feet.

RECHARGE TO THE GROUND-WAT7.R RESERVOIR

Under natural conditions, virtually all ground-wate 

recharge on Long Island resulted from the infiltraticr 

of precipitation into the zone of aeration and subse 

quent downward percolation through the zone o 

aeration to the water table (fig. 13). As with evapo 

transpiration, available data do net permit measure 

ment of recharge directly. In the present report, a^
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F21

<eo

.Z Ltl

2: ac 2

s lu..lJ,. ..Ilk ..!.... ,*&.. J I,. .... i , d I j.ILl i L M ,Ul

Z 10

<£> uj a

~ -1 °

£ = 7

o_ O c

o. a: 6

=>°- 5

I 9

p 10

13

14 l I I l l l i I I I I I I l I i I I i I I I i i i i i i I l I I I l l l l l I I I i i i i I i i i i i i i i i i i i i I I l I I I I l l l l I

10 20 

JAN

10 20 

FEB

10 20 

MAR

10 20 

APR

10 20 

MAY

10 20 

JUNE

10 20 

JULY

10 20 

AUG

10 20 

SEPT

10 20 

OCT

10 20 

NOV

10 20 

DEC

"VURE 16. Daily precipitation, average water content in the soil profile at one measuring site, and depth to water in an adjacent 

well, Brookhaven National Laboratory, in 1966. Data courtesy of G. M. Woodwell, Brookhaven National Laboratory.

:f*imate of average annual recharge to the groundv^.ter reservoir can be made by first recognizing that 

inder natural conditions long-term average annual 

T",harge to, and discharge from, the ground-water 

T^ervoir were equal. An estimate of average annual

-'-liarge is obtained, therefore, by summing the estimtes of average annual discharge for each element 

N : discharge from the ground-water reservoir. These 

xbments, which include base flow of streams, groundv^ter evapotranspiration, and subsurface outflow, are 

evaluated in a subsequent section of this report. 

Previous investigators estimated average annual

 enlarge by subtracting estimates of average annual 

)i apotranspiration and other water-budget components 

Tom average annual precipitation. These estimates 

^ average annual recharge were equal to about oneirlf the average annual precipitation (about 22-23 

r, of water), or about 1 million gallons per day per 

;<"uare mile (Cohen and others, 1968, p. 44). The 

Y.ta presented subsequently in this report indicate 

rat these previous estimates are in line with the best 

r formation presently available. Cohen, Franke, and 

Toxworthy also estimated that annual recharge ranged

*,">m about 10 to 35 inches of water.

Although no direct measurements of the quantity 

of recharge on Long Island are available, some info^- 

mation is available on the rate of movement of recharge 

water in the zone of aeration. Average times of travel 

through the zone of aeration in the till-covered areas 

of northeastern Nassau County as determined by Isbi?- 

ter (1966) are given in table 7. Isbister equipped 

several wells having different depths to the water 

table with water-level recorders. He then observed 

the time until the water levels in the wells responded 

to recharge from an identifiable large storm. Wells 

with progressively smaller depths to water generally 

showed smaller ranges in lag time. However, t] n, 

response times in a single well ranged widely. For 

example, in a well where the depth to water was 

about 180 feet, the response time ranged from 5 to 

16 months as compared to an average of 9-10 month" 

(table 7).

Although the lag times given in table 7 may b«, 

considered reasonably representative for the tillcovered northern part of Long Island, these times are 

undoubtedly too large for the more permeable glacialoutwash deposits in the southern part of Long Island. 

Wells in these deposits with depths to water of 30-40
F22 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

TABLE 7. Relation of depth to the water table and average time lag 

in response to recharge in till-covered areas of northeastern Nassau 

County, Long Island, N.Y.

[After Isbister (1966, table 10)]

Depth to water table 

(feet)

0-10____-_______

10-25___________

25-40___ ________

40-60______.____

60-80 __ ________

Average 

response time 

(months)

0-1

1-2

2-3

3-4

4-5

Depth to water table 

(feet)

80-100__.___-_-_

100-120________.

120-140________.

140-160________.

160-180. ________

Average 

response time 

(months)

5-6

6-7

7-8

8-9

9-10

feet often show a marked water-level response within 

hours or within a day or two after a large storm.

MOVEMENT WITHIN THE GROUND-WATER 

RESERVOIR

An idealized cross section of part of a ground-water 

reservoir is shown in figure 17. The dimensions of the 

cross section are similar to the Long Island groundwater reservoir in a north-south cross section south 

of the ground-water divide. The potential and flow 

lines in figure 17 were derived in part from an 

electric-analog model using graphite paper as the 

conducting medium (Wyckoff and Reed, 1935). In 

this model and in figure 17, the vertical exaggeration 

is about 15 to 1 compared to the Long Island groundwater reservoir. The water table was simulated by 

10 discrete potential drops from the maximum potential in the system at the water-table divide (designated 

arbitrarily as 1000 in figure 17) to base level (zero 

potential or ground). No attempt was made to model 

a salt-fresh water interface.

The flow pattern in figure 17 was constructed for 

the following idealized conditions: (1) The flow was 

two dimensional, (2) the flow medium was homogeneons, (3) the upper boundary of tlie flow system (th 

water table) was a constant source, of recharge, an< 

(4) the lower boundary (impermeable bedrock) wa 

a stream surface. Despite the idealized assumption 

used to construct this flow net, several significan 

observations concerning the Long Island flow systen 

can be made from the net. Except for narrow area 

near the left- and right-hand margins of figure 17 

the predominant directional component of flow i 

horizontal. In a model without vertical exaggeratioi 

the horizontal character of the flow would be evei 

more pronounced. Furthermore, the flow line originat 

ing at the water-table divide follows a path neares 

the bedrock and discharges farthest from the shore 

line. The flow lines originating progressively shore 

ward of the water-table divide penetrate less deeph 

into the flow system and discharge nearer the shoreline

Another significant observation from figure 17 ii 

that, with the particular geometry and potentials 

fixed in the model, some discharge (electrical output) 

from the system occurs landward of the shoreline 

Because this model is reasonably analogous to th< 

flow system of the Long Island ground-water reservoir 

the results suggest that some discharge mechanism maj 

also be acting in this area in the prototype. On Lon£ 

Island this discharge mechanism is largely associate, 

with the flowing parts of the streams.

Seepage of ground water to the streams is a majoi 

factor in modifying the two-dimeninonal flow patterr 

in the shallow part of the ground-water reservoii 

in figure 17. East-west flow components that art 

perpendicular to the idealized flow section in fig 

ure 17 are clearly indicated in figure 18, which is $ 

water-table contour map of the southeastern part c> 

Nassau County. North of the flowing parts of the

Ground-water divide

1000'

900

acsaocs a a

^C\j 00 *; IO <O ^

dodo odd

Shoreline

, Bottom of ocean 

(zero potential)

700

Bedrock surface

FIGURE 17. Idealized cross section showing potential and fflow lines in part of a homogeneous grornd-water reservoir.

Q is total discharge through system.
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F23

F\

2 MILES

CONTOUR INTERVAL 20 FEET 

DATUM IS MEAN SEA LEVEL

EXPLANATION 

 40 

Water-table contour

: altitude of water table, October 1961. Contour interval 

5 feet. Datum is mean sea level

FIGURE 18. Water-table contours near Massapequa Creek in 

October 1961.

streams, the water-table contours show relatively even 

and slight curvatures. In the neighborhood of their 

flowing parts, however, the water-table contours are 

bent sharply towards the streams, which clearly indicates that ground water discharges into them.

The ground-water system on Long Island ca.n be 

divided into two general subsystems a shallow circulating subsystem and a deep circulating subsystem. 

Ground water in the shallow subsystem, which is 

particularly well developed south of the main 

water-table divide, discharges mainly into the streams; 

ground water in the deep subsystem discharges into 

the bays, the Atlantic Ocean, and Long Island Sound. 

Flow paths in the deep subsystem range in length 

from one to several miles, and the flow is generally 

two dimensional (fig. 19). On the other hand, flow 

paths in the shallow7 subsystem range from a few feet 

to several thousand feet, and the flow is generally 

three dimensional.

Representative geohydrologic sections of the natural 

flow" system in the northern and southern parts of Long 

Island are shown in figures 20 and 21, respectively. 

These sections show some of the principal geologic 

features of the ground-water reservoir that are responsible for modifying the idealized flow pattern shown 

in figure 17. The presence of almost horizontal and 

poorly permeable beds in the flow section tends to 

accentuate the horizontal components of flow, except 

near the ground-water divide and in discharge areas 

near the shorelines. Despite the obvious differences 

in detail, most of the major features of the flow 

pattern in figures 20 and 21 clearly are similar to 

those of the flow pattern in figure 17.

Profiles of heads in the major aquifers (fig. 22) 

show that a relatively small head difference o?curs 

between the water table and the base of the Magothy 

aquifer as compared to the difference in head between 

the base of the Magothy aquifer and the Lloyd 

aquifer. This relatively large difference in head 

between the base of the Magothy aquifer anc1 the 

Lloyd aquifer reflects the low hydraulic conductivity 

of the intervening Earitan clay, the principal confining layer of the Lloyd aquifer. Upward components 

of flow exist near the bottom of the Magothy aquifer 

seaward of the intersection of the piezometric surface 

at the bottom of the Magothy aquifer and the water 

table. Similarly, upward components of flow exist 

seaward of the intersection of the piezometric surface 

of the Lloyd aquifer and the piezometric surface at 

the bottom of the Magothy aquifer.

Another modification of the idealized flow pattern 

in figure 17 is caused by the salty ground water that
F24 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

NORTH 

Ground-water divide

SOUTH

Sloping water table

Three-dimensional flow 

to streams Shoreline

Bottom of ocean 

(zero potential)

/ /

Primarily two-dimensional flow

VERTICAL EXAGGERATION X 15

FIGURE 19. Diagrammatic cross section of the southern half of the ground-water reservoir showing the part of the reservoir with 

primarily two-dimensional flow and the part of the reservoir with three-dimensional flow to streams.

72°

10 20 30 MILES 

I

A

400S

A

Upper glacial Water 

aquifer

Ground-water 

divide EXPLANATION

Line of equipotential 

surface

Direction of groundwater flow

Hydrogeologic 

boundary

VERTICAL SCALE GREATLY EXAGGERATED

FIGURE 20. Geohydrologic section of the ground-water reservoir in northeastern Nassau County in March 1901. Adapted from

Isbister (1966, fig. 11).
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F25

72°

74

41°

0 10 20 30 MILES 

Location of section B-B I , I____I____|

EXPLANATION

Line of equipotential 

surface

Direction of groundwaterflov

Hydrogeolc°ric 

boundary

VERTICAL SCALE GREATLY EXAGGERATED

FIGURE 21. Geohydrologic section of the ground-water reservoir in southwestern Suffolk County in October 1960. Adapted from

Pluhowski and Kantrowitz (1964, fig. 13).

bounds the fresh ground-water reservoir of Long 

Island. The presence of the salty ground water results 

in several salt-fresh water interfaces at various depths 

in the Long Island ground-water reservoir. As stated 

previously, these interfaces are dynamic boundaries 

that change position in response to changes in head 

within the ground-water reservoir. The positions of 

these interfaces are undoubtedly at least partly related 

to the location of the relatively permeable and impermeable layers in the ground-water reservoir.

DISCHARGE FROM THE GROUND-WATER RESERVOIR

The main elements of discharge from the 

ground-water reservoir are seepage to streams and 

springs, ground-water evapotranspiration, and subsurface outflow (fig. 13).

STREAMFLOW AND SPRINGFLOW

Those aspects of streamflow that are emphasized 

in this report are the annual and daily streamflow 

from the water-budget area, streamflow in the near-
F26 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

sff~ Piezometric surface at 

base of Magothy aquifer

LEVEL

VERTICAL SCALE GREATLY 

EXAGGERATED

FIGURE 22. Profiles of the water table and piezometric surfaces at the base of the Magothy aquifer and in th? Lloyd aquifer 

in 1963. Based on unpublished maps prepared by John Isbisher (written eommun., 1966).

shore areas, and the relation between ground-water 

levels and streamflow. Unless otherwise stated, all 

values of streamflow are for total streamflow and, 

therefore, include direct runoff. Most of the information presented in this section is derived from a summary of streamflow on Long Island by Vaupel and 

Spinello (written eommun., 1968).

The average base flow of the streams (that is, 

seepage from the ground-water reservoir) is about 

90-95 pecent of total average steamflow at present 

(1968). The percentage of total average streamflow 

that is direct runoff presently is somewhat greater than 

the estimate for natural conditions, because direct 

runoff to many streams has been materially increased 

by urban development. (See section on "Disposal of 

direct runoff to streams.")

In overall aspect, the present locations of Long 

Island's streams were determined mainly by the 

ancient drainage pattern that developed during the 

last ice age. Accordingly, most of the streams flow 

in broad, shallow valleys that were formed by the 

much larger streams that existed" during melting of 

the ice sheet. All the southward-flowing streams have 

gentle gradients that, throughout most of their reaches, 

average about 10 feet per mile. The northward-flowing 

streams, especially in the western half of the island,

generally have steeper gradients that average about 

20-40 feet per mile. The lengths of these streams 

(distance from gaging station to start of flow along 

the main channel) range from less than 1 mile to 

somewhat less than 10 miles (fig. 3). In addition, all 

the streams are estuarine in their lower reaches.

The names, surface drainage areas and average 

flows at the gaging stations of the 19 continuously 

gaged streams in the water-budget area for the period 

water years 1940-65 are given in table 8. The gaging 

stations of these streams were established at points 

sufficiently upstream from the ocean, b<\ys, and Long 

Island Sound so that the records would not be affected 

by tidal fluctuations. The data obtained at these stations, therefore, are not indicative of the total flow 

of these streams.

The average flows given in table 8 r^nge from less 

than 5 cfs to slightly more than 40 cfs, and the total 

average discharge of the 19 streams is about 300 cfs. 

Moreover, the data in table 8 indicate that there is a 

very poor correlation between the surface drainage 

areas of the streams and their average flows.

The average annual discharge of all measured 

streams (continuously gaged and miscellaneous measuring sites) in the water-budget area for the period 

1940-65 was about 475 cfs. A graph of the recurrence
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F27

340 mgd (million gallons per day) for the 2C-year 

period 1940-65. Of this total, about 50 mgd discharged 

from the northern part of the water-budget area and 

290 mgd from the southern part of the water-bndget 

area, which includes streamflow discharging into 

Peconic Bay from the water-budget area.

As shown in figure 24, the median of the average 

daily measured flows from the water-budget area for 

the period 1940-65 was about 440 cfs, which was 

slightly less than the average daily flow for this period. 

Furthermore, the average daily flow ranged from 

about 250 cfs to more than 1,000 cfs, which wa? considerably greater than the range in annual average 

flows.

A large amount of additional water undoubtedly 

seeps from the ground-water reservoir into the lower 

tidal reaches of the streams in the nearshore areas 

particularly the southern nearshore area. Most of this 

water is derived from precipitation that recharges the 

ground-water reservoir in the nearshore areas that is, 

it is not part of the deep circulating ground-water 

subsystem. The estimated average amount of this additional unmeasured streamflow is on the order of 

40-80 mgd for the southern nearshore area and 10-15 

mgd for the northern nearshore area. These very 

approximate estimates were developed as follows: The 

area of the "southern nearshore area" is about 80 square 

miles. If the average recharge rate in this area is about 

1 mgd per sq mi (see section on "Summary of relpjtions

TABLE 8. Surface drainage areas and average flows of the 19 

continuously gaged streams in the water-budget area of Long 

Island, N.Y., water years 1940-1965

Identification Surface Average flow 

number of stream- Name of stream drainage area (cubic feet 

flow measuring (square miles) per second) station

1-3025. __.

3030___.

3035. _..

3040- __.

3045. __.

3050____

3055__._

3060. __.

3065_ __.

3070-__.

3075____

3080. __.

3085_ __.

3090. _..

3095___.

3100-__.

3105-__.

3110___.

3115____

_ _ . . Mill Neck Creek _ _ .

____ Cold Spring Brook _ __

__-_ Peconic River. __

--__ Carmans River _ _ _ _

____ Swan River.______ _

__ _ Patchogue Creek. _____

____ Champlin Creek. __

____ Penataquit Creek . __

. _ _ _ Carlls River _ _ _ _

-___ Bellmore Creek..

-__ Valley Stream...

11 

12 

7 

27 

75 

71 

9 

14 

24 

7 

5 

23 

35 

7 

38 

17 

31 

10 

4

7.2 

9.5 

4.6 

42. 2 

35. 5 

24. 2 

13.0 

21. 2 

39. 4 

7.5 

6. 2 

9.8 

27. 7 

4.6 

11.9 

11. 2 

17.5 

5. 1 

4. 8

interval for annual average discharge of all measured 

streams from the water-budget area based on the 

period 1940-65 (fig. 23) indicates that the annual 

average discharge of all measured streams has varied 

from about 300 cfs to somewhat more than 600 cfs 

during this period. This variation in annual streamflow by a factor of about 2 over a period of more 

than 25 years is small compared to corresponding 

variations in the annual flow of streams in other areas 

of the humid Northeastern United States.

On the average, an estimated additional 25-50 cfs 

is discharged from the water-budget area in small 

unmeasured streams and springs. Thus, the estimated 

total average discharge of streams and springs from 

the water-budget area was about 500-525 cfs, or about

1000

o 800 

o 

S 600

£ 500 Q.

5 400

1 300

200

100

EXPLANATION

On the average, annual average 

discharge equal to or greater than 

value shown once during recurrence 

interval.

On the average, annual average 

discharge equal to or less than 

value shown once during recurrence 

interval.

4 5 6 7 8 9 10 

RECURRENCE INTERVAL, IN YEARS

20 30

FIGURE 23. Magnitude and frequency of annual average digr 

charge of streams from the water-budget area D. E. Vaupel 

and A. G. Spinello (written commun., 1968).

10,000

1000

100

0.01 0.05 0.5 1 2 5 10 20 30 40 50 60 70 80 90 95 98 9999.5 

PERCENTAGE OF TIME INDICATED DISCHARGE EQUALED OR EXCEEDED THAT SHOWN

FIQUBE 24. Estimated duration curve of daily streamflow from 

the water-budget area. D. E. Vaupel and A. G. 

(written commun.. 1968).

427-144 O - 71 - 5
F28 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

between components of the hydrologic system") and if 

all the recharge ultimately discharged into nearby tidal 

reaches of the streams, the resulting average increase 

in flow in tidal reaches of streams in the "southern 

nearshore area" would be about 80 mgd. However, a 

considerable amount of ground water probably is discharged by evapotranspiration (see next section of 

report) in this area because of the shallow depth to 

ground water and the high density of vegetation associated with the many swampy areas. Moreover, the 

average percentage of direct runoff in this area may 

be higher than the percentage in the water-budget 

area. Accordingly, an 80 mgd increase in streamflow 

is considered to be an upper limit, and the correct 

value is believed to lie between 40 and 80 mgd. The 

same lines of reasoning were applied to develop

estimates of the increase in streamflow in the "northern nearshore area."

The close relation between streamflow and water 

levels in nearby water-table wells is shown in figures 

25-27. The good correlation between the two hydrographs in figure 25 is evident. In figure 26 both sets 

of data from figure 25 were averaged for each month, 

which resulted again in two curves of very similar 

shape. Finally, the relation between the average 

monthly water-level data and the streamflow data in 

figure 26 is shown in figure 27. A straight line of best 

fit was estimated for the points representing October through March, which show an approximately 

linear relationship between stream discharge and 

ground-water-level altitude. The obviously different 

relationship between the two variables during the

EXPLANATION

oN1251 

Well

Stream-gaging 

station

Location of selected 

wells and streams

47

46

45

I I I I I I I I T 1 I I I I I I I I

I I I I I I I I I I

Composite of East Meadow Brook, 

Bellmore Creek, and Massapequa Creek

ill III

1940 1941 1949 1950

FIGURE 25. Composite average monthly ground-water levels in selected wells and composite average monthly discharge

of selected streams in Nassau County for the period 1940-50.
SUMMARY OF HYDBOLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F29

20

,j 10

Average stream discharge

46

45

44 £ 

S

43

OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT

FIGURE 26. Average monthly discharge of selected streams and average monthly ground-water levels: in selected wells in

Nassau County for the period 1940-50.

summer months (April-September) is undoubtedly 

due in part to ground-water evapotranspiration. (See 

next section of report.)

The regular seasonal variation in ground-water 

levels and streamflow, which is primarily the result 

of a seasonal variation in total evapotranspiration 

and ground-water recharge, is also shown in figures 

25 and 26. In figure 26, ground-water levels and 

streamflow reach their maximums on the average in 

March or April and their minimums in September 

or October. The ratio of the maximum to minimum 

average monthly flows in figure 26 is slightly less than 

2 to 1. Although this ratio varies from about 1.2 to 2 

for individual streams on Long Island, this variation is 

small in comparison with many streams elsewhere 

and reflects the close relationship between the streams 

and the ground-water reservoir.

GROUND-WATER EVAPOTRANSPIRATION

The separation between the summer and winter 

recession curves for Carmans Kiver (fig. 28) indicates 

that some factor that is not operative during the 

winter months reduces streamflow during the summer 

months or during periods without precipitation. In

an unregulated stream under natural conditions such 

as Carmans Kiver in the summer months, this frctor 

probably is evapotranspiration of shallow ground 

water and evapotranspiration of soil moisture which, 

in turn, results in decreased recharge. In the absence 

of active evapotranspiration, this ground water would 

have seeped into the stream channel and increased 

streamflow. The separation between recession curves 

of other streams on Long Island (developed by 

D. E. Vaupel and A. G. Spinello, written commun., 

1968) varies widely some pairs of curves show more 

separation than Carmans Kiver, and some show virtually no separation. The amount of separation in 

these curves seems to correlate very roughly with the 

size of the area adjacent to the stream whose altitude 

is almost the same as the stream and which is occupied 

by vegetation.

Pluhowski and Kantrowitz (1964) estimated the 

quantity of ground-water evapotranspiration in southwestern Suffolk County from observations of c'aily 

cyclic fluctuations in ground-water levels of a shallow 

well during the summer months. The well was located 

near Sampawams Creek in an area where the d?-pth 

to ground water was less than 5 feet. From a hydro-
E30 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YOPK

20

£ 15

MAR

JUNE

JULY

- Nor

AUG

SEPT

43 44 45 

AVERAGE GROUND-WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL

46

FIGURE 27. Relation between average monthly discharge of 

selected streams and average monthly ground-water levels 

in selected wells in Nassau County for the period 1940-50.

graph of this well and a knowledge of the area in 

which the depth to ground water was less than 5 feet 

(about 30 sq mi), they estimated that the average 

ground-water evapotranspiration within their study 

area was about 11 mgd.

The depth to the water table is less than 10 feet 

in about 50 square miles and less than 5 feet in an 

estimated 30 square miles of the water-budget area. 

According to the previous estimate, therefore, the 

estimated average ground-water evapotranspiration 

from the water-budget area is on the order of 10-15 

mgd. Most of the ground-water evapotranspiration 

on Long Island occurs in the low-lying nearshore 

areas north and south of the water-budget area 

particularly south. No data are presently available 

to estimate the quantity of water consumed by 

ground-water evapotranspiration in these areas.

SUBSURFACE OUTFLOW OF GROUND WATER

Subsurface outflow of ground water is the second 

largest element of discharge from the water-budget 

area. To help estimate subsurface outflow, maps showing the transmissivity of the principal aquifers of 

Long Island (fig. 29) were developed in a report 

by McClymonds and Franke (1971). The Jameco 

aquifer was not included in figure 29 because it occurs, 

except for a small area in southwestern Nassau County, 

outside the water-budget area.

As the starting point in their investigation, 

McClymonds and Franke estimated the average

hydraulic conductivity of the deposits opposite the 

screened interval of more than 2,000 wells by calculating modified specific-capacity numbers for each 

well, QjsL, which is the specific capacity of the well 

(Q/s, or well discharge divided by drawdown in the 

well) divided by the screen length (L). The distribution of QjsL numbers for the prncipal aquifers 

of Long Island (fig. 30) clearly differentiates the 

ability of the screened intervals in the three principal aquifers to transmit water to the wells. The estimated median hydraulic conductivities of the screened 

intervals in the wells from which data were used 

to construct the curves in figure 30 are 2,500, 1,000, 

and 600 gallons per day per square foot in the upper 

glacial, Magothy, and Lloyd aquifers respectively.

By correlating the QjsL numbers vith the various 

observed lithologies in the screened intervals of many 

wells, estimated values of average hydraulic conductivity were assigned to each lithology in each aquifer. 

These average hydraulic conductivity values were 

then applied to each layer in the entire aquifer for 

individual wells, and the average hydraulic conductivity of the material penetrated by each well for which 

logs were available was computed. Although considerable variation was found between estimates of 

average hydraulic conductivity in r?arby wells, a 

reasonable regional pattern of average hydraulic 

conductivity could be mapped where, on the average, 

one or more data points were available for every

30

20

o 2

Winter

Summer

10 20 30 40 

TIME, IN DAYS

50 60 70

FIGURE 28. Summer and winter recession crtves for Carmans 

River. D. E. Vaupel and A. G. Spinello (written commun., 

1968).
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES

45' 72"00' 71°45'

41'00'

EXPLANATION

200

Line of equal transmissivity

(in thousands)

Intervals 100,000 and 200,000

gallons per day per foot

f I

Area where water table 

is below glacial deposits

74° 15

41°00' I- NEW

JERSEY

EXPLANATION

Line of equal transmissivity

(in thousands)

Intervals 50,000 and 100,000

gallons per day per foot

Approximate limit 

of Magothy aquifer

EXPLANATION

Line of equal transmissivity

(in thousands)

Interval 20,000 gallons

per day per foot

Approximate limit 

of Lloyd aquifer

15 20 25 MILES 

I I I

71-45'

40° 30'

FIGURE 29. Estimated transmissivity of (A) upper glacial aquifer, (B) Magothy aquifer, and (C) Lloyd aquifer. After McOlymonds and Franke (1971). Transmissivity lines1 on these maps were developed by combining data from aquifer-thickness 

maps and maps of average hydraulic conductivity for the respective aquifers. (See McOlymonds and Franke, 1971.) The high 

degree of detail shown for the transmissivity lines is not meant to imply a high degree of accuracy for transmissivity at any 

specific location. Rather, it largely reflects a fairly high degree of accuracy in the information shown on the aquifer-thickness 

maps and only a moderate degree of accuracy in the information shown on the maps of average hydraulic conductivity.
F32 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

3.00

h- 2.00 

o 

o

LL. 

UJ

< 1.00 

o

CO

oe

LiJ

°- 0.50

UJ I 

ZJ

| 0.30 

§jj 0.20

CO z. 

o

_l

< 0.10

CD

 z.

° 0.05

o

<

LL.

J

<r>

x

a

0.01

o

* '

0

o

o

 a 

^^

o

^

 H-

^x

^^b

o

^

^

^x

"3f^

J

xtf

^

r*>

^

s<

 ^

£^

'

7*

s*

/*

-

^

^

s

sf

JT

Y

^

<

^

^f " 

xf r^3

j

,^x

r

**"

r

^

^x

P

X

^

X

EXPLANATION

o 

Upper glacial aquifer (1,547 wells)

D 

Magothy aquifer (735 wells)

Lloyd aquifer (94 wells)

j_,

^

f

0.01 0.1 0.5 1 5 10 20 30 40 50 60 70 80 90 95 98 

PERCENTAGE OF TOTAL NUMBER OF WELLS FOR WHICH Q/sL FACTOR 

EQUALED OR IS LESS THAN THAT SHOWN

99 99.5 99.9 99.99

FIGURE 30. Relation between a modified specific capacity factor (Q/sI/) and percentage of total numl^r of wells for 

the principal aquifers of Long Island, N.Y. After McClymonds and Franke (1971).

2 or 3 square miles. Average-hydraulic conductivity 

maps were prepared for each aquifer in the manner 

described above. The average-hydraulic conductivity 

maps and thickness maps of each aquifer were used 

to construct the transmissivity maps in figure 29. 

Average values of thickness, hydraulic conductivity, 

and transmissivity of the principal aquifers in the 

water-budget area, which were derived from figure 29 

and from additional maps in the report by McClymonds and Franke, are given in table 9.

Estimated rates of subsurface outflow from the 

water-budget area and for each aquifer are given in

TABLE 9. Average transmissivity of the principal aquifers for the 

water-budget area, Long Island, N.Y.

Aquifer

Average Average 

Average hydraulic transmissivity 

thickness conductivity (gallons per day 

(feet) (gallons per day per foot) 

per square foot)

Upper glacial _

Magothy _ __ _ __

Lloyd _____ _____

______ 120

______ 620

-_--__ 350

1,800

400

OKfJ

210, 000

250, 000

ec nnn

table 10. These estimates were computed by applying 

Darcy's law, Q = TIL, to appropriate parts of each 

aquifer and by summing the flow from each part. 

In this formula, Q is the flow of ground water, in 

gallons per day; T is the transmissivity, in gallons 

per day per foot; / is the hydraulic gradient, in feet 

per foot; and L is the width, in feet, of the cross 

section through which the flow occnrs. Appropriate 

T values were obtained from figure 29, and approximate values of the hydraulic gradient / were obtained 

from water-level contour maps.

Estimating the quantity of subsurface outflow from 

the upper glacial aquifer presented special difficulties 

because much of the water in the upper part of this 

aquifer discharges into streams. Thus, for the purpose of calculating subsurface outflow, it was assumed 

that ground water in the upper 40-50 feet of the 

upper glacial aquifer discharged to streams (see previous discussion on movement through the ground-water 

reservoir), and calculations of underflow were made 

only for the material below the upp?,r 40-50 feet. In
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES T33

rddition, the estimates of subsurface outflow from the 

northern part of the water-budget area were somewhat less certain than those from the southern part 

because water-level gradients are steeper and subject 

to wider variation along the north shore compared to 

the south shore, which makes the selection of average 

gradients subject to greater error.

TABLE 10. Estimated average subsurface outflow of ground water 

from the principal aquifers and total average subsurface outflow 

from the northern part, the southern part, and the entire waterbudget area of Long Island, N.Y.

[In millions of gallons per day]

Aquifer

Water-budget area, average subsurface 

outflow from 

Northern 

part

Southern 

part

Entire area

Toper glacial. 

I agothy_ 

Lloyd. __-.__

130

120

20

40

120

20

170

240

40

Total. 270 180 450

Because of possible errors in the estimates of transnissivity and in the selection of average water-level 

gradients, the possible error in the estimated total subs irface outflow from the water-budget area in table 10 

i.- probably on the order of plus or minus 25 percent. 

The possible error in the estimate of subsurface outf'ow from the northern part of the water-budget area 

and from the individual aquifers may be even larger.

SUMMARY OF RELATIONS BETWEEN COMPONENTS 

OF THE HYDROLOGIC SYSTEM

Water budgets for the northern and southern 

parts of the water-budget area and for the entire 

YTater-budget area are given in table 11. The values 

ri table 11 are averages, and can be considered valid 

for the 26-year period water years 1940-65, although 

not all these averages have been calculated or estimated for exactly this period in this report. Although 

fie amount of fresh ground water in storage locally 

i^ the water-budget area has decreased markedly in 

fiis period, the average decrease in storage is small. 

I Moreover, in comparison with the total inflow and 

outflow, the decrease in storage is insignificant and, 

therefore, is disregarded in the water-budget analysis. 

If the additional simplifying assumption is made 

that, during the index period (water years 1940-65), 

changes in natural ground-water recharge and discharge were roughly compensated for by artificial 

recharge and discharge, the values in table 11 provide reasonable estimates for water-budget components 

H the water-budget area under natural conditions.

The most reliable estimates in table 11 are for 

precipitation and streamflow. The possible error in 

the budget figures for precipitation is probably not 

greater than 5-10 percent. The possible error in the 

estimates of average streamflow, on the other hand, 

is probably on the order of about plus or minus 15 

percent. This possible error is primarily due to the 

uncertainty in estimating the flow of the ungag^.d 

streams from several miscellaneous measurements each 

year.

An indirect estimate of ground-water recharge under 

natural conditions can be developed from the data 

in table 11 if it is assumed that average annual 

ground-water recharge and discharge were approximately equal for the budget period 1940-65. Acco^dingly, the estimated average annual natural recharge 

is equal to the estimated average annual natural 

discharge about 800 mgd (table 11). This value is 

equal to about 1.05 mgd of recharge per square mile 

for the water-budget area. This figure is very close 

to previous indirect estimates for average recharge 

of about 1 mgd per sq mi (Pluhowski and Kant~owitz, 1964, p. 38; Swarzenski, 1963, p. 35).

A comparison of the figures in table 11 shows a 

marked difference in the ratio of streamflow and 

subsurface outflow to precipitation in the two parts 

of the water-budget area. In the southern part, about 

30 percent of total precipitation discharges as streaHITABLE 11. Water budgets of the northern and southern part? of 

the water-budget area and the entire water-budget area of Long 

Island, N.Y., water years 1940-65 1

[In millions of gallons per day]

Type of water- No. Water-budget element 

budget element

Water-budget area

Northern Southern 

part part

Inflow.......... 1 Precipitation.-.-.--------. 660 950 1,600

Internal dis- 2 Direct runoff-... --------- 5 15 20

tribution. 3 Ground-water recharge *.. 320 465 785 

4 Ground-water discharge 45 275 320

to streams.'

Outflow.._._.._ 5 Evapotranspiration of 325 470 795 

precipitation.*

6 Subsurface outflow of 270 180 450 

ground water.

7 Streamflow discharging to 50 290 340 

salt water.

8 Evapotranspiration of 5 10 15 

ground water.s

' The quantities in this table were derived with the assumption that no significant 

change in ground-water storage occurred in the water-budget area during the pe~iod, 

water years 1940-65. Independent quantitative estimates were made for all com^onents in the table unless otherwise noted. None of the values in this table are accrrate 

to more than 2 significant figures, and many values are accurate to less. (See text 

discussion.) Where more than 2 significant figures are shown, the entry was derived 

from other entries in the table, and an additional significant figure was retained to 

balance inflow and outflow. (See footnotes below.)

2 The estimate of ground-water recharge was obtained by adding components 4, 6, 

and 8.

s The estimate of ground-water discharge to streams was obtained by subtracting 

component 2 from component 7. 4 The estimate of evapotranspiration of precipitation was obtained by ad Ting 

components 6, 7, and 8 and subtracting the total from component 1. Therefore, the 

subtotal of components 5,6,7, and 8 (total outflow) equals component 1 (total inn -w).

5 These values may be in error by as much as 100 percent or more. Values are included mainly to indicate order of magnitude.
F34 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

flow and 15 percent as subsurface outflow of ground 

waiter. The corresponding values for the northern 

part are about 10 and 35 percent, respectively. As 

discussed previously, estimates of subsurface outflow 

may be significantly in error, particularly the estimate 

from the northern part of the water-budget area. 

This large possible error may hide real differences 

in evapotranspiration and recharge in the two parts 

of the water-budget area, which might be caused by 

lower infiltration capacities in the surficial soils and 

greater evapotranspiration in the northern part compared to the southern part of the water-budget area.

Unfortunately, however, presently available information is inadequate to evaluate this possibility.

WATER QUALITY

The general paths followed by liquid water through 

the hydrologic system of Long Island under natural 

conditions and related water-quality features are 

shown schematically in figure 31. As air moved across 

the bodies of salty water bordering Long Island, it 

picked up small quantities of salts from the ocean 

spray (fig. 31, item 1). Some of thes^ substances were 

dissolved in the precipitation that fell on the island

1 Air moving over the ocean 

picks up salty spray

2 Rain and snow pick up dust 

and gases from the atmosphere

3 Evaporation and transpiration 

of precipitation from the land 

surface and from the soil zone 

increase the dissolved-solids 

content of the water

4 Physical, chemical, and biological processes modify the 

dissolved-solids content of the 

water percolating through the 

zone of aeration

5 Flow through sedimentary 

deposits in the zone of saturation modifies the total dissolved-solids content of the 

ground water only slightly

6 Physical, chemical, and biological processes modify the 

dissolved-solids content of 

streamflow

7 Fresh stream water and salty 

water mix in estuarine reaches

8 Fresh ground water and salty 

ground water mix in the zone 

of diffusion

^^

FIGURE 31. Changes in the chemical quality of the water under natural conditions. After Cohen, Franke, and Foxworthy

(1968, pi. 5A).
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F35

along with particles of dust and gases from the 

atmosphere (item 2).

Evaporation from the land surface and the soil 

zone, and transpiration by plants, increased the 

dissolved-solids content of the precipitation after it 

reached the ground (item 3). As the water that originated as precipitation moved through the uppermost 

part of the zone of aeration (item 4), it came into contact with, and partly dissolved, compounds that were 

formed in the biologically and chemically active soil 

zone. After passing through the soil zone, the water 

continued, but at a slower rate, to dissolve additional 

substances from the remainder of the less chemically 

active zone of aeration.

Most of the materials in the zone of saturation on 

Long Island are only slightly soluble in water. Accordingly, the dissolved-solids content of the ground water 

generally increased only slightly as it moved through 

this zone (item 5).

Some of the ground water ultimately discharged 

into the streams where it mixed with direct runoff. 

The dissolved-solids content of the water flowing in 

the streams increased, owing to biological activity 

and the solution of substances in the stream channels 

(item 6). The stream water underwent a marked 

further increase in dissolved-solids content (from less 

than 50 mg/1 to hundreds and thousands of milligrams 

per liter) as the fresh water discharged into, and mixed 

with, the salty water in the estuarine reaches of the 

streams (item 7). Similarly, the dissolved-solids content of the ground water increased markedly (to 

thousands of milligrams per liter) as the fresh ground 

water mixed with salty ground water in the zone of 

diffusion (item 8).

Chemical analyses of waters representing various 

stages in the geocheniical cycle shown in figure 31 

are given in table 12. These analyses include one of 

precipitation (analysis 1), two each of samples from 

the three major aquifers (analyses 2-7), two of 

ground water near the fresh-salt water interface 

(analyses 8, 9), two of streams (analyses 10, 11), and 

two of lakes (analyses 12, 13). The salient features 

of the analyses in table 12 are summarized as follows:

1. The natural fresh water of Long Island had a 

remarkably low dissolved-solids content, which 

was always less than 50 mg/1 and in some cases 

was as little as 20 mg/1.

2. Because the deposits of the Long Island 

ground-water reservoir were relatively inert 

chemically, the dissolved-solids content of the 

ground water changed very little as it moved 

through the reservoir.

3. Some of the fresh ground water (analyses 3,4, 6, 7) 

had a high iron content, which was considerably 

above the 0.3 mg/1 limit recommended for publicsupply use (U.S. Public Health Service, 1962, 

p. 7). The source of the iron in the Magothy 

aquifer was probably pyrite nodules that occur 

locally.

4. The pH of Long Island ground water was generally low (commonly less than 6), which made the 

water very corrosive to metals. 

Except for items 3 and 4, which may necessitate 

minor treatment of the water before use, the natural 

water of Long Island was suitable for most purposesPrecipitation has the lowest dissolved-solids content 

(about 10 mg/1) of the analyses in table 12. Morec^er, 

the surface-waiter samples have about the s'Mne 

dissolved-solids content as the ground water because 

most of the surface water is derived directly from 

the ground-water reservoir. The ground-water analyses 

in table 12 do not show a progressive increase in 

dissolved-solids content with increasing time of travel 

and length of flow path through the ground-water 

reservoir. On the contrary, the dissolved-solids content 

seerns to decrease with depth, as shown, for example, 

by the analyses of water from the upper glrcial 

aquifer and from the Magothy aquifer (table 12). 

Undoubtedly, at least a partial explanation of this 

apparent anomaly is that virtually no sampler of 

completely uncontaminated water are available from 

the upper glacial aquifer. Furthermore, the data in 

table 12 represent a very limited sampling of water 

within the ground-water reservoir.

As noted in item 3 of figure 31, evapotranspiration 

increases the dissolved-solids content of the precipitation water as it moves through the upper part of the 

zone of aeration en route to the water table. Increases 

in the chloride content of the shallow ground water 

are almost entirely the result of this concentrating 

process because precipitation was virtually the only 

source of chloride in the waters of Long Island under 

natural conditions. Therefore, an indication of the 

ratio of precipitation to evapotranspiration is obtained 

by comparing the chloride content of rainfall and the 

shallow ground water. The chloride content of water 

from both these sources shows considerable variation 

in space and time. As is evident from analyses 1-3 in 

table 12, however, evapotranspiration has markedly 

increased the chloride content of water in the upper 

glacial aquifer compared to precipitation. These analyses indicate a ratio of precipitation to evapotranspiration ranging between approximately 2 to 1 and 1.5 

to 1. This compares with a ratio of about 2 to 1
TABLE 12. Selected chemical analyses of natural 1 water on Long Island, N.Y. 

[Analyses made by U.S. Geological Survey and reported in milligrams per liter]

Sam- Source of water 

pie

1 Precipitation..............

2 Ground water: 

Upper glacial aquifer 

(well S5618). 

3 Upper glacial aquifer 

(well N1243). 

4 Magothy aquifer 

(wellN4149). 

5 Magothy aquifer 

(wellN5655). 

6 Lloyd aquifer 

(wellN5227). 

7 Lloyd aquifer 

(wellS6409). 

8 Salty ground water: 

Magothy aquifer 

(weilN4062). 

9 Magothy aquifer 

(well N6707). 

Stream water: 

10 Cold Spring Brook- . .

12 Lake water:

13 Lake Ronkonkoma...

Date Silica 

collected (SiOj)

Oct. 15,1948 6.0 

Dec. 5,1960 5.4 

Sept. 30,1953 6.5 

Mar. 26,1957 7.5 

Nov. 14,1961 ........

Nov. 8,1948 7.5

Aug. 1, 1962 20 

July 11,1960 9.3

May 6,1966 ........

Apr. 14,1948 0

Jan. 11, 1949 1. 6 

Apr. 29,1948 1.5

Iron Cal- Mag- Sodium Potas- Bicar- 

(Fe) cium nesium (Na) slum bonate 

(Ca) (Mg) (K) (HC08)

........ 0.6 0.3 1.6 0.1 ..........

0.01 1.5 1.3 3.2 .6 4 

3.3 4.0 1.0 3.0 1.2 11 

.61 .5 .1 2.4 .3 3 

.01 1.3 .1 2.7 .7 5 

1.5 .9 .5 6.2 .5 4 

1.3 1.5 1.6 4.4 2.2 16

2.5 10 4.0 18 2.8 60 

39 82 76 520 8.0 ..........

1.8 3.3 1.3 4.9 .5 14 

.03 5.2 2.1 4.8 .9 15

.01 1.9 1.0 3.8 1.3 5 

.01 2.4 1.1 4.1 .8 5

1 The precipitation sample and the 2 samples of ground water from the upper glacial aquifer may be 

ghtly contaminated because of the activities of man. However, these samples are among the least

Sul- Ohio- Fluofate ride ride 

(804) (Cl) (F)

3.8 2.7 .--...,

6.0 5.0 ........

6.9 3.9 ........

1.6 2.5 ........

1.0 4.3 0.1 

14 2.0 ........

3. 5 4. 1 .1

3. 7 29 .1 

76 1,160 .1

3. 2 7. 2 .1 

8.4 6.6 .0

5.6 5.4 .1

8.2 5.8 .0

Total 

Ni- dissolved Specific Tempertrate solids conduct- pH ature Remarks 

(NOj) (residue on ance (° C) 

evaporation (KX10«) 

at 180° C)

0.8 10 ...

.1 36 

1.9 36 

.1 15 

1.4 25 

.1 36 

.1 32

.1 117 

. 4 2,180

.8 37 

2.2 49

.2 24 

.5 28

contaminated that are presently available. 

72°

samples collected from rain gage a 

x Brookhaven National Laboratory 

for the period Oct. 1966-Mar. 1966.

39 6.5 .......... Depth 54 ft; depth to water 32 ft;

diameter 6 in. (De Laguna, 1964). 

66 6.1 14 Depth 16 ft; depth to water 6 ft. 

diameter \V\ in. 

22 5.8 13 Depth 500 ft; diameter 6 in.

24 6.1 11 Depth 255 ft; diameter 12 in. 

60 5.3 .-.-...-.. Depth 1,250 ft; diameter 8 in.

diameter 8 in. (De Laguna, 1964).

187 6.6 17 Depth 142 ft; diameter 4 in. (Luscyznski and Swarzenski, 1966). 

3,760 4.4 16 Depth 506 ft; diameter 4 in. (Lusczynski and Swarzenski, 1966).

56 6.8 14 Sample collected at gaging station; 

stream discharge 0.40 cfs.

estimated stream discharge 30 cfs 

(De Laguna, 1964).

46 6.5 .......... De Laguna (1964).

47 7.1 .......... Do.

See text for further discussion.

HYDROLOGY SOMEEFFECTS ANDOFURBANIZATION ON LOGISLA

H

Location of sampling points
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F37

which was previously determined indirectly from the 

water-budget analysis.

HOW MAN HAS MODIFIED THE NATURAL 

HYDROLOGIC SYSTEM

The following discussion summarizes the effects 

of man's activities on the hydrologic system of Long 

Island. For the most part, the discussion is concerned 

with the effects of man's activities on the ground-water 

reservoir. An understanding of these effects provides 

valuable insight into the possible effects of future 

management alternatives on the hydrologic system.

In this section of the report the calendar year is 

generally used as the annual period of reference 

instead of the water year. In addition, succeeding 

quantitative estimates are generally made for all of 

Nassau and Suffolk Counties instead of only the 

water-budget area.

HISTORY AND PRESENT STAGE OF DEVELOPMENT

Ground-water development on Long Island has 

progressed through three major stages (Heath and 

others, 1966; Cohen and others, 1968). In the first 

stage of development, which began with the arrival 

of the first European settlers, almost every house 

had a shallow dug well from which water was withdrawn from the upper glacial deposits. Most of the 

domestic waste water was returned to the glacial 

deposits through individually owned cesspools. As 

the population increased, many individually owned 

wells were abandoned, and public-supply wells were 

installed in the upper glacial deposits; however, the 

disposal of waste water through individually owned 

cesspools continued. Although the quality of the water 

gradually deteriorated as a result of these practices, 

the amount of water permanently removed from the 

ground-water system (the "net withdrawal") was 

negligible.

Pollution of the shallow part of the ground-water 

reservoir by water from cesspools eventually forced the 

abandonment of many wells tapping the upper glacial 

deposits. In the second stage of development, these 

wells were replaced by deeper public-supply wells, 

mainly tapping the artesian Magothy and Jameco 

aquifers. Most of the domestic and industrial sewage, »- O 7

however, was still returned to the upper glacial deposits through cesspools and septic tanks. Accordingly, the 

net withdrawals from the entire ground-water reservoir remained negligible.

The third major stage of ground-water development 

was characterized mainly by the introduction of largescale sewage systems first in Kings and Queens 

Counties and then in the western one-third of Nassau

County. After the sewers were installed, most of the 

once-used water that previously had been returned to 

the ground-water reservoir through cesspools and septic tanks was thereafter discharged to the sea, which 

represented a permanent loss of water from the system. The resulting disruption of the hydrologic balrnce 

caused large-scale salt-water encroachment, first in 

Kings County, then in Queens County, and most 

recently in the southwestern part of Nassau Count;T .

The three major stages of development, as well as 

transitional stages, can presently be observed in different subareas of Long Island (fig. 32). Subarea A is 

largely rural and has the lowest population density on 

the island. In general, most of the subarea is in the first 

major stage of development. Subarea B is mainly in 

a stage of development intermediate between the first 

and second stages of development. Farms in this subarea are rapidly being replaced by housing deve^pments, and the new homes are being supplied vdth 

water from large-capacity public-supply wells tapping 

the shallow glacial deposits. Most of the new homes 

have individual cesspools to dispose of domestic waste 

water. The ground-water system in this subarea also 

is still in a virtual state of dynamic equilibrium, 

although the quality of the shallow ground witer 

undoubtedly is being degraded in the vicinity of the 

cesspools and septic tanks.

Because it is closer to New York City, subarea C 

experienced intensive suburban development earlier 

than subarea B. Most of the subarea is not sewered, 

and as a result, fairly large parts of the shallow upr>er 

glacial deposits have become polluted with cesspool 

effluent. This pollution, in turn, has forced the aH.ndonment of many of the shallow wells, and most of the 

water supply for the subarea presently is obtained 

from deep wells tapping the Magothy aquifer. The 

subarea, therefore, is in the second stage of groundwater development.

Subarea D is in the third major stage of development, Public-supply water is derived mainly f~om 

large-capacity wells tapping the Magothy and Jameco 

aquifers, and most of the sewage water is discharged 

to the sea by way of large-capacity sewage-treatment 

plants. The ground-water system in the Magothy and 

Jameco deposits is no longer in quantitative equilibrium (inflow is less that outflow), and salty water f-om 

the ocean is invading these deposits.

Subarea E also is in the third major stage of development. It differs from subarea D mainly because the 

salty water has not yet invaded the aquifers in this 

subarea. If the trend continues, however, subarer D 

will expand at the expense of subarea E, and the
F38 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

74-00' 45' 30' 15' 73°00' 45' 30' 15' 72°00f

5 0 5 10 15 20 25 MILES

I i i i i I I I I I I

EXPLANATION

SUBAREA CHARACTERISTICS

A Hydrologic system mainly is in a state of virtual quantitative equilibrium. 

B Transitional in development between subareas A and C. 

C Hydrologic system is locally out of balance; local salt-water intrusion. 

D Hydrologic system is out of balance; widespread salt-water intrusion. 

E Hydrologic system is out of balance; may be subject to salt-water intrusion in the future. 

F Ground-water development is negligible, and the hydrologic system is in balance. 

G Large parts of the subarea are contaminated with salty ground water owing to 

former intensive ground-water development and related salt-water intrusion.

FIGURE 32. Status of water development in 1966. After Heath, Foxworthy, and Oohen (1966, fig. 8).

aquifers in subarea E also will be contaminated with 

salty water.

Almost all the public-supply water for subarea F, 

which is in northeastern Queens County, is derived 

from surface-water supplies imported from upstate 

New York. The subarea is sewered, and because 

ground-water development is negligible, the groundwater system is still in balance.

All of subarea G, the most highly urbanized part 

of Long Island, is sewered. Presently, the subarea 

receives more than 85 percent of its public-supply 

water from the upstate surface-water reservoirs of 

the New York City municipal-supply system. As is 

described in a subsequent part of the report, large parts 

of the ground-water reservoir in the subarea have been 

contaminated with salty water because of substantial 

overdevelopment. Since the mid-1940's, when pumpage 

in the subarea had to be drastically reduced because of 

the salt-water contamination, ground-water levels in 

the subarea have recovered markedly.

EFFECTS OF MAN'S ACTIVITIES ON THE MOVEMENT 

AND DISCHARGE OF-WATER

The following discussion of the effects of man's 

activities on the movement and discharge of water on 

Long Island is facilitated by reference to the flow diagram in figure 33. A comparison of this diagram and 

the diagram showing the flow system under natural 

conditions (fig. 13) indicates that a number of "boxes" 

have been added. These new boxes represent manniade 

structures, including recharge basins, cesspools and 

septic tanks, water pipes, diffusion and recharge wells, 

storm drains, and sewer drains. In p.ddition, one of 

man's activities namely, pumping of ground water 

is also shown diagrammatically. As in figure 13, only 

flow paths that represent large quantities of water or 

those that are of particular significance are shown 

in figure 33.

In addition to the structures mentioned above, man 

has greatly modified the land surface of Long Island 

by large-scale construction of streets, parking lots, 

buildings, and other impervious surfaces. This construction has not only greatly reduced and modified 

the natural vegetative cover, but it plso has necessitated the construction of adequate facilities for storm 

drainage. The methods of solving the problems of 

storm drainage on Long Island constitute one of the 

most important ways in which man's activities have 

modified the natural hydrologic system. The other 

major activities of man related to the hydrologic 

system of Long Island involve the development of 

ground water and the disposal of used water.
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES

EXPLANATION

F39

ATMOSPHERE

PRECIPITATION

I 

I

EVAPOTRANSPIRATION

Solid lines represent flow of liquid water 

Dashed lines represent movement of water vapor

EVAPOTRANSPIRATION

* EVAPORATION

LAND SURFACE

Partially covered by impervious surfaces

BODIES OF 

SURFACE WATER

INFILTRATION ZONE OF 

AERATION

i

EVAPOTRANSPIRATION 

A

 I

PUMPING 

t

PERCOLATION

SEEPAGE AND 

SPRING FLOW

DIFFUSION

AND

RECHARGE 

WELLS

I STORM DRAINS

i SEWER - DRAINS 

ZONE OF SATURATION

SURFACE-WATER 

 * OUTFLOW 

SEWAGE-EFFLUENT 

 * OUTFLOW *

_*. EXPORTED 

WATER OUTFLOW

SUBSURFACE_ 

GROUND-WATER 

OUTFLOW

FIGURE 33. Flow diagram of the hydrologic system, Nassau and Suffolk Counties, in the 1960's.

DISPOSAL OF DIRECT RUNOFF

Direct runoff from urban areas on Long Island flows 

by gravity through gutters and street inlets to storm 

sewers. The storm sewers generally transmit the runoff 

to either recharge basins or nearby streams (fig. 33).

RECHARGE BASINS

Recharge basins are imlined excavations in the 

glacial deposits; they range from about 10 to 20 feet 

in depth and from less than 1 to about 30 acres in 

area. In Nassau and Suffolk Counties there are more 

than 2,000 recharge basins, most of which are in the 

water-budget area. In the past two decades, most new 

housing and industrial developments in these counties 

have been required to include the construction of one 

or more basins, the size and number of which were 

related to the size of the drainage area. Moreover, 

most of the runoff from highways in these counties is 

collected in recharge basins. A recharge basin is generally used only where the water table is sufficiently 

deep to remain below the floor of the basin at least 

most of the time. Therefore, only a few recharge basins 

are located in nearshore areas where the water table 

is within a few feet of the land surface. In addition,

on Long Island many street inlets are open bottomed 

and, therefore, function as small recharge basins.

Seaburn (1970) studied the inflow of two recharge 

basins in residential developments in Nassau County. 

From the rainfall-inflow relation for one of these 

basins (fig. 34), Seaburn estimated that, on the average, about 15 percent of the total precipitation falling 

on the drainage area of the basin discharged into the 

basin. In this particular drainage area (15 acres) about 

11 percent of the total drainage area was streets, and 

the total impervious area, including streets, sidewalks, 

driveways, and roofs was about 32 percent.

The total drainage area of all the recharge basirs in 

Nassau and Suffolk Counties is probably on the o^der 

of 250 square miles at present (1968). If it is assumed 

that 15 percent of total rainfall on this area erters 

recharge basins and that virtually all this water 

recharges the ground-water reservoir, average annual 

recharge to the ground-water reservoir from these basins is on the order of 80 mgd. The assumption that 

most of the water entering a recharge basin ultimately 

recharges the ground-water reservoir is based on the 

observation that water entering most basins percolates 

into the ground fairly rapidly (commonly within a 

day or so).
F40 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YOBK

0.1

x 

u

z

o

0.01

0.001

TL

Z

0.01 0.1 1 10

RAINFALL, IN INCHES 

FIGURES 34. Relation between rainfall and inflow to the Westbury recharge basin, Nassau County, 1966-67. After Seaburn (1970).

Insufficient information is available to determine 

whether present recharge in the drainage areas of 

recharge basins has increased, decreased, or remained 

the same as compared to recharge under natural conditions. According to the previous water-budget 

analysis, on the average about one-half the precipitation falling on any part of the recharge basin drainage 

area returned to the atmosphere as evapotranspiration 

and about one-half recharged the ground-water reservoir under natural conditions. Inflow to a recharge 

basin probably includes most of the precipitation that

fell on the streets and some of the precipitation that 

fell on areas immediately adjacent to the streets. Thus, 

a larger proportion of the precipitation falling on this 

part of the drainage area of a recharge basin probably 

recharges the ground-water reservoir than under 

natural conditions. On the other hand, no information 

is presently available to compare the average recharge 

through lawns and other uncovered areas, which comprise more than one-half the drainage area of most 

recharge basins, to the recharge in these areas under 

natural conditions.
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES JP41

STREAMS

Direct runoff to some streams on Long Island has 

greatly increased because of increased direct runoff 

from urban areas. The values of direct runoff to 

streams as a percentage of total annual streamflow are 

given in table 13 (D. E. Vaupel and A. G. Spinello, 

written commun., 1968) for the gaged streams on Long 

Island in water years 1958 and 1964. These were years 

of relatively high and low precipitation, respectively. 

In general, values greater than 6-8 percent in table 13 

indicate an increase in direct runoff compared to 

natural conditions, and these increases are related to 

urban development.

Seaburn (1969) studied the effects of urban development on direct runoff to East Meadow Brook in Nassau 

County for the period 1937-62. In 1937 the drainage 

area of East Meadow Brook was almost completely 

rural. After a period of intensive development in the 

1950's, the southern part of the drainage area was 

almost completely occupied by housing developments. 

A cumulative plot of annual direct runoff to East 

Meadow Brook is shown in figure 35. The marked 

changes in the slope of the curve coincided with 

increases in annual direct runoff resulting from the

1200

construction of storm sewers draining to East Meadow 

Brook. The virtually straight curve of cumulative 

precipitation on the same graph implies that p^ecipitation did not significantly cause the observed increases 

in direct runoff.

The relation between rainfall and runoff in East 

Meadow Brook for individual storms in the pre urban 

(1937-43) and urban (1964-66) periods are shown in 

figure 36. Although the data points show considerable 

scatter, a marked difference is evident for the two 

periods particularly for the larger storms. On the 

basis of figures 35 and 36 and an accurate delineation 

of the urbanized areas that were equipped with storm 

sewers that drain to East Meadow Brook, Seaburn 

estimated that between 10 and 15 percent of the total 

rainfall falling on that urbanized area appeared as 

direct runoff in the stream.

The total area of highly developed land in Fassau 

and 'Suffolk 'Counties from which direct runoff drains 

directly to streams or into the surrounding bodies of 

salty water is probably on the order of 200 square 

miles. If it is assumed that on the average abcTit 15 

percent of total rainfall dicharges from this area as

1937 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 1962

FIGURE 35. Cumulative curves of annual direct runoff in East Meadow Brook and annual precipitation at MineoiX

After Seaburn (1969).
F42 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YOFK

TABLE 13. Annual direct runoff of the 19 continuously gaged 

streams on Long Island, N.Y., for water years 1958 and 1964

[After D. E. Vaupel and A. Q. Spinello, written commun., 1968]

Water year 1958

Gaging station

Valley Stream _____ _

Pines Brook. _ _ _ _ _

East Meadow Brook

Bellmore Creek______ _

Massapequa Creek_____

Santapogue Creek _ ___.

Carlls River.________

Sampawams Creek_____

Penataquit Creek......

Champlin Creek____ __

Connetquot River

Patchogue Creek. _ ____

Swan River. _ _____ _ .

Carmans River.. ____ _

Cedar Swamp Creek

Mill Neck Creek. ___ .

Cold Spring Brook

Nissequogue River. _ __

Water year 1964

Total Total Total Total 

discharge direct discharge direct 

(cubic feet runoff (cubic feet runoff 

per second- (percentage per second- (percentage 

days) of total days) of total 

discharge) discharge)

.._ 2,600

.__ 2,400

7 700

... 5,500

... 5,500

. . . 1, 900

.._ 11,000

... 4,700

.__ 2,500

... 3,300

... 16,000

.__ 9,300

. _ . 5, 600

... 11,000

... 3,200

.__ 3,900

. . _ 1, 800

... 17,000

.__ 20,000

32 

26 

19 

11 

12 

12 

10 

10 

10 

6 

6 

12 

5 

3 

24 

10 

9 

7 

8

340 

460 

1 3, 000 

4,400 

3, 100 

1, 100 

8,600 

3, 100 

2,400 

2,200 

12, 000 

7,100 

4,400 

7,700 

1,800 

2,600 

1,200 

14, 000 

11, 000

52 

49 

22 

11 

15 

11 

8 

10 

9 

5 

5 

7 

5 

3 

23 

10 

6 

5 

7

i Total for 9-month period January-September 1964.

direct runoff, the estimated average direct runoff from 

these areas is on the order of 60 mgd.

The significant feature of the increased direct runoff 

to streams resulting from urban development is that 

the direct runoff rapidly discharges into salty water 

and is therefore lost from the fresh-water system of 

Long Island. Some of the lost water would probably 

have been lost by evapotranspiration and direct runoff 

under natural conditions. However, much of this water 

undoubtedly represents a loss of recharge to the 

ground-water reservoir, and this loss causes groundwater levels to decline. In comparing average groundwater levels in urbanized and unurbanized areas by 

means of double-mass curves, Franke (1968) found 

evidence that the loss of recharge resulting from 

increased direct runoff caused average ground-water 

levels in an urbanized area in southeastern Nassau 

County to decline about 1-2 feet.

PUMPING AND DISTRIBUTION OF GROUND WATER

Two undesirable effects, both resulting from 

changes in the position of the two moveable boundaries 

of the ground-water reservoir (the water table and 

the salt-fresh water interface) are associated with 

large-scale pumping of ground water on Long Island. 

These effects are (1) a regional decline in groundwater levels and (2) an increase in the chloride content 

of the water in some wells. For these undesirable effects 

to occur, the pumped ground water must be permanently removed from the ground-water reservoir.

Sanitary sewers are the major cause of a permanent 

loss of water from the ground-water reservoir of Long 

Island. Instead of returning used water to the groundwater reservoir through cesspools and septic tanks, 

the sanitary sewers dispose of the usec1 water directly 

into salty water.

PUMPING OF GROUND WATER

Gross ground-water pumpage in Nassau and Suffolk 

Counties in selected years is given in table 14. Inasmuch as ground water has been practically the only 

source of water in these counties, grors pumpage has 

increased as the population has increased. In Nassau 

County, gross pumpage increased from about 75 mgd in 

1940 to nearly 210 mgd in 1965. Similarly, gross pumpage in Suffolk County increased from about 30 mgd 

in 1940 to almost 120 mgd in 1965. During the same 

period, gross ground-water pumpage on all of Long 

Island increased from about 220 mgd to about 430 

mgd. Furthermore, tabulations of pumpage and water 

use prepared by the New York State Vrater Resources 

Commission indicate that the average per capita use 

of ground water in Nassau and Suffolk Counties was 

about 140 gallons per day in 1965.

Not all the gross pumpage represents a loss of water 

from the hydrologic system of Long Island. As is discussed subsequently, much of the pumpage particularly in Nassau and Suffolk Counties is returned to 

the ground-water reservoir following its use. The 

proportion that actually is lost (net withdrawal) 

depends upon the type of water use # nd the method 

of waste-water disposal.

TABLE 14. Gross ground-water pumpage in Nassau and Suffolk 

Counties, Long Island, N.Y., 1940-65 l

[In millions of gallons per day]

Year

1940-_---_-_------

1945-_---__--_--_-

IQKfl

1955 __ ______-----

I960.- ___ 

1965-- 

Nassau Su^olk Total 

County County (rounded)

_.__--__ 75

.____.__ 63

________ 110

________ 130

________ 150

_______ 210

30 

31 

42 

67 

75 

120

100 

94 

150 

200 

220 

330

»Based mainly on data obtained from the New York State Water Resources 

Commission.

LEAKY WATER PIPES

The two flow paths in figure 33 water pipes to zone 

of aeration and water pipes to zone of saturation 

represent leakage from water-distribution systems. 

Except in areas of very shallow ground-water 

levels near the shorelines, most pipelines on Long 

Island are in the zone of aeration, ard most of the 

leakage from them ultimately recharges the groundwater reservoir.
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F43

3.0

2.0

1.0

0.5

0.1

0.05

0.01

0.1

 Storm during 1964-66 

6 Storm during 1937-43

0.5 1

TOTAL RAINFALL. IN INCHES

5 6 7 8 9 10

FIGURE 36. Relation between rainfall and runoff for individual storms in the East Meadow Brook drainage area, Nassau 

County, for urban (1964-66) and preurban (1987-43) periods. After Seaburn (1969).
F44 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YOPK

Informal discussions with some managers of watersupply companies on Long Island indicate that in 

well-maintained water-distribution systems the average 

quantity of leakage is about 10-15 percent of total 

water input to the systems. If it is assumed that about 

15 percent of total public-supply pumpage leaks from 

the system before use and recharges the ground-water 

reservoir, the resulting leakage figure for Nassau and 

Suffolk Counties was about 35 mgd in 1965.

EXPORTED WATER

The flow path designated "exported water outflow" 

in figure 33 represents an element of discharge from 

Nassau and Suffolk Counties that is completely controlled by man. Since the beginning of this century, 

New York City has imported water to Kings and 

Queens Counties from several well fields near the 

south shore of Nassau County. Before 1920 the maximum annual-average withdrawals from this system 

were slightly more than 50 mgd. Since that time, withdrawals have decreased. In the decade 1940-49, the 

average withdrawal was less than 20 mgd, and since 

1950, it was less than 5 mgd. Because the amount of 

exported water is small compared to natural discharge 

from the ground-water reservoir, the effect of exporting water on the ground-water reservoir in Nassau 

and Suffolk Counties is negligible at present.

LAWN SPRINKLING AND IRRIGATION

Two flow paths in figure 33, "water pipes to land 

surface" and "pumping to land surface," represent 

lawn sprinkling and other water used for irrigation. 

The amount of water used in this way is significant 

because a large part of it is lost from the hydrologic 

system by evapotranspiration.

A compilation of pumpage by all public watersupply companies in Nassau County for the years 

1954-63 showed that, on the average, about 60 percent 

of the total withdrawals occurred during the summer 

months (April-September), and that 40 percent 

occurred in the winter months (October-March). 

Roughly, three-fourths of the 20 percent difference 

in seasonal pumpage, or 15 percent of total publicsupply pumpage, is assumed to be related to lawn 

sprinkling. Because most people tend to overirrigate 

their lawns, it is further assumed that, on the average, 

about half the water used for lawn sprinkling is lost 

to evapotranspiration and that, the remaining half 

eventually returns to the ground-water reservoir. Thus, 

the estimated total quantity of public-supply pumpage 

lost by evapotranspiration in Nassau and Suffolk 

Counties in 1965 is on the order of 20 mgd.

The flow path "pumping to land surface" represents 

several additional situations where ground water is 

pumped and used locally, including (1) pumping from 

private wells for lawn sprinkling by owners whose 

other water-supply needs are supplied by a watersupply company; (2) pumping from "Hckyard" wells 

for lawn sprinkling where all the other water supply 

needs are derived from that well; and (3) pumping 

for commercial purposes, such as golf-course sprinkling and irrigation of crops. The first two items listed 

above vary considerably from year to year and are 

difficult to estimate. There are probably about 60,000 

private wells in Nassau and Suffolk Counties, most of 

which are small-diameter driven welh that extend a 

few feet into the glacial deposits. The estimated total 

average pumpage from these wells for lawn sprinkling 

and related uses is on the order of 10 mgd or less in 

most years. According tx> an unpublished estimate by 

the New York State Water Resources Commission, 

pumping for commercial purposes, as described above, 

was about 35 mgd in 1965. This included about 15 mgd 

for golf-course sprinkling and 20 mgi for farm and 

nursery irrigation. As is the case with lawn sprinkling, 

probably 25-50 percent of this water infiltrates into 

the zone of aeration and ultimately returns to the 

ground-water reservoir.

DISPOSAL OF USED WAT^R

Used water on Long Island is disposed of in three 

major ways through recharge wells, cesspools and 

septic tanks, and sanitary sewers. Hydrologically, 

these methods differ in their effect on both the water 

balance and the quality of the water in the groundwater reservoir. The effect of these methods of wastewaiter disposal on the quality of the water is considered 

in a subsequent section of the report.

RECHARGE WELLS

In 1933 the New York State Legislature enacted a 

water-conservation law to protect the ground-water 

resources of Long Island. The law empowered the New 

York State Water Power and Control Commission 

(subsequently the New York Water Resources Commission) to regulate the construction of all wells on 

Long Island that withdraw more than 100,000 gpd 

(gallons per day) from the ground-water reservoir. 

In 1954 the law was modified to include all wells having capacities of 45 gpm (gallons per minute) or more 

(about 65,000 gpd).

The State regulatory agency established a policy 

in 1933 prohibiting, "the drilling of new industrial 

wells with capacities in excess of 69.4 gpm (100,000 

gpd), unless the water pumped is returned in an
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F45

r contaminated condition into the ground through 

iffusion wells or other approved structures" (Johnson, 

f48, p. 1160-1161). The term "diffusion well" as used 

v Long Island is virtually identical to the more 

~ : dely used terms, "artificial-recharge well" or "injecion well."

Presently, more than 1,000 recharge or diffusion 

^lls return used ground water to the ground-water 

^v-ervoir of Long Island. According to unpublished 

Y,ta supplied by the New York Water Resources Commission, an average of about 77 mgd was injected into

*f- charge wells on Long Island in 1965, including about 

"':' mgd in Nassau and Suffolk Counties. Most of the 

v^ter was used for air-conditioning (cooling), which 

Tused its temperature to rise markedly before it was 

turned to the ground-water reservoir. Although the 

^rality of the recharged water is changed, the use 

x: ground water for air conditioning causes virtually

10 net loss to the ground-water reservoir. Because the 

D imping and recharge wells are usually very close 

c one another, the flow path in figure 33 designating 

ris activity is drawn from "pumping" directly to 

T^charge wells." Although most recharge wells are 

;creened in the zone of saturation (commonly at vir11 ally the same depth as the supply well), some 

T°harge wells are screened in the zone of aeration.

CESSPOOLS AND SEPTIC TANKS

In most of Nassau and Suffolk Counties, used houselold water is discharged into cesspools and septic tanks 

Tow paths "water pipes to cesspools and septic tanks" 

vrd "pumping to cesspools and septic tanks" in figure 

<] ). Virtually all this water is derived from the 

2TX>und-water reservoir. Because most cesspools and

 ':ptic tanks are at least 3 feet below land surface, the 

ir°xl water discharging into them commonly percoates through the zone of aeration or enters the groundv^ter reservoir directly without appreciable losses 

rr evapotranspiration (see flow paths "cesspools and

 ^ptic tanks to zone of aeration" and "cesspools and 

:f ^tic tanks to zone of saturation" in figure 33). 

^ erefore, discharge of used water to cesspools and 

flv>tic tanks, although causing a marked change in the

-rality of the shallow ground water, does not appreci- 

.1 ly disturb the quantitative balance in the ground- 

\^<ter reservoir.

In 1965, total public-supply pumpage in those parts 

N :" Nassau and Suffolk Counties where cesspools and 

^ptic tanks were used to dispose of used water was 

^,1 out 160 mgd. Based on pumping and sewage disr1 arge tabulations in 1965 and 1966 for the sewered 

"^a (see section on "Sanitary Sewers") in southwest 

Nassau County, the estimated discharge into cesspools

and septic tanks was about 70 percent of the tot"! 

public-supply pumpage, or about 110 mgd. The remaining 30 percent was diverted between the pumpir^ 

wells and the cesspools and septic tanks by pipe leakage and various uses of water such as lawn sprinkling. 

Reportedly, about 260,000 people were not served by 

a public water-supply system in Suffolk County in 

1965, but they obtained their water supply from privately owned wells. If the household use of wator 

(excluding that used for lawn and garden sprinkling) 

is assumed to be about 50 gallons per day per person, 

the estimated additional discharge in 1965 to cesspocls 

and septic tanks in Suffolk County from areas served 

by private wells was about 15 mgd. Therefore, the 

estimated total discharge in 1965 to cesspools and septic 

tanks in Nassau and Suffolk Counties was abo^t 

125 mgd.

SANITARY SEWERS

The flow paths "water pipes to sewer drains" ard 

"sewer drains to ocean" (fig. 33) represent discharjre 

from the fresh-water system to salty water usually 

from a sewage-treatment plant. Some water leaks from 

the sewers to the zone of aeration where the sewers 

are above the water table (flow path not shown in 

fig. 33). If it is assumed that about 10-15 percent of 

the raw sewage entering the sewer-pipe network leaked 

from the system before reaching the sewage-treatment 

plant, the resulting leakage figure for Nassau ard 

Suffolk Counties was about 10 mgd in 1965. In addition, water locally leaks from the sewers to the groundwater reservoir and from the ground-water reservoir 

into the sewers where the sewers are below the water 

table (flow paths not shown in fig. 33). However, it is 

virtually impossible to evaluate quantitatively the 

amounts of water involved. All the water that discharges to salt water from the sewage-treatment-plant 

system is ultimately derived, and represents a net Ic^s 

from, the ground-water reservoir. The sewers are in a 

sense analogous to the streams in that they "short circuit" the flow of ground water from a point within the 

ground-water reservoir some distance inland to a point 

of discharge into salty water.

Total annual average discharge of treated sewage 

effluent to salty water in Nassau and Suffolk Counties 

for the period 1950-65 is shown in figure 37. T/e 

marked increase from 1950 to 1965 was mainly tHe 

result of the completion of the Nassau County Sewer 

District No. 2 secondary-treatment plant (locally 

referred to as the Bay Park sewage-treatment plant), 

which discharged an average of about 50 mgd in 19C5. 

During this period the discharge of treated sewage 

effluent to salty water in Suffolk County was less than
F46 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

exceeded 75 mgd. In addition, natural ground-watei 

recharge had decreased substantially because mucl 

of the land surface had been covered with impermeable 

surfaces such as streets, highways, and buildings. Thest 

factors resulted in a marked imbalance in the ground 

water system causing a net deerea^ in the amounl 

of fresh ground water in storage as evidenced 03 

declining ground-water levels.

By 1936 the water table in practically all of King 

County had declined below sea level (fig. 38#); locally 

it had declined about 50 feet to a d-^pth of more thai 

35 feet below sea level. As a result, a landwarc 

hydraulic gradient had developed, and salty grounc 

water invaded the fresh ground-water reservoir.

As wells in Kings County became contaminated witl 

salty water, more and more of the county was supplie< 

with water obtained from upstate New York source! 

through the New York City public-supply system. Ii 

1946 all pumping of ground water in Kings Counts 

for public-supply use was discontinued. In addition 

the mandatory use of recharge wells, which returnee 

water used for air conditioning and other purpose 

to the ground-water reservoir, resulted in the conser 

vation of large amounts of ground v^ater. Accordingly 

ground-water levels in Kings County began to recove 

substantially in the latter 1940's. By 1965, when gros 

pumpage was about 24 mgd and net pumpage probabl; 

was about 10 mgd, the water table in all but th 

northern part of Kings County had recovered to 

position above sea level (fig. 386').

Ground-water pumpage continued to increase i 

Queens County during the period in which it decrease 

in Kings County (from the late 192O's to the present^ 

As a result, the water table in Queens County in 196 

locally declined to a level more than 10 feet belo* 

sea level (fig. SStf), and salty water began to invad 

the ground-water reservoir in the southwestern par 

of the county.

Contamination of well water by salty ground wate 

in southwestern Nassau and southeastern Queer 

Counties has been the cause of considerable concerr 

and, therefore, the subject of intensive study (Per 

mutter and Geraghty, 1963; Lusczynski and Swarzer 

ski, 1966). As noted previously (fig. 10), three majc 

tongues or wedges of salty ground water are foun 

in the area: (1) A shallow unconfined wedge in th 

upper glacial aquifer, (2) an intermediate confine 

wedge in the Jameco aquifer and in the upper part c 

the Magothy aquifer, and (3) a deep confined wedr. 

in the Magothy aquifer and in the Raritan clay.

For the most part, the position o* the shallow wedc 

of salty water has not changed significantly durin 

historic time. However, locally, esp^ially in and ner

FIGURE 37. Total treated sewage effluent discharged from 

Nassau and Suffolk Counties for the period 1950-65. Data 

from annual reports of the New York, New Jersey, and 

Connecticut Interstate Sanitation Commission and local 

agencies.

5 mgd. This low rate of discharge in Suffolk County 

mainly reflected the fact that most of the sewage in 

that county was disposed of through individually 

owned cesspools and septic tanks and the capacity of 

the sewage-treatment facilities in the county has not 

increased appreciably in the past 15 years.

The hydrologic consequences of the disposal of used 

water through sanitary sewers on Long Island are 

discussed in historical sequence in the following 

paragraphs.

In the past 60 years, intensive ground-water development accompanied by the disposal of used water 

through sanitary sewers has caused major changes in 

the altitude of the water table in Kings and Queens 

Counties. The 1903 water-table contour map shown 

in figure 38A is based on the earliest available waterlevel data. Nevertheless, these contours partly reflect 

the impact of ground-water development because net 

pumpage at the time already was substantial. In Kings 

County, for example, net pumpage at that time averaged about 28 mgd (Lusczynski, 1952, p. 4).

By the early 1930's, net ground-water withdrawals 

for public-supply and industrial use in Kings County
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES P47

1903

(After Lusczynski, 1952 )

/ QUEENS COUNTY \5

1936

(After Suter, 1937 )

101234 MILES 

I , I I I I I

EXPLANATION 

 10 

WATER-LEVEL CONTOUR

Shows altitude of water level.

Contour interval 5 and 10 feet.

Datum is mean sea level

1965

(Adapted from an,unpublished map prepared by the 

New York State Water Resources Commission, 1966 )

FIGURE 38. Ground-water levels in Kings and Queens Counties in (A) 1903, (B) 1936, and (C) 1965. After Cohen, Franke, and

Foxworthy (1968, pi. 8B).
F48 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

several areas of intensive pumping, the deep body 

seems to be actively moving landward. Pumpage from 

the Jameco aquifer and the Magothy aquifer in southwestern Nassau and southeastern Queens Counties is 

presently more than 100 mgd, and much of this pumpage is ultimately discharged to the sea through 

sewage-treatment plants. As a result, the amount of 

fresh ground water in storage in the area is decreasing 

and thereby causing the salty ground water to move 

inland.

Lusczynski and Swarzenski (1966, p. 50-52) estimated that the deep salty-water wedge in the Magothy 

aquifer has moved inland an average of about 1,000 

feet (at rates ranging from 10 to 50 ft per yr) since 

the early 1900's; locally, however, in the vicinity of 

some well fields, it has moved more than 1 mile inland 

since 1952, at a rate of about 300-400 feet per year. 

Lusczynski and Swarzenski (1966, p. 55) also noted 

that, on the average, the intermediate salty-water 

wedge in the Jameco aquifer has moved inland less 

than 1,000 feet since the early 1900's.

Waste water has been disposed of through sewers 

in southwestern Nassau County since 1951. In 1966 the 

total sewered area was about 70 square miles, and the 

annual average discharge of treated-sewage effluent 

from this area to the sea was about 50 mgd. The estimated average decline of ground-water levels in a 

50-square-mile area in southwestern Nassau County 

due to sewering was about 7 feet in 1966 (Franke, 

1968, p. 209).

In summary, although water of relatively poor 

quality from cesspools and septic tanks is no 

longer contaminating the ground-water reservoir in 

sewered areas, the net loss of water to the groundwater reservoir due to sewering can and has caused 

extensive lowering of ground-water levels, which, in 

turn, is accelerating the encroachment of salty water 

into the aquifers of Long Island.

SUMMARY OF EFFECTS OF MAN'S ACTIVITIES ON 

THE MOVEMENT AND DISCHARGE OF WATER

In this section of the report the effects of man's 

activities are considered from two points of view 

artificial ground-water recharge and losses of water 

from the hydrologic system.

SUMMARY OF ARTIFICIAL RECHARGE

Most of the artificial ground-water recharge on 

Long Island results from cesspools and septic tanks, 

recharge basins, injection wells, and leaking water and 

sewer pipes. The estimated artificial recharge in 

Nassau and Suffolk Counties in 1965 from these sources 

is as follows:

Million

gallons

Source per day

Cesspools and septic tanks.__________________________ 125

Recharge basins:

Direct runoff__________________.________________ 60

Waste water.__________________________________ 25

Injection wells___________________________________ 55

Leaking water and sewer pipes_______________________ 45

Total- 310

The large amount of artificial ground-water recharge 

in Nassau and Suffolk Counties significantly affects 

the hydrologic regimen, and a large decrease in this 

recharge, which, for example, would result from discontinued use of cesspools and septic tanks, would 

materially alter the quantitative balance of the groundwater system. The imbalance would, as has been discussed previously, cause a decline in ground-water 

levels and the landward movement of salty ground 

water, at least locally, into the fresl -water aquifers.

LOSS OF WATER FROM THE HYDROLOGIC SYSTEM 

AS A RESULT OF MAN'S ACTIVITIES

The activities of man which result in a loss of water 

from the hydrologic system in Nassau and 'Suffolk 

Counties are (1) watering of vegetation (lawn and 

golf-course sprinkling and irrigation), (2) disposal of 

direct runoff from urban areas to streams and subsequent outflow to the sea, (3) disposal of sewage effluent 

to salty water, and (4) export of water to New York 

City. The estimated total amount of water lost from 

the hydrologic system of Long Island as a result of 

these activities for selected years are shown in figure 

39. The largest single loss, about 60 percent of the total 

in 1965 (about 75 mgd), was the discharge of sewage 

effluent to salty water. In 1940 and 1945, New York 

City imported about 26 and 10 mgd of ground water, 

respectively, from Nassau County. These large exports 

of water from Nassau County caused the trend 

anomaly that is evident for those years in figure 39.

The estimated total loss from the hydrologic system 

in Nassau and Suffolk Counties in 1965 resulting from 

the activities of man, about 125 mgd (fig. 39), is less 

than 10 percent of the estimated average annual input 

of water to the hydrologic system within the waterbudget area, and less than 20 percent of the estimated 

total discharge from the ground-water reservoir under 

natural conditions (table 11). However, much of this 

loss is concentrated in the 70-square-mile area in 

southwestern Nassau County that is sewered, and its 

effect in this area on ground-water levels and streamflow has been marked.
SUMMARY OF HYDBOLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F4.Q

125

1940 1945 1950 1955 1960 1965

FIGURE 39. Estimated discharge of wlater from Nassau and 

Suffolk Counties, as a result of man's activities, 1940-65.

EFFECTS OF MAN'S ACTIVITIES ON THE QUALITY 

OF THE WATER

Man has affected the quality of the water on Long 

"eland primarily through the disposal of wastes, 

r eluding (1) the discharge of smoke and other parioulate matter into the atmosphere, (2) the discharge 

N : household waste waters into the ground-water resrvoir through cesspools and septic tanks, and (3) the 

'^charge of industrial wastes directly into streams or 

r+o the ground-water reservoir through recharge 

)r sins. In addition, the dissolved-solids content of the 

r-rmnd water in many areas has increased markedly 

x cause of leaching of fertilizers. Selected chemical 

ralyses of water that has been polluted by these 

T.rious means are given in table 15. In the following 

' : scussion the analyses in table 15 are compared to 

hs analyses of natural water in table 12.

Sample 1 of precipitation in table 15 has a high 

r If ate content (SO4 ), which is undoubtedly due in 

Dp.rt to contamination of the air as a result of burning 

hrels. Although in different proportions, samples 2 and

of shallow ground water show a particularly high 

cntent of calcium, sodium, chloride, sulfate, and 

^trate, and the increase in these constituents prob- 

^ntent of calcium, sodium, chloride, sulfide, and 

 ^spool effluent, respectively (De Laguna, 1964).

Sample 4 represents water that is contaminated with 

ndustrial plating wastes (cadmium and hexavalent 

and cesspool effluent. This specific occurof pollution by industrial wastes has been

studied in considerable detail (Davids and Lieber, 

1951; Lieber and Welsch, 1954; Welsch, 1955; Perimutter and others, 1963). The chromium and cadmium 

content in sample 4 is considerably in excess of tH 

limits recommended by the U.S. Public Health Service 

(1962) for these metallic ions (0.05 and 0.01 ppm, 

respectively).

Sample 5 is characterized by a high nitrate center*:, 

which results from the disposal of duck-farm wastes 

directly into the stream. De Laguna (1964) showed a 

marked contrast in the amount of dissolved nitrate in 

water from streams located adjacent to duck farms ard 

those distant from duck farms. The introduction of 

stream water into Great South Bay which is rich in 

nitrate and phosphate has caused extensive alg^l 

blooms and a resulting upset in the chemical and nutrient balance of this brackish-water body; efforts are 

being made at present to alleviate this source of 

pollution.

Sample 6 is representative of ground-water seepage 

to a stream in a highly urbanized area. In this area, 

household wastes are discharged into the ground-water 

reservoir through cesspools and septic tanks. Other 

streams that derive ground-water seepage from similar 

areas commonly have a total dissolved-solids content 

ranging between 150 and 200 mg/1. This range is particularly significant because it represents an approximate average dissolved-solids content of the shallow 

ground water beneath the highly urbanized areas on 

Long Island which are not sewered. Locally, of course, 

the shallow ground water may have a considera^y 

higher dissolved-solids content.

Locally, salt-water encroachment has also adversely affected the quality of the ground wate-. 

However, this type of contamination of the fresh 

ground-water reservoir differs from those just mentioned in that man's activities have not added dissolved 

constituents to the water, but these activities have 

changed the location of the naturally occurring salty 

ground water. Selected analyses of salty ground water 

in the zone of diffusion are given in table 12.

Man has also affected the temperature of the grourd 

water locally. Brashears (1941) described a case history 

of thermal pollution resulting from recharge of cooling water used in the manufacture of ice in Kings 

County. Similar situations, although not common, have 

occurred in other areas where water used for cooling 

was returned to the ground-water reservoir through 

recharge wells. In addition, Pluhowski and Kantrowitz (1964, p. 65-66) noted small increases in the 

temperature of the shallow ground water in the 

vicinity of housing developments.
8

TABLE 15. Selected chemical analyses of water contaminated by the activities of man on Long Island, N.Y. 

[Analyses made by U.S. Geological Survey and reported in milligrams per liter]

a

Gal- MagneSam- Source of water Date col- Silica Iron cium sium 

pie lected (SiO2) (Fe) (Ca) (Mg)

1 Precipitation.......... Feb. 1,1967 ................ 4.4 1.7

Ground water, upper 

glacial aquifer: 

2 Well N2403.. ...... Jan. 21,1962 9.1 0.04 46 7.3

3 Well S7144.. ....... Feb. 13,1960 8.4 2.0 18 6.7

4 Well N8194.. ...... Nov. 7,1962 13 .22 4.8 1.1

Stream water: 

6 Forge River, West Apr. 29,1948 9.9 .02 8.1 2.6

Branch.

6 Massapequa May 11,1966 6.8 .36 13 4.3 

Creek.

' ABS (alkylbenzensulfonate). 

3 MB AS (methylene blue active substance).

«_ i

Total 

Sodi- Potas- Bicarbon- Ohio- Fluo- dissolved Specific 

um sium ate Sulfate ride ride Nitrate Additional solids conduc- pH Remarks 

(Na) (K) (HCOs) (SO4 ) (Cl) (F) (NOj) constituents (residue on tance 

evaporation (KX10«) 

at 180° C)

3.9 0.4 4 16 3.4 ........ 3.6 .......................... 76 6.4 Partial analysis; composite sample,

collected from rain gage at Mineola, 

N.Y., for period Jan. 3-Feb. 1 

1967.

16 2.6 9 96 22 0.0 46 .............. 247 389 6.8 Depth 84 ft; diameter 12 in.; water

probably contaminated by fertilizer (De Laguna, 1964). 

29 4.4 3 20 60 .1 62 .............. 208 360 4.9 Depth 40 ft; depth to water about

20 ft; diameter 2 in.; water probably contaminated by cesspool 

effluent (De Laguna, 1964). 

39 6.7 19 67 16 1 16 Hexavalent 173 270 6.2 Water contaminated by metalchromium, plating wastes (hexavalent chro6.2; Cd, mium and cadmium) and cesspool 

0.4; ABS, effluent (Perlmutter, and others, 

0.26 1. 1963).

6.3 4.2 13 7.0 8.8 .3 22 .............. 93 114 6.0 Sample collected at Route 27; water

probably contaminated by duckfarm wastes (De Luguna, 1964). 

16 2.6 12 32 20 .1 12 MB AS, 146 211 6.2 Sample collected at gaging station; 

0.4 2. stream discharge 3.1 cfs.

72° 

73° ^/^^^r^^

^^-^ ^£^

L^

O

s

H

S

0

URBAI P 

>q

0 

0

s

2!

M

CO

p2!

0

Location of sampling points
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F51

iVATER-MANAGEMENT IMPLICATIONS OF THE 

HYDROLOGIC ANALYSIS

The goal of water-resources planning on Long 

sland is to provide sufficient water of suitable quality 

o meet the present needs of the residents of Long 

sland and to meet their needs for a reasonable period 

^f years in the future. This section of the report relates 

\e hydrologic analysis in the previous sections to the 

: lanning and development of the local water resources 

f the area, with special emphasis on Nassau and 

"uffolk Counties.

THE PRESENT DILEMMA

Future water-resources planning in Nassau and 

: nffolk Counties must build on the existing state of 

rater-resources development in the area, and it must 

;^ke into account many complex hydrologic, economic, 

md political factors. The major features of present 

rater-resources development in the area are (1) withdrawal of ground water from both the shallow 

;nconfined aquifers and from the deeper confined 

squifers (2) artificial recharge of polluted waste water 

t".rough cesspools and septic tanks, (3) injection of 

relatively uncontaminated waste water through diffusion wells, (4) artificial recharge of direct-runoff water 

t rough shallow basins, and (5) discharge of treated 

nwage water, which was initially derived from the 

Erround-water reservoir, into the sea.

At present (1968), as a result of these waterrianagement practices, total fresh-water outflow from 

t e ground-water reservoir within the water-budget 

a rea is greater than total fresh-water inflow, and the 

a mount of fresh ground water in storage is decreasing. 

This decrease is indicated by declining ground-water 

hvels and the encroachment of salty ground water 

iito the fresh ground-water reservoir. If the present 

management practices continue, it is likely that, within 

t x e water-budget area, (1) the hydrologic imbalance 

rill increase, (2) ground-water levels will continue to 

c'^cline, and (3) salty ground water will continue to 

nove inland. Accordingly, the present management 

practices, including particularly the seaward discharge 

c f sanitary sewers, is equivalent to a method of planned 

c ^erdevelopment.

The complex economic, sociologic, and political factors associated with water-resources development are 

partly related to the sometimes conflicting interests and 

c ->sires of the citizens in Nassau and Suffolk Counties. 

Many citizens are interested in maintaining the size 

and chemical purity of the lakes and streams for recreation. Others are concerned with maintaining the 

:-?ologic balance in the salty bays along the south

shore of Long Island to preserve the fauna, flora, a nd 

natural beauty of the area. County and State health 

officials strive to fulfill their responsibilities of assuring 

a water supply that is completely without hazard to 

health. All the citizens are, of course, concerned about 

the cost of future water-resources development.

The present controversy of whether or not to construct sanitary sewers in parts of Nassau and Suffolk 

Counties is an example of largely valid but conflicting 

points of view. The present method of disposing of 

household waste through cesspools and septic tanks 

in most of Nassau and Suffolk Counties helps maintain the quantity of water in the ground-water reservoir, but causes a deterioration of the quality of the 

water in the shallow aquifers, which poses a possivl e 

health hazard. The construction of sanitary sewers vill 

help preserve the chemical quality of the shallow -aquifers, but this construction will result in an increase 

in the net loss of water from the ground-water reservoir if other conservation procedures are not adopted.

SOME CONCEPTS RELATED TO WATER MANAGEMENT 

PRINCIPLE OF CONTINUITY

As a consequence of the principle of continuity, the 

quantities of water entering and leaving any arbitrary 

volume (for example, the L/ong Island ground-water 

reservoir) within a given time are related by the 

so-called hydrologic equation:

Inflow = Outflow ± Change in storage. 

If the change in storage is positive (denoting an 

increase in the quantity of water in storage), it is 

added to the right side of the equation; if it is negative (denoting a decrease in the quantity of water 

in storage), it is subtracted.

The hydrologic system of Long Island must respond 

to any water-management program in a way that is 

consistent with the hydrologic equation. If one of the 

management objectives is to use the water in a way 

that will not result in a continued decrease in the 

amount of fresh ground water in storage, it follows 

from the equation that a balance between total grourdwater inflow (recharge) and outflow must be attained. 

That is, increased consumptive use of ground water 

must be balanced by increased inflow (such as artificial recharge) or by a reduction of natural outflow 

(such as ground-water discharge to streams) to avoid 

a continued decrease in the amount of fresh ground 

water in storage.

A management program that causes a continual 

hydrologic imbalance in which the total inflow to the 

ground-water reservoir is less than the total net outflow (the total quantity permanently lost from the 

system by evapotranspiration or by discharge to the
F52 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

sea) necessarily will result in the eventual depletion 

of the fresh ground water in storage. However, if the 

concept of temporary overdraft of fresh water from 

the ground-water reservoir is incorporated into a management program, the number of management choices 

increases markedly. For example, increased net 

ground-water withdrawals from the water-budget area 

could be accomplished if the decision is made to tolerate (1) declining ground-water levels, (2) the landward movement of salty ground water, (3) decreased 

streamflow, or (4) a combination of these factors.

YIELD OF THE SYSTEM

Discussions on the development of the water resources 

of Long Island often focus on the "yield" or the "safe 

yield" of the ground-water system. Probably, the most 

commonly cited definition of safe yield is that given by 

Meinzer (1923, p. 55); he defined safe yield as, "the 

rate at which water can be withdrawn from an aquifer 

for human use without depleting the supply to such 

an extent that withdrawal at this rate is no longer 

economically feasible." Todd (1959, p. 200-214) 

reviewed the concept of safe yield in considerable 

detail and redefined the term as follows: "The safe 

yield of a ground-water basin is the amount of ground 

water which can be withdrawn from it annually without producing an undesired result." Todd's definition is 

a somewhat more general statement of the concept of 

safe yield than the definition by Meinzer and, therefore, expands its applicability and enhances its 

usefulness. Accordingly, the definition of safe yield 

developed by Todd (1959, p. 200) is adopted i,n this 

report.

One of the most significant aspects of the concept 

of the safe yield of any hydrologic system, including 

the ground-water system of Long Island, is that a 

quantitative value for safe yield must be determined 

within the framework of (1) the hydrologic equation 

and (2) a precise definition of the extent to which 

certain undesirable results will be tolerated. Accordingly, the safe yield of any ground-water system is 

not a single, fixed value, but is a variable that depends 

upon many complexly interrelated factors.

Safe yield is a useful concept in evaluating the 

possible alternatives of managing a hydrologic system. 

However, in practice, the concept has been greatly 

misused usually, because an 'attempt is made to 

develop a single value for the safe yield of an area. 

This misuse of the concept of safe yield is detrimental 

to constructive and intelligent water-resources planning, and under these circumstances effective planning 

might be facilitated by abandoning the concept 

altogether.

CONSERVATION OF GROUND WATER

Conservation is usually defined as the careful preser 

vation and protection of a resour^ especially tin 

planned management of a natural resource to prevenl 

its exploitation, destruction, or neglect. Managemem 

of the water resources of Long Island involve! 

many complex cause-and-effect relationships, particu 

larly within the ground-water reservoir. Therefore, i 

diversity of opinion exists regarding which factors 

involve exploitation of the water resources, and what 

is desirable and undesirable with regard to develop 

ing and managing the water resources. Some people 

believe that it is highly desirable, to preserve th< 

present size of the ground-water reservoir that is 

not to decrease the amount of fresl ground water ir 

storage. Others believe that conservation of watei 

involves the most effective use of tl ?, available watei 

by man, which may or may not be compatible witl 

preserving the present size of the ground-water reservoir. Despite the fact that they also may share these 

different points of view, most engineers and scientists 

would probably agree that the tost procedure in 

planning the water-resources development of Long 

Island is to evaluate the various ^ater-management 

alternatives from as many valid points of view as 

possible and then to select the alternative or combination of alternatives which produces the most desirable, or least undesirable, results in accordance with 

the wishes of the citizens of Long Island.

WATER-MANAGEMENT ALTERNATIVES

The following alternatives for developing the water 

resources of Long Island are classified according to 

the terms of the 'hydrologic equaticn which are most 

affected by the alternatives. Pertinent information 

developed for eadi alternative includes (1) changes 

in the volumes of fresh water flowing into and out o' 

the hydrologic system, (2) changes in storage within 

tine system, (3) changes in internal routing of the 

water in the hydrologic system (fig. 33), and (4) 

changes in the quality of the water.

INCREASE INFLOW TO THE HYDROLOGIC SYSTEM 

Inasmuch as precipitation was the only source o' 

fresh water on Long Island under natural conditions 

increased precipitation and the importation of fresh 

water from sources other than those on the island 

are the only methods of increasing the total amount 

of fresh water on and beneath I^ong Island. The 

potential outside sources of fresh water include mainland sources, desalination of sea water or salty ground 

water, and perhaps the constructior of a fresh-water 

reservoir in Long Island Sound (Gerard, 1966; A. J.
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F53

^ansini, written commun., 1967). However, because the

iresent study was concerned mainly with the development of the local water resources, a detailed discusYion of these possibilities is beyond the scope of this

SALVAGE OUTFLOW FROM THE HYDROLOGIG

SYSTEM

The estimated average rate at which ground water 

discharges into streams and thence into the bodies 

of salty surface water bordering the island is about 

T20 mgd in the water-budget area of Long Island 

Stable 11). Much of this water could probably be 

ralvaged by means of a network of carefully spaced 

i hallow wells and pumping galleries adjacent to the 

rtreams, particularly near the south shore of Long 

"sland. Such shallow wells are commonly referred 

( o as "skimming wells" because they skim fresh water 

"rom very near the top of the ground-water reservoir. 

"Vith careful spacing of the wells, a large volume 

of water could probably be withdrawn with only 

>rnall and local decreases in ground-water levels result- 

: ng therefrom. Thus, this method of development 

^ould be accompanied by only a minimal decrease 

in the total volume of ground water in storage.

Salvaging natural ground-water discharge by the 

use of skimming wells would be largely at the expense 

of streamflow. The resulting decrease in streamflow 

x> the sea would change the salinity of the bays and 

estuaries, and thus might alter the plant and animal 

1 ife therein. The resulting possible harmful effects and 

'he loss of some of the esthetic features associated 

T*dth the streams would therefore have to be con- 

" idered carefully when evaluating the possible application of skimming wells.

Because the chemical quality of much of the shallow 

ground water has been affected adversely by cesspools

 *nd septic tanks, the quality of the water withdrawn 

erom the skimming wells might be less than optimum, 

<:<nd, therefore, the water might require some treatment 

Drier to use. Nevertheless, skimming wells, galleries, 

or collectors seemingly could increase the yield of 

,he Long Island ground-water reservoir substantially 

compared to the present program of development.

If the total ground-water inflow remains unchanged, the only possibility of significantly decreasing 

rround-water outflow from the hydrologic system of 

'jong Island without a concurrent decrease of ground 

^ater in storage is to decrease evapotranspiration 

losses. As discussed previously, the quantity of ground

-vater consumed by evapotranspiration in the waterT"udget area is small. Moreover, the likelihood of 

salvaging large amounts of precipitation and surface water that are lost by evapotranspiration on 

Long Island seems remote at present. Accordingly, 

an attempt to salvage evapotranspiration losses on 

Long Island does not seem to be a significant watermanagement alternative at present.

PERMIT A PLANNED DECREASE OF FRESH GROUND 

WATER IN STORAGE

The ultimate stable positions of the wedges of 

salty ground water are dependent upon water-level 

altitudes in the fresh ground-water reservoir. When 

fresh ground-water levels rise, the wedges of salty 

ground water move seaward, and, at the same time, 

subsurface outflow of fresh ground water increases. 

When ground-water levels decline, the reverse occurs.

Experiments have shown that the landward extent 

or length of a wedge of salty water in a given 

aquifer is about inversely proportional to the rate 

at which ground water is discharging from the acuifer into the ocean (Todd, 1959, p. 281). It follows, 

therefore, that if a management decision is made 

to maintain the positions of the interfaces between 

fresh and salty ground water that existed under ratural conditions, then roughly, 400 mgd of fresh ground 

water (table 11) must be allowed to discharge by 

subsurface outflow from the water-budget area toward 

the sea. On the other hand, if the salt-water wedges 

are permitted to move inland, an additional quantity 

of fresh ground water could be withdrawn from the 

aquifers and used consumptively.

If the goal of water-resources planning were to 

salvage as much outflow from the ground-water reservior as possible and at the same time the decision 

was made to tolerate a large decrease in the volume 

of ground water in storage, it might be possible to 

salvage as much as half the total subsurface outf ow 

of fresh ground water, or about 200 mgd (table II). 

Moreover, much of the base flow of the streams that 

discharges into the sea could be salvaged. It probably would not be feasible to salvage all the base 

flow of the streams (an average of about 320 mgd), 

but at least 200 mgd probably could readily be salvaged. Under conditions of intensive development, 

therefore, extensive and carefully planned lowering 

of ground-water levels could result in salvaging on 

the order of 400 mgd 200 mgd of subsurface outf ow 

plus 200 mgd of streamflow.

Ground-water development that results in salvaging 

large amounts of subsurface outflow and streamf ow 

will result in a decrease of ground water in storage 

beneath the water-budget area and beneath the bordering bays and the ocean. Sustained regional dr>wdowns in the ground-water reservoir beneath the
F54 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YC^K

water-budget area on the order of tens of feet would 

ultimately result in the landward movement of the 

fresh-salt water interfaces of several thousands of 

feet or more. The change in storage of fresh ground 

water beneath the water-budget area would be many 

times smaller than the change in storage of fresh 

ground water beneath the bordering bays and ocean.

The amount of fresh ground water in storage 

beneath the bays and the ocean can only be roughly 

estimated (table 4). However, even if this quantity 

of fresh water in storage was accurately known, the 

amount that could be salvaged as the fresh-salt water 

interfaces moved landward would be uncertain. Wide 

variations in hydraulic conductivity in adjacent and 

overlying layers in the ground-water reservoir could 

cause an uneven or fingering pattern of salt-water 

encroachment, which could result in local bodies of 

fresh ground water being isolated and rendered virtually unrecoverable.

The principle of permitting the salt-water wedges 

to move inland to new stable positions that require 

less subsurface outflow of fresh ground water to the 

sea is, in effect, a method of planned overdevelopment. 

This method could be employed, to whatever extent 

deemed desirable, in conjunction with any one of 

the several other alternative methods of development. 

In summary, the safe yield of the ground-water reservior of Long Island could be increased substantially 

if it were deemed tolerable to permit the salt-water 

wedges to move inland, and thereby allow some of the 

present wells to become contaminated with salty water.

MAINTAIN APPROXIMATE BALANCE BETWEEN INFLOW 

AND OUTFLOW BY MEANS OF ARTIFICIAL RECHARGE

According to the principle of continuity, if outflow 

exceeds inflow the volume of water in storage in the 

ground-water reservoir must decrease. In the previous 

section of this report, the advantages of decreasing 

outflow from the ground-water reservoir accompanied 

by a planned decrease in the volume of ground water 

in storage were discussed. At some time in the future, 

however, the water managers may deem it desirable 

to maintain the salt-water wedges ait approximately 

constant positions. When this point has been reached, 

a balance between total fresh ground-water inflow and 

outflow must be maintained.

Various proposals are now under consideration on 

Long Island to maintain the balance between fresh 

ground-water outflow and inflow by artificially recharging treated waste water into the ground-water reservoir. These proposals include (1) injecting renovated 

water into the deeper aquifers through a line of 

barrier-injection wells near the south shore (and

perhaps also near the north shore at a later date) 

of Long Island and (2) recharging renovated water 

into the shallow aquifers through basins that would 

be located near the center of the island. (

Water injected into the deeper aquifers will increase 

the artesian pressure in the vicinity of each injection 

well in proportion to the quantity of injected water, 

and the injected water will move radially away from 

the well. The seaward hydraulic gradient from the 

injection well will increase, and a landward hydraulic 

gradient also will be established. If the wells are 

properly spaced, the individual mounds of artesian 

pressure around each well will coalesce, and a pressure 

ridge will form parallel to the coast. The extent to 

which the pressure ridge will be effective in preventing the landward movement of salty water will depend 

upon many complexly interrelated factors, especially 

(1) the magnitude of the increase in artesian pressure 

in both the horizontal and vertical directions and (2) 

the location and magnitude of nearby ground-water 

withdrawals.

Irrespective of the size and shape of the pressure 

ridge formed by injecting a given quantity of water 

into a network of barrier injection wells, theoretically, 

the yield of the system will be increased by the amount 

of additional fresh-water recharge to the ground-water 

system. In practice, however, not all the injected 

water will be recovered, but a large proportion probably could be salvaged under a careful program of 

development.

Some of the injected water will mo^e inland toward 

wells that are withdrawing public-supply water; 

eventually, diluted treated effluent, and under some 

circumstances undiluted treated effluent, might be withdrawn from nearby pumping wells. For this reason, 

the sewage-plant effluent that is injected will receive 

tertiary treatment to upgrade the quality of the water 

so that it meets or exceeds virtually all the commonly 

accepted standards for drinking water.

Shallow basins provide an additional significant 

option to the water manager as a means of recharging 

renovated water into the ground-water reservoir 

either used alone or in conjunction with injection 

wells. In Suffolk County a regulation recently established by the Suffolk County Health Department 

requires that all new housing developments in the 

county having 100 or more individual homes must 

be equipped with communal sewagvtreatment and 

disposal facilities. As a result, several housing developments in Suffolk County presently are discharging 

treated sewage-plant effluent into recharge basins, and 

the total quantity of such artificial re-charge probably 

will increase markedly in the future.
SUMMARY OF HYDROLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES T55

Shallow basins have the advantage that they are

risy to construct and maintain. Furthermore, expeience with storm-runoff and disposal basins on Long

"sland has shown that most such 'basins can readily

rispose of large quantities of treated waste water.

A major disadvantage of basins, however, is the

Inrge land area that they require.

Theoretically, if after it is used, all the water 

]>umped from the ground-water reservoir is returned 

1 y means of injection wells, recharge basins, or other 

methods, the yield of the system would be almost 

limitless were it not for water-quality considerations 

r.nd for the differences between horizontal and vertir,al hydraulic conductivities. Each time that the water 

: ^ recirculated (pumped from the ground, used, treated, 

r.nd returned underground) the quality of the water 

^ould deteriorate unless certain demineralizing treatment methods were used. Such methods are possible, 

1 ut are at present relatively expensive. Even if demini ralization is not employed, tertiary treatment of 

TTTaste water and subsequent recharging of the 

j;*round-water reservoir could increase the safe yield 

rf the system manyfold, and might extend the use- 

' ulness of the ground-water reservoir of Long Island 

i>ver hundreds of years.

If most of the future pumpage is from the deeper 

: rtesian aquifers and if the pumped water is returned 

to the shallow aquifers after use, a local imbalance 

might result hi the deeper aquifers. Because vertical 

" ydraulic conductivities ordinarily are much less than 

1 orizontal hydraulic conductivities, water returned 

fo the shallow aquifers may not move downward 

:nto the deeper aquifers as rapidly as it is pumped 

'Tom these aquifers, with the result that some water 

mumped from the deeper aquifers will be replaced 

: nstead by laterally encroaching salty water.

CONCLUDING COMMENTS ON WATER-MANAGEMENT 

ALTERNATIVES

Several major questions must be answered in order 

fo develop a rational and comprehensive plan for 

managing the water resources of Long Island. Two of 

fhe most significant questions that have been consid- 

(red thus far in the report are (1) should salty 

ground water be permitted to move inland, and if so, 

! ow far inland? and (2) what role should renovated 

^ater play in water-resources planning? A third major 

question and a question that could materially affect 

'he planning process, relates to the length of time 

'or which comprehensive plans should be designed 

br 25, 50, or 100 years, or longer. None of these 

major questions can be answered independently, but

each must be answered in the context of the answers 

to the other questions.

The advantages and disadvantages of permitt;ng 

planned salt-water encroachment are considered in 

previous sections of the report. However, an additional word regarding the effect of planned salt-water 

encroachment on the optimum use of water by man 

is appropriate. A decrease in the subsurface outflow 

of ground water from the deeper aquifers on Long 

Island will be accompanied by a decrease in the volume of water in storage within these aquifers. OTTer 

a period of many years the amount of water salvaged 

as a result of reduced outflow will undoubtedly be 

greater than the net decrease of ground water removed 

from storage. Under these circumstances, the argument 

can be made that, to achieve the optimum use of water 

by man, some encroachment of salty water would be 

beneficial.

Several of the apparently most feasible watermanagement alternatives involve the use of renovated 

water. From the hydrologic point of view, these 

alternatives are mainly concerned with achieving the 

optimum pattern of ground-water withdrawals r.nd 

artificial recharge of ground water. Another important consideration, however, is the reaction of the 

citizens of Long Island to the use of renovated water. 

Instead of recharging renovated waiter into the groundwater reservoir and allowing it to mix there with 

unused water before possible withdrawal again by 

pumping, the same degree of dilution could be 

obtained by mixing renovated water and unused water 

in the water mains. This procedure would avoid the 

cost of recharging much of the renovated water. This 

course of action, however, may not be acceptable to 

the citizens of Long Island at present for psychological or other reasons.

The significance of the time factor in water-resources 

planning cannot be over emphasized. Within the n°.xt 

25 or 50 years, for example, the technical ability to 

economically convert salty water to fresh wster 

may be greatly improved. Also, many other watermanagement alternatives may become technically and 

economically feasible. In the meantime, the citizens 

and water planners of Long Island are fortunate 

because of the large size of the fresh ground-wrter 

reservoir. This large volume of high-quality fresh 

water in storage lends time, which, in turn, provides 

the opportunity for a careful consideration of the 

available alternatives and considerable flexibility to 

the water manager.

This report has shown the close interrelations betw°ien 

the various components of the hydrologic system.
F56 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

Although the fresh ground-waiter reservoir of Long 

Island is very large, the activities of man in one 

part of the reservoir iiltimately will also affect other 

parts of the reservoir. For this reason, the most 

efficient planning to utilize and manage the groundwater reservoir can be achieved if the reservoir is 

developed and managed as a unit without regard 

for political boundaries.

An adequate evaluation of the various alternatives 

for developing and managing the water resources of 

Long Island will require the combined efforts of 

many specialists including hydrologists, engineers, 

geologists, ecologists, economists, sociologists, and 

regional planners. The complexity of the problems 

involved and the possibly great impact of a final 

overall plan on the lives of the citizens of Long 

Island requires such a multidisciplinary approach. 

Moreover, because of the great cost involved in implementing some of the alternatives, a substantial effort 

in the planning phase is warranted. As stated previously, because of the great size of 'the fresh groundwater reservoir, adequate time is available for such 

careful planning.

A continuing program of hydrologic studies is 

mandatory to provide the necessary input of hydrologic information to an overall planning effort. The 

present data-collection activities on Long Island, 

which provide a continuous record of the state of the 

hydrologic system, should be continued and further 

refined. In particular, a more intensive study and 

monitoring of water quality in various parts of the 

island would be helpful. Previous efforts to define the 

shape and areal extent of the various aquifers should 

also be continued. This is particularly true in eastern 

Suffolk County where many deep public-supply wells 

are being drilled in areas where very few deep wells 

previously existed. The data from these wells will 

provide much valuable lithologic, water quality, and 

test information.

As shown in this report, man has already altered 

both the internal routing within and outflow from 

the hydrologic system and the quality of the water 

therein. Man's future role in causing further changes 

will undoubtedly be even greater. As a result, an 

increasing amount and intensity of hydrologic study 

will be necessary to keep abreast of these continual 

changes.

Finally, the present intensity of water-resources 

development on Long Island and the projected future 

development of these resources warrant the use of the 

most sophisticated tools now available to the hydrologist. An electric-analog model study of most of the 

Long Island ground-water reservoir is now underway.

Studies with this model should help define and evaluate the hydrologic results of some of the management 

alternatives considered in this report. These studies 

should be followed by other types of analog studies., 

Furthermore, it is now possible to simulate at least 

some problems associated with the Long Island groundwater reservoir on a digital computer. All these tools 

will aid the water manager in formulating a rational 

and comprehensive plan for developing the water 

resources of Long Island.

SELECTED REFERENCES

Baffa, J. J., and others, 1958, DevelorTients in artificial 

ground-water recharge: Am. Water ^orks Assoc. Jour., 

v. 50, no. 7, p. 812-871.

Brashears, M. L., Jr., 1941, Ground-wat^r temperatures on 

Long Island, New York, as affected tor recharge of warm 

water: Econ. Geology v. 36, no. 8, F. 811-828.

Burr, W. H., Hering, Rudolph, and Frogman, J. B., 1904, 

Report of the Commission on addition! water supply for 

the City of New York: New York, Martin B. Brown 

Co., 980 p.

Cohen, Philip, and Durfor, C. N., 1967, Artificial-recharge 

experiments utilizing renovated sewrsre-plant effluent a 

feasibility study at Bay Park, I T<w York, U.S.A.: 

Internat Assoc. Sci. Hydrology Pub. 72, p. 194-199.

Cohen, Philip, Franke, O. L., and Fox^<>rthy, B. L., 1968, 

An atlas of Long Island's water resources: New York 

State Water Resources Comm. Bull. 62, 117 p.

Cohen, Philip, Franke, O. L., and MeClymonds, N. E., 1969, 

Hydrologic effects of the 1962-66 drorght on Long Island, 

New York: U.S. Geol. Survey Vater-Supply Paper 

1879-F, 18 p.

Cooper, H. H., Jr., 1964, A hypothesis con-erning the dynamic 

balance of fresh water and salt water in a coastal aquifer, 

in Sea water in coastal aquifers: U.S. Geol. Survey 

Water-Supply Paper 1613-C, p. C1-C11.

Davids, H. W., and Lieber, Maxim, 1951, Underground water 

contamination by chromium wastes: Water and Sewage 

Works, v. 98, no. 12, p. 528-534.

de Laguna, Wallace, 1963, Geology of F^ookhaven National 

Laboratory and vicinity, Suffolk County, New York: 

U.S. Geol. Survey Bull. 1156-A, 35 p.

 1964, Chemical quality of water, PTookhaven National 

Laboratory and vicinity, Suffolk Courty, New York: U.S. 

Geol. Survey Bull. 1156-D, 73 p.

de Laguna, Wallace, and Brashears, M. L., Jr., 1948, The 

configuration of the rock floor in western Long Island, 

New York: New York State Water Power and Control 

Comm. Bull. GW-13, 32 p.

Faust, G. T., 1963, Physical properties and mineralogy of 

selected samples of the sediments f~om the vicinity of 

the Brookhaven National Laboratory, Long Island, New 

York: U.S. Geol. Survey Bull. 1156-B, 34 p.

Fleming, W. L., 1935, Glacial geology of central Long Island: 

Am. Jour. Sci., v. 30, p. 216-238.

Flynn, J. M., and others, 1958, Study of synthetic detergents 

in ground water: Am. Water Works Assoc. Jour., v. 50, 

no. 12, p. 1551-1562.
SUMMARY OF HYDROLOGIC SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES F57

Franke, O. L., 1968, Double-mass-curve analysis of the effects 

of sewering on ground-water levels on Long Island, New 

York, in Geological Survey research 1968: U.S. Geol. 

Survey Prof. Paper 600-B, p. B205-B209.

Fuller, M. L., 1914, The geology of Long Island, New York: 

U.S. Geol. Survey Prof. Paper 82, 231 p.

Gerard, R. D., 1966, Potential freshwater reservoir in the 

New York area: Science, v. 153, no. 3738, p. 870-871.

Harder, J. A., Simpson, T. R., Lau, L. K., Hotes, F. L., and 

McGawhey, P. H., 1953, Laboratory research on sea-water 

intrusion into fresh ground-water sources and methods 

of its prevention final report: Univ. Calif., Berkeley, 

Sanitary Eng. Research Lab., 68 p.

Heath, R. C., Foxworthy, B. L., and Oohen, Philip, 1966, The 

changing pattern of ground-water development on Long 

Island, New York: U.S. Geol. Survey Circ. 524, 10 p.

Isbister, John, 1966, Geology and hydrology of northeastern 

Nassau County, Long Island, New York: U.S. Geol. 

Survey Water-Supply Paper 1825, 89 p.

Jacob, C. E., 1945a, The water table in the western and 

central parts of Long Island, New York: New York State 

Water Power and Control Comm. Bull. GW-12, 24 p. 

| 1945b, Correlation of ground-water levels and precipitation on Long Island, New York: New York State Water 

Power and Control Comm. Bull. GW-14, 20 p.

Johnson, A. H., 1948, Ground-water recharge on Long Island : 

Am. Water Works Assoc. Jour., v. 49, no. 11, p. 1159-1166.

 1955, Conservation of ground water on Long Island: 

Am. Water Works Assoc. Jour., v. 47, no. 4, p. 348-354.

Kohout, F. A., 1964, The flow of fresh water and salt water in 

the Biscayne aquifer of the Miami area, Florida, in Sea 

water in coastal aquifers: U.S. Geol. Survey Water-Supply 

Paper 1613-C, p. 12-32.

Leggette, R. M., 1936, Long-time records of ground-water levels 

on Long Island, New York: Am. Geophys. Union Trans., 

v. 17, p. 341-344.

 1937, The mutual interference of artesian wells on

Long Island, New York: Am. Geophys. Union Trans.,

18th Ann. Mtg., pt. 2, p. 490-494. 

Leggette, R. M., and Brashears, M. L., Jr., 1938, Ground water

for air-conditioning on Long Island, New York: Am.

Geophys. Union Trans., 19th Ann. Mtg., pt 1, p. 412-418. 

Lieber, Maxim, Perlmutter, N. M., and Frauenthal, H. L.,

1964, Cadmium and hexavalent chromium in Nassau

County ground water: Am. Water Works Assoc. Jour.,

v. 56, no. 6, p. 739-747. 

Lieber, Maxim, and Welsch, F. W., 1954, Contamination of

ground water by cadmium: Am. Water Works Assoc.

Jour., v. 46, no. 6, p. 541-547. 

Lounsbury, Clarence, and others, 1928, Soil survey of Suffolk

and Nassau Counties, New York: U.S. Dept. Agriculture,

Bur. Chemistry and Soils, ser. 1928, no. 28, 46 p. 

Lubke, E'. R., 1964, Hydrogeology of the HuntingtonSmithtown area, Suffolk County, New York: U.S. Geol.

Survey Water-Supply Paper 1669-D, 68 p. 

"msczynski N. J., 1952, The recovery of ground-water levels

in Brooklyn, New York, from 1947 to 1950: U.S. Geol.

Survey Circ. 167, 29 p.

 1961, Head and flow of ground water of variable density: Jour. Geophys. Research, v. 66, no. 12, p. 4247-4256.

"jusczynski, N. J., and Johnson, A. H., 1951, The water table 

in Long Island, New York, in January 1951: New York 

State Water Power and Control Comm. Bull. GW-27, 28 p.

Lusczynski, N. J., and Swarzenski, W. V., 1960, Position of 

the salt-water body in the Magothy(?) Formation ir the 

Cedarhurst-Woodmere area of southwestern Nrssau 

County, Long Island, New York: Econ. Geology v. 55, 

no. 8, p. 1739-1750.

 1962, Fresh and salty ground water in Long Is1 and, 

New York: Am. Soc. Civil Engineers Proc., v. 88, 

no. 3207, p. 173-194.

 1966, Salt-water encroachment in southern Nassau and

southeastern Queens Counties, Long Island, New York: 

U.S. Geol. Survey Water-Supply Paper 1613-F, 76 p.

McClymonds, N. E., and Franke, O. L., 1971, Watertransmitting properties of Long Island's aquifers: U.S. 

Geol. Survey Prof. Paper 627-E (in press).

Meinzer, O. E., 1923, Outline of ground-water hydrology with 

definitions: U.S. Geol. Survey Water-Supply Faper 

494, 71 p.

Meyer, A. F., 1928, The elements of hydrology: New York, 

John Wiley & Sons, 522 p.

Miller, J. F., and Frederick, R. H., 1969, The precipitf tion 

regime of Long Island, New York: U.S. Geol. Survey 

Prof. Paper 627-A, 21 p.

Nassau County Planning Commission, 1959, Planning Nassau 

County A compilation of land uses: Mineola, Nassau 

County Planning Comm., 17 p.

New York City Department of Planning, 1962, Land use 

in New York City: New York, Newsletter Dept City 

Planning, April 1962.

New York State Water Pollution Control Board, 1960, Effect 

of synthetic detergents on the ground waters of ]"x*ng 

Island, New York: New York State Water Pollrtion 

Control Board Research Rept. 6, 17 p.

Perlmutter, N. M., and Crandell, H. C., 1959, Geology and 

ground-water supplies of the south-shore beaches of 

Long Island, New York: New York Acad. Sci. Annals, 

v. 80, p. 1060-1076.

Perlniutter, N. M., and DeLuca, F. A., 1963, Availability of 

fresh ground water, Montauk Point area, Su^olk 

County, Long Island, New York: U.S. Geol. Survey 

Water-Supply Paper 1613-B, 39 p.

Perlmutter, N. M.. and Geraghty, J. J., 1963, Geology and 

ground-water conditions in southern Nassau and southeastern Queens Counties, Long Island, New York: U.S. 

Geol. Survey Water-Supply Paper 1613-A, 205 p.

Perlmutter, N. M., Geraghty, J. J., and Upson, J. E., 1959, 

The relation between fresh and salty ground water in 

southern Nassau and southeastern Queens Counties, 

Long Island, New York: Econ, Geology, v. 54, no, 3, 

p. 416-435.

Perlmutter, N. M., Lieber, Maxim, and Frauenthal, H. L., 

1963, Movement of waterborne cadmium and hexavalent 

chromium wastes in South Farmingdale, Nassau County, 

Long Island, New York, in Short papers in geology and 

hydrology: U.S. Geol. Survey Prof. Paper 47>-C, 

p. C179-C184.

 1964, Contamination of ground water by detergents in 

a suburban environment South Farmingdale area, Long 

Island, New York, in Geological Survey research 1964: 

U.S. Geol. Survey Prof. Paper 501-C, p. C170-C175.

Perlmutter, N. M., and Soren, Julian, 1962, Effects of m^jor 

water-table changes in Kings and Queens Counties, New 

York City, in Short papers in geology, hydrology, and 

topography: U.S. Geol. Survey Prof. Paper 45T-E, 

p. E136-E139.
F58 HYDROLOGY AND SOME EFFECTS OF URBANIZATION ON LONG ISLAND, NEW YORK

Pluhowski, E. J., 1961, Variation in temperature of two 

streams on Long Island, New York, in Geological Survey research 1961: U.S. Geol. Survey Prof. Paper 

424-D, p. D55-D58.

Pluhowski, E. J., and Kantrowitz, I. H., 1962, Source of 

ground-water runoff at Champlin Greek, Long Island, 

New York, in Short papers in geology, hydrology, and 

topography: U.S. Geol. Survey Prof. Paper 450-B, 

p. B95-B97.

 1963, Influence of land-surface conditions on groundwater temperatures in southwestern Suffolk County, Long 

Island, New York, in Short papers in geology and 

hydrology: U.S. Geol. Survey Prof. Paper 475-B, 

p. B186-B188.

 1964, Hydrology of the Babylon-Islip area, Suffolk

County, Long Island, New York: U.S. Geol. Survey 

Water-Supply Paper 1768, 119 p.

Reiners, W. A., and Woodwell, G. M., 1966, Water budget of a 

forest damaged by ionizing radiation: Ecology, v. 47, 

no. 2, p. 303-306.

Sanford, J. H., 1938, Report on the geology and hydrology 

of Kings and Queens Counties, Long Island: New York 

State Water Power and Control Oomm. Bull. GW-7, 

68 p.

Sawyer, R. M., 1963, Effect of urbanization on storm discharge and ground-water recharge in Nassau County, 

New York, in Short papers in geology and hydrology: 

U.S. Geol. Survey Prof. Paper 475-C, p. C185-C187.

Seaburn, G. E., 1969, Effects of urban development on direct 

runoff to East Meadow Brook, Long Island, New York: 

U.S. Geol. Survey Prof. Paper 627-B, 14 p.

 1970, Preliminary results of hydrologic studies at two

recharge basins on Long Island, New York: U.S. Geol.

Survey Prof. Paper 627-C, 17 p. 

Spear, W. E., 1912, Long Island sources an additional supply

of water for the City of New York: New York City

Board Water Supply, 708 p. 

Suffolk County Planning Commission, 1962, Existing land

use: Hauppauge, Suffolk County Dept. Planning, 42 p. 

Suter, Russell, 1937, Engineering report on the water supplies

of Long Island, New York: New York State Water

Power and Control Oomm. Bull. GW-2, 64 p. 

Suter, Russell, de Laguna, Wallace, and Perlmutter, N. M.,

1949, Mapping of geologic formations and aquifers of

Long Island, New York: New York State Water Power

and Control Comm. Bull. GW-18, 212 p. 

Swarzenski, W. V., 1963, Hydrology of northwestern Nassau

and northeastern Queens Counties, Long Island, New

York: U.S. Geol. Survey Water-Supply Paper 1657, 90 p. 

Thornthwaite, C. W., and Mather, J. R., 1955, The water

balance: Drexel Inst. Technology Pubs, in Climatology,

v. 8, no. 1, p. 1-86.

 1957, Instructions and tables for computing potential

evapotranspiration and the water balance: Drexel Inst.

Technology Pubs, in Climatology, v. 10, no. 3, p. 185-311. 

Todd, D. K., 1959, Ground water hydrology: New York,

John Wiley & Sons, 336 p. 

Upson, J. E., 1955, Ground-water sources on Long Island:

Am. Water Works Assoc. Jour., v. 47, no. 4, p. 341-347.

 1959a, Relation of Long Island ground-water resources' 

to regional needs: Am. Water Works Assoc. Jour., v. 51, 

no. 2, p. 286-300.

1959b, Ground-water problems in lT«w York and New

England: Am. Soc. Civil Engineers Proc., v. 85,'

no. HY 6, 12 p. 

U.S. Public Health Service, 1962, Public Health Service

drinking water standards 1962: Pulfic Health Service]

Pub. 956, U.S. Govt. Printing Office, fl p. | 

Veatch, A. C., and others, 1906, Underground water resources

of Long Island, New York: U.S. Geol. Survey Prof.

Paper 44, 394 p. 

Welsch, F. W., 1955, Ground-water pollution from industrial

wastes in Nassau County, New York: Sewage and

Industrial Wastes, v. 27, no. 9, p. 1065-1069. 

 1956, Conservation of ground water practices on Long'

Island: Water and Sewage Works v. 103, no. 10,

p. 468-473.

1960j Conservation in Nassau County, New York: Am.

Water Works Assoc. Jour., v. 52, no. 12, p. 1494-1498. 

White, W. N., 1932, A method of estimating ground-water

supplies based on discharge by plante and evaporation

from soil: U.S. Geol. Survey Water-Supply Paper

659-A, 105 p. 

Wyckoff, R. D., and Reed, D. W., 1935, E'-^cbrical conduction

models for the solution of waste seepage problems:

Physics, v. 6, p. 395-401.

TENTATIVE WATER BUDGETS

Tentative water budgets for subareas of the waterbudget area are given in tables 16-19. The areas of the 

subareas are about 100, 210, 125, and 325 square 

miles, respectively, and the locations of the subareas 

are shown in figure 2. These water budgets are consistent with the budgets in table 11. For example, the 

sum of the same budget items in tables 16 and 17 

are equal to the corresponding budget item relating 

to the northern part of the water-budget area in 

table 11. To achieve this consistency and at the same 

time subdivide the values in table 11 in proportions 

most consistent with available hydrologic information, 

the number of significant figures in many entries 

in tables 16-19 is greater than the a°<curacy of these 

entries warrants.

A possible inconsistency in (these data is evident from 

calculating the recharge per square mile in the four 

parts of the water-budget area. This inconsistency is 

due in part to errors in the estimates of individual 

entries and in part to some deviation from the underlying assumption made in this analysis especially 

the assumption that no appreciable change in storage 

has occurred in these areas during the water-budget 

period, 1940-65. This assumption is least vaild for 

southern Nassau County.
SUMMARY OF HYDBOLOGIO SITUATION AS A GUIDE TO WATER-MANAGEMENT ALTERNATIVES

?ABLE 16. Water budget of the northern part of the water-budget 

area within Nassau County, Long Island, N.Y., water years 

1940-66 l

Type of waterbudget element

No. Water-budget element

Estimated value 

of water-budget 

element (millions of gallons 

per day)

nflow..-------

Internal 

distribution.

)utflow.

.1 Precipitation....---_-.---.._-.----

2 Direct runoff-.----------------

3 Ground water recharge *- ------

4 Ground-water discharge to streams'..

5 Evapotranspiration of precipitation *_.

6 Subsurface outflow of ground water...

7 Streamflow discharging to salt water..

8 Evapotranspiration of ground water 5 -

210

2

100

14

108

85

16

1

i The quantities in this table were derived with the assumption that no significant 

hange in ground-water storage occurred in the water-budget area during the period,

*ater years 1940-65. Independent quantitative estimates were made for all components 

n the table unless otherwise noted. None of the values in this table are accurate to 

lore than 2 significant figures, and many values are accurate to less. Where more 

ban 2 significant figures are shown, the entry was derived from other entries in the 

able, and an additional significant figure was retained to balance inflow and outflow.

* The estimate of ground-water recharge was obtained by adding components 4, 

!, and 8.

' The estimate of ground-water discharge to streams was obtained by subtracting 

">mponent 2 from component 7.

* The estimate of evapotranspiration of precipitation was obtained by adding 

components 6, 7, and 8 and subtracting the total from component 1. Therefore, the 

subtotal of components 5,6,7, and 8 (total outflow) equals component 1 (total inflow).

4 These values may be in error by as much as 100 percent or more. Values are included mainly to indicate order of magnitude.

"ABLE 17. Water budget of the northern part of the water-budget 

area within Suffolk County, Long Island, N.Y., water years 

1940-65 l

Type of waterbudget element

No. Water-budget element

Estimated value 

of water-budget 

element (millions of gallons 

per day)

""flow..--.-.------- 1 Precipitation...-----.-.---....--....

Internal 2 Direct runofl . .. .

distribution. 3 Ground water recharge 2 ... . ..-

4 Ground-water disch arge to streams'..

Outflow............ 5 Evapotranspiration of precipitation *..

6 Subsurface outflow of ground water...

7 Streamflow discharging to salt Water. -

8 Evapotranspiration of ground water *_

440

3

220

31

217

185

34

4

' The quantities in this table were derived with the assumption that no significant 

< vange in ground-water storage occurred in the water-budget area during the period, 

'"ater years 1940-65. Independent quantitative estimates were made for all components 

i i the table unless otherwise noted. None of the values in this table are accurate to 

riore than 2 significant figures, and many values are accurate to less. Where more 

i'ian 2 significant figures are shown, the entry was derived from other entries in the 

n ble, and an additional significant figure was retained to balance inflow and outflow.

* The estimate of ground-water recharge was obtained by adding components 4, 

II, and 8.

a The estimate cf ground-water discharge to streams was obtained by subtracting 

component 2 from component 7.

4 The estimate of evapotranspiration of precipitation was obtained by adding 

components 6, 7, and 8 and subtracting the total from component 1. Therefore, the 

r'btctal of components 5,6,7, and 8 (total outflow) equals component 1 (total inflow).

5 These values may be in error by as much as 100 percent or more. Values are included mainly to indicate order of magnitude.

TABLE 18. Water budget of the southern part of the water-budget 

area within Nassau County, Long Island, N.Y., water years 

1940-66 l

Type of waterbudget element

No. Water-budget element

Estimated value 

of water-budget 

element (millions of gallons 

per day)

distribution.

Outflow...-. __ .

3 Ground water recharge*..-. __ . ....

4 Ground-water discharge to streams * . .

6 Subsurface outflow of ground water ... 

7 Streamflow discharging to salt water.. 

8 Evapotranspiration of ground water 8 _

2fiO

5

113

50 

142

60 

55 

3

> The quantities in this table were derived with the assumption that no significant 

change in ground-water storage occurred in the water-budget area during the p°riod, 

water years 1940-65. Independent quantitative estimates were made for all components 

In the table unless otherwise noted. None of the values in this table are accurate to 

more than 2 significant figures, and many values are accurate to less. Where more 

than 2 significant figures are shown, the entry was derived from other entries in the 

table, and an additional significant figure was retained to balance inflow and outflow.

8 The estimate of ground-water recharge was obtained by adding components 4, 

6, and 8.

' The estimate of ground-water discharge to streams was obtained by subtracting 

component 2 from component 7.

* The estimate of evapotranspiration of precipitation was obtained by adding 

components 6, 7, and 8 and subtracting the total from component 1. Therefore, the 

subtotal of components 5,6,7, and 8 (total outflow) equals component 1 (total in«ow).

5 These values may be in error by as much as 100 percent or more. Values are included mainly to indicate order of magnitude.

TABLE 19. Water budget of the southern part of the water-budget 

area within Suffolk County, Long Island, N.Y., water years 

1940-66 >

Type of waterbudget elementNo. Water-budget element

Estimated value 

of water-budge t 

element (millions of ga"ons 

per dar)

Outflow..---..-.-.

4 Ground-water discharge to streams ' . . 

5 Evapotranspiration of precipitation *..

6 Subsurface outflow of ground water . - . 

7 Streamflow discharging to salt water. . 

8 Evapotranspiration of ground water *.

AQft

10

352

225 

328

120 

235

7

1 The quantities in this table were derived with the assumption that no significant 

change in ground-water storage occurred in the water-budget area during the period, 

water years 1940-65. Independent quantitative estimates were made for all components 

in the table unless otherwise noted. None of the values in this table are accurate to 

more than 2 significant figures, and many values are accurate to less. Where more 

than 2 significant figures are shown, the entry was derived from other entries in the 

table, and an additional significant figure was retained to balance inflow and outflow.

* The estimate of ground-water recharge was obtained by adding components 4, 

6, and 8.

' The estimate of ground-water discharge to streams was obtained by subtracting 

component 2 from component 7.

* The estimate of evapotranspiration cf precipitation was obtained by adding 

components 6, 7, and 8 and subtracting the total from component 1. Therefor?, the 

subtotal of components 5,6,7, and 8 (total outflow) equals component 1 (total inlow).

5 These values may be in error by as much as 100 percent or more. Values ere included mainly to indicate order of magnitude.

U. S. GOVERNMENT PRINTING OFFICE : 1971 O - 427-144