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Figure
1.
Freshwater withdrawals in Delaware by county,
1995. (A) Total freshwater withdrawals;
(B) Fresh surface-water withdrawals; and
(C) Fresh ground-water withdrawals.
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Figure 2.
Freshwater withdrawals in Delaware, by category
of use and water sources, 1995 (does not
include public-supply deliveries to Domestic,
Commercial, or Industrial uses).
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This
fact sheet describes the results of a study
of water use in the State of Delaware that was
conducted by the U.S. Geological Survey (USGS),
in cooperation with the Delaware Geological
Survey (DGS) and the Delaware Department of
Natural Resources and Environmental Control
(DNREC), as part of the National Water-Use Information
Program of the USGS. The Program is based on
Federal and State cooperative agreements to
collect, store, and disseminate water-use information
nationally and locally.
As the demand for freshwater increases, the
stress placed on the surface-water and ground-water
resources of Delaware increases. Effective water-resources
management depends in part on current and accurate
water-use data. Such data are valuable for evaluating
the effects of withdrawals on the State’s
water resources, identifying current water-use
patterns, and estimating future water demands.
Together, DNREC and USGS collect, compile, estimate,
and store site-specific and aggregated water-use
data that are useful for State water-resources
management.
Delaware water-use data have been published
in reports such as the “Water 2020”
series (Water Resources Agency for New Castle
County, 1990) and USGS publications by Phelan
(1987 and 1990). Delaware water-use data are
also included in USGS national water-use compilations,
which have been published every five years since
1950. State data for 1995 are in USGS Circular
1200, “Estimated Use of Water in the United
States in 1995” (Solley, Pierce, and Perlman,
1998).
Total Freshwater Withdrawals
A water user withdraws water from a surface-water
or ground-water source (self-supplied), or receives
water from a public-supply system or both. Water
withdrawn by a public or private water utility
and delivered to a variety of users is designated
as a “public supply.” Homes and
small communities relying on individual wells
are classified as domestic “self-supplied”
water users. Water use for thermoelectric power
includes the water used for the generation of
electricity by steam-electric plants fueled
by conventional fuels. Commercial use includes
not only businesses such as restaurants, motels,
and car washes, but also institutions such as
churches, schools, and military installations.
Most of the withdrawal data presented in this
report were obtained from DNREC; however, some
water-use data such as withdrawals for domestic,
irrigation, and livestock watering were estimated
using water-use coefficients.
During 1995, about 752 million gallons per day
(Mgal/d) of freshwater was withdrawn from the
surface-water and ground-water sources in Delaware.
Surface-water sources provided 85 percent (642
Mgal/d) of all freshwater used in the State
during 1995. About 83 percent (534 Mgal/d) of
surface-water withdrawals were for cooling condensers
in thermoelectric power generation; nearly all
of the water withdrawn was returned to the surface-water
source. Ground-water sources provided 15 percent
(110 Mgal/d) of all freshwater used in Delaware
during 1995. Most ground-water withdrawals (57
percent, or about 63 Mgal/d) were from the unconfined
(surficial) aquifer, followed by the Potomac
Group aquifers which supplied about 23 Mgal/d;
the Cheswold Group aquifers with about 15 Mgal/d;
and the Piney Point and Aquia aquifers with
about 6 Mgal/d. The remaining 3 Mgal/d of ground-water
withdrawals were supplied by the Magothy, Piedmont,
and carbonate aquifers. Withdrawals of freshwater
by county and water source are shown in figure
1.
The demand for freshwater in Delaware is highest
in the densely populated and industrialized
northern part of the State, and lowest in the
agricultural central and southern parts. Generally,
water supplies are adequate in all areas of
the State. Sometimes, however, available water
supplies are marginal or less than adequate
to meet demands, such as during low-flow periods
and high seasonal-demand periods, particularly
in New Castle County (northern Delaware) (S.
Lovell, Delaware Department of Natural Resources
and Environmental Control, oral commun., 1998).
New Castle County has the largest population
in the Delaware (nearly 468,000), and freshwater
withdrawals in the County account for more than
80 percent (625 Mgal/d in 1995) of all freshwater
used in the State. Most of the water withdrawn
(nearly 95 percent) is surface water and is
used for cooling in the production of electricity
(534 Mgal/d) and for public-supply distribution
(69 Mgal/d). Kent County, in the central part
of the State, has a population of about 121,000
and freshwater withdrawals account for about
5 percent (34 Mgal/d in 1995) of the total freshwater
used in the State; almost 85 percent of the
water used in this County is ground water. More
than one-half of the water used in the County
is withdrawn for agricultural irrigation. Sussex
County, in the southern part of the State, has
a population of about 128,000. The County’s
freshwater withdrawals account for about 12
percent (93 Mgal/d in 1995) of the freshwater
used in the State; nearly 90 percent of this
water is from ground-water sources and is used
by industries and for irrigation.
Types of Freshwater Use
The major uses of freshwater in Delaware during
1995 included thermoelectric power, public supply,
industrial, irrigation, domestic, commercial,
and livestock watering (fig. 2).
Thermoelectric
Power (TH)
Freshwater withdrawals by thermoelectric powerplants
during 1995 were 534 Mgal/d, nearly all of which
was from surface-water sources. Most of the
surface water was used for cooling condensers
and then returned to the water source. Only
about 0.23 Mgal/d was from ground-water sources
and about 0.45 Mgal/d was delivered from public
suppliers.
Public
Supply (PS)
More than 300 public water-supply systems in
Delaware provide water to about 564,000 people
(79 percent of the State’s population).
Total withdrawals for public supply during 1995
were 89 Mgal/d, of which 49 Mgal/d was from
surface-water sources and 40 Mgal/d was from
ground-water sources.
The largest withdrawals for public supply were
in New Castle County (69 Mgal/d). Of this amount,
49 Mgal/d was from surface-water sources and
20 Mgal/d was from ground-water sources. Public
suppliers in Kent and Sussex Counties relied
solely on ground-water sources and withdrew
9 Mgal/d and 11 Mgal/d, respectively.
Industrial
(IN)
During 1995, about 77 Mgal/d of freshwater was
used by industries in Delaware, primarily for
making chemicals, plastics, and food products.
Of this amount, 16 Mgal/d was provided by public
suppliers. The remaining 61 Mgal/d was self-supplied,
of which 43 Mgal/d was from surface-water sources
and 18 Mgal/d was from ground-water sources.
Sussex County had the most withdrawals for industrial
use (43 Mgal/d), followed by New Castle County
with 16 Mgal/d, and Kent County with 2 Mgal/d.
Irrigation
(IR)
The amount of freshwater used for irrigation
can vary from year to year and among users.
Differences in rainfall distribution and soil
type are important factors in determining how
much and when water is applied. During 1995,
about 49 Mgal/d of freshwater was used for irrigation
of primarily farm crops, golf courses, and nursery
stock. Of this amount, 15 Mgal/d was from surface-water
sources and 34 Mgal/d was from ground-water
sources.
Domestic
(DO)
Domestic users in Delaware obtain freshwater
from public suppliers and from their own wells
(self-supplied). During 1995, total use (withdrawals
and deliveries) was 55 Mgal/d, of which 43 Mgal/d
was delivered by public suppliers. About 153,000
residents (21 percent of the State’s total
population) withdrew about 12 Mgal/d from individual
house wells for water supply.
Commercial
(CO)
Commercial users obtained freshwater from public
suppliers and from self-supplied sources. Total
commercial use during 1995 was 22 Mgal/d, of
which about 19 Mgal/d was provided by public
suppliers. The remaining 3 Mgal/d was self-supplied
and came from ground-water sources.
Livestock
(LV)
During 1995, about 4.13 Mgal/d of freshwater
was used for livestock activities, mainly livestock
watering, feedlot, and dairy operations. Of
the total water withdrawn, 0.35 Mgal/d was from
surface-water sources and 3.78 Mgal/d was from
ground-water sources. Sussex County withdrew
the most water for livestock use (3.36 Mgal/d),
followed by Kent County with 0.65 Mgal/d, and
New Castle County with 0.12 Mgal/d.
Selected References
Hodges, A.L., Varrin, R.D., and Cherry, P.J.,
1990, Delaware water supply and use in U.S.
Geological Survey, 1990, National water summary
1987—Hydrologic events and water supply
and use: U.S. Geological Survey Water-Supply
Paper 2350, p. 201-206
Phelan, D.J., 1987, Water levels, chloride concentrations,
and pumpage in the Coastal Plain aquifers of
Delaware and Maryland: U.S. Geological Survey
Water-Resources Investigations Report 87-4229,
106 p.
_____1990, Water use in the St. Jones River
Basin, Kent County, Delaware, 1983-86: U.S.
Geological Survey Water-Resources Investigations
Report 90-4094, 30 p.
Solley, W.B., Pierce, R.R., and Perlman, H.A.,
1998, Estimated Use of Water in the United States
in 1995: U.S. Geological Survey Circular 1200,
71 p.
Water Resources Agency for New Castle County,
1990, Water 2020 series, Volume III, Water Use
in New Castle County: Water Resources Agency
for New Castle County, Newark, Delaware, 33
p.
For
additional information contact:
District Chief
U.S. Geological Survey
8987 Yellow Brick Road
Baltimore, MD 21237
Visit the Maryland/Delaware/D.C. District Homepage
on the World Wide Web at: http://md.water.usgs.gov/
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