This Fact Sheet describes the results

of a water-use study for 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-resource management depends, in part, on up-to-date

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 water-resources management in

Delaware.

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 Wheeler (1999) and Phelan

(1987, 1990). Delaware water-use data

also are included in USGS National WaterUse Circulars, published every 5 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 

Water users may be self-supplied

(withdrawing water from a surface-water or

ground-water source) or receive water from

a public-supply system or both. Water

withdrawn by a public or private water purveyor and delivered to a variety of users is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 “selfsupplied” water users. 

Thermoelectric power includes 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 2000, about 584 Mgal/d (million gallons per day) of freshwater was

withdrawn from surface-water and groundwater sources in Delaware. Surface-water

sources provided 80 percent (467 Mgal/d)

of all freshwater used in Delaware during

2000. About 80 percent (366 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 20 percent

(117 Mgal/d) of all freshwater used in

Delaware during 2000. Most ground-water

withdrawals (57 percent, or about 67

Mgal/d) were from the surficial unconfined

aquifer, followed by the Potomac Group

aquifers, which supplied about 22 Mgal/d,

the Cheswold Group aquifers with about

15 Mgal/d, and the Piney Point and Aquia

aquifers with about 7 Mgal/d. The remaining 6 Mgal/d of ground-water withdrawals

were supplied by the Mount Laurel,

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 in

meeting demands, such as during low-flow

periods and high seasonal-demand periods,

particularly in New Castle County (northU.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS 111-03

2003
ern Delaware) (fig.1), (Stewart Lovell,

Delaware Department of Natural

Resources and Environmental Control, oral

commun., 1998).

New Castle County has the largest

population in the State (about 500,000

people) and freshwater withdrawals in the

County account for 79 percent (462

Mgal/d in 2000) of all freshwater used in

the State. Most of the water withdrawn

(nearly 93 percent) is surface water and is

used for cooling in the production of electricity (366 Mgal/d) and for public-supply

distribution (50 Mgal/d). Kent County, in

the central part of the State, has a population of about 127,000 and freshwater withdrawals account for about 5 percent (31

Mgal/d in 2000) of the total freshwater

used in the State; almost 90 percent of the

water used in this County is ground water.

Nearly 75 percent of the water used in the

County is withdrawn for agricultural irrigation (12 Mgal/d) and public-supply distribution (10 Mgal/d). Sussex County, in the

southern part of the State, has a population

of about 157,000. Freshwater withdrawals

in the County account for about 16 percent (91 Mgal/d in 2000) of the freshwater

used in the State; about 60 percent of this

water (55 Mgal/d) is from ground-water

sources and is used primarily for publicsupply distribution (13 Mgal/d) and irrigation (24 Mgal/d). Most of the fresh surface

water withdrawn in the County (32

Mgal/d) is used by industries.

Types of Freshwater Use 

During 2000, the major uses of freshwater in Delaware included thermoelectric

power, public supply, industrial, irrigation,

domestic, commercial, and livestock watering (fig. 2). 

Thermoelectric Power 

Freshwater withdrawals by thermoelectric powerplants during 2000 were 366

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 0.47 Mgal/d was from ground-water

sources and about 0.65 Mgal/d was delivered from public suppliers. 

Public Supply 

More than 300 public water-supply

systems in Delaware provide water to

about 617,000 people (79 percent of the

State’s population). Total withdrawals for

public supply during 2000 were 95

Mgal/d, of which 50 Mgal/d was from surface-water sources and 45 Mgal/d was

from ground-water sources.

The largest withdrawals for public supply were in New Castle County (72

Mgal/d). Of this amount, 50 Mgal/d was

from surface-water sources and 22 Mgal/d

was from ground-water sources. Public

suppliers in Kent and Sussex Counties

relied solely on ground-water sources and

withdrew 10 Mgal/d and 13 Mgal/d,

respectively. 

Industrial 

During 2000, about 73 Mgal/d of

freshwater was used by industries in

Delaware, primarily for making chemicals,

plastics, and food products. Of this

amount, 14 Mgal/d was provided by public

suppliers. The remaining 59 Mgal/d was

self-supplied, of which 42 Mgal/d was from

surface-water sources and 17 Mgal/d was

from ground-water sources. Sussex County

had the most withdrawals for industrial use

(39 Mgal/d), followed by New Castle

County with 18 Mgal/d, and Kent County

with 2 Mgal/d.

Irrigation 

The amount of freshwater used for irrigation can vary from year to year and

among users. Differences in rainfall distribution, crops grown, and soil type are

important factors in determining how much

and when water is applied. During 2000,

about 43 Mgal/d of freshwater was used

for irrigation of primarily farm crops, golf

courses, and nursery stock. Of this

amount, 8 Mgal/d was from surface-water

sources and 35 Mgal/d was from groundwater sources.

Domestic 

Domestic users in Delaware obtain

freshwater from public suppliers and from

their own wells (self-supplied). During

2000, total use (withdrawals and deliveries)

was 63 Mgal/d, of which 50 Mgal/d was

delivered by public suppliers. About

166,000 residents (21 percent of the

State’s total population) withdrew about 13

Mgal/d from individual house wells for

water supply.

Commercial 

Commercial users obtained freshwater

from public suppliers and from self-supplied sources. Total commercial use during

2000 was 23 Mgal/d, of which about 21

Mgal/d was provided by public suppliers.

The remaining 2 Mgal/d was self-supplied

and came from ground-water sources.

Livestock 

During 2000, about 3.99 Mgal/d of

freshwater was used for livestock activities,

mainly livestock watering, feedlot, dairy

operations, and aquaculture. Of the total

water withdrawn, 0.22 Mgal/d was from

surface-water sources and 3.77 Mgal/d was

from ground-water sources. Sussex County

withdrew the most water for livestock use

(3.04 Mgal/d), followed by Kent County

with 0.86 Mgal/d, and New Castle County

with 0.09 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:

Newark, Delaware, Water Resources

Agency for New Castle County, 33 p.

Wheeler, J.C., 1999, Freshwater use in

Delaware, 1995: U.S. Geological Survey

Fact Sheet FS-126-99, 2 p.

FS 111-03