U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 021-99

August 1999

Maryland

Chesapeake Bay Studies

The Chesapeake Bay Program (CBP),

a multiagency restoration effort, has

set a goal of reducing controllable

nutrients entering the Chesapeake

Bay by 40 percent by the year 2000.

The reduction is expected to improve

dissolved-oxygen levels in the Bay.

The U.S. Geological Survey (USGS)

Ecosystem Program is coordinating

USGS and other agencies’ studies to

understand the response of water

quality and living resources in the

Bay and its watershed to nutrient

reduction and natural variability. The

USGS is analyzing trends, identifying

nutrient-source areas, addressing

nutrient traveltimes in ground water,

determining the relation of nutrients

to fish health, and documenting the

long-term change of the ecosystem.

Since 1985, the USGS has provided

water-quality information and analyzed the amounts of nutrients and

sediments entering the Bay (fig. 1).

An analysis of the data collected from

rivers in the Bay watershed from

1985 to 1997 shows that although the

amounts of nutrients and sediments

delivered to the Bay may have

increased, the concentrations of

nutrients and sediments in many

rivers are decreasing or remain the

same.

The USGS also is relating sources of

nutrients to amounts of nutrients

delivered to the Bay by using a

statistical model called SPARROW.

The SPARROW model is being

adopted by the CBP as one of the

tools used for identifying Nutrient

Areas of Concern. SPARROW

calculations also will be used to

explain the trend results and to link

nutrient sources to nutrients in

ground-water loads and their delivery

to surface water.

The USGS is providing preliminary

information on the amount and

traveltime of nutrients in shallow

aquifers in the Bay watershed. Initial

findings indicate that about half of the

water and nutrients entering the Bay

travel through the ground-water

system. Nutrients may move through

ground water for several years or

several decades before reaching rivers

or the Bay, thus significantly delaying

the benefits of nutrient-reduction

measures implemented on land.

Reports of high numbers of fish with

skin lesions in the Pocomoke River

and other tributaries of the Chesapeake Bay have stimulated a great

deal of public and scientific interest

(fig. 2). The USGS, in cooperation

with the State of Maryland, assessed

fish health in five tributaries of the

Chesapeake Bay throughout the

spring, summer, and fall of 1998 in

response to concerns about Pfiesteria,

a toxic marine microorganism. This

microorganism is believed to be the

cause of some estuarine fish kills and

lesion outbreaks, primarily in menhaden, as well as having potential

human-health implications. Although

fish kills of this origin did not occur

in 1998, lesioned menhaden were

collected from the Pocomoke, Wicomico, and Choptank Rivers during the

USGS fish-health assessments.

Examination of the lesions showed

that all of them contained an invasive

fungus, suggesting that these particular lesions were not necessarily

caused by Pfiesteria. Further research

will be directed toward understanding

the invasiveness of the fungus, causes

of stress that may be necessary for

infection, and what environmental

factors are related to the high incidence of these fungal lesions in

menhaden.

Although environmental problems

such as pollution, urbanization, and

Figure 2. Menhaden with lesions;

Wicomico River, August 1998.

Figure 1. Total nitrogen yields from

stream reaches in the

Chesapeake Bay watershed.

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

in grams per square 

meter per year

Incremental yield,

TOTAL NITROGEN

Less than 0.2

0.2 – 0.4

0.4 – 0.6

0.6 – 0.8

0.8 – 1.0

1.0 – 1.2

1.2 – 1.4

1.4 – 1.6

1.6 – 1.8

Greater than 1.8

No Data

MARYLAND

PENNSYLVANIA

NEW YORK

VIRGINIA

DELAWARE

Chesapeake 

Bay
science for a changing world

deforestation commonly are attributed to human activities in the Bay’s

watershed, it is now recognized that

climatic factors also strongly influence the salinity, temperature, and

water quality of the Bay. Concern

about the Bay’s future is especially

acute for policymakers and landresource managers who are faced

with questions such as: Will the

anomalously high and variable river

discharge of the past decade continue? What will be the future effect

of possible changes in mean-annual

rainfall projected by climate models?

How will the changes in river discharge and rainfall affect nutrients

and levels of dissolved oxygen in the

Bay? Have unique climatic and

hydrologic conditions contributed to

recent toxic algal blooms?

The above subjects are being addressed as part of a USGS interdisciplinary research project investigating

year-to-year through long-term

variability in salinity, sediment

accumulation rates and budgets,

dissolved oxygen, temperature, sea

level, and plant and animal trends,

using fossil and geochemical data

from Chesapeake Bay sediment

cores.

Stream-Gaging Network

The USGS and its cooperative

partners are developing an approach

to maintaining an efficient streamgaging network in Maryland (fig. 3)

through the Maryland Water Monitoring Council. These efforts produced a

gain of several important gages in the

statewide network in 1998.

A Council workgroup investigated the

status of stream gaging in Maryland

and the issues related to continued

operation and needed growth of the

current network. A workgroup is

focusing on two specific aspects of

stream gaging: the representativeness

of the principal physical characteristics of Maryland watersheds, and an

inventory of streamflow data users

and their applications. Preliminary

analyses show that some important

geographic areas of Maryland and

certain significant physical characteristics are not well represented by the

current network.

Geology of the WashingtonBaltimore Area

The USGS, in cooperation with the

Maryland Geological Survey (MGS),

produces technical papers and maps

about the geology of Maryland. Since

1968, these organizations have

mapped bedrock and surface geology

throughout Maryland at scales of

1:62,500 and 1:24,000. This includes

1:24,000-scale mapping of the

Maryland Piedmont region since

1974. Geologic maps contain information that can be used for a wide

range of public and private applications such as land-use planning;

ground-water availability and quality

studies; finding and making the best

use of earth resources, such as natural

aggregate for construction; hazard

assessment; and engineering and

environmental studies for wastedisposal sites and construction

projects.

The USGS, in cooperation with the

MGS, is producing a geologic map of

the Chesapeake and Ohio Canal

National Historical Park for the

National Park Service. Personnel of

the Appalachian Geology and Hydrology Project (conducted in cooperation

with the MGS) map geology in the

urban, suburban, and outlying rural

areas of the Washington-Baltimore

region. The results of the project will

be 1:100,000-scale geologic maps on

paper and in electronic formats.

Destruction of Marsh by South

American Nutria

A USGS study of South American

nutria showed the destructive effect

of these large exotic rodents on marsh

habitats in Maryland’s Blackwater

National Wildlife Refuge. The

research was conducted with the

USGS Maryland Cooperative Fish

and Wildlife Research Unit, Maryland Department of Natural Resources (DNR) and the U.S. Fish and

Wildlife Service.

Research on the role of the planteating nutria in marsh loss is also of

special interest to the Chesapeake

Bay Program, which seeks to achieve

“no net loss” of wetlands within the

Bay watershed. Introduced in the

Figure 3. Locations of USGS stream-gaging stations in Maryland.

MARYLAND

CHESAPEAKE BAY

Baltimore

Washington DC

0 25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

Blackwater NWR
Maryland

1940’s to bolster Maryland’s Eastern

Shore fur industry, the South American nutria (fig. 4), which is 4 to 10

times as large as a native muskrat, has

been implicated in the loss of emergent marsh, especially along the

Blackwater River in Dorchester

County. Marsh loss has coincided

with the introduction and expansion

of the nutria population.

A recent study found that within the

Blackwater National Wildlife Refuge,

3,500 acres of marsh have been lost

to open water since the late 1930’s,

and 53 percent of remaining marsh is

considered unhealthy. Although other

factors, such as rising sea level, also

contribute to marsh loss, nutria have

accelerated the problem during the

past two decades—primarily because

a decline in the fur industry has led to

overpopulation of the rodent in lower

Eastern Shore marshes.

The overabundance of nutria and the

rapid loss of marsh in this region

have prompted State legislation

proposing a 10-year nutria eradication

program. The relation between nutria

feeding habits and marsh loss,

however, remains unclear, and a longterm eradication program awaits

evidence of cause and effect. The

USGS study is intended to determine

if excluding nutria from emergent

marsh habitats can stabilize or

recover marsh vegetation. Aerial

photography and ground-plot measurements are being used to detect

changes.

Research results have already demonstrated the need for animal-control

activities to preserve the marsh.

Future results are intended to enable

natural-resource management agencies to determine if more intensive

marsh recovery efforts are needed to

restore the more heavily damaged

areas.

Urban Growth in the BaltimoreWashington Area

A study team from the USGS and the

University of Maryland Baltimore

County (funded by NASA’s Mission

to Planet Earth) is developing a data

base reflecting 200 years of urban

development in the BaltimoreWashington metropolitan area. Other

organizations, such as the Smithsonian Institution and the Bureau of

the Census, have entered into this

partnership to enhance the scope of

the data base.

Urban areas have a strong impact on

local land use and land cover. Modern

urban settlements are characterized

by the proliferation of asphalt and

concrete surfaces. Land-cover

changes associated with an urban area

can be immense. The effect of urban

land on economic and environmental

systems is significant compared to its

areal extent.

The Chesapeake Bay’s delicate

ecosystem has been affected negatively by increasing urban growth. A

data base has been developed by

combining information from a variety

of sources into an integrated, multiscale, multiresolution data set. This

data base reflects regional urban

growth from 1792 to 1992.

Temporal urban maps depict past

landscapes by combining historical

maps, census statistics, and commerce records to generate progressive

pictures of urban growth in the

Baltimore-Washington region during

the past two centuries. Remotely

sensed data, existing digital land-use

data, digital census information,

earth-science data such as digital line

graphs, digital elevation models, and

demographic information are used for

analysis.

Mid-Atlantic Region WaterQuality Studies

The USGS is conducting environmental assessments in the MidAtlantic region, including parts of

Maryland and the District of Columbia. The USGS assessed regional

water quality in the Delmarva Peninsula (1986–91) and the Potomac

River Basin (1991–98) as part of the

National Water-Quality Assessment

(NAWQA) Program.

The Delmarva study showed that

agricultural and residential land use

have affected ground-water quality.

High concentrations of nitrate are

found in ground water in most parts

of the surficial aquifer, including deep

parts of the aquifer used for water

supply. Pesticides used on common

crops were found at trace concentrations in very shallow ground water,

but pesticides generally were not

found in deeper parts of the groundwater system.

The Potomac study also showed that

land use is an important factor in

water quality. The highest concentrations of nutrients and pesticides in

streams and ground water in the

Potomac River Basin were found in

areas of intensive row cropping

underlain by carbonate rock. The

study also showed that concentrations

of nutrients and pesticides in ground

water and streams generally are less

than levels that would adversely

affect human health or most ecosystems.

In addition the USGS is developing

hydrologic and water-quality inforFigure 4. Large South American

nutria.
Printed on recycled paper

USGS office locations USGS State Representative

8987 Yellow Brick Road

Baltimore MD 21237

(410) 238-4200

FAX (410) 238-4210

USGS Home Page

http://www.usgs.gov

Reports and products

1-888-ASK-USGS

mation that is intended to assist U.S.

Environmental Protection Agency

(EPA) researchers in the Landscape

Ecology Branch in developing

landscape indicators for pesticides

and nutrients in surface water. This

project, which includes regionwide

sampling of streams, is being done in

conjunction with NAWQA studies of

regional ground-water-quality

patterns in the Mid-Atlantic Coastal

Plain (from New Jersey to North

Carolina).

Topographic Mapping

The USGS ensures the availability of

map data in paper and electronic form

by fostering partnerships among State

and Federal agencies to improve data

collection and resource sharing. The

DNR, in cooperation with the USGS,

is producing 571 1:12,000-scale

color-infrared digital orthophoto

quadrangles (DOQ). The DNR will

produce the DOQ’s to be fully

compliant with the current Federal

Geographic Data Committee metadata standards. This will complete the

DOQ-data coverage in Maryland,

which will be made available to the

public through the USGS Earth

Resources Observation Systems Data

Center in Sioux Falls, South Dakota.

Mid-Atlantic Infrastructure Case

Study

USGS scientists, in cooperation with

the MGS, Virginia Division of

Mineral Resources, Resources for the

Future, National Center for Resource

Innovations, and the National Stone

Association, are analyzing how

population growth and development

zoning regulations, and changes in

land-management practices have

influenced and controlled the availability of sand, gravel, and crushed

stone (aggregate) and aggregate

production in the WashingtonBaltimore urban corridor during the

past 20 years. Projecting these trends

into the future is intended to aid

planners with resource allocation.

Estimates of the end uses for aggregates suggest that about 78 percent of

aggregates produced in the region is

used to maintain, improve, and

modify existing buildings and roads,

and 22 percent of produced aggregate

is for constructing new buildings and

roads.

Regional growth during the last 10

years includes increased population,

housing units, and roads in the

17,000-square-mile region. In 1995,

76 million metric tons of natural

aggregates, worth $480 million, were

produced and consumed. By 2010,

the population of the region is

projected to grow by 14 percent, and

demand for natural aggregates is

projected to exceed 86 million metric

tons per year. The projections suggest

that vast quantities of crushed stone

and sand and gravel will be needed.

Most of this aggregate will have to

come from resources yet to be

delineated or defined.

Coastal Plain Drinking-Water

Studies

The Safe Drinking Water Act Amendments of 1996 establish an emphasis

on delineation of source-water areas

and require an inventory of the

potential sources of contamination for

each public water supply. In response

to this directive, the USGS is cooperating with the Maryland Department of

the Environment (MDE), MGS, and

Baltimore City on several source-water

assessment projects. The USGS, MGS,

and MDE are conducting ground-waterquality surveys of gross-alpha and radium

content of water in water-supply wells

throughout the outcrop portions of the

Magothy, Patapsco, and Patuxent aquifers

in the Atlantic Coastal Plain to determine

the distribution and concentrations of

radium. In addition, these studies are

correlating contributing factors, such as

low pH and high chloride content of

ground water, to observed radium

concentrations greater than the EPA’s

Maximum Contaminant Levels for

drinking water.

Many water-supply wells in the Coastal

Plain tap the shallow unconfined aquifer,

which makes them vulnerable to contamination from disease-causing organisms. To determine the susceptibility of

these water-supply wells to such pathogens, the USGS and MDE are identifying

and documenting the occurrence of

organisms such as viruses in the shallow

unconfined aquifer on the Eastern Shore

of Maryland.

Loch Raven Reservoir, created in 1881,

supplies drinking water to the Baltimore

metropolitan area. The USGS, MGS,

Baltimore City, and MDE are creating a

bathymetric map of the reservoir from

field data and developing maps of

sediment deposition since 1914, to record

the change in storage capacity and

sediment accumulation over time.

The USGS has 238

employees in Maryland

Cumberland

Greenbelt

Laurel

Aberdeen

Annapolis

Princess

Anne

Baltimore