The Importance of Water in

Maryland

Water is one of the most valuable natural resources in

Maryland. It is essential to the life and

health of all Maryland residents, the

quality of the State’s environment, and

the vitality of its economy. In 2000,

Marylanders used an estimated 1.45 billion gallons per day of freshwater for

public supply, commercial, industrial,

irrigation, and other purposes (Wheeler,

2003). Although there usually is more

than enough water to meet that level of

water demand, periodic droughts like

the ones in the early 1930s, the mid1960s, 1999, and 2002 can cause serious water shortages in some parts of

the State. As the population of

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS 2005-3030

2005
Maryland and the demand for water

continue to increase, water shortages

are expected to become more common. Long-term planning for the efficient use of Maryland’s water resources

is critical for avoiding major water shortages in the future.

The State Advisory Committee

Report

The Governor’s Advisory

Committee on the Management and

Protection of Maryland’s Water

Resources was established in late 2003

to map out a long-term plan for managing and protecting the State’s water

resources. In August 2004, the

Committee released a report (State of

Maryland, 2004) containing numerous

recommendations, including one for

maintaining and enhancing the monitoring of Maryland’s water resources. The

Committee’s report recognized that

without adequate monitoring data, “...it

will become difficult or impossible to

determine the availability of surface

water or ground water, to assess and

react to droughts, to determine the

potential interference of competing

water users, and to assess the impacts

of water use on the State’s aquifers and

streams, while maintaining minimum

stream flows” (State of Maryland,

2004). 

Two Major Water-Monitoring

Components

Two critical components of waterresources monitoring in Maryland are

the monitoring of streamflow and the

monitoring of ground-water levels.

Maryland is fortunate to have a long history of streamflow and ground-waterlevel monitoring. Streamflow in most

major streams in the State has been

monitored for about the last 50-100

years, and ground-water levels in most

major aquifers in the State have been

monitored for about the last 50 years.

Both of these long-term monitoring programs have been operated primarily by

the U.S. Geological Survey (USGS), in

partnership with the Maryland

Geological Survey (MGS), and with the

financial support of many other Federal,

State, and local agencies.

Streamflow Monitoring Network

Currently (2005), the USGS operates 119 streamflow-monitoring gages

in Maryland (fig. 1). Stream stage is

monitored at each gage every 15 minutes. Streamflow is calculated from

stream stage through the use of rating

curves that have been developed over

time and frequently updated.

Streamflow data for 83 of 119 gages

are available in near real time on the

USGS website

(http://waterdata.usgs.gov/md/nwis/rt).

All streamflow data are reviewed and

published annually, and are available on

the USGS website. A streamflow hydrograph for Deer Creek at Rocks,

Maryland, for the period October 1,

1998 through September 30, 2003, is

shown in figure 2; the hydrograph illustrates the low streamflows during the

2 The Status of Streamflow and Ground-Water-Level Monitoring Networks in Maryland, 2005
droughts of 1999 and 2002.

Streamflow data are used by many

Federal, State, and local agencies in

Maryland. Some of the many uses of

streamflow data include: (1) water-supply assessment; (2) watershed management; (3) stream restoration; (4) bridge

design; (5) flood warning; (6) sediment

and contaminant loading; and (7) recreational activities. The principal funding

agencies for the Maryland streamflowmonitoring network are USGS, MGS,

Maryland State Highway Administration,

U.S. Army Corps of Engineers,

Maryland Department of the

Environment, Maryland Department of

Natural Resources, Baltimore County,

and Baltimore City.

The number of Maryland’s streams

that are monitored each year depends

on the availability of funding. In 1996,

the number of gages in Maryland

totaled only 75, the lowest number in

recent years (fig. 3). In the late 1990s,

as a result of an interagency workshop

and a concerted effort by many agencies working together through the

Maryland Water Monitoring Council, a

report that presents a design for an

optimal gage network in Maryland was

published (Cleaves and Doheny, 2000).

As a direct result of that effort, as well

as the reaction to the droughts of 1999

and 2002, the number of gages had

risen to 110 by 2002. By the beginning

of 2005, the number of gages was 119

(fig. 3). 

Even though the number of gages

has increased fairly steadily over the last

decade, the number of long-term

(greater than 50 years of record) gages

threatened by funding shortages has

been increasing in the last few years. A

threatened gage is sometimes “saved”

at the last minute by funding from an

interested Federal, State, or local

agency. In some cases, however, a

gage is discontinued when replacement

funding is not available. Stable, longterm funding would guarantee the continuation of these especially valuable

long-term gages, as well as the gage

network as a whole.

The Advisory Committee’s report

(State of Maryland, 2004) suggests that

all currently operating gages be maintained with stable, long-term funding to

prevent breaks in the long-term continuous records at the monitoring sites. In

addition, the report recommends that

gages be added on 43 other streams in

Maryland as funds allow, for the purposes of addressing unmet small-watershed, core-network, and geographiccoverage needs. The desired complete

network of gages would provide the

data needed to make sound management and protection decisions for all

important streams and watersheds in

the State.

Ground-Water-Level Monitoring

Networks

Ground-water-level data provide

one of the only direct measures of the

health of Maryland’s aquifers. Groundwater-level data are used by many

Federal, State, and local agencies to: (1)

discern long-term trends; (2) provide

drought warning and tracking; and (3)

inform the State’s ground-water appropriation permitting process. The funding agencies for Maryland’s large-scale

ground-water-level networks are USGS

and MGS. Other smaller networks are

operated by USGS and MGS for specific local purposes, and are supported by

the Interstate Commission on the

Potomac River Basin, Calvert County,

Charles County, Anne Arundel County,

and other local jurisdictions.

The USGS and MGS measure

ground-water levels in aquifers in

Maryland for two primary purposes.

The water table in the fractured-rock

and unconsolidated-sediment aquifers is

monitored statewide for the effects of

climate variability; the water levels in

the confined unconsolidated-sediment

aquifers of the Atlantic Coastal Plain are

monitored for the effects of ground3 The Status of Streamflow and Ground-Water-Level Monitoring Networks in Maryland, 2005
water pumpage (M.T. Duigon, Maryland

Geological Survey, written commun.,

2004). In each network observation

well, water level is either measured by

hand using an electric tape, or continuously using an automated logging

device. Nine wells are equipped with

near-real-time capability.

Under the auspices of the

Maryland Water Monitoring Council, a

multi-agency workshop was convened

in June 2002 to begin the process of

redesigning the ground-water-level monitoring networks for Maryland. By

2004, new optimal designs had been

adopted for both the water-table-aquifer

and the confined-aquifer observationwell networks.

Water-Table-Aquifer Network

The first of the two ground-waterlevel networks in Maryland—the watertable-aquifer network (fig. 4)—ideally

would include 81 observation wells and

is designed to capture the effects of

precipitation on ground-water levels in

key topographic settings in all major

physiographic and geologic units in

Maryland. In the fractured-bedrock

aquifers west of the Fall Line, most wells

would be paired, with one in the

bedrock and one in the weathered

material above the bedrock; in the

unconsolidated-sediment aquifers east

of the Fall Line, single wells would be

used (fig. 4). Water-level data from this

network would be used to track the

progress of droughts and subsequent

recovery from them, and would be used

by the State as a guide for imposing

drought-related water restrictions on a

regional basis. The water-level hydrograph in figure 5 covers a 5-year period

from October 1, 1998 through

September 30, 2003 for well MO Eh 20

in Montgomery County, and shows the

low water levels during the droughts of

1999 and 2002. 

Unfortunately, the optimal watertable-aquifer network currently is not

complete. Water levels have been

measured in 30 of the 81 wells for

many years, but 51 additional wells are

needed to complete the network and

fully represent all the key topographic

settings in the major hydrogeologic

units in Maryland. The Advisory

Committee’s report (State of Maryland,

2004) recommends that all current

wells be maintained and that the additional needed wells be added as funding permits. 

Confined-Aquifer Network

The second of the two groundwater-level networks in Maryland—the

confined-aquifer network—is designed

to capture the effects of ground-water

pumpage, and ideally would include

159 observation wells in the seven most

important aquifers in Maryland’s

Coastal Plain (the Chesapeake Group,

Piney Point-Nanjemoy, Aquia, Magothy,

upper Patapsco, lower Patapsco, and

Patuxent aquifers). The optimal network for one of these aquifers, the

Aquia, is shown in figure 6 and indicates the number of wells that are currently being monitored and the number

of additional wells needed to meet the

optimal network design. Similar optimal

4 The Status of Streamflow and Ground-Water-Level Monitoring Networks in Maryland, 2005
networks have been designed for each

of the other six major Coastal Plain

aquifers. 

As ground water is pumped from

these confined aquifers, the pressure in

the aquifers decreases, causing water

levels in observation wells to decline. A

water-level hydrograph for an observation well (CA Gd 6) in the Aquia aquifer

near Solomons in Calvert County,

where the water level has been declining since the 1960s due to groundwater pumpage, is shown in figure 7.

The hydrograph shows that the rate of

decline increased significantly in the

mid-1980s, with the total decline over

the past 45 years being about 120 feet.

The amount and rate of water-level

decline are valuable indicators used in

determining the availability of ground

water to meet future demands from

each of these aquifers. 

As is the case with the water-tableaquifer network, the confined-aquifer

network is also incomplete. The current

observation-well networks for all seven

major Coastal Plain aquifers consist of

110 observation wells, but 49 additional

wells are needed to complete the networks as designed and to provide all

the necessary data to support sound

ground-water allocation decisions for all

areas in Maryland where the seven

major confined aquifers are present.

The Advisory Committee’s report (State

of Maryland, 2004) recommends maintenance of the current number of observation wells and the addition of new

wells, including drilling when necessary,

as funding permits.

5 The Status of Streamflow and Ground-Water-Level Monitoring Networks in Maryland, 2005
Summary

Monitoring of streamflow and

ground-water levels in Maryland is necessary for the sound management and

protection of the State’s water

resources. Numerous Federal, State,

and local agencies support the current

monitoring efforts, and use the streamflow and ground-water-level data to

inform many important decisions being

made in Maryland. The Advisory

Committee on the Management and

Protection of Maryland’s Water

Resources strongly supports the continuation and enhancement of streamflow

and ground-water-level monitoring in

Maryland. Long-term data on streamflow and ground-water levels are readily

available on the U.S. Geological Survey

website, and optimal networks for

streamflow and ground-water-level monitoring have been designed through

multi-agency efforts. The full implementation of the optimal networks, which

will supply the water data necessary to

provide sound and efficient waterresources management and protection

decisions, depends on adequate funding from Federal, State, and local agencies. Stable, long-term funding support

is needed to guarantee that streamflow

and ground-water-level data are available when needed.

References Cited

Cleaves, E.T., and Doheny, E.J., 2000, A

strategy for a stream-gaging network in Maryland: Maryland

Geological Survey Report of

Investigations No. 71, 72 p.

State of Maryland, 2004, Advisory

Committee on the Management

and Protection of the State’s Water

Resources, Final Report: [variously

paged.]

Wheeler, J.C., 2003, Freshwater use

trends in Maryland, 1985-2000:

U.S. Geological Survey Fact Sheet

112-03, 4 p.

For further information, please contact:

District Chief, MD-DE-DC District

U.S. Geological Survey

8987 Yellow Brick Road

Baltimore, Maryland 21237

or visit the Maryland-Delaware-District

of Columbia District homepage on the

World Wide Web at:

http://md.water.usgs.gov

To access near-real-time streamflow

data for Maryland, visit: http://waterdata.usgs.gov/md/nwis/rt 

For information about the Maryland

Department of Natural Resources, visit:

http://www.dnr.state.md.us

To learn more about the Maryland

Water Monitoring Council, visit:

http://www.mgs.md.gov/mwmc

Additional Information

Editor: Valerie M. Gaine

Graphics and design: Timothy W. Auer

USGS Fact Sheet FS 2005-3030