The 2008 Final Report of the Advisory Committee on the Management and Protection of the State’s Water Resources recommended 

that the State conduct a comprehensive study of the water-supply resources of the fractured-rock area of Maryland to provide the 

data and scientifi c tools needed to ensure that water is allocated and used in a sustainable fashion, without causing ecological 

damage. Through funding and support from the Maryland Department of the Environment (MDE), the Maryland Department of 

Natural Resources’ Maryland Geological Survey (MGS), and the U.S. Geological Survey (USGS), this assessment will begin in 2009. 

Water Resources of the 

Fractured-Rock Area of 

Maryland

T

he fractured-rock area of Maryland 

encompasses the region of the 

State west of the Fall Line, which 

is approximated by the Interstate 95 corridor. 

It includes the Piedmont, Blue Ridge, 

Ridge and Valley, and Appalachian Plateau 

Physiographic Provinces (fi g. 1). Surface 

water and ground water are important and 

interconnected water sources in this area. 

Streamfl ow characteristics vary in response 

to different land use, geology, topography, soil, 

and other factors. Ground-water fl ow is quite 

localized, tending to be controlled by local 

watersheds. Water in this region moves down 

through the soil and decomposed rock (saprolite) and along joints, faults, and fractures in 

the underlying rock (fi g. 2). Water availability 

depends upon the size of fractures as well as 

the interconnections between fractures. 

Why is this assessment 

necessary?

1. Water resources in the area are very 

vulnerable during drought.

Unlike in the Maryland Coastal Plain, 

ground water in the fractured-rock area of 

Maryland is found mostly under water-table 

conditions. As a result, ground-water levels 

rise and fall in response to seasonal precipitation. During periods of drought, ground-water 

levels can drop rapidly, particularly if drought 

occurs in the winter and spring, when most 

aquifer recharge occurs (fi g. 3). Many wells 

in the region went dry during the droughts in 

1999 and 2002, and some towns were forced to 

consider alternative water sources as declining ground-water levels threatened municipal 

water supplies. Because ground water is the 

source of stream base fl ow and critical to 

maintaining fl ows during summer and autumn 

months, declining ground-water levels can 

cause streams to go dry. An assessment 

of the fractured-rock water resources will 

increase our knowledge of aquifer recharge 

and discharge processes. This will provide 

water managers, policy makers, and planners 

with a sound basis for determining how much 

water is potentially available for future growth, 

and help them weigh the costs and benefi ts of 

current water management practices against 

alternatives.

2. Better information and tools are needed 

to estimate the availability of water.

Water regulators, planners, and policy 

makers need to know how much water can 

be withdrawn from wells and streams without 

causing adverse impacts to the resource or 

other users. Studying the effects of water 

withdrawals may indicate that the cumulative impacts of increased population growth 

combined with other consumptive uses are 

resulting in adverse impacts or highlight 

specifi c areas of Maryland’s fractured-rock 

terrain that are more susceptible to adverse 

impacts from consumptive uses. Conversely, 

investigation may 

show that current 

allocation methods 

are not resulting in 

adverse impacts 

and are suffi ciently 

protective of the 

resources. Both 

ground- and surfacewater appropriations 

are assessed using 

streamfl ow statistics; however, since 

most streams do not 

have stream gages, 

streamfl ow statistics 

for a particular watershed are usually 

estimated from a gaged watershed with similar characteristics. This project will provide 

new tools, such as StreamStats (Ries and others, 2008), that can more accurately estimate 

these statistics for ungaged streams, resulting 

in better-informed permitting decisions. 

Current methodologies evaluate one 

permit request at a time; tools need to be 

developed that can assess the cumulative effects of multiple withdrawals on a watershed. 

Accurate estimates of consumptive water use 

(water that is not returned to the watershed 

where it originated) are also needed. Finally, 

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 2009–3009

2009

Figure 1. Fractured-rock area of Maryland (includes the Piedmont, 

Blue Ridge, Ridge and Valley, and Appalachian Plateau Physiographic 

Provinces) (modifi ed from Maryland Geological Survey).

Drought conditions in Prettyboy Reservoir, 

April 2002. Photograph by USGS.
these tools and water data need to be incorporated into an integrated water-information 

system that can be effi ciently and accurately 

employed to make informed decisions on 

water appropriation.

3. Minimum stream fl ow-by requirements 

need to be evaluated to determine if they 

are adequate to maintain the ecological 

integrity of Maryland’s streams.

Water managers and planners need 

better information about when a water withdrawal is likely to impact the stream ecology. 

Currently, surface-water users are permitted 

to withdraw water only if the streamfl ows 

remain above minimum fl ow-by requirements to ensure that adequate water remains 

in the stream for human use and healthy 

stream ecology. However, different minimum 

streamfl ows may be needed to maintain the 

ecological integrity of a stream and the health 

of aquatic biota. Using data collected by the 

Department of Natural Resources (MD DNR) 

for the Maryland Biological Stream Survey, 

this study will assess the adequacy of statistically determined stream fl ow-by amounts. 

Research watersheds will also be established 

and studied in combination with this assessment. 

4. Hydrologic and geologic factors related 

to water supply need to be assessed.

In order to prudently manage the water 

resources of the fractured-rock area of 

Maryland, it is necessary to understand the 

hydrologic processes involved in the storage, 

movement, and use of water within and 

between watersheds. This project will study 

how different factors affect the availability of 

water, such as variations in saturated saprolite 

thickness, saprolite characteristics, rock type, 

and impervious land cover. Studying these 

processes will involve analyzing existing data 

in combination with the research watersheds 

for integrated hydrologic monitoring.

Goals of the Assessment

• Develop a comprehensive database 

of streamfl ow, hydrogeologic, wateruse, and other appropriate surfacewater and ground-water information.

• Develop a statistically based software tool to estimate water availability.

• Determine streamfl ow requirements 

for aquatic organisms in streams in 

different settings.

• Determine the factors affecting 

ground-water availability in different 

hydrogelogic settings.

• Assess watershed processes in 

different settings by establishing 

research watersheds.

Figure 2. Cross section 

showing saprolite and 

fractured-rock system in 

crystalline rocks.

Figure 3. Hydrograph 

showing ground-waterlevel fl uctuation in 

relation to precipitation. 

Note drop in water level 

during 2002 drought.

References

Heath, R.C., 1983, Basic ground-water 

hydrology: U.S. Geological Survey 

Water Supply Paper 2220, 84 p.

Ries, K.G. III, Guthrie, J.D., Rea, A.H, 

Steeves, P.A., and Stewart, D.W., 2008,

StreamStats: A water resources web 

application: U.S. Geological Survey 

Fact Sheet 2008–3067, 6 p.

State of Maryland, 2008, Water for 

Maryland’s future: What we must do 

today, Final Report of the Advisory 

Committee on the Management 

and Protection of the State’s Water 

Resources: Prepared by the Maryland 

Department of the Environment, 32 p.

Authors

David W. Bolton

Maryland Geological Survey

Maryland Department of Natural Resources

2300 St. Paul Street

Baltimore, MD 21218

(dbolton@dnr.state.md.us)

Plans for a Comprehensive 

Assessment of Water Resources 

in the Fractured-Rock Area of 

Maryland

A 5-year study plan has been developed 

jointly by MDE, MD DNR, and USGS. Products 

planned for this assessment will include:

• geospatial data sets of streamfl ow, 

hydrogeology, water use, and other appropriate information;

• software that can be used to estimate 

water availability in watersheds that lack 

stream gages;

• a digital atlas of water use and water 

availability for the fractured-rock area of 

Maryland; and

• watershed-based fact sheets describing water withdrawals, availability, and other 

information for selected watersheds.

Start-up of the fractured-rock waterresources assessment is planned for early 

2009, with MDE, MD DNR, and USGS providing fi nancial and technical support for the 

project. Signifi cant funding for the completion 

of the entire assessment will be required from 

current and additional partners over the next 

5 years.

James M. Gerhart

U.S. Geological Survey

5522 Research Park Drive

Baltimore, MD 21228

(jgerhart@usgs.gov)

Saeid Kasraei

Maryland Department of the Environment

1800 Washington Blvd.

Baltimore, MD 21230

(skasraei@mde.state.md.us)