U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5160

Prepared in cooperation with the

Maryland Department of the Environment

and the

Maryland Department of Natural Resources

A Science Plan for a Comprehensive Assessment of 

Water Supply in the Region Underlain by Fractured 

Rock in Maryland
Cover. Map showing the region underlain by fractured rock in Maryland.
A Science Plan for a Comprehensive 

Assessment of Water Supply in the Region 

Underlain by Fractured Rock in Maryland

By Brandon J. Fleming, Patrick A. Hammond, Scott A. Stranko, Mark T. Duigon, 

and Saeid Kasraei

Scientific Investigations Report 2012–5160

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the 

Maryland Department of the Environment

and the

Maryland Department of Natural Resources
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Fleming, B.J., Hammond, P.A., Stranko, S.A., Duigon, M.T., and Kasraei, Saeid, 2012, A science plan for a comprehensive assessment of water supply in the region underlain by fractured rock in Maryland: U.S. Geological Survey 

Scientific Investigations Report 2012–5160, 29 p

ISBN 978-1-4113-3442-7
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Water Management Issues and Assessment Questions...............................................................2

Need for a Comprehensive Assessment ..........................................................................................3

Improved Information Systems and Tools ...............................................................................3

Population Growth.......................................................................................................................4

Marcellus Shale Exploration......................................................................................................5

Drought Susceptibility and Climate Change............................................................................6

Protecting Aquatic Habitats.......................................................................................................6

 Hydrogeologic Setting ........................................................................................................................9

Appalachian Plateau...................................................................................................................9

Valley and Ridge...........................................................................................................................9

Blue Ridge...................................................................................................................................10

Piedmont......................................................................................................................................10

Previous Studies .................................................................................................................................13

Description of Science Goals and Assessment Activities....................................................................13

Science Goal 1: Develop Tools for the Improved Management and Investigation 

of Groundwater and Surface-Water Resources..............................................................14

Need for New Work...................................................................................................................14

Objectives and Proposed Assessment Activities.................................................................14

Science Goal 2: Characterize Factors Affecting Reliable Yields of Individual 

Groundwater and Surface-Water Supplies ......................................................................15

Need for New Work...................................................................................................................15

Objectives and Proposed Assessment Activities.................................................................16

Science Goal 3: Investigate Impacts on Other Water Withdrawal Users Caused 

by Surface-Water and Groundwater Withdrawals .........................................................16

Need for New Work...................................................................................................................16

Objectives and Proposed Assessment Activities.................................................................17

Science Goal 4: Assess the Role of Streamflow and Water Withdrawals on 

the Ecological Integrity of Maryland’s Streams...............................................................18

Need for New Work...................................................................................................................18

Objectives and Proposed Assessment Activities.................................................................19

Science Goal 5: Improve Understanding of the Distribution of Water-Quality 

Conditions in Fractured Rock Aquifers..............................................................................20

Need for New Work...................................................................................................................21

Objectives and Proposed Assessment Activities.................................................................21

Assessment Implementation......................................................................................................................22

Products and Benefits.................................................................................................................................22

Interagency Coordination and Outreach .................................................................................................22

Concluding Remarks....................................................................................................................................23

Acknowledgments.......................................................................................................................................23

References Cited..........................................................................................................................................23
iv

Figures

1. Map showing counties within study area for a comprehensive assessment 

of water supply in the region underlain by fractured rock in Maryland..............................3

2. Graph showing 2005 water withdrawals for all counties in the fracturedrock area of Maryland by water-use category........................................................................4

3. Map showing projected population increase in Maryland by county from 

2010 to 2040....................................................................................................................................5

4. Map and graphs showing (A) central Maryland and hydrographs of 

groundwater levels for (B) water-table well BA Ea 18, Baltimore County, 

(C) water-table well FR Df 35, Frederick County, and streamflow for 

(D) Bennett Creek (01643500), and (E) North Branch Patapsco River at 

Cedarhurst, Md. (01586000).........................................................................................................6

5. Graph showing example flow-ecology response curves showing relations 

between alterations in streamflow and ecological conditions for (A) linear, 

(B) critical thresholds, and (C) non-linear curves ...................................................................9

6. Map and diagrams showing (A) physiographic provinces and conceptual 

groundwater-flow diagrams for (B) carbonate rocks, (C) coal-bearing 

rocks in the Appalachian Plateau, (D) crystalline rocks in the Piedmont 

Uplands, and (E) Mesozoic basin in the Piedmont Lowlands..............................................10

7. Map showing location of the Maryland Biological Stream Survey 

Sentinel sites ...............................................................................................................................20

Tables

1. Projected population increase in Maryland by county from 2010 to 2040 ..........................5

2. Percent of population served by domestic groundwater wells for each 

county in the fractured-rock region of Maryland, 2005........................................................21
v

Conversion Factors and Datums

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2)

Volume

gallon (gal) 0.003785 cubic meter (m3)

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3)

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

Specific capacity

gallon per minute per foot 

[(gal/min)/ft)]

0.2070 liter per second per meter [(L/s)/m]

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Transmissivity*

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

 °C = (°F - 32) / 1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot 

times foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.
vi

Abbreviations

BIBI Benthic Macroinvertebrate Index of Biotic Integrity

MDDNR Maryland Department of Natural Resources

ELOHA Ecological Limits of Hydrologic Alteration 

FIBI Fish Index of Biotic Integrity

FR-AIS Fractured Rock Aquifer Information System

GIS Geographic Information System

HIP Hydroecological Integrity Assessment Process

ICPRB Interstate Commission on the Potomac River Basin

MANTA Monitoring and Non-Tidal Assessment Division (MDDNR)

MBSS Maryland Biological Stream Survey

MCL Maximum Contaminant Level (USEPA)

MDE Maryland Department of the Environment

MDE WSP Maryland Department of the Environment Water Supply Program

MGS Maryland Geological Survey

NAWQA National Water-Quality Assessment Program (USGS)

NWIS National Water Information System

PDWIS Public Drinking Water Information System

USEPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey

7Q10 7-day, 10-year low flow
A Science Plan for a Comprehensive Assessment of 

Water Supply in the Region Underlain by Fractured 

Rock in Maryland

By Brandon J. Fleming1, Patrick A. Hammond2, Scott A. Stranko3, Mark T. Duigon4, and Saeid Kasraei2

Abstract

The fractured rock region of Maryland, which includes 

land areas north and west of the Interstate 95 corridor, is 

the source of water supply for approximately 4.4 million 

Marylanders, or approximately 76 percent of the State’s 

population. Whereas hundreds of thousands of residents rely 

on wells (both domestic and community), millions rely on 

surface-water sources. In this region, land use, geology, topography, water withdrawals, impoundments, and other factors 

affect water-flow characteristics. The unconfined groundwater 

systems are closely interconnected with rivers and streams, 

and are affected by seasonal and climatic variations. During 

droughts, groundwater levels drop, thereby decreasing well 

yields, and in some cases, wells have gone dry. Low groundwater levels contribute to reduced streamflows, which in turn, 

can lead to reduced habitat for aquatic life. Increased demand, 

over-allocation, population growth, and climate change can 

affect the future sustainability of water supplies in the region 

of Maryland underlain by fractured rock.

In response to recommendations of the 2008 Advisory 

Committee on the Management and Protection of the 

State’s Water Resources report, the Maryland Department 

of the Environment’s Water Supply Program, the Maryland 

Geological Survey, the Maryland Department of Natural 

Resources, Monitoring and Non-Tidal Assessment (MANTA) 

Division, and the U.S. Geological Survey have developed a 

science plan for a comprehensive assessment that will provide 

new scientific information, new data analysis, and new tools 

for the State to better manage water resources in the fractured 

rock region of Maryland. The science plan lays out five goals 

for the comprehensive assessment: (1) develop tools for the 

1

 U.S. Geological Survey

2

 Maryland Department of the Environment

3

 Maryland Department of Natural Resources

4

 Formerly of Maryland Geological Survey

improved management and investigation of groundwater and 

surface-water resources; (2) characterize factors affecting 

reliable yields of individual groundwater and surface-water 

supplies; (3) investigate impacts on nearby water withdrawal 

users caused by groundwater and surface-water withdrawals; 

(4) assess the role of streamflow and water withdrawals on 

the ecological integrity of streams; and (5) improve understanding of the distribution of water-quality conditions in 

fractured rock aquifers. To accomplish these goals, accurate 

data collection, review, and analysis are needed, including 

the study of “Research Watersheds” that can provide detailed 

information about the potential effects that climate change and 

water withdrawals may have on groundwater, streamflow, and 

aquatic life. 

The assessment planning started in 2009 and is being 

conducted with close interagency coordination. A Fractured 

Rock Aquifer Information System is currently (2012) undergoing initial development. Other major tasks that will be 

performed include the development of work plans for each 

science goal, the estimation of daily streamflow at ungaged 

streams, and the design and implementation of Research 

Watersheds. Finally, scenarios will be modeled to evaluate 

current water allocation permitting methodologies, investigate 

effects on nearby water withdrawal users caused by groundwater and surface-water withdrawals, and assess the potential 

impacts of climate change on water resources. 

Desktop and Web-based tools will be developed in order 

to meet the diverse research needs of the assessment. These 

tools, including the Fractured Rock Aquifer Information 

System will be continuously improved during the assessment 

to store relevant groundwater and surface-water data in 

spatially referenced databases, estimate streamflows, locate 

higher-yielding wells, estimate the impacts of withdrawals 

on nearby users, and assess the cumulative impacts of withdrawals on the aquatic resource. Tools will be developed to 

serve the needs of many audiences, including water resource 

managers, water suppliers, planners, policymakers, and other 

scientific investigators.
2 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Introduction

 The Maryland Department of the Environment (MDE) is 

responsible for managing the State’s water resources through 

a permitting program that has been in place since the 1930s. 

The program has evolved through legislative action and 

scientific advances. In 2008, the Advisory Committee on the 

Management and Protection of the State’s Water Resources, 

which was established by an Executive Order of the Governor, 

completed its review of the State’s program and issued its 

final report, outlining a number of recommendations to assist 

the State in better meeting its obligations. The Committee 

identified the need for accurate, comprehensive data to support 

planning, management, and permitting decisions, and recommended that the State conduct studies in both the Coastal 

Plain and fractured rock regions of Maryland. The investigations that are planned will provide the data and scientific tools 

needed to ensure that water is allocated and used in a sustainable manner, while minimizing adverse impacts to water 

supplies and aquatic ecosystems. In response to the Advisory 

Committee’s recommendations, MDE has formed an interagency partnership with the Maryland Department of Natural 

Resources (MDDNR) Maryland Geological Survey (MGS), 

Monitoring and Non-Tidal Assessments (MANTA) Division, 

and the U.S. Geological Survey (USGS), to oversee and conduct this study of the fractured rock region. The fractured rock 

region of Maryland (fig.1), which includes land areas north 

and west of the Interstate 95 corridor, is the source of water 

supply for approximately 4.4 million Marylanders, or approximately 76 percent of the State’s population. The majority of 

water use is for thermoelectric (electricity produced by steamdriven turbine generators) and public supply (fig. 2). Whereas 

hundreds of thousands of residents rely on wells (both domestic and community), millions rely on surface-water sources. 

This Science Plan describes the goals of the Fractured 

Rock study and presents the general methods for conducting 

the study. This Science Plan also presents guidelines for 

conducting a comprehensive assessment of the water supply 

resources in the region of Maryland underlain by fractured 

rock aquifers. It describes the scientific and water management 

issues motivating the comprehensive assessment, science 

goals, objectives within each goal, and potential implementation activities. To prudently manage the water resources of 

Maryland, it is imperative to gain an improved understanding 

of the interactions between surface and subsurface water 

resources in the fractured rock region. This is a vital aspect of 

the study, as this understanding is essential for the preservation 

of Maryland’s water supplies, the ecological health of streams, 

and planning for potential climate change impacts on water 

resource availability. 

Once completed, the comprehensive assessment will provide the State with improved scientific knowledge and tools 

that will assist in the management of water resources, the use 

of science-based policies for water allocation, and heightened 

preparedness for climate variation. Results of the assessment 

will also guide water suppliers in selecting additional water 

sources, and water-supply planning efforts, which are a critical 

component to future growth and development in the State. 

Water Management Issues and Assessment 

Questions 

In Maryland, surface-water and groundwater withdrawals over 10,000 gallons per day are managed by MDE through 

the Water Supply Program. Permit applications are evaluated 

to ensure that the amount of the withdrawal is reasonable, 

that the proposed withdrawal will not jeopardize the State’s 

natural resources, and impacts on other water users (including 

nearby private, commercial, and industrial withdrawals) are 

not unreasonable. In the region underlain by fractured rock, 

MDE has used various methods to evaluate the reasonableness 

of proposed water withdrawals. 

For groundwater uses, data from water-level monitoring 

during aquifer tests and fracture trace analyses are most commonly evaluated to aid in the determination of well yield, the 

assessment of potential impacts on other users, and the need 

and location of future water-level monitoring. Water balance 

calculations are utilized to ensure aquifer sustainability and 

the protection of stream base flow. In the case of proposed 

surface-water withdrawals, available streamgage data from 

the USGS are used to conduct mass-flow and frequency-flow 

analyses. These analyses determine reliable reservoir yields, 

adequacy of off-stream storage or back-up supplies for withdrawals through simple intakes (direct extraction from stream 

or water body), and necessary flow-by or seasonally adjusted 

flow releases required to protect downstream users and aquatic 

habitats. 

Decisions regarding the management of the State’s water 

supply must be based on sound, comprehensive knowledge 

and assessment techniques. Making these decisions requires 

foresight into issues that currently (2012), or could potentially, 

affect the State. Some of the issues specifically considered 

during the development of this Plan included: 

•	 How can the scientific methods for evaluating water

allocation permits be improved?

•	 How will Maryland’s population growth and new

natural gas resource extraction methods affect water

supply and demand?

•	 How will water availability be affected by droughts

that are potentially longer, more frequent, and more

intense as a result of climate change?

•	 What streamflows are necessary to ensure ecological

integrity of streams?

•	 How can water suppliers and water resource managers

identify the best locations for wells to ensure sustainable use?
Introduction 3

•	 What is the distribution of regulated drinking-waterquality constituents in areas where residents rely on

private water wells?

To address these questions, new data-management 

systems and tools will need to be developed. New hydrologic 

data will need to be collected in order to update and enhance 

tools developed during this assessment. These tools will be 

used primarily by water managers and scientists, and will also 

be made available to planners, decision makers, local governments, and the public. 

Need for a Comprehensive Assessment 

Understanding the factors related to groundwater availability in central and western Maryland is an important component of water resources management. Because stream base 

flow is derived entirely from groundwater discharge, factors 

affecting groundwater availability will have a direct bearing 

on streamflow (Wolman, 2008). This study will attempt to 

identify factors that influence current and future groundwater 

availability and ecological flow needs. 

Improved Information Systems and Tools

MDE water resource managers have been issuing water 

withdrawal permits in fractured rock aquifers using the 

watershed water balance method modified from Willey and 

Achmad (1986) as one component of their analysis for nearly 

20 years. The water balance method is used to determine if the 

requested withdrawal is reasonable to maintain the resource 

and to evaluate reserves for future allocations. Although this 

method has served the State well, it does not account for seasonal variability because it is based on an annual recharge rate 

during a drought. Therefore, objective scientific comparisons 

and evaluations of known methods and practices are needed. 

Comparisons of results from aquifer tests with production 

capacities have shown the difficulty in correctly estimating 

future well performance. Applicants often have overestimated 

well yields from the aquifer test results. Standard methods for 

interpreting test results need to be published to ensure that the 

public interest is protected. 

This comprehensive assessment is designed to provide 

information and tools to improve permitting methods and the 

determination of sustainable allocation quantities. In addition, 

Figure 1. Counties within study area for a comprehensive assessment of water supply in the region underlain by fractured rock 

in Maryland.
4 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Figure 2. 2005 water withdrawals for all counties in the fractured-rock area of Maryland by water-use category 

(Susan Hutson, U.S. Geological Survey, written commun., 2012).

there is a need for the increased accessibility of geospatially 

referenced data for permit managers. The necessary enhancements to datasets include water quality, current permitted 

allocations and water-use data, aquifer test data, hydrogeologic 

data, and flow data at ungaged streams. 

Water resource managers rely on data and information 

from many sources to make decisions on water allocations and 

future supply plans. They have expressed the need for a computerized system that will allow them to access all available 

data, and to summarize, graphically display, and visualize the 

data and interpretive information for specific areas of interest. 

A computerized system will allow managers to evaluate water 

allocations on a seasonal basis and at a sub-watershed scale 

to provide improved estimates of water availability. In addition, new modeling tools are needed to evaluate current and 

updated methods for determining the impacts of water allocations to assure that decisions are made from the best available 

science and information. Numerical modeling techniques have 

greatly improved over the last decade, and now incorporate 

both surface-water and groundwater programs capable of 

providing a more comprehensive representation of watershed 

water budgets.

Population Growth

The surface-water and groundwater resources in the fractured rock region are crucial to the State of Maryland (Bolton 

and others, 2009). The demand for water generally increases 

in proportion to population growth, which then increases pressure on water supplies. According to the 2010 U.S. Census, the 

population of Maryland has increased by over 500,000 since 

2000 to 5.8 million people in 2010. The Maryland Department 

of Planning projects that by 2040, the State’s total population 

will be approximately 6.9 million, representing a growth rate 

of almost 20 percent over the 30-year period. 

The spatial distribution of projected population growth 

from 2000 to 2040 is uneven in the fractured rock region of 

Maryland (fig. 3). The largest growth rates are expected to 

occur in Frederick and Cecil Counties at 57 and 62 percent, 

respectively. Counties east of Frederick (Carroll, Harford, 

Howard, and Montgomery) are expected to see a growth rate 

averaging 26 percent. In addition, Harford County is projected 

to undergo a population increase of 22 percent by 2040. Over 

this period, Baltimore County is expected to grow by about 

8 percent, while Allegany and Garrett Counties are projected 

to expand more slowly, growing at rates of 3 and 7 percent, 

respectively (table 1). 

The anticipated increase in water demand will stress aquifer systems and surface-water supplies in Maryland. Resource 

managers must ensure that the effects of new surface-water 

and groundwater withdrawals on other water users are minimal. This includes impacts to streamflow and nearby groundwater wells. Communities are already challenged to plan for 

growth. In some cases, a viable water supply can be the limiting factor for continued growth. 
Introduction 5

Figure 3. Projected population increase in Maryland by county from 2010 to 2040 (Maryland Department of Planning, 2010).

Table 1. Projected population increase in Maryland by county 

from 2010 to 2040.

County

Projected population increase 

from 2010 to 2040

(percent)1

Cecil 62

Frederick 57

Washington 37

Carroll 26

Montgomery 22

Harford 22

Howard 18

Baltimore 8

Garrett 7

Allegany 3

1

 Maryland Department of Planning, 2010.

Marcellus Shale Exploration

Gas exploration in the Marcellus Shale has occurred 

in both Pennsylvania to the north and West Virginia to the 

south and west of Maryland’s Garrett and Allegany Counties. 

Concerns over the availability of water for extracting natural 

gas have been well documented across the Mid-Atlantic 

region. Maryland’s Governor, Martin O’Malley, issued an 

Executive Order on June 6, 2011 establishing an Advisory 

Commission to undertake a study of the extraction of natural 

gas from shale formations. One component of the study 

addresses the water resources required to support hydraulic 

fracturing (hydrofracking) activities, whereas other components address potential water-quality impacts. The amount 

of water necessary for hydraulic fracturing of one well 

averaged over 2.5 million gallons (Susquehanna River Basin 

Commission, 2010). Water managers need to be prepared to 

assess the aggregate and cumulative impacts of these new 

operations.
6 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Drought Susceptibility and Climate Change

Climatic variations affect water supplies more directly 

and more immediately in Maryland’s fractured rock region 

than in the Coastal Plain because of the interconnected 

nature of the unconfined groundwater systems to rivers and 

streams in the fractured rock region. The hydrologic relation 

among climate, surface water, and groundwater was evident 

during the droughts of 1999 and 2002 when groundwater and 

streamflow were at their lowest levels in decades as a result of 

significant below-normal recharge from a lack of precipitation 

(fig. 4). 

Surface water and groundwater systems can respond 

differently to drought conditions, even though they are often 

studied as a single resource (Winter and others, 1998). The 

timing and magnitude of declines in streamflow and groundwater levels in response to drought conditions are poorly 

understood. Geology and landscape characteristics are important factors affecting drought response in streams and aquifers. 

The heterogeneous nature of the fractured rock in Maryland 

can increase the variability of hydrologic response to drought 

across the region for comprehensive assessment. 

Increases in interannual precipitation variability and more 

frequent and intense extreme events have been observed globally (Bates and others, 2008). The effects of global climate 

change on Maryland’s water resources are unknown, but 

possible impacts include more frequent and longer droughts 

and more frequent and severe storms (Boicourt and Johnson, 

2010). To better protect and manage Maryland’s water 

resources, and prepare for the effects of drought and climate 

variability, a better understanding of the interactions between 

climate, streams, and aquifers in the fractured rock region of 

Maryland is needed. 

Protecting Aquatic Habitats

Scientists, water resource managers, and policy makers 

need to understand the characteristics of streamflow that must 

be maintained to ensure the persistence of the full complement 

of biological taxa and prevent the degradation of the ecological integrity of Maryland streams. There is a need for a greater 

understanding of the sensitivity of various species to alterations in natural flow regimes. Although biological inventories 

and streamflow records have been collected from Maryland 

streams for many years, the relations between streamflow and 

biological taxa are not well understood. A framework for the 

necessary analyses has been developed (Poff and others, 1997) 

for the different flow-ecology thresholds (fig. 5), but the relation between hydrologic alteration and ecological condition 

varies greatly and is not yet defined for streams in Maryland. 

Figure 4. (A) central Maryland and hydrographs of groundwater levels for (B) water-table well BA Ea 18, 

Baltimore County, (C) water-table well FR Df 35, Frederick County, and streamflow for (D) Bennett Creek 

(01643500), and (E) North Branch Patapsco River at Cedarhurst, Md. (01586000).
Introduction 7

Figure 4. (A) central Maryland and hydrographs of groundwater levels for (B) water-table well BA Ea 18, Baltimore County, 

(C) water-table well FR Df 35, Frederick County, and streamflow for (D) Bennett Creek (01643500), and (E) North Branch Patapsco 

River at Cedarhurst, Md. (01586000).—Continued
8 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Figure 4. (A) central Maryland and hydrographs of groundwater levels for (B) water-table well BA Ea 18, Baltimore County, 

(C) water-table well FR Df 35, Frederick County, and streamflow for (D) Bennett Creek (01643500), and (E) North Branch Patapsco 

River at Cedarhurst, Md. (01586000).—Continued
Introduction 9

Figure 5. Example flow-ecology response curves showing 

relations between alterations in streamflow and ecological 

conditions for (A) linear, (B) critical thresholds, and (C) nonlinear curves (modified from Davies and Jackson, 2006).

Hydrogeologic Setting

The fractured rock region of Maryland can be divided 

into four physiographic provinces: the Appalachian Plateau, 

Valley and Ridge, Blue Ridge, and Piedmont (Fenneman 

and Johnson, 1946). The eastern boundary of the Piedmont 

Province is the Fall Line (fig. 6A), named for the rapids and 

waterfalls that often occur at contact between the sedimentary 

deposits of the Coastal Plain and the crystalline bedrock of 

the Piedmont. Groundwater flow occurs primarily in the 

secondary porosity of the rocks (fractures, joints, and faults), 

with some groundwater flow in the intergranular space within 

sandstones. In areas underlain by carbonate rocks, fractures 

may become enlarged by the dissolution of rock by circulating 

groundwater. It is important not to associate aquifers with individual geologic units, because water-bearing properties can be 

affected by regional geologic structure as well as lithology. 

The unconsolidated overburden, or regolith, covering 

bedrock has hydrologic properties distinct from the underlying 

rock and may be a significant factor in the recharge and storage of groundwater. The hydrologic properties of overburden 

depend on its origin. In much of the Piedmont Physiographic 

Province, saprolite has formed in place by prolonged weathering of crystalline bedrock. Saprolite thickness depends on its 

parent material and location relative to surface drainage (it is 

thinnest near large streams). Elsewhere in the fractured rock 

region, overburden consists of alluvium and colluvium, sediments that have been transported and deposited along streams 

and the base of hill slopes. These are particularly thick along 

the slopes of Catoctin Mountain and South Mountain (that 

lie on the east and west side of the Blue Ridge Physiographic 

Province, respectively), and the mountains just to the west of 

the Hagerstown Valley. 

Appalachian Plateau

The Appalachian Plateau in Maryland covers all of 

Garrett County and the western edge of Allegany County. 

Bedrock consists mostly of sandstone, shale, and siltstone, but 

conglomerate, limestone, and coal are also present. Ridges 

mark where resistant layers are exposed. One of these ridges, 

Backbone Mountain-Big Savage Mountain, spans Garrett 

County and includes the highest point in Maryland 3,360 feet 

(ft). The drainage networks are deeply incised and controlled 

by geologic structure. In most areas, soils have formed from 

in situ weathering; some soils have also formed in alluvium 

(water-transported sediments) or colluvium (gravity-transported sediments). 

Most groundwater movement occurs along fractures and 

bedding planes, although sandstones (particularly those of 

Pennsylvanian and Mississippian age) also possess intergranular permeability (Amsden and others, 1954). Groundwater 

flow takes place at local scales (generally under water-table 

conditions) and regional scales, under artesian conditions 

(Duigon and Smigaj, 1985). There are numerous areas where 

the land has been disturbed by surface or underground coal 

mining. Mine dewatering can have a substantial impact on 

groundwater levels near active mines, but water levels can 

also be affected by mineral exploration (Duigon and Smigaj, 

1985) and post-mining activities. This area also overlies the 

Marcellus Shale, which is being developed for natural gas production (Soeder and Kappel, 2009). It is unclear what impacts 

the development of the Marcellus Shale will have on water 

resources within this region. 

Valley and Ridge

The Valley and Ridge Province in Maryland covers 

Allegany and Washington Counties and the very southwestern 

edge of Frederick County. This province is characterized by 

alternating ridges and valleys. The predominant lithology is 

shale and limestone. The ridges are formed by sandstones, 

with lesser amounts of limestone and siltstone. Geologic structure is oriented primarily northeast-southwest and because of 

the variable resistance to erosion of sandstone and shale, is 

responsible for the parallel ridges and valleys. 

The folded rocks of this section are well consolidated, 

with little primary porosity. Groundwater generally moves 

through fractures and bedding-plane separations, much like 

the Appalachian Plateau. The limestone rocks can have karstic 

conditions, namely, enlargement of fracture and bedding-plane 

voids by the solvent action of circulating groundwater, but 

karst development is limited because of the narrow extent of 

limestone formations in this region. 

In the Hagerstown Valley, the Maryland part of the Great 

Valley, the outstanding characteristic is the development of 

karst, a collection of landforms and hydrologic characteristics 

that derive from the solubility of the carbonate bedrock. Karst 

development is more extensive in the Hagerstown Valley 

because of more substantive limestone deposits. 
10 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Figure 6. (A) physiographic provinces and conceptual groundwater-flow diagrams for (B) carbonate rocks, (C) coal-bearing 

rocks in the Appalachian Plateau, (D) crystalline rocks in the Piedmont Uplands, and (E) Mesozoic basin in the Piedmont 

Lowlands.

Blue Ridge

This province encompasses the area from South 

Mountain (adjacent to the Hagerstown Valley) to Catoctin 

Mountain. The core (Middletown Valley) is underlain mainly 

by gneiss, metabasalt, and metarhyolite; the mountains are 

underlain primarily by metasedimentary rocks. Metabasalt and 

metarhyolite also underlie the northern part of the province in 

Maryland where the mountains converge in Frederick County. 

Bedrock permeability of the Blue Ridge rocks is secondary, whereas intergranular permeability of colluvium may be 

fairly high if clay content is low. The water table is typically 

below the base of the colluvium in many areas, however, 

Fauth (1977) and Dine and others (1985) reported water levels 

within colluvium deposits in several observation wells. 

Piedmont

The Piedmont has three distinct geologic areas—carbonate, siliciclastic, and igneous and metamorphic crystalline 

rocks. The Piedmont carbonate area consists of limestone and 

dolomite in the Frederick Valley. To the east, limestone and 

dolomite have been metamorphosed into marble in various 

subdivisions of the crystalline region. Areas underlain by these 

rocks tend to be flat-bottomed valleys caused by the solubility 

of the rock, and their broadness depends on the width of the 

carbonate rocks near land surface. These rocks possess low 

primary permeability, but in many places, fractures have been 

enlarged by dissolution of wall rock, locally providing very 

high permeability.

To the north and south of the Frederick Valley are the 

Piedmont sedimentary deposits, commonly referred to as the 

Mesozoic Lowlands or Piedmont Lowlands (fig. 6A), underlain by shale, sandstone, and conglomerate rocks. These rocks 

are mostly well compacted and cemented; therefore, groundwater circulation in them depends on the presence of interconnected fractures. Joints tend to be more closely spaced in the 

sandstone and conglomerate, making the rock more transmissive (Nutter, 1975). Significant water-bearing zones can be 

found at depths greater than 500 ft (unlike in the crystalline 

rocks of the Piedmont Uplands) (Nutter, 1975). 
Introduction 11

Spring

Fracture

NOT TO SCALE Saline water

EXPLANATION

Colluvium and alluvium

Weathered bedrock

Sandstone

Siltstone

Shale

Coal seam

Direction of groundwater 

movement

Water table

Solution

opening

Joint

Carbonate rocks

NOT TO SCALE

Regolith

Sinkhole Alluvium

Precipitation

Intermittent

stream Overland

ow

B. Carbonate rocks

C. Coal-bearing rocks in the Appalachian Plateau

Modified from Nutter, 1973.

Modified from Harlow and LeCain, 1993.

Figure 6. (A) physiographic provinces and conceptual groundwater-flow diagrams for (B) carbonate rocks, (C) coalbearing rocks in the Appalachian Plateau, (D) crystalline rocks in the Piedmont Uplands, and (E) Mesozoic basin in the 

Piedmont Lowlands.—Continued
12 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Water table

NOT TO SCALE

Fracture

Spring

Regolith

Bedrock

Fracture

Groundwater

ow

Modified from Heath, 1980. 

NORTHWEST SOUTHEAST

Brunswick

Group

Passaic

Formation Lockatong

Formation Stockton

Formation

Fans

(debris ow)

Fans

(alluvial)

Nearshore-lacustrine siltstone

and mudstone

Nearshore-lacustrine siltstone

and mudstone

Fluvial-lacustrine sandstone

Lacustrine mudstone

and carbonate

NOT TO SCALE

EXPLANATION

Conglomerate

Sandstone

Siltstone

Mudstone

Dolomite

Diabase and basalt

Crystalline rocks

Fault—Arrows show relative 

direction of movement

Modified from Turner-Peterson and Smoot, 1985.

D. Crystalline rocks in the Piedmont Uplands

E. Mesozoic basin in the Piedmont Lowlands

Figure 6. (A) physiographic provinces and conceptual groundwater-flow 

diagrams for (B) carbonate rocks, (C) coal-bearing rocks in the Appalachian 

Plateau, (D) crystalline rocks in the Piedmont Uplands, and (E) Mesozoic 

basin in the Piedmont Lowlands.—Continued
Description of Science Goals and Assessment Activities 13

The igneous and metamorphic Piedmont area consists 

of crystalline rocks, encompassing most of the physiographic 

province. The province includes terranes accreted during plate 

tectonic activity, evinced by the type and degree of metamorphism, and displacement of rock. The crystalline rocks 

are generally covered by saprolite. Permeability tends to be 

somewhat higher in the upper part of the modern soils that 

have developed in the top of the saprolite, where clay has been 

eluviated, and lower at depth, where the clay has been transported. The highest permeabilities are typically found at the 

saprolite/fresh-rock interface or transition zone (Harned and 

Daniel, 1992). Saprolite thickness and properties vary according to rock type and topographic position. Within the competent bedrock, groundwater flow is dominated by secondary 

porosity of fractures and joints. 

Previous Studies

From 1952 to 1962, several water resource bulletins were 

published for the Baltimore area (Bennett and Meyer, 1952), 

Garrett County (Amsden and others, 1954), Howard and 

Montgomery Counties (Dingman and others, 1954), Baltimore 

and Harford Counties (Dingman and others, 1956), Carroll and 

Frederick Counties (Meyer and Beall, 1958), and Allegany and 

Washington Counties (Slaughter and Darling, 1962). These 

reports were typically divided into sections on groundwater 

and surface water. Groundwater sections contained a well 

inventory and groundwater-quality data for the assessment 

area. The surface-water sections presented monthly discharge 

at selected streamgages. From 1969 to 1975, several studies 

were carried out on groundwater resources in distinct physiographic provinces (fig. 6A): the Piedmont (Nutter and Otton, 

1969), the Triassic Rocks of Maryland (Nutter, 1975) and 

the Frederick and Hagerstown Valleys (Nutter, 1973). From 

1975 to 1999, reports were published that describe a statewide 

groundwater-quality network (Bolton, 1996), Piedmont 

springs (Otton and Hilleary, 1985), Garrett County (Duigon 

and Smigaj, 1985; Hiortdahl, 1988; Nutter and others, 1980), 

Carroll County (Hilleary and Weigle, 1981), Westminster, Md. 

(Duigon, 1992), Frederick County (Dine and others, 1985; 

Duigon and Dine, 1987), Harford County (Nutter, 1977), Cecil 

County (Otton and others, 1988), Howard County (Dine and 

others, 1995), and Washington County (Duigon and others, 

1989; Duigon and Dine, 1991). 

These studies provided a significant amount of basic 

data, including: well-construction information, driller’s estimated yields, as well as descriptions of the groundwater flow 

systems and groundwater quality. Collectively, the reports 

have provided the scientific understanding that is still widely 

used to describe groundwater-flow systems; however, several 

decades of additional data are available that could improve our 

understanding of these systems. MDE and various permittees 

have conducted numerous studies as part of the exploration 

and development of public water supplies. Other work on the 

impact of water withdrawals on aquatic biota has recently been 

initiated. Long-term monitoring of water levels associated 

with water withdrawals highlights the potential for impacts on 

other users as well as the sustainability of various uses. A substantial amount of unpublished data were collected during the 

earlier studies that may be useful for identifying the best yielding areas for the development of new water supplies without 

causing unreasonable impacts, including decreased streamflows and well yields from withdrawals. Beyond the State 

boundary, regional studies (Swain and others, 2004; Trapp 

and Horn, 1997) described conceptual models of groundwater 

flow, water-use summaries, and broad groundwater-quality 

issues in the Mid-Atlantic region. Recent studies in Virginia 

(Nelms and Moberg, 2010, 2011) described the complex fractured rock aquifer systems in Clarke and Warren Counties. In 

addition, groundwater systems in the North Carolina Piedmont 

have been studied (Chapman and others, 2005; Daniel, 1989; 

Daniel and others, 1997).

Officials from scientific and resource management agencies in Maryland such as MDE and MDDNR recognize that 

for this assessment to be comprehensive, the assessment area 

will need to extend to adjacent watersheds in Pennsylvania, 

Virginia, and West Virginia. The utilization of information 

from previous studies and readily available data from adjacent 

states is necessary as Maryland contains many watersheds 

with headwaters in surrounding states. 

Description of Science Goals and 

Assessment Activities

The comprehensive assessment of groundwater and 

surface-water supply in the fractured rock region of Maryland 

(referred to hereafter as the Maryland Fractured Rock Study), 

was developed on the basis of five “Science Goals.” In this 

section, each goal is discussed, the need for new work is 

explained, and the assessment activities necessary to achieve 

the goal are outlined. The science goals are:

1. Develop tools for the improved management and investigation of groundwater and surface-water resources.

2.Characterize factors affecting reliable yields of individual groundwater and surface-water supplies.

3.Investigate impacts to other water withdrawal users 

caused by surface-water and groundwater withdrawals. 

4. Assess the role of streamflow and water withdrawals 

on the ecological integrity of Maryland’s streams.

5.Improve understanding of the distribution of waterquality conditions in fractured rock aquifers. 

The information needs for this assessment are related 

to the reliability of groundwater resources and the in-stream 

flows needed to sustain healthy aquatic habitats in Maryland 

streams. Water chemistry and water quality will be an 
14 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

important component of this assessment as they relate to the 

availability of potable groundwater supplies, stream health, 

and the impacts of human activities such as coal and gas 

extractions. The effects of global climate change on streamflow and groundwater supplies in Maryland are unknown. 

This assessment will include analysis of climatic impacts on 

surface-water and groundwater supplies. 

The Maryland Fractured Rock Study is very broad in 

scope. Scientists from different backgrounds will need to work 

closely with resource managers. A multidisciplinary approach 

is required to address the issues described in this assessment. 

New analytical methods will be developed and a variety of 

modeling and statistical approaches will be applied. 

Science Goal 1: Develop Tools for the Improved 

Management and Investigation of Groundwater 

and Surface-Water Resources

The Water Supply Program at MDE is tasked with ensuring the equitable allocation of water among users without 

causing unreasonable impacts on the environment. An example of an unreasonable impact from a withdrawal at a nearby 

high-volume production well would be the loss of a domestic 

water supply due to water-level declines. An unreasonable 

impact from a stream withdrawal would be the depletion of 

critical habitat of a high-value surface-water resource during 

critical flow periods (summer low-flow conditions). Maryland 

water resource managers need new and more efficient tools to 

apply the best available scientific knowledge to the fractured 

rock region. Currently (2012), water-appropriation applications are evaluated by professional staff using analyses and 

data from published reports and other agency resources. These 

reports are often in a hard-copy format and contain detailed 

information on well locations, stream impacts from withdrawals, streamflow statistics, aquifer test results, and geologic 

descriptions. 

Need for New Work

To efficiently evaluate water-allocation requests, information on water use, groundwater levels, and the location of 

monitoring sites is needed in a timely fashion. These data currently reside in multiple State and Federal databases and need 

to be compiled for use in both management and research applications. Water resource managers have expressed the need for 

a computerized system that will allow them to access all available data and summarize, graphically display, and visualize the 

data and interpretive information for specific areas of interest. 

Water Supply Program staff need Geographic Information 

Systems (GISs) containing comprehensive groundwater, 

surface-water, and water-use information that will allow users 

full access to all pertinent aquifer and stream data. 

Existing water resources databases must be migrated, 

new data must be incorporated as they are collected, and historical data must be digitized for inclusion in a computerized 

system. Systematically organizing all relevant data will 

improve the efficiency of water allocations. A GIS framework 

for water resources (Maidment, 2002) describes a data model 

for organizing data in a GIS for surface-water resources and 

more recently, Strassberg and others (2011) presented a data 

model specifically for groundwater data. Both data models will 

be used to compile Maryland’s water resource data from multiple sources including: the USGS National Water Information 

System (NWIS), the MDE Water Supply Program’s Public 

Drinking Water Information System (PDWIS), and the 

MDDNR Maryland Biological Stream Survey (MBSS) into a 

GIS system for the fractured rock region. 

Reliable streamflow data are crucial for permit evaluators 

of surface-water and groundwater allocations in the fractured 

rock region of Maryland. Streamflow targets, such as the 

7-day, 10-year low flow (7Q10) are used by MDE when 

considering a new water allocation permit. StreamStats is a 

Web-based GIS application that was created by the USGS, in 

cooperation with Environmental Systems Research Institute, 

Inc. to provide users with access to an assortment of analytical 

tools that are useful for water-resources planning and management (Ries and others, 2008). Many statistics derived from the 

StreamStats application, including the 7Q10 flow, are used by 

the MDE Water Supply Program for water allocation permits 

using the water-balance method. However, StreamStats has 

only been implemented near the Interstate 95 corridor. An 

expansion of its geographic extent could provide the State 

with another tool to assist in water allocation permitting. 

GIS will allow integration of diverse datasets and facilitate spatial analyses that will be required to meet the needs of 

water resource managers. Many of the interpretive products 

from this assessment will be integrated into a GIS work 

platform.

Objectives and Proposed Assessment Activities

Objective A—Develop a database to assist permit managers, 

scientists, and planners with accessing and evaluating data 

related to water supply. 

• Develop a Fractured Rock Aquifer Information System 

(FR-AIS) that will provide users with access to pertinent hydrologic data in a GIS software environment. 

• Integrate water-use data into the FR-AIS.

Objective B—Develop statistical and analytical tools to assist 

water managers.

• Expand the StreamStats application to all of Maryland.

• Develop statistical and analytical models to assist MDE 

in allocating permits.
Description of Science Goals and Assessment Activities 15

Science Goal 2: Characterize Factors Affecting 

Reliable Yields of Individual Groundwater and 

Surface-Water Supplies

The sustained yields of wells in fractured rock aquifers 

can decline significantly in response to dry climatic conditions 

(Hammond, 2004). During the regional drought of 1998–2002, 

which was one of the three worst droughts on record (in 

addition to the droughts of 1930–32 and 1962–68), the major 

surface-water suppliers in the Baltimore-Washington metropolitan area were able to meet customer demand; however, 

Prettyboy Reservoir in Baltimore County was significantly 

depleted. In contrast, many of the small to medium-sized 

towns (populations less than 50,000) in the fractured rock 

region instituted voluntary or mandatory water-use restrictions 

as a result of declining well yields and reservoir storage. 

Most of the water-supply yields were substantially less than 

those estimated by hydrologists or engineers who conducted 

initial aquifer tests of the water-supply wells or evaluations of 

reservoir capacities. In the case of groundwater exploration 

programs, some were more successful than others, likely due 

to differing hydrologic factors in the areas where drilling 

occurred. Finally, there were reports of many failures of individual domestic wells of private homeowners, which required 

replacement wells to be drilled.

Need for New Work

In order to prevent well failure in the future and better 

estimate drought yields, new methods of characterization 

and analysis in fractured rock systems need to be applied and 

refined. Commonly, multidisciplinary approaches are being 

used to evaluate regional groundwater systems. The combined 

use of aquifer tests, geophysical logs, groundwater-level 

observations, and statistical and numerical models, can provide a greater understanding of a groundwater system than one 

method alone (Shapiro and others, 2007). 

Aquifer tests that run for 24 hours or longer have been 

a requirement for permit evaluation by MDE for several 

decades. MDE has compiled several hundred aquifer tests 

in the fractured rock region of Maryland. The methods used 

by MDE for evaluating aquifer tests and estimating yields of 

wells in fractured rock aquifers were developed prior to the 

start of the 1998–2002 drought, beginning in the early 1990s. 

In a study performed by MDE staff (Hammond, 2004), production data were collected from supply wells and springs during 1998–2002 and compared to original yield estimates from 

aquifer tests. The study revealed that original estimates using 

commonly applied analytical techniques consistently overestimated the yield of wells during drought conditions. A subset 

of aquifer tests was re-evaluated using a variety of analytical 

methods, including derivative analysis, and yield results more 

closely matched actual yields determined from production 

data. This highlights the importance of collecting operational 

data over a period of years, and the need to re-evaluate 

existing aquifer tests from supply wells in the fractured rock 

region of Maryland. 

Although there have been numerous studies attempting to 

define the sustainable yield of aquifers, there have been very 

few studies that address how to estimate the reliable yield of 

individual water-supply wells in fractured rock aquifers. In 

two studies conducted in similar hydrogeologic settings to 

Maryland—a carbonate aquifer in Pennsylvania (Parizek and 

Siddiqui, 1970) and a crystalline rock Piedmont aquifer in 

North Carolina (Daniel, 1989)—predicted yields significantly 

overestimated actual yields. In addition, a study in crystalline 

rocks in South Africa (van Tonder and others, 2001) provided 

well yield predictions; however, a post audit to confirm study 

predictions was not performed.

To better predict reliable yields, factors affecting well 

yields need to be determined for different hydrogeologic 

regions in Maryland. Many studies concerning factors affecting yields of wells in fractured rock aquifers depend largely 

on data collected from residential wells (Dine and others, 

1995; Mabee, 1999). The studies usually examine similar 

factors (such as well depth, diameter, casing depth, rock type, 

topographic position, and driller’s estimated yield) and often 

only provide qualitative insights. However, advances in computational ability allow for more robust spatial and statistical 

analysis. Multivariate analyses have been conducted to estimate well yield probabilities (Moore and others, 2002), and 

geostatistical methods have been used to relate well yields to 

structural controls in New Hampshire and Virginia (Drew and 

others, 1999; Drew and others, 2003; Drew and others, 2004). 

Further development of statistical and spatial analysis methods 

could lead to quantitative relations between well yields and 

hydrogeologic factors. For this comprehensive assessment, 

relevant data will be compiled and stored in the FR-AIS and 

greater emphasis will be placed on the detailed review of 

public supply wells. 

An important factor in understanding reliable yields 

of wells in fractured rock is the identification of the most 

productive water-bearing zones in a borehole. Unlike wells 

constructed in unconsolidated sediments with fully penetrating well screens, most wells in fractured rock are cased to 

competent rock with open borehole for tens to hundreds of feet 

below. Water enters the well from fractures or discrete zones 

within the geologic formation penetrated by the borehole. The 

depth of the fractures or water-bearing zones in the well bore 

can determine the reliable yield for that well. Shallow waterbearing zones may be more susceptible to decreased yields 

during drought than deeper water-bearing zones. Geophysical 

logging methods have been used to determine major flow 

zones in fractured rock wells (Paillet and Ollila, 1995; 

Williams and others, 2002). In North Carolina and Georgia, 

geophysical logging studies in the Piedmont and Blue Ridge 

Provinces were conducted (Chapman and Huffman, 2011; 

McSwain and others, 2009; Williams and others, 2005). To 

date, only a small number of supply wells have had geophysical logs collected using these methods in Maryland. 
16 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

 Surface-water systems supply most of the demand in the 

fractured rock region of Maryland and need to be considered 

in any assessment of water availability. Reliable yields of 

surface-water supplies have been determined for most of the 

major reservoirs in central and western Maryland, using flow 

mass analysis techniques that rely on estimates of inflow and 

reservoir geometry (Beard, 1966; Riggs and Hardison, 1973). 

However, the aggregate and cumulative impacts of withdrawals from reservoirs and simple intakes generally have not been 

considered when making previous water allocation decisions. 

In addition, most permits for withdrawals from existing reservoirs and many stream withdrawals were issued more than 

25 years ago, when the most common flow-by condition was 

based on the 7Q10 low-flow value, whereas subsequent standards include higher and more variable environmental flows. 

Objectives and Proposed Assessment Activities

Objective A—Evaluate factors that affect yields of public 

water supply wells.

• Collect and compile aquifer test, production, geophysical, and other appropriate geologic data for public 

supply wells.

• Re-analyze existing aquifer test data and evaluate factors that impact well yields of public water supplies 

both individually and spatially.

• Evaluate numerical and analytical methods to estimate 

drought yields of individual wells in each hydrogeologic setting.

Objective B—Evaluate factors that impact yields of domestic 

wells.

• Delineate areas with similar hydrogeologic characteristics that may affect well yield.

• Identify factors including rock type, degree of fracturing, correlation with surface geologic structural 

controls, and other factors and their relative influence 

on domestic well yields.

Objective C—Improve methods for estimating yields of 

surface-water reservoirs and simple intakes.

• Estimate reliable yields of surface-water reservoirs and 

simple intakes.

Science Goal 3: Investigate Impacts on Other 

Water Withdrawal Users Caused by SurfaceWater and Groundwater Withdrawals 

Determining the area of influence from withdrawal wells 

completed in fractured rock aquifers is difficult because the 

hydrogeologic characteristics of fractured rocks are complex 

(Barton and others, 2003). In Maryland, aquifer tests of 

wells in fractured rock are used to evaluate the impacts of 

groundwater withdrawals on nearby water supplies. MDE 

requires monitoring programs during aquifer tests; however, 

observation wells are not always available to account for 

anisotropic and heterogeneous water-level responses that commonly occur during aquifer tests in fractured rock aquifers. 

This can lead to substantial uncertainty in the assessment of 

potential impacts on other users. To avoid impacts to streams, 

MDE assigns minimum flow conditions to surface-water 

permits and has recently considered requiring biological 

assessments, on a case-by-case basis, to determine impacts 

on aquatic habitat caused by groundwater and surface-water 

withdrawals.

Need for New Work 

Data from the monitoring programs required by MDE 

indicate that there can be substantial errors when estimating 

drawdown in nearby wells caused by groundwater withdrawals. To date, most of the errors involved drawdown that was 

underestimated, primarily because of the unreliability of data 

taken from open-borehole observation wells. In several cases, 

there was no measured drawdown in nearby observation wells 

when pumping a proposed production well; however, followup studies or post-audits indicated that there was severe interference between the wells.

The Water Supply Program uses relatively simple analytical techniques to define an effective well radius (equal to 

one-quarter fracture length determined by iteratively adjusting 

the storage coefficient and radius terms in the Theis equation 

until calculated and observed drawdown in the pumping well 

match) instead of the actual well radius to calculate drawdown 

in pumping wells. The heterogeneity of an aquifer is estimated 

by assigning higher storage and transmissivity values to the 

weathered zone than to the bedrock part of the aquifer. The 

calculated fracture length and estimated hydraulic parameters are then used to model drawdown in monitoring wells 

to predict impacts on nearby wells belonging to other users. 

Although this improves the estimates of drawdown made with 

commonly used methods that were derived for porous media 

systems (Theis, 1935; Cooper and Jacob, 1946), there are still 

substantial errors (approximately 50–100 percent) associated 

with the technique. These methods were developed in lieu 

of numerical models, since reliable numerical analyses often 

require more data than is commonly available at most sites. A 

number of studies, including those by van Tonder and others 

(2001), Rushton and Chan (1976) and Tiedeman and Hsieh 

(2001), have utilized numerical analyses to define groundwater flow in fractured rock aquifers. Over the past two decades, 

MDE has collected aquifer test and groundwater-level-monitoring data from several dozen sites throughout the study area 

that can be used to improve both numerical and analytical 

methods for evaluating potential impacts to other groundwater 

users. 

Reasonable estimates of interference between wells can 

be made based on a good deal of experience and knowledge 

of local hydrogeology. Even the best projections can have 
Description of Science Goals and Assessment Activities 17

substantial errors, but the most reliable method for demonstrating the degree of interference between wells has been 

consistent monitoring that has included periods of drought.

In Pennsylvania, where hydrogeologic regions are 

similar to Maryland, a multidisciplinary approach (aquifer 

test analysis, geophysical logging, water-level observations, 

and groundwater-flow modeling) was developed to delineate 

the contributing area to wells in crystalline rocks (Barton and 

others, 2000) and siliciclastic rocks (Barton and others, 2003). 

In Massachusetts, geologic mapping, borehole geophysics, 

aquifer tests, and numerical models were used to delineate 

the contributing areas to public supply wells completed in 

fractured rock (Lyford and others, 2003). In Connecticut, 

groundwater-flow models were used to determine sourcewater areas for bedrock wells at different topographic positions with varying surficial aquifer thickness (Starn and Stone, 

2005). MDE requires that an inventory be completed to identify nearby water supplies and determine which ones should 

be monitored during aquifer tests. The radial distances from 

a proposed production well within which inventories have to 

be completed have been based on case studies conducted by 

MDE over the past 20 years: 1,500 ft for crystalline rocks; 

2,000 ft for carbonate rocks; and 3,000 ft for siliciclastic rocks 

(though changes in groundwater levels have occurred at more 

than 5,000 ft). Using other methods in addition to aquifer tests 

and water-level observations can help to determine whether 

the existing radial distances are sufficient to identify potential 

impacts on other water users. 

For surface waters, low-flow releases or flow-bys are 

used to protect downstream users from impacts caused by 

upstream surface-water withdrawals. For low-flow analyses, a 

USGS continuous-record streamgage applicable to the project 

site is selected, on the basis of similarity of lithology and climate, period of record, and lack of impacts on the streamgage 

by upstream regulation. Although the best professional judgment can lead to acceptable streamgage selection for this 

analysis, additional statistical approaches would improve the 

selection of the best-correlated available streamgage record. 

A flow duration curve is then constructed from the selected 

streamgage data. Seasonal flow-bys are then calculated from 

the monthly 85-percent exceedance values. This approach is 

referred to as the Maryland Method. For permits issued prior 

to adoption of the present criteria and agricultural uses, the 

7Q10 value was commonly used to determine flow-bys.

To determine if currently used methods are sufficient to 

avoid adverse impacts on other water users, case studies using 

a multidisciplinary approach including numerical models are 

needed. As previously noted, the data required for numerical 

models are often not available, but with the development of 

several Research Watersheds, sufficient data will be available 

to calibrate numerical models and test adverse impact scenarios. The Research Watersheds will include groundwater 

observation wells and streamgages; aquifer tests and geophysical logging will be performed to characterize each setting. 

These Research Watersheds will integrate geologic, hydrologic, and biological data to examine processes and impacts. 

Models with information from these watersheds can be scaled 

to perform case studies and used to evaluate drought scenarios and potential associated impacts. Analytical methods 

to determine the distance of potential impacts from groundwater withdrawals, the depth of groundwater-flow systems, 

and the water balance method currently used by MDE can all 

be assessed with Research Watershed models. Supplemental 

work, such as groundwater sampling for environmental tracers, can improve our ability to model these complex systems 

(Cook and Herczeg, 2000; Cook and others, 2005; Cook and 

others, 1996). Groundwater-flow models alone may not be sufficient to characterize Research Watersheds and evaluate current water balance methods. Groundwater systems in fractured 

rock settings interact more readily with streams and climate 

than the confined aquifers in Coastal Plain settings. Recent 

developments in coupled surface- and groundwater modeling 

such as GSFLOW (Markstrom and others, 2008) allow for 

more realistic representations of the hydrologic system than 

groundwater-flow models alone. In addition to streamflow and 

groundwater levels, additional data including air temperature, 

precipitation, estimated solar radiation, and land-surface characteristics are needed. Contributions of groundwater to streamflow, and potential impacts that groundwater withdrawals may 

have on streamflow can also be investigated with numerical 

models of selected watersheds. 

Objectives and Proposed Assessment Activities

Objective A—Identify and assess the influence of factors that 

affect the impact of withdrawals on other water users.

• Select Research Watersheds. 

• Install field monitoring wells and streamgages.

• Collect and compile data needed to build surfacewater/groundwater models.

• Develop coupled surface-water/groundwater models 

for selected watersheds.

• Evaluate the relation of groundwater withdrawals to 

potential impacts on streamflow. 

• Analyze environmental tracers from samples in 

Research Watersheds to characterize groundwater-flow 

systems.

• Utilize coupled surface-water/groundwater models to 

investigate the impact on water resources from projected climate change impacts, such as more frequent 

or more severe droughts, and more frequent extreme 

storms.

Objective B—Evaluate methods for determining impacts of 

withdrawals on other water users.

• Use numerical and analytical models to test effective 

radii for aquifer tests in different hydrogeologic 

settings.
18 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

• Evaluate current water balance methods using coupled 

surface-water/groundwater models in selected watersheds.

Science Goal 4: Assess the Role of Streamflow 

and Water Withdrawals on the Ecological 

Integrity of Maryland’s Streams 

It is fundamental to the sustainability of water resources 

in the fractured rock region of Maryland to gain an improved 

understanding of the potential impacts of water withdrawals 

on the ecology of streams (Wolman, 2008). MDE’s Water 

Supply Program makes water resource permitting decisions 

with the goal of ensuring that no unreasonable impacts are 

made on the State’s resources or the ecological health of nontidal streams. Streams in poor ecological condition are listed 

on Maryland’s list of impaired waters and require a restoration 

plan. According to Maryland’s anti-degradation regulation, 

high quality Tier II waters (designated based on ecological 

condition) are afforded special protection. Regulations also 

afford special protection to natural trout waters (designated as 

Use Class III), recreational trout waters (Use-IV), public water 

supplies (Use I-P, III-P, and IV-P), and streams with rare, 

threatened, or endangered State species. Although biological 

inventories and streamflow records have been collected in 

Maryland for many years, the relations between them are not 

well understood. Obtaining a better scientific understanding 

of the relation between water withdrawals and the ecological 

health of streams will aid MDE in achieving its objectives of 

protecting aquatic ecosystems.

In 2011, MDE and MANTA developed seven management questions which will guide hydroecological integrity 

assessment activities: 

1.Which Maryland stream species (including rare, threatened, endangered, game, invasive, and migratory species) and ecosystems are most/least sensitive to flow 

alterations? Are there specific biological indicators of 

water withdrawal?

2.Which aspects of flow regimes have the most/least 

influence on stream species and ecosystems? How do 

alterations in flow affect species and ecosystems? Can 

the specific mechanisms responsible for flow alterations be determined and described?

3.Which components of flow-ecology relations are most/

least affected by surface (intake and impoundment) 

and groundwater withdrawals?

4.What relations between surface-water and groundwater 

withdrawals and stream ecological integrity can be 

established? 

5. For past and future water-uses, how have/might 

surface-water and groundwater withdrawals impact 

individual species and ecosystems (including possible 

scenarios such as: flooding, drought, increasing population, cumulative impacts, climate change, confounding factors, and so forth)? 

6.What spatial and seasonal aspects of flow need to 

be maintained for specific streams, including under 

drought conditions to ensure the protection of stream 

species and ecosystems? 

7.Is additional research/monitoring needed? 

Need for New Work

In order to address these management questions, an 

investigation to assess the relations among water withdrawals, 

flow alteration, and aquatic biota in Maryland is needed. Water 

quality and quantity are vitally important to aquatic biota 

(such as stream-dependent fish, benthic macroinvertebrates, 

freshwater mussels, crayfish, amphibians, and reptiles). Flow 

is strongly related to many critical physiochemical components of streams, such as water temperature, dissolved oxygen, 

channel morphology, and habitat. Many recent studies indicate 

that streamflow is a “master variable,” limiting the distribution, abundance, and diversity of many aquatic plant and animal species, and thus the overall ecological integrity of stream 

ecosystems (Poff and others, 1997; Kennen and Ayers, 2002; 

Olden and Poff, 2003; Richter and others, 2003; Carlisle and 

others, 2010). The alteration of flowing waterways has had 

dire consequences on aquatic biota that have been well documented (Allan and Flecker, 1993). To avoid adverse impacts, 

the range of natural flows found in Maryland’s streams must 

be identified and the influence these natural flows have on 

aquatic biota must be understood (fig. 5). With an adequate 

understanding of natural flow regimes, the potential influences 

of altered flow regimes that could result from water withdrawals can subsequently be investigated. Detailed streamflow data 

are available from over 100 streamgages in Maryland and can 

be estimated for ungaged sites. In addition, extensive biological and physiochemical stream information has been collected 

from more than 3,700 sites since 1995. 

The Hydroecological Integrity Assessment Process (HIP) 

(Henriksen and others, 2006; Kennen and others, 2007) and 

the Ecological Limits of Hydrologic Alteration (ELOHA) 

(Arthington and others, 2006; Aspe and others, 2008; The 

Nature Conservancy, 2008) are two relatively new procedures 

that correlate large amounts of hydrological and ecological 

data as a means of defining stream types within a region and 

determining flows needed to sustain riverine ecosystems. 

Both processes are based largely on the methods described by 

(Olden and Poff, 2003).

To estimate a broader set of streamflow statistics, such 

as those required for HIP and ELOHA, estimates of daily 

time-series of streamflow are needed. The USGS has developed regression equations for estimating various streamflow 

statistics for every state in the Nation, and methods for 

developing such equations are well documented in USGS 
Description of Science Goals and Assessment Activities 19

publications, such as Ries and Dillow (2006). Analyses to 

develop these conventional equations require computation 

of the streamflow statistic of interest and measurement of 

various physical and climatic characteristics of the drainage 

basins for a group of streamgages within a region with flows 

that are minimally impacted by human activities. A regression 

analysis to determine the best equation for use in estimating 

the flow statistic for ungaged sites in the region must then be 

performed. Statistical methods for estimating daily time series 

at ungaged sites are have been effective in southern New 

England (Fennessey, 1994; Waldron and Archfield, 2006). 

These methods have been refined, modified, and applied to 

additional sites in New England and Pennsylvania (Archfield 

and others, 2010; Archfield, 2009; Archfield and Vogel, 2010; 

Marla Stuckey, U.S. Geological Survey, oral commun., 2012).

MDE’s Water Supply Program has compiled a database 

that tracks water withdrawal permit information from over 600 

(more than 200 surface-water and 400 groundwater) fractured 

rock water withdrawal locations. This database includes the 

monthly permitted and reported amounts of water, and each 

permit can be linked to a specific watershed. These data 

provide valuable information for determining where water 

withdrawal impacts on aquatic biota are most likely to occur. 

Through the MBSS, MANTA has compiled an extensive 

database of stream biological data for nontidal streams 

(Heimbach and others, 1999). Examples of the biological 

data collected by the MBSS since 1995 include fish, benthic 

macroinvertebrates, freshwater mussels, crayfishes, amphibians, reptiles, physical habitat, water quality, riparian 

characteristics, and catchment land use. Fish and Benthic 

Macroinvertebrate Indices of Biotic Integrity (FIBI and BIBI) 

were developed for use in Maryland streams using MBSS data 

(Southerland and others, 2007). MANTA also annually monitors 27 high quality streams (“Sentinel” sites) across the State 

(fig. 7). Data collected at these sites are used to assess natural 

variability in stream conditions. MBSS data have been widely 

used to investigate ecological correlations with water quality, 

physical habitat, and land use (Hilderbrand and others, 2010; 

Morgan and Cushman, 2005; Morgan and others, 2007; Pinder 

and Morgan, 1995; Stranko and others, 2008; Utz and others, 

2009) and are used by MDE and MDDNR to establish regulations that restore and protect streams (such as impaired waters, 

high quality waters, designated use, and endangered species). 

However, this comprehensive assessment represents the first 

time these data will be used to investigate potential impacts on 

biology from water withdrawal or other flow alterations. Sites 

determined to have the highest probability of impact from 

water withdrawal will be monitored annually for biological 

condition. Data from these sites will be compared with annually collected data from MBSS Sentinel Sites to determine if 

temporal changes in stream conditions at sites with substantial 

withdrawal significantly differ from conditions at reference 

sites. 

Estimates of streamflow statistics that describe the 

magnitude, frequency, duration, timing, and rate of change 

of streamflow at currently ungaged streams including MBSS 

sites, as well as water-use information, would allow a statistical analysis that could define relations among biotic integrity, 

streamflow, water use, water quality, and watershed physical 

characteristics. Recently developed methods to estimate daily 

flow at ungaged streams (Archfield and others, 2010) will 

be implemented for streams in Maryland. Before estimates 

of daily flow can be made, prior work identifying index 

streamgages (Armstrong and others, 2008; Falcone and others, 2010) must first be completed. Other streamflow modeling efforts with some common geographic area, including 

those by the Interstate Commission on the Potomac River 

Basin (ICPRB) and The Nature Conservancy for the Middle 

Potomac Watershed will be assessed for their applicability for 

use as a permitting tool for MDE. Results from the overall 

hydroecological assessment will be used to implement 

scientifically sound methods for planning and evaluating 

water withdrawal applications, consider potential effects of 

withdrawals to streamflow and ecological integrity, and avoid 

potential water-quality and biological degradation.

Objectives and Proposed Assessment Activities

Objective A—Evaluate flow regimes.

• Determine existing index streamgages.

• Refine and implement statistical methods for estimating daily streamflow at ungaged streams. 

• Derive required streamflow statistics from estimated 

daily time series of streamflow at ungaged sites.

Objective B—Assess the relation of changes in flow regimes 

to stream ecological health.

• Perform an extensive literature review to assess previously documented results and trends.

• Evaluate the health and streamflow needs of aquatic 

species and their habitats using information from the 

MBSS, the MDE Water Supply Program, and USGS 

streamgage network data.

• Design and implement field studies to investigate critical and potentially complex factors that impact aquatic 

biota (such as water withdrawal, thermal regimes, 

natural flow regimes, water quality, and land-use 

alteration) in Research Watersheds.

Objective C—Develop guidelines/recommendations and (or) 

tools for water managers. 

• Determine whether existing models or other watershed 

assessment models can be adapted for use as MDE 

planning and permitting tools.

• Evaluate current MDE flow-by methodologies; develop 

post-decision permit monitoring protocols.

• Update the FR-AIS with applicable data resulting from 

this assessment.

• Publish reports with assessment results.
20 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Figure 7. Location of the Maryland Biological Stream Survey Sentinel sites.

Science Goal 5: Improve Understanding of 

the Distribution of Water-Quality Conditions in 

Fractured Rock Aquifers 

In the fractured rock region of Maryland, untreated 

groundwater from individual domestic wells is a significant 

source of potable water for much of the population (table 2). 

Water-quality constituents of concern for domestic groundwater supply vary by rock type and land use. Naturally occurring 

constituents such as radionuclides are more commonly found 

at higher concentrations in the felsic igneous and metamorphic rocks of the Piedmont and Blue Ridge Provinces. Shale 

in both the Valley and Ridge and Mesozoic basin with felsic 

minerals in the source rocks also tends to have higher concentrations of radionuclides including radon, radium, and 

uranium (Johnson and others, 2011) whereas sandstone and 

carbonate rocks tend to have lower concentrations of radionuclides. Radium and other radionuclides have been detected 

in isolated locations of the fractured rock region of Maryland, 

but their occurrence and distribution are not well understood. 

Arsenic has been detected in wells drilled in the siliciclastic 

rocks of Garrett County (David Bolton, Maryland Geological 

Survey, written commun., 2011), where domestic wells are 

the major source of drinking water. Nitrate and fecal-indicator 

bacteria are also groundwater-quality concerns. Groundwater 

samples from both the Potomac and Lower Susquehanna 

River Basins, which include wells in the fractured rock 

region of Maryland in the Valley and Ridge, Blue Ridge, 

and Piedmont Physiographic Provinces, have contained 

nitrate concentrations near or above 10 milligrams per liter 

(mg/L), the U.S. Environmental Protection Agency (USEPA) 

Maximum Contaminant Level (MCL), with the highest mean 

nitrate concentrations in carbonate aquifers of the Piedmont 

aquifer system (Lindsey and others, 2006). Because of the 

potential for rapid infiltration of runoff into the groundwater 

system, carbonate aquifers are susceptible to other surface 

contaminants including fecal-indicator bacteria. In the Valley 

and Ridge aquifers, the highest colony count of fecal-indicator 

bacteria tend to be in samples from wells in agricultural areas 

overlying carbonate rock aquifers (Johnson and others, 2011). 
Description of Science Goals and Assessment Activities 21

Table 2. Percent of population served by domestic 

groundwater wells for each county in the fractured-rock region 

of Maryland, 2005.

County Percent of population served by 

domestic groundwater wells1

Garrett 72

Cecil 59

Carroll 51

Frederick 38

Washington 38

Harford 31

Howard 18

Allegany 14

Baltimore 8

Montgomery 2

1

 Susan Hutson, U.S. Geological Survey, written commun., 2012

Need for New Work

Groundwater-quality data have been collected across the 

fractured rock region of Maryland by many studies at various 

scales. As part of the National Water-Quality Assessment 

(NAWQA) Program, the USGS has collected and analyzed 

water-quality data across the fractured rock region in the 

Potomac River Basin (Ator and Denis, 1997; Blomquist and 

others, 1996; Ferrari and Ator, 1995; Gerhart and Brakebill, 

1998) and the Lower Susquehanna River Basin (Lindsey and 

others, 1998). MGS established a statewide groundwater-quality network beginning in 1989 (Bolton, 1996). Hydrogeologic 

investigations of the carbonate valleys and the Triassic rocks 

of Maryland (Nutter, 1973, 1975) reported groundwater-quality results but focused more on groundwater availability than 

water quality. County-scale studies of water resources (Dine 

and others, 1995; Dine and others, 1985) and water quality 

(Bolton, 1998) have compiled a broad suite of water-quality 

data, including major ions, nutrients, and metals, and County 

health departments also require that groundwater-quality 

samples be collected for selected constituents. Additionally, 

several unpublished studies of specific groundwater-quality 

issues have been conducted by MGS (David Bolton, Maryland 

Geological Survey, written commun., 2011). 

Substantial amounts of groundwater-quality data from 

fractured rock aquifers in Maryland have been collected and 

analyzed. Methods for sample collection, laboratory analysis, 

and data storage vary and are dependent on the goals of the 

individual study in which they were obtained. With existing 

data from multiple studies of various scales, improved 

understanding of groundwater-quality patterns can likely be 

accomplished by summarizing and categorizing existing data 

to characterize the distribution of groundwater-quality patterns 

across the fractured rock region of Maryland that may affect 

water-use decisions. 

In addition to the interpretation of existing data, there 

may be a need to enhance the existing groundwater-quality 

network. New data collection for constituents such as methane that are associated with hydrocarbon extractions may be 

warranted in shallow aquifers that overlie coal deposits and 

the Marcellus Shale Formation. Additional sampling may be 

required to determine the age of groundwater to improve the 

conceptual frameworks of groundwater chemistry for selected 

aquifers in the Research Watershed studies. Groundwater 

in some hydrogeologic settings has not been adequately 

evaluated for many constituents that have USEPA Primary 

Drinking-Water Standards. 

Individual groundwater-quality studies involving extensive collection and analysis of groundwater samples may be 

beyond the scope of this assessment. However, compiling 

available groundwater-quality information from local and 

national sources will assist in future investigations of groundwater quality in the fractured rock region of Maryland. 

Objectives and Proposed Assessment Activities

Objective A—Make groundwater-quality data more accessible 

to researchers and resource managers.

• Compile available groundwater-quality information 

from multiple sources into the FR-AIS.

• Prepare selected groundwater-quality data analysis 

products for integration into management tools (GIS) 

as needed. 

Objective B—Evaluate and improve the adequacy of waterquality data.

• Enhance water-quality networks in selected locations to 

track changes in water quality with respect to USEPA 

Primary or Secondary MCLs. 

• Evaluate existing groundwater-quality data to identify 

areas that have not been fully evaluated with respect to 

USEPA Primary Drinking-Water Standards and other 

criteria.

• Establish hydrologic and water-quality monitoring sites 

to fill in data gaps. 

• Establish monitoring sites to use as a baseline to determine potential impacts of future activity, such as gas 

extraction from the Marcellus Shale.
22 A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland

Assessment Implementation

The science goals for this comprehensive assessment 

will be addressed throughout the long-term, multi-year 

study. Whereas many tasks throughout the assessment can be 

performed simultaneously because of the assessment’s broad 

nature, some tasks provide the foundation or tools for subsequent tasks and others are simply precursory. In order to take 

full advantage of available resources, the development of an 

overall work plan is crucial in identifying the dependency of 

individual tasks and to lay out the critical path of the project. 

The assessment will begin by building partnerships with 

Federal, State, and local agencies, and assembling a multidisciplinary team of scientists and regulators to perform the 

comprehensive assessment. Information gaps will be identified 

and detailed work plans will be developed to address those 

gaps and address each science goal. The initial development 

of the FR-AIS is one of the principal efforts required to begin 

the assessment. Data compilation from various sources will be 

incorporated into the FR-AIS. Along with FR-AIS development, hydrogeologic regions for the fractured rock region will 

be classified, low-flow frequency statistics for streams will be 

updated, the StreamStats web application will be expanded 

to encompass the entire State, geophysical logging data from 

production wells will be collected, and Research Watersheds 

will be identified. 

Once these activities are complete, significant effort will 

be placed on activities including the analysis of potential factors affecting groundwater availability in different hydrogeological regions, the refinement of methods used to estimate the 

daily streamflow time series from which relevant streamflow 

statistics can be derived, monitoring Research Watersheds, and 

studying the potential relation between hydrology and aquatic 

habitats. 

Compared to the Maryland Coastal Plain, the hydrogeological characteristics of the fractured rock region are more 

heterogeneous, and this makes simulation of the groundwaterflow system a more challenging task. With adequate hydrologic data at appropriate scales, groundwater models (or 

coupled surface-water and groundwater models) of Research 

Watersheds will allow the evaluation of conceptual models 

(Weathered Zone, Transition Zone, Fractured Bedrock), 

assumptions about recharge, base flow and groundwater interactions with streams, as well as hypotheses concerning the 

potential impacts due to climate change. 

Throughout the assessment, the science team comprised 

of personnel from MDE, MGS, MANTA, and USGS, will continue to seek opportunities to apply various scientific findings 

by developing new tools, improving existing methodologies, 

developing models and simulations, and providing education 

and outreach. The FR-AIS will house data such as aquifer-test 

data, well-construction information, geophysical logs, and 

many other spatial data as they become available. Data from 

the FR-AIS will allow the development of tools to interpret 

and display results for desktop and Web-based applications. 

Products and Benefits

Implementation of the Maryland Fractured Rock Study 

is designed to provide an enhanced understanding of the 

fractured rock aquifer systems and the response of stream 

ecosystems to water withdrawals in Maryland. Additionally, 

the assessment aims to provide information related to the 

integrated nature of climate, ecosystems, and water resources 

in the region. The broad scope of the assessment necessitates 

expertise from multiple disciplines allowing for a unique 

opportunity to develop an interdisciplinary team of water 

resource managers, ecologists, geologists, and hydrologists. 

A number of important products and tools resulting from 

this assessment will benefit water resource managers, decision 

makers, planners, policy makers, stakeholders, and scientists 

including:

• A GIS-based Aquifer Information System specific to 

the fractured rock regions of Maryland FR-AIS to 

assist MDE Water Supply Program decision making 

regarding future water allocations.

• An improved understanding of factors affecting reliable 

yields in individual water supply wells.

• Estimates of mean daily flow at ungaged streams.

• An improved understanding of the distribution of water 

quality, particularly with regard to USEPA drinkingwater standards.

• An improved understanding of the impacts of withdrawals on other water withdrawal users.

• A better understanding of stream ecosystem thresholds.

• A better understanding of hydrologic response to climate change. 

• Improved communication between Federal, State and 

local water resource managers.

Interagency Coordination and Outreach

The diverse nature of the assessment will require the participation of scientists and managers with different technical 

backgrounds and presents an excellent opportunity to advance 

the current knowledge of Maryland’s water resources and 

ecology in an interdisciplinary fashion. This will in turn lead 

to improved management of water resources north and west of 

the Fall Line in Maryland. To take advantage of this opportunity, a significant effort will be placed on interagency coordination. Coordination between MDE, MGS, MANTA, and 

the USGS has taken place throughout the development of this 

Science Plan and will continue as work plans are developed. 

Work teams have been established for developing new tools, 

planning and performing the hydroecological analysis, and 
References Cited 23

assessing reliable well yields. Continued coordination is necessary to establish the details of future assessment activities. 

To reach a larger audience, Web sites will be developed 

and made publicly accessible. Other planned outreach endeavors include presentations and posters at local and regional 

technical meetings to disseminate interim findings, describe 

the assessment plans, and solicit feedback from stakeholders. 

It is anticipated that a number of scientific reports and 

journal articles will be published by coordinating agencies. 

Anticipated reports will be written on topics including (1) the 

hydrogeologic regions west of the Fall Line, (2) the estimation 

of daily streamflow at ungaged sites, (3) factors affecting 

the reliable yield of water supply wells, and (4) the relations 

between streamflow and stream ecology.

Concluding Remarks

The fractured rock region in Maryland includes a significant variety of topographic, hydrogeologic and climatic 

settings that impact the quantity of available water, the 

distribution of streamflow, water quality, the abundance and 

health of aquatic organisms, and the safety of water for human 

consumption. Human activities affect the need for water, alter 

the hydrologic cycle, and impact water quality, which in turn 

affects the abundance and health of aquatic organisms and the 

safety of water for human consumption. Activities conducted 

during this comprehensive assessment will be designed to 

acquire and analyze sufficient data to better understand these 

relations in order to develop improved predictive tools to help 

water resource managers, water suppliers, policy makers, scientists, planners and others address the following questions: 

• What are the flow characteristics at locations without 

streamgages? 

• What are the groundwater recharge rates at any location? 

• How do groundwater withdrawals impact streamflows?

• What are the best methods for estimating the reliable 

yields of water supplies? 

• What are favorable locations to explore for additional 

groundwater supplies that minimize impacts, ensure 

sustainability, and increase the potential for highyielding wells? 

• What are the streamflow characteristics that need to be 

preserved to ensure a healthy aquatic ecosystem? 

• What methods can best predict if a proposed use will 

negatively impact other water withdrawal users? 

• What are the cumulative impacts of multiple groundwater and surface-water withdrawals on streamflow in 

a particular watershed? 

• In what areas are domestic wells at greater risk to naturally occurring contaminants? 

• In what areas are certain activities more likely to negatively impact water quality?

• What are the impacts that may occur due to the implementation of revised reservoir release rules, flow-by 

requirements, or water balance criteria? 

A better understanding of these issues will help the Maryland 

water resource community address both anticipated and unexpected current and future water resource challenges. 

Acknowledgments

The authors wish to thank John Grace, Lyn Poorman, and 

John Smith for their contributions to this report with a special 

thanks to Stacy Boyles and Jason Zhao, fractured rock study 

project managers (Maryland Department of the Environment). 

Thanks are also extended to David Bolton (Maryland 

Geological Survey), and James Gerhart (formerly of the U.S. 

Geological Survey) for suggestions on an early draft of this 

report. Additional thanks are extended to Matthew Pajerowski, 

Kernell Ries, and Susan Hutson (U.S. Geological Survey) for 

providing background and supporting information, and finally 

to Melinda Chapman and Leslie DeSimone (U.S. Geological 

Survey) for thorough peer review that substantially improved 

the report. 

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Fleming, B.J., and others—A Science Plan for a Comprehensive Assessment of Water Supply in the Region Underlain by Fractured Rock in Maryland—Scientific Investigations Report 2012–5160

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