Maryland Water Resources - 28-may-2004 - Southern Maryland by uoi11893

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									APPENDIX E–SOUTHERN MARYLAND PILOT STUDY

Introduction

The counties of Southern Maryland have experienced significant population growth over
the last thirty years and the Maryland Department of Planning’s (MDP) population
projections show that the region’s growth will continue over the next thirty years
(Figure E-1). The Southern Maryland counties were chosen as a pilot study area in an
effort to study the relationship between demand for water and the available supply in a
rapidly growing region and because the region is representative of the Coastal Plain
physiographic province of the State. Coastal Plain hydrogeology shapes the region and
as a result the population relies almost exclusively on ground water for water supply.
The exceptions are in Prince George’s County where the large majority of the population
is served by the Washington Suburban Sanitary Commission (WSSC) water utility and a
small portion of northern Anne Arundel County where water is provided by Baltimore
City. Residents of southern and eastern Prince George’s County outside of WSSC’s
service area, and the majority of Anne Arundel County residents remain dependent on
ground water for water supply. Residents of Calvert, Charles, and St. Mary’s counties
rely solely on ground water.

In Southern Maryland, the predominant source of potable water is ground water. The use
of the Chesapeake Bay or the large tidal rivers is not feasible due to their brackish nature.
The exception is for thermoelectric and nuclear power generation, which use large
quantities of brackish water for once-through cooling. Because the surficial aquifer does
not provide an adequate supply for large users, the large majority of ground water use in
the region is from the major confined aquifers.


                                        ,  000
                                       1000,


                                          000
                                       900,
                                                             2030 (Projected)
                                          000
                                       800,
                                                             2000
             Total County Population




                                           000
                                        700,


                                       600,
                                          000                1970

                                           000
                                        500,


                                          000
                                       400,


                                          000
                                       300,

                                          000
                                       200,


                                         00,
                                        1 000


                                           -

                                                  Anne     Calvert       Charles    Prince    St. Mary's
                                                 Arundel                           George's

                               Figure E-1: Population in Southern Maryland - 1970 to 2030
                               (Source of Data: Maryland Department of Planning)


                                                                     1                                     Appendix E
Conducting a water supply and demand study in this region is difficult due to the
complexity involved in predicting recharge for this type of hydrologic system. The basic
principles of mass balance apply, i.e. the total water entering the system as recharge
equals the amount leaving through discharge. In the confined aquifer system, however,
ground water may travel great distances across several counties after it infiltrates in a
recharge area. While precipitation is the source of recharge to the aquifers, it does not
have an immediate effect on ground water levels due to confining layers of clay or silt
that isolate the deeper parts of the aquifers from direct infiltration. Therefore, in order to
analyze supply and demand in this complex hydrologic system, it is essential to have
adequate data on the aquifer properties as well as water level measurements distributed
over space and time. The approach taken in this pilot study is to discuss what is known
and documented about the five major water supply aquifers and evaluate previous studies
that have predicted their water supply potential.


Water Supply in Southern Maryland - Occurrence, Distribution, and Properties of
the Five Major Aquifers

The geology of the Southern Maryland region is made up of layers of unconsolidated
sediments of sand, clay, silt, and gravel, which gradually become deeper and thicker to
the southeast. The sand and gravel layers form water-bearing aquifers, and the silt and
clay deposits form confining layers. Major aquifers in the region include (from shallow
to deep) the Piney Point, Aquia, Magothy, Upper Patapsco, Lower Patapsco, and
Patuxent aquifers (Figure E-2). Sediment layers are underlain by hard bedrock, which is
2,515 feet below sea level at Lexington Park in southern St. Mary’s County. The
surficial aquifer is used for existing domestic supplies in some locations, but it is not a
major source and new users are likely to obtain their water supplies from the confined
aquifers.




          Figure E-2. Generalized cross-section of Southern Maryland, showing the
          major aquifers.


                                              2                                  Appendix E
Description and Extent of the Aquifers

The area where the aquifers are exposed at the land surface is known as the outcrop area .
The five aquifers outcrop in northeast trending bands of varying widths across the central
portions of Prince George’s and Anne Arundel Counties, and a small portion of
northeastern Charles County. The aquifers extend in the subsurface through the entire
five-county region of Southern Maryland, however not every aquifer is present in every
location (Figure E-3). The depths to the top of the confined aquifers range from as little
as 50 feet below mean sea level (bmsl) near their outcrop areas up to 1,800 feet bmsl
where the Patuxent aquifer is mapped at the southern tip of Prince George’s county.
Aquifer thickness also varies with specific location, but thickness generally increases
with depth in a southeasterly direction. Published values for aquifer thickness along with
other aquifer properties are given in Table E-1. Each of the aquifers is separated from
overlying or underlying aquifers by a confining unit that, while less permeable, still
allows exchange of ground water through leakage. These confining units are, in general,
laterally continuous. However, where they are non-continuous the aquifers may interact
hydraulically.

Aquifer Properties

Transmissivity is a measure of an aquifer’s ability to produce water and is directly related
to the aquifer’s physical properties, namely its hydraulic conductivity and thickness.
Transmissivity is usually well correlated with the thickness of the aquifer and this holds
true for most of the aquifers in Southern Maryland. An exception is the Aquia aquifer, in
which the transmissivity is more closely related to the composition and percent of clay,
which varies by location. Transmissivity values are determined from localized pump
tests that provide a value in a specific location, but these values can be extrapolated to a
larger area where the aquifer properties are similar. Transmissivity values for each of the
five aquifers have been published throughout the five-county region and the ranges are
given in Table E-1. In general, the locations where large users utilize the aquifer are also
the locations where transmissivity values are highest.

Aquifer Modeling

The aquifers in Southern Maryland have been modeled to predict future ground water
conditions in several reports, the most recent of which contain projected demands up to
the year 2025 (Fleck and Wilson, 1990, Achmad and Hansen, 1997, Andreason 1999 and
2002). Each report assessed the water supply potential of one or more of the major
aquifers within a limited area of Southern Maryland. The aquifers were modeled to
predict their response to pumping at various rates in several locations. In some models,
the water level response in the overlying aquifer was also modeled based on pumping the
underlying aquifer. In general, the pumping scenarios fell under one of several categories
based on 1) pumping at current average and maximum permitted withdrawals into the
future, 2) increased pumping at existing wellfields using county population growth
projections, 3) increased pumping at new wellfield locations using county population
projections, and 4) increasing water use in an aquifer based on increased domestic supply
use from county population projections.


                                             3                                  Appendix E
Piney Point Aquifer                                          Aquia Aquifer
                                                                Outcrop Area
      Subsurface Extent

      (Aquifer Does Not                                         Subsurface Extent
      Outcrop at Surface)




      Magothy Aquifer                                       Patapsco Aquifer
                                                            (Upper and Lower)
             Outcrop Area

                                                                 Outcrop Area
             Subsurface Extent

                                                                 Subsurface Extent




      Patuxent Aquifer

            Outcrop Area

            Subsurface Extent

            Unexplored/Unknown




                      Figure E-3. Areal Extent of the Five Major Aquifers in Southern Maryland

                                                      4                                  Appendix E
 Table E-1. Characteristics of the Five Major Aquifers in Southern Maryland
  Aquifer         Overlying          Thickness       Transmissivity           Counties of
   Name         Confining Unit         (feet)          (feet2/day)            Primary Use
               Chesapeake                                                  St. Mary’s,
 Piney Point                       10 -130         100 - 500
               Group Clays                                                 Calvert
                                                                           Calvert,
 Aquia         Marlboro Clay      125 - 200        0 - 3,000               Anne Arundel,
                                                                           St. Mary’s
                                                                           Anne Arundel,
 Magothy       Brightseat and
                                   50 - 200        1,000 - 12,000          Prince George’s,
               Matawan Fms.
                                                                           Charles
 Patapsco
                                                   1,000 - 10,000
  Upper        Patapsco Fm.                                                Charles,
                                   50 - 250
               Clays                                                       Anne Arundel
                                                   1,000 - 5,000
  Lower
                                                                           Anne Arundel,
 Patuxent      Arundel Clay        20 – 250(?*)    200 - 8,000
                                                                           Charles
 *Total thickness of the Patuxent formation is an unknown in many areas.

In some instances, the models also provide estimates of recharge, a water budget, or a
total available supply for an aquifer based on inflow and outflow estimates. Recharge
was estimated from the outcrop areas, leakage from the adjacent confined aquifers or the
water table aquifer, and storage. Outflow was estimated from pumping wells and natural
discharge. Since the relationship between aquifer recharge and yield is complex in these
confined systems, it is difficult to estimate a total amount of available water in each
aquifer. The total available amount is likely to vary based on the location of pumping
centers and the assumptions made about recharge and storage in the aquifer. The
aquifer’s response to pumping is the best indicator of an aquifer’s reliability. Water
level declines at specific locations are affected by transmissivity, storage, recharge,
leakage, and proximity to aquifer boundaries, which impose a practical limit on aquifer
yield despite sufficient recharge rates.

Sustainable Withdrawals

Water levels in the Aquia, Magothy and Patapsco aquifers have declined over the years
due to increases in use. Water levels measured in an aquifer provide an indication of the
impacts of pumpage on the aquifer’s water-producing capabilities. Changes in water
level s also provide a measure of the reduction in recharge due to development in outcrop
areas. As pumpage from an aquifer increases, water levels will decline; the amount of
decline for a given time period is called the drawdown. Measured water levels in an
aquifer, when related to sea level and plotted on a map, show the potentiometric surface
of the aquifer, which is the level to which water in a given aquifer rises in a well that is
screened in that aquifer. The potentiometric surface is above the top of the aquifer
because the water in the aquifer is under pressure. Each aquifer has its own
potentiometric surface and these are mapped annually through cooperative programs of
the U.S. Geological Survey, Maryland Geological Survey, and participating agencies.


                                              5                                     Appendix E
The deep water levels near large pumping centers produce an inverted cone shape in the
potentiometric surface, which is referred to as a cone of depression.

The total sustainable withdrawal rate of a confined aquifer is determined by the rate at
which the aquifer is recharged and the hydraulic characteristics of the aquifer, primarily
the transmissivity. Unlike a water table aquifer, the total available water in a confined
aquifer is not necessarily the primary limiting factor for its productive use. Therefore,
management strategies have been adopted that utilize the best-known limiting factors for
water use in the confined aquifers. In a confined aquifer, it is critical that water levels do
not drop below the top of the aquifer. The current method used in regulating water use in
the confined aquifers in Maryland is the 80% Management Level. The 80% Management
Level represents 80% of the drawdown from the pre-pumping potentiometric surface to
the top of the aquifer (Figure E-4).




   Figure E-4. Schematic Illustration of the 80% Management Level in the Confined Aquifers. The
   water level rises above the top of the aquifer because it is under pressure and is lowered due to
   withdrawals from the pumping well. The water level measured at the pumping well is much lower
   than the water level in the observation well due to the formation of a cone of depression.

Water Level Trends in the Confined Aquifers

In order to assess the effects of long-term ground water use in the Southern Maryland
pilot study area, hydrograph records were examined for each aquifer. Figures E-5
through E-10 present the results of this evaluation for each of the major aquifers from
shallowest to deepest. Each hydrograph record is plotted with the pre-pumping water
level and the derived 80% management level at the given location. Monitoring wells
were chosen to represent the extent of the aquifer as well as areas where there are
significant users in the aquifer. The locations also attempt to cover a cross-sectional area
of the aquifer to capture the differences in water level trends in the areas of the aquifer
closest to the outcrop and down gradient from the outcrop (known as the updip and
downdip areas, respectively). A limitation of this analysis was the availability of pre-
pumping measurements in proximity of the monitoring well. A long-term monitoring


                                                  6                                       Appendix E
          Piney Point Monitoring Well Locations



                                                  ANNE
                                                 ARUNDEL




                               PRINCE
                              GEORGES




                                                     CALVERT


                          CHARLES
                                                                                                                Schematic Cross-Section of the Piney Point in Southern MD
                                                                     #CA Fd
                                                                     S                       51
                                                ST MARYS
                                                                    S
                                                                    # SM Df                 66

                                                                              # SM Eg
                                                                              S                    27

                                                                              S
                                                                              #
                                                          SM Fg 45                                                                            Meas ured Water Level
                                                                                                                                              Pre-Pumping Level
                                                                                                                                              80% Management Lev el

                    40
                                  W ell CA Fd 51                                                                                                   W ell S M Df 66
                      0
     50                                                                                                               50
                    -40


      0
                    -80
                                                                                                                       0
                   -120

    -50                                                                                                              -50

   -100                                                                                                             -100

   -150                                                                                                             -150

   -200                                                                                                             -200
          Sep-76

                     Sep-79

                              Sep-82

                                       Sep-85

                                                 Sep-88

                                                           Sep-91

                                                                     Sep-94

                                                                               Sep-97

                                                                                         Sep-00

                                                                                                   Sep-03




                                                                                                                            Jul-76

                                                                                                                                     Jul-79

                                                                                                                                               Jul-82

                                                                                                                                                        Jul-85

                                                                                                                                                                 Jul-88

                                                                                                                                                                           Jul-91

                                                                                                                                                                                     Jul-94

                                                                                                                                                                                               Jul-97

                                                                                                                                                                                                         Jul-00

                                                                                                                                                                                                                    Jul-03




                                 W ell S M E g 27                                                                                                 W ell S M Fg 45
     50                                                                                                               50

      0                                                                                                                 0

    -50                                                                                                              -50

   -100                                                                                                             -100

   -150                                                                                                             -150

   -200                                                                                                             -200

   -250                                                                                                             -250
                                                                                                                            May-66

                                                                                                                                     May-70

                                                                                                                                               May-74

                                                                                                                                                        May-78

                                                                                                                                                                 May-82

                                                                                                                                                                          May-86

                                                                                                                                                                                    May-90

                                                                                                                                                                                              May-94

                                                                                                                                                                                                        May-98

                                                                                                                                                                                                                  May-02
          Jul-76

                     Jul-79

                              Jul-82

                                       Jul-85

                                                 Jul-88

                                                           Jul-91

                                                                    Jul-94

                                                                              Jul-97

                                                                                        Jul-00

                                                                                                  Jul-03




Figure E-5. Hydrograph Records of USGS/MGS Monitoring Wells in the Piney Point Formation
Showing Current Water Levels, Pre-pumping conditions and the 80% Management Level.


                                                                                                            7                                                                                    Appendix E
                   Aquia Monitoring Well Locations



                                                   ANNE
                                                  ARUNDEL




                                 PRINCE
                                                           #AA Fd
                                                           S
                                GEORGES                                                                                  i
                                                                                                                 Schem atc C ross-    i     he   an      her    yl
                                                                                                                                  Secton oft A qui i Sout n M ar and
                                                                             43

                                                                S
                                                                #CA Cc                18                                                       Well AA Fd 43
                                                      CALVERT
                                                                                                                    40
                                                           #CA Db
                                                           S                 47
                          CHARLES
                                                                                                                     0

                                                 ST MARYS
                                                                        # CA Gd
                                                                        S                       6
                                                                                                                   -40


                                                                                                                   -80
                                          SM Fe 31                  S
                                                                    #
                                                                                                                  -120
                                                                                                                         Aug-79

                                                                                                                                    Aug-82

                                                                                                                                               Aug-85

                                                                                                                                                         Aug-88

                                                                                                                                                                    Aug-91

                                                                                                                                                                                Aug-94

                                                                                                                                                                                            Aug-97

                                                                                                                                                                                                         Aug-00

                                                                                                                                                                                                                       Aug-03
                               Measured Water Level
                               Pre-Pumping Level
                               80% Management Level

                                 Well CA Cc 18                                                                                                Well CA Db 47
                    40

                      0

     50             -40                                                                                              50
      0             -80                                                                                               0
     -50           -120                                                                                             -50
    -100                                                                                                           -100
    -150                                                                                                           -150
    -200                                                                                                           -200
    -250                                                                                                           -250
    -300                                                                                                           -300
                                                                                                                           Jul-79

                                                                                                                                     Jul-82

                                                                                                                                               Jul-85

                                                                                                                                                         Jul-88

                                                                                                                                                                   Jul-91

                                                                                                                                                                               Jul-94

                                                                                                                                                                                           Jul-97

                                                                                                                                                                                                       Jul-00

                                                                                                                                                                                                                     Jul-03
           Sep-58

                      Sep-63

                               Sep-68

                                        Sep-73

                                                  Sep-78

                                                           Sep-83

                                                                    Sep-88

                                                                             Sep-93

                                                                                       Sep-98

                                                                                                    Sep-03




                                  Well CA Gd 6                                                                                                Well SM Fe 31
    100                                                                                                            100

      0                                                                                                               0

   -100                                                                                                           -100

   -200                                                                                                           -200

   -300                                                                                                           -300

   -400                                                                                                           -400
                                                                                                                          Oct-78

                                                                                                                                    Oct-81

                                                                                                                                              Oct-84

                                                                                                                                                        Oct-87

                                                                                                                                                                  Oct-90

                                                                                                                                                                             Oct-93

                                                                                                                                                                                         Oct-96

                                                                                                                                                                                                     Oct-99

                                                                                                                                                                                                                  Oct-02
          Oct-49

                     Oct-55

                               Oct-61

                                        Oct-67

                                                 Oct-73

                                                           Oct-79

                                                                    Oct-85

                                                                             Oct-91

                                                                                       Oct-97

                                                                                                    Oct-03




Figure E-6. Hydrograph Records of USGS/MGS Monitoring Wells in the Aquia Formation
Showing Current Water Levels, Pre-pumping conditions and the 80% Management Level.


                                                                                                             8                                                                                       Appendix E
      Magothy Monitoring Well Locations



                                                              A NNE
                                                             ARUNDEL



                      PG De 21
                                                 S
                                                 #
                                   PRINCE
                                  GE ORGES                                         S
                                                                                   # AA Fe                47
     PG Fd 41
                                 S
                                 #                                                                                            Schematic Cross-Section of the Magothy in Southern MD

                                 S
                                 #                                   CALVERT
                                                                                                                                                                    W ell P G De 21
          CH Bf 133
                           CHARLE S                                                S
                                                                                   # CA Dc                  35                     80


                                                                                                                                   40
                                                            ST M ARYS

                                                                                                                                     0


                                                                                                                                   -40


                                                                                                                                   -80
                                 Measured Water Lev el                                                                                   A pr-56

                                                                                                                                                     A pr-61

                                                                                                                                                                A pr-66

                                                                                                                                                                           A pr-71

                                                                                                                                                                                       A pr-76

                                                                                                                                                                                                   A pr-81

                                                                                                                                                                                                                A pr-86

                                                                                                                                                                                                                               A pr-91

                                                                                                                                                                                                                                              A pr-96

                                                                                                                                                                                                                                                             A pr-01
                                 Pre-Pumping Level
                                 80% Management Lev el


                                    W ell A A Fe 47
                     40
                                                                                                                                                                    W ell P G Fd 41
                      0

    50               -40                                                                                                           100
                     -80

    -50             -120
                                                                                                                                    50

                                                                                                                                     0
   -150
                                                                                                                                   -50
   -250
                                                                                                                                  -100

   -350                                                                                                                           -150
          Nov-74

                      Nov-77

                                 Nov-80

                                              Nov-83

                                                            Nov-86

                                                                          Nov-89

                                                                                      Nov-92

                                                                                                Nov-95

                                                                                                         Nov-98

                                                                                                                   Nov-01




                                                                                                                                          A pr-67

                                                                                                                                                      A pr-71

                                                                                                                                                                 A pr-75

                                                                                                                                                                             A pr-79

                                                                                                                                                                                         A pr-83

                                                                                                                                                                                                      A pr-87

                                                                                                                                                                                                                    A pr-91

                                                                                                                                                                                                                                   A pr-95

                                                                                                                                                                                                                                                   A pr-99

                                                                                                                                                                                                                                                                   A pr-03




                                   W ell CH B f 133                                                                                                                  W ell CA Dc 35
   100                                                                                                                             100
    50                                                                                                                               0

     0                                                                                                                            -100
                                                                                                                                  -200
    -50
                                                                                                                                  -300
   -100
                                                                                                                                  -400
   -150                                                                                                                           -500
   -200                                                                                                                           -600
          May -70

                       May -74

                                    May -78

                                                  May -82

                                                                     May -86

                                                                                   May -90

                                                                                               May -94

                                                                                                         May -98

                                                                                                                    May -02




                                                                                                                                           Oc t-74

                                                                                                                                                      Oc t-77

                                                                                                                                                                 Oc t-80

                                                                                                                                                                           Oc t-83

                                                                                                                                                                                       Oc t-86

                                                                                                                                                                                                   Oc t-89

                                                                                                                                                                                                                Oc t-92

                                                                                                                                                                                                                              Oc t-95

                                                                                                                                                                                                                                             Oc t-98

                                                                                                                                                                                                                                                         Oc t-01




Figure E-7. Hydrograph Records of USGS/MGS Monitoring Wells in the Magothy Formation
Showing Current Water Levels, Pre-pumping conditions and the 80% Management Level.


                                                                                                                              9                                                                                                               Appendix E
   Upper Patapsco Monitoring Well Locations




                                                            ANNE
                                                           ARUNDEL
                                                                             S
                                                                             # AA Df                   19


                                   PRINCE
                                  GEORGES

                                                                                                                                 i
                                                                                                                         Schem atc C ross-Secton oft UpperP at
                                                                                                                                              i     he              n     her
                                                                                                                                                              apsco i Sout n M d.
                                                            CALVERT
                                                                        S
                                                                        # CA Cc                 55
                                   PG Hf 38                                                                                                                   Well AA Df 19
     CH Ce 16#
             S                                             S
                                                           #
                                                                                                                                 50
                                CHARLES
                                                                                                                                  0
                                                                                                                                -50
                                                      ST MARYS                                                                 -100
                                                                                                                               -150
                                                                             S
                                                                             # SM Df                    84                     -200
                                                                                                                               -250
                                                                                                                               -300
                                                                                                                               -350
                                                                                                                               -400
                                Measured Water Level
                                                                                                                                       Mar-77

                                                                                                                                                  Mar-80

                                                                                                                                                              Mar-83
                                                                                                                                                                             Mar-86

                                                                                                                                                                                         Mar-89

                                                                                                                                                                                                      Mar-92

                                                                                                                                                                                                                   Mar-95

                                                                                                                                                                                                                                Mar-98

                                                                                                                                                                                                                                             Mar-01
                                Pre-Pumping Level
                                80% Management Level

                    40

                     0
                                   Well CH Ce 16                                                                                                              Well PG Hf 38
      50            -40                                                                                                        100

       0
                    -80                                                                                                           0
                -120
                                                                                                                               -100
     -50
                                                                                                                               -200
    -100
                                                                                                                               -300
    -150                                                                                                                       -400
    -200                                                                                                                       -500
    -250                                                                                                                       -600
                                                                                                                                      Mar-74
                                                                                                                                                Mar-77
                                                                                                                                                           Mar-80
                                                                                                                                                                       Mar-83

                                                                                                                                                                                      Mar-86
                                                                                                                                                                                                  Mar-89
                                                                                                                                                                                                              Mar-92
                                                                                                                                                                                                                         Mar-95
                                                                                                                                                                                                                                    Mar-98
                                                                                                                                                                                                                                                  Mar-01
           May-63

                       May-68

                                    May-73

                                                  May-78

                                                               May-83

                                                                         May-88

                                                                                     May-93

                                                                                                   May-98

                                                                                                                May-03




                                   Well CA Cc 55                                                                                                             Well SM Df 84
     100                                                                                                                       100
       0                                                                                                                         0
    -100                                                                                                                      -100
    -200                                                                                                                      -200
    -300                                                                                                                      -300
    -400                                                                                                                      -400
    -500                                                                                                                      -500
    -600                                                                                                                      -600
    -700                                                                                                                      -700
           Jan-74
                     Jan-77

                                Jan-80
                                         Jan-83

                                                     Jan-86
                                                               Jan-89

                                                                        Jan-92
                                                                                  Jan-95
                                                                                              Jan-98
                                                                                                       Jan-01




                                                                                                                                     Jan-83

                                                                                                                                                  Jan-86

                                                                                                                                                                    Jan-89

                                                                                                                                                                                      Jan-92

                                                                                                                                                                                                     Jan-95

                                                                                                                                                                                                                       Jan-98

                                                                                                                                                                                                                                         Jan-01

                                                                                                                                                                                                                                                       Jan-04




Figure E-8. Hydrograph Records of USGS/MGS Monitoring Wells in the Upper Patapsco Formation
Showing Current Water Levels, Pre-pumping conditions and the 80% Management Level.



                                                                                                                         10                                                                                                       Appendix E
   Lower Patapsco Monitoring Well Locations




                                                                                ANNE
                                                                               ARUNDEL
                                                     S
                                             PG Cf 44#


                                                      PRINCE
                                                     GEORGES




           S
  CH Bc 24 #                                                                     CALVERT                                             Schematic Cross-Section of the Lower Patapsco in Southern MD
                                                      #
                                                      S
                         CH Bf 146                                             S
                                                                               #PG Hf                 32
                                            CHARLES



                                                                             ST MARYS




                                                                                                                                                                 Meas ured Water Level
                                                                                                                                                                 Pre-Pumping Level
                                                                                                                                                                 80% Management Lev el

                       40

                        0
                                          W ell P G Cf 44                                                                                                                 W ell CH B c 24
     100               -40
                                                                                                                                              40
                       -80
      50                                                                                                                                       0
                     -120

       0
                                                                                                                                             -40
     -50
                                                                                                                                             -80
    -100
                                                                                                                                           -120
    -150

    -200                                                                                                                                   -160
           A ug-61

                         A ug-66

                                         A ug-71

                                                         A ug-76

                                                                     A ug-81

                                                                                 A ug-86

                                                                                            A ug-91

                                                                                                           A ug-96

                                                                                                                           A ug-01




                                                                                                                                                   Mar-88

                                                                                                                                                              Mar-90

                                                                                                                                                                          Mar-92

                                                                                                                                                                                      Mar-94

                                                                                                                                                                                                  Mar-96

                                                                                                                                                                                                              Mar-98

                                                                                                                                                                                                                          Mar-00

                                                                                                                                                                                                                                       Mar-02




                                         W ell CH B f 146                                                                                                                 W ell P G Hf 32
     100                                                                                                                                     200
       0
                                                                                                                                                0
     -100
     -200                                                                                                                                   -200
     -300                                                                                                                                   -400
     -400                                                                                                                                   -600
     -500
                                                                                                                                            -800
     -600
     -700                                                                                                                                  -1000
     -800                                                                                                                                  -1200
                                                                                                                                                     May-73

                                                                                                                                                                 May-77

                                                                                                                                                                             May-81

                                                                                                                                                                                         May-85

                                                                                                                                                                                                     May-89

                                                                                                                                                                                                                 May-93

                                                                                                                                                                                                                              May-97

                                                                                                                                                                                                                                           May-01
             Dec -83


                               Dec -86


                                                   Dec -89


                                                                   Dec -92


                                                                                  Dec -95


                                                                                                 Dec -98


                                                                                                                     Dec -01




Figure E-9. Hydrograph Records of USGS/MGS Monitoring Wells in the Lower Patapsco Formation
Showing Current Water Levels, Pre-pumping conditions and the 80% Management Level.


                                                                                                                                     11                                                                                   Appendix E
      Patuxent Monitoring Well Locations


                                                 S
                                         AA Ad 29#


                              AA Cb 1               S
                                                    #            ANNE
                                                                ARUNDEL




                                         PRINCE
                                        GEORGES

                                            S
                                            #
                                                 PG Fd 62
    CH Bc 78           S
                       #                                            CALVERT


                                                                                                                        Schematic Cross-Section of the Patuxent in Southern MD
                                 CHARLES



                                                            ST MARYS




                                                                                                                                                      Meas ured Water Level
                                                                                                                                                      Pre-Pumping Water Level
                                                                                                                                                      80% Management Lev el

                  80
                  40
                   0
                 -40
                 -80
                               W ell A A A d 29                                                                                                                    W ell A A Cb 1
                -120
                -160
                -200
     100        -240
                -280                                                                                                           150
                -320
                -360
      50        -400
                -440                                                                                                           100
                -480
                -520
       0                                                                                                                        50
     -50                                                                                                                          0
    -100                                                                                                                       -50

    -150                                                                                                                      -100

    -200                                                                                                                      -150

    -250                                                                                                                      -200
                                                                                                                                      Sep-59

                                                                                                                                                    Sep-64

                                                                                                                                                                 Sep-69

                                                                                                                                                                            Sep-74

                                                                                                                                                                                       Sep-79

                                                                                                                                                                                                  Sep-84

                                                                                                                                                                                                            Sep-89

                                                                                                                                                                                                                       Sep-94

                                                                                                                                                                                                                                   Sep-99
            Jun-48

                     Jun-54

                              Jun-60

                                        Jun-66

                                                   Jun-72

                                                                Jun-78

                                                                          Jun-84

                                                                                       Jun-90

                                                                                                   Jun-96

                                                                                                              Jun-02




                               W ell CH B c 78                                                                                                                   W ell P G Fd 62
     100                                                                                                                        200
       0                                                                                                                              0
    -100                                                                                                                        -200
    -200                                                                                                                        -400
    -300                                                                                                                        -600

    -400                                                                                                                        -800

    -500                                                                                                                      -1000

    -600                                                                                                                      -1200
                                                                                                                                          A ug-56

                                                                                                                                                       A ug-61

                                                                                                                                                                  A ug-66

                                                                                                                                                                             A ug-71

                                                                                                                                                                                       A ug-76

                                                                                                                                                                                                 A ug-81

                                                                                                                                                                                                           A ug-86

                                                                                                                                                                                                                     A ug-91

                                                                                                                                                                                                                                A ug-96

                                                                                                                                                                                                                                            A ug-01
           Sep-95

                     Sep-96

                               Sep-97

                                          Sep-98

                                                       Sep-99

                                                                     Sep-00

                                                                                   Sep-01

                                                                                                Sep-02

                                                                                                            Sep-03




Figure E-10. Hydrograph Records of USGS/MGS Monitoring Wells in the Patuxent Formation
Showing Current Water Levels, Pre-pumping conditions and the 80% Management Level.



                                                                                                                       12                                                                                            Appendix E
record of at least twenty years was attempted for each aquifer. Monitoring wells with a
shorter period of record were used, if necessary, to capture an area where drawdown is
evident due to significant use in the aquifer.

Examination of the hydrograph records for the five major aquifers reveals that drawdown
is occurring throughout the aquifers to varying degrees. As expected, drawdown is
greatest in close proximity to the largest users. The 80% Management Level is being
approached in some aquifers in their updip areas where available drawdown is the
smallest. In downdip locations, several hundred feet of drawdown is available for each
aquifer. A drawdown rate was calculated for each monitoring well based on the period of
record (Table E-2). Well CA Gd 6 (Figure E-6) shows a long-term decline in water
levels in an area where there has been continuous growth and increased use of an aquifer.
Conversely, in an area of similar growth, well SM Df 66 (Figures E-5 and E-11) shows
the effects of shifting pumpage to a deeper aquifer; water levels in the Piney Point aquifer
have significantly recovered since 1988.

   Table E-2. Drawdown Rates in the Southern Maryland Pilot Study Monitoring Wells
                               Average Drawdown Rate            Range of Drawdown
            Aquifer               in Monitoring Wells        Rates in Monitoring Wells
                                       (feet/year)                   (feet/year)
   Piney Point                             -0.3                      +0.2 to -0.6

   Aquia                                   -1.6                      -0.9 to -4.4

   Magothy                                 - 1.4                     -0.5 to -2.8
   Patapsco - Upper                        -3.0                      -0.4 to -7.4
   Patapsco - Lower                        -1.8                      -0.4 to -3.6
   Patuxent                                -1.9                      -0.8 to -3.8



Some areas of Southern Maryland are of concern with respect to managing sustainable
ground water levels due to a combination of the effects described above. An example of
this is in western Charles County near the Waldorf area (well CH Bf 133, Figure E-7 and
well CH Ce 16, Figure E-8). The large use coupled with the updip extents of the
Magothy and Upper Patapsco aquifers is resulting in water levels approaching the 80%
management level in this area. In a small area of Southern Anne Arundel County that is
in close proximity to the outcrop area of the Aquia aquifer (well AA Fd 43, Figure E-6),
water levels are approaching, or in some cases have exceeded, the 80% management
level due to the combination of localized domestic use and large users in neighboring
Calvert County.




                                            13                                  Appendix E
                                                  -10
   Water Level in Feet (reference is sea level)

                                                  -15



                                                  -20



                                                  -25



                                                  -30



                                                  -35



                                                  -40
                                                        07/15/76


                                                                   07/15/78


                                                                              07/15/80


                                                                                         07/15/82


                                                                                                    07/15/84


                                                                                                               07/15/86


                                                                                                                          07/15/88


                                                                                                                                     07/15/90


                                                                                                                                                07/15/92


                                                                                                                                                           07/15/94


                                                                                                                                                                      07/15/96


                                                                                                                                                                                 07/15/98


                                                                                                                                                                                            07/15/00


                                                                                                                                                                                                        07/15/02
  Figure E-11. Hydrograph showing water level decline and recovery in Monitoring Well
  SM Df 66 in the Piney Point aquifer (see Figure E-5 for well location.)


Figure E-12 shows the potentiometric surface for the Aquia aquifer in 2002. Water
withdrawals from major pumping centers at Chesapeake Ranch Estates, Solomons, and
Lexington Park have resulted in the development of a large cone of depression. At
Lexington Park, near the center of the cone, water levels have declined to about 160 feet
below sea level. Between 1982 and 2001, Aquia water levels declined over 100 feet in
the Lexington Park area, about 40 to 50 feet in northern St. Mary’s County, and 30 to 40
feet in northern Calvert County. A deep cone of depression in the potentiometric surface
has developed in the lower Patapsco aquifer in the Waldorf area that extends outward to
include the La Plata, Indian Head, and Bryans Road areas of Charles County and the
Accokeek and Brandywine areas of Prince George’s County (Figure E-13). Water levels
exceeding 170 feet below sea level have been recorded. Between 1990 and 2001, water
levels declined about 50 feet at La Plata, 30 feet at Waldorf, and 20 feet at Bryans Road.
As expected, drawdown is greatest where the use is greatest, as shown by the cones of
depression.




                                                                                                                               14                                                                      Appendix E
Figure E-12. Potentiometric Surface Map of the Aquia Aquifer (Curtin et al. 2002)




                                       15                                  Appendix E
  Figure E-13. Potentiometric Surface Map of the Lower Patapsco Aquifer (Curtin et al. 2002)


Demand Analysis

Current water demand is separated into several categories based on type of use
(Table E-3). Public supply and self-supplied domestic use together make up more than
86% of the total fresh water use in Southern Maryland. Additional water transported to
Prince George’s County by WSSC, which is withdrawn from the Potomac River and
Patuxent Reservoir, was not considered in the demand projections. A significant amount
of water is used in thermoelectric power generation, however this is predominantly saline
water and is not taken into consideration for the purposes of this pilot study. In order to


                                             16                                  Appendix E
  project water demand in the future, historical records of water use by county were
  analyzed relative to changes in population. Three categories, public supply, self-supplied
  domestic, and aquaculture correlated well with changes in population. The other
  categories did not correlate well with population, as was expected. Future demands
  cannot be projected for these other categories due to the lack of a definable factor to
  analyze water use trends. The public supply and self-supplied domestic categories are
  discussed further in this section, since they represent the most significant use of water in
  Southern Maryland.

Table E-3. Total water withdrawals by Category and County in 2000 (in MGD)




                                                                                                                                 Aquaculture*
                       Commercial


                                     Domestic*




                                                                                                                   Livestock
                                                     Industrial




                                                                                                                                                       Irrigation
                                                                             Thermo-
             Supply*




                                                                                                   Mining
                                                                             electric
             Public




                                                                                                                                                                          Total
 County      Fresh Fresh            Fresh        Fresh        Saline     Fresh    Saline       Fresh Saline Fresh Fresh Saline Fresh Fresh                                    Saline

 Anne
 Arundel     31.23        3.48       10.93         1.78           0.60     0.00     778.21       0.55       0.00      0.04     0.01             0.01    0.55          48.57       778.82


 Calvert       2.30       0.50          3.69       0.05           0.00     0.41 3,270.70         0.00       0.00      0.02     0.00             0.00    0.06           7.03 3,270.70


 Charles       7.48       1.69          3.29       0.01           0.00     0.60 1,192.55         1.13       0.00      0.05     0.00             0.00    0.08          14.33 1,192.55

 Prince
 George's    52.15        0.82          1.24       0.02           0.00     0.75     569.45       0.92       0.00      0.05     0.01             0.00    0.57          56.53       569.45


 St Mary's     3.68       1.44          4.40       0.01           0.00     0.00         0.00     0.44       0.01      0.10     0.00             0.79    0.16          10.23         0.80

  Total:      96.84   7.93 23.55      1.87   0.60    1.76 5,810.91   3.04                                   0.01      0.26     0.02             0.80    1.42 136.69 5,812.32
(*Categories that can be projected based on population correlation.)

  Public Supply and Self-supplied Domestic Projections.

  The USGS tracks and compiles water use data across the State annually (Figure E-14).
  The most recent analysis was completed for 2000 and current water demand figures
  discussed here are based on this data. Water use data is compiled from two main sources
  of information: appropriation permits issued by MDE and U.S. Census Bureau population
  data. Permittees using an average of 10,000 gpd or greater report water use. For permits
  issued for less than 10,000 gpd, the average daily permitted amount is used as an estimate
  of water use. Self-supplied domestic use is based on population data from the U.S.
  Census and is calculated from an average per capita rate of 80 gpd. While the rate of 80
  gpd per capita use for self-supplied domestic is widely accepted, this rate is not specific
  to water use in this region and incorporates some uncertainty into current and projected
  water demands. Further investigation of domestic water use could improve the
  confidence in this rate and would improve self-supplied domestic demand figures.

  Current ground water use was separated by aquifer (Table E-4). This separation is based
  on permit data for public supplies and the assumption that self-supplied domestic users
  are using the shallowest available confined aquifer. Separate totals for each of the


                                                                                        17                                                                          Appendix E
Patapsco and Patuxent formations were tabulated only for the category of public supply
water because the available data is insufficient to separate these aquifers for self-supplied
domestic use.


                                  90

                                  80

                                  70
           Total Pumpage in MGD




                                  60                                                          Piney Point
                                  50                                                          Aquia
                                                                                              Magothy
                                  40
                                                                                              Patapsco
                                  30                                                          Patuxent

                                  20

                                  10

                                  0
                                   55

                                         60

                                               65

                                                     70

                                                           75

                                                                 80

                                                                       85

                                                                             90

                                                                                   95

                                                                                         00
                                  19

                                        19

                                              19

                                                    19

                                                          19

                                                                19

                                                                      19

                                                                            19

                                                                                  19

                                                                                        20
         Figure E-14: Pumpage From Major Confined Aquifers in Southern Maryland

To define a relationship between population increases and water use in the pilot study area,
water use data compiled by USGS for the years 1985 through 2001 were compared to
changes in population during the same period. Ground water use generally correlated well
with changes in population and the data was mathematically regressed against public supply
and domestic ground water use for each of the Southern Maryland Counties. The regression
equations that were developed were then utilized with MDP’s population projections for
2020 and 2030 to project public supply and self-supplied domestic ground water uses for
each county for the years 2020 and 2030 (Tables E-4, E-5).

In the cases of Prince Georges and Charles Counties, it was found that the correlations
between population and self-supplied domestic use were poor or inconclusive. Upon further
investigation, it was determined that the poor correlations are due to the tendency to require
much of the new growth in water supplies to be connected to public supplies in these two
counties. Thus it was concluded that, for the purposes of this pilot study, self-supplied
domestic use should remain constant for these two counties from present to 2030. The most
recent domestic water use data in these counties verifies this trend (Figure E-15).

The final step in this analysis was to determine the percentage that each aquifer contributed
to the total public and self-supplied domestic uses for each county in 2000. For the
purposes of this pilot study, future projected demands were distributed among the aquifers
in the same proportions determined for current use. This may not be a realistic scenario,
however, since there may be a need in the future to utilize the deeper aquifers at a higher
percentage rate in order to reduce the impacts of drawdown in the shallower aquifers.




                                                                      18                                 Appendix E
                             4.00

                             3.50



          Water Use in MGD
                             3.00

                             2.50                                       Charles
                             2.00

                             1.50

                             1.00                                       Prince
                                                                        George's
                             0.50

                             0.00
                                    1985   1990   1995   2000


        Figure E-15: Self- Supplied Domestic Water Use in Charles and Prince
        George's Counties


Meeting Projected Demands: Results of Aquifer Modeling Studies

By examining the water level trends as discussed previously, the effects of pumping on
water levels can be assessed in relation to the 80% management level. Comparison of
current potentiomentric surfaces with the 80% management surfaces may indicate
potential problem areas, but a method is needed to assess the effects of future increased
ground water withdrawal rates. The best available method of determining whether the
confined aquifers can meet the projected demands is ground water flow modeling.
Building these models requires the accumulation of large amounts of data, proper
calibration, and time for analysis. The existing literature was reviewed to determine
where ground water flow models have been developed and to decipher what results they
provide for evaluating the water supply based on projected demands in the Southern
Maryland pilot study area. An initial effort to construct multi-aquifer models in Calvert,
St. Mary’s, and Charles counties is currently underway by MGS, and is scheduled for
completion by September 2005.

Several publications have used ground water flow models to assess the potential of the
major aquifers to meet projected water demands in various locations across the Southern
Maryland pilot study area. These studies were designed to answer specific questions
relating to the effects of increased pumping in certain aquifers over a limited area (Table
E-6). Therefore, they cannot incorporate the overall projected water demands derived in
this report for each county (Tables E-4, E-5). In addition, these studies generally do not
address regional hydrologic issues such as reduced recharge areas or baseflow in aquifer
outcrop areas. The literature review indicates that a larger-scale model is needed to
understand and manage the water supply in the region as a whole. The localized studies
do indicate areas where projected demands can be met for certain aquifers and,
conversely, where increased withdrawals may result in significant water level declines in
localized areas. Each study simulated a multitude of pumping scenarios and their key
results are summarized in the following section.


                                                  19                               Appendix E
Table E-4. Current and Projected Public Supply Water Use in Southern Maryland Aquifers ( in MGD)

                 Anne Arundel Prince Georges                                         Calvert                  Charles                  St. Marys                  Total Aquifer
   Aquifer


                 2000

                               2020

                                         2030

                                                   2000

                                                             2020

                                                                      2030

                                                                              2000

                                                                                       2020

                                                                                               2030

                                                                                                       2000

                                                                                                                2020

                                                                                                                         2030

                                                                                                                                   2000

                                                                                                                                             2020

                                                                                                                                                        2030

                                                                                                                                                                      2000

                                                                                                                                                                                2020

                                                                                                                                                                                        2030
Piney
                 0.00          0.00      0.00      0.00      0.00     0.00    0.23    0.33     0.37   0.00      0.00    0.00      0.36       0.55   0.64          0.59         0.88     1.01
Point

Aquia            0.18          0.20      0.21      0.00      0.00     0.00    1.90    2.87     3.21   0.05      0.08    0.09      3.12       4.79   3.55          5.34         7.94     9.06


Magothy 2.11                   2.43      2.47      0.46      0.39     0.37    0.08    0.12     0.13   2.52      3.96    4.46      0.00       0.00   0.00          5.17         6.90     7.43


Patapsco         21.5          24.8      25.2      1.04      0.88     0.82    0.00    0.00     0.00    4.8      7.55     8.5      0.20       0.31   0.36          27.5         33.6     34.8


Patuxent         5.28          6.1       6.18      0.88      0.74     0.7     0.00    0.00     0.00   0.11      0.17     0.2      0.00       0.00   0.00          6.27         7.01     7.08



Total For
          29.05 33.54 34.01 2.38 *2.01 *1.89 2.21 3.32 3.71                                           7.48 11.76 13.25 3.68                  5.65   6.55 44.89 56.28 59.41
County



Table E-5. Current and Projected Self-Supplied Domestic Water Use in the Southern Maryland Aquifers (in MGD)

                                                           Prince
                    Anne Arundel                                                     Calvert            Charles*                 St. Marys                      Total Aquifer
                                                          Georges*
       Aquifer


                        2000

                                  2020

                                            2030

                                                      2000

                                                               2020

                                                                       2030

                                                                               2000

                                                                                       2020

                                                                                               2030

                                                                                                      2000

                                                                                                               2020

                                                                                                                       2030

                                                                                                                                2000

                                                                                                                                          2020

                                                                                                                                                 2030

                                                                                                                                                               2000

                                                                                                                                                                             2020

                                                                                                                                                                                        2030
Piney Point 0.03 0.03                      0.04       .00      .00     .00    1.85 2.38 2.55 0.01 0.01 0.01 3.30 4.23 4.65                                 5.19              6.65      7.25


Aquia               7.10 8.02              8.30      0.31 0.31 0.31 1.84 2.37 2.53 1.84 1.84 1.84 1.10 1.41 1.55 12.19 13.95                                                           14.53


Magothy             2.19 2.47              2.56      0.56 0.56 0.56 0.00 0.00 0.00 0.35 0.35 0.35 0.00 0.00 0.00                                           3.10              3.38      3.47


Potomac
Group
(Includes           1.61 1.82              1.88      0.37 0.37 0.37 0.00 0.00 0.00 1.09 1.09 1.09 0.00 0.00 0.00                                           3.07              3.28      3.34
Patapsco &
Patuxent)


Total For
                   10.93 12.34 12.78 1.24 1.24 1.24 3.69 4.75 5.08 3.29 3.29 3.29 4.40 5.64 6.20 23.55 27.26                                                                           28.59
County

* Amounts not projected, no correlation




                                                                                              20                                                                Appendix E
Key Results of Modeling Studies

Lower Patapsco and Upper Patuxent in northwestern Charles County (Andreason, 1999):

   !   Model simulations for 2020 indicate that an additional (relative to 1997
       withdrawals) 0.6 mgd is available from the Lower Patapsco aquifer and a total of
       3.4 mgd is available from the Upper Patuxent in northwestern Charles County.
   !   Model simulations indicate that significant water level declines will result from
       projected 2020 water use. Water level declines will exceed the Lower Patapsco’s
       80% management level along the Potomac River in the central part of the Indian
       Head peninsula and a small area northwest of Bryans Road.
   !   Model simulations of 3.4 mgd withdrawals in the Upper Patuxent aquifer have
       minimal impacts on water levels in the Lower Patapsco aquifer.

Magothy and Patapsco Aquifers in Waldorf, north-central Charles County (Fleck and
Wilson, 1990)

   !   Model simulations for 2020 indicate that additional pumpage (relative to 1985
       withdrawals) of 4.2 and 1.9 mgd will result in 95 and 225 feet of additional
       drawdown in the La Plata (Lower Patapsco aquifer) and White Plains (Upper
       Patapsco) aquifer systems respectively.
   !   The Waldorf aquifer system (Magothy and Upper Patapsco aquifers) can
       withstand withdrawal rates of 6.6 mgd before the 80% management level is
       reached.
   !   The White Plains aquifer system can withstand a maximum withdrawal rate of 6.1
       mgd before the 80% management level is reached.
   !   The La Plata aquifer system can withstand a maximum withdrawal rate of 15.2
       mgd before the 80% management level is reached.

Aquia and Piney Point Aquifers in Calvert and St. Mary’s counties (Achmad and Hansen,
1997 and 2001)

   !   Model simulations for 2025 indicate that total projected withdrawals of 19.5 mgd
       in St. Mary’s and 9.1 mgd in Calvert from the Aquia and Piney Point aquifers
       could result in significant water level declines. Water levels in the Aquia aquifer
       in some locations in St. Mary’s county exceed 80% management levels, but
       remain above the 80% management level in locations in Calvert County.
   !   An alternate model simulation for 2025, which represents moderate increases to
       19.9 mgd and 12.2 mgd in St. Mary’s and Calvert counties, respectively, result in
       additional water level declines. Water levels at two locations in the Aquia aquifer
       in Calvert County reach the 80% management level under these increasingly
       stressed conditions.
   !   A second alternate model simulation for 2025, which reduces withdrawals 20% in
       the Aquia and Piney Point to 15.5 mgd in St. Mary’s and 9.7 mgd and assumes
       deeper aquifers will be used for additional needs, results in substantially higher
       water levels which remain above the 80% management levels in all locations.



                                           21                                 Appendix E
Aquia and Magothy Aquifers in Southern Anne Arundel County (Andreason, 2002)

   !   Model simulations for 2020 representing an increase of 0.8 mgd in the Aquia
       aquifer result in water level declines in a 3.5 mile wide area of Southern Anne
       Arundel County that exceed 80% management levels. In the remainder of the
       study area, water levels in the Aquia remain above 80% management levels.
       Identical withdrawals in the Magothy aquifer result in about 20 feet of drawdown,
       but water levels are considerably above management levels due to the greater
       amounts of available drawdown.
   !   When withdrawals in the Aquia aquifer are limited to 2000 withdrawal rates,
       simulated water levels stabilize in less than one year.
   !   Increases in withdrawals from the Aquia aquifer will cause water levels to exceed
       the 80% management levels in the central part of Southern Anne Arundel County.
       Therefore, as defined by present management level guidelines, the Aquia aquifer
       in Southern Anne Arundel County has reached its maximum allowable yield.
   !   The maximum simulated yield of the Magothy aquifer is approximately 38 mgd
       based solely on available drawdown in the Magothy. This results in water level
       declines of 22 feet in the Aquia aquifer. Reducing pumpage in the Aquia aquifer
       will allow a greater amount to be pumped from the Magothy aquifer.
   !   Simulated withdrawals for 2020 in Calvert and St. Mary’s Counties result in
       water levels in a 3-mile wide band of Southern Anne Arundel County to exceed
       80% management levels in the Aquia aquifer.
   !   Constraining withdrawals in Calvert County will reduce the amount of future
       drawdown in Southern Anne Arundel County.

The key results in each of these studies provide valuable information, however the model
projections for a single study or county cannot adequately incorporate the projections of
neighboring users in the region. The 2002 report, for example, incorporates the
influences of users in Calvert County on those in Southern Anne Arundel County and
suggests that reduced withdrawals in Calvert County will alleviate the water level
declines Southern Anne Arundel. However, no alternative for the users in Calvert
County is identified. In another example, the 1997 report suggests the use of the
Magothy or Upper Patapsco aquifers as alternatives in Calvert and St. Mary’s counties,
however no attempt can be made to illustrate the effects of this shift in use on users of
these aquifers in Charles County. The constraints of ground water flow models result in
these shortcomings. In general, as the model area increases, increasing amounts of data
are needed to calibrate the model for accurate results. In the past, attempts at modeling
large areas resulted in less detailed results. However, with continuing improvements in
software and hardware, it is likely that these deficiencies could be remedied and a
regional model that incorporates the regional stresses on all of the aquifers could be
developed.

These studies have proven invaluable to MDE in issuing appropriation permits and
managing the water supply. However, due to the growing demand on the resource, it is
clear that these localized studies cannot provide sufficient data to assess regional impacts



                                             22                                 Appendix E
in the aquifers. Large scale, regional ground water models for the major aquifers are
needed to address the management issues associated with regional stresses on the
aquifers. Based on these studies, it is evident that without careful management, there will
be areas in which the water supply potential (as defined by the 80% management level)
of some of the aquifers could be reached in the next 30 years. Some of the various
pumping scenarios were constructed to address what best management practices could be
used to maximize the potential of the aquifers while minimizing the impacts of
drawdown. In some areas, deeper aquifers may have to be explored to avoid such
impacts. Without a regional model that incorporates all the aquifers, these issues cannot
be adequately resolved or managed.

In general, a model is only as valid as the data that are used and the assumptions that are
made to create it. Models give ground water managers predictive tools that allow for
different conditions and assumptions, the net results of which are not the absolute effects,
but resulting scenarios by which planning decisions can be made. The modeling results
listed above show that management levels in some areas have and will be exceeded. This
has only occurred in areas where the available drawdown is smallest near recharge areas.
The appropriateness of the 80% management level in such areas needs to be addressed,
since the impacts of drawdown near outcrop areas are reduced due to available recharge.


Table E-6. Summary of Recent Ground water Modeling Studies in Southern Maryland
                                                Highest
                                                                                Source of
                  Area          Aquifers      Projected        Projected
  Report                                                                       Population
                Covered         Included    Demand Used to Year(s)
                                                                               Projections
                                               in Model
                                                                           Anne Arundel Co.
                             Aquia          2.6 Mgal/day                   Planning, Calvert
Andreason Southern Anne
                                                              2020, 2025   Co. Dept. of
(2002)       Arundel
                             Magothy        0.8 Mgal/day                   Planning and
                                                                           Zoning
             Northwestern    Lower
                                            7.7 Mgal/day                   Charles Co. Dept.
Andreason Charles Co         Patapsco
                                                              2020         of Planning and
(1999)       (Indian Head
                             Patuxent       7.7 Mgal/day                   Growth Mgmt.
             -Bryans Road)
                                                                           MD. Dept. of
                             Piney Point    8.9 Mgal/day
Achmad                                                                     Planning, Calvert
and Hansen Calvert and St.                                                 Co. Dept. of
(1997)       Mary’s                                           2020, 2025   Planning and
and          Counties        Aquia          28.6 Mgal/day                  Zoning, St.
(2001)                                                                     Mary’s Co. Metro.
                                                                           Commission
                             Magothy/
                             Patapsco (as                     2020 and
Fleck and    North-central                  6.6 Mgal/day
                             the Waldorf                      Total        Charles Co. Dept.
Wilson       Charles Co.
                             aquifer)                         Available    of Public Works
(1990)       (Waldorf)
                                                              Drawdown
                             Patapsco       15.2 Mgal/day




                                            23                                 Appendix E
Conclusions

The Southern Maryland Pilot Study was conducted, as directed by the Committee, in
order to demonstrate the methodologies that could be used in a statewide assessment of
water supply and demand. In the process of developing a methodology for assessing the
ground water supply in the Southern Maryland Counties, several issues arose that point to
a need for additional information and resources to perform an adequate assessment and to
extend this analysis to other areas of the State. In order to remedy these issues, the
following areas of “need” have been identified:

   !   A regional, multi-aquifer ground water flow model developed for the entire
       Coastal Plain, that can be used by ground water managers as a tool for assessing
       the water supply and the impacts of future applications for withdrawals. The
       development of this model will require additional data on aquifer leakage and
       recharge rates, aquifer structure, and water yielding characteristics in some
       portions of the aquifers.
   !   Additional monitoring wells near large pumping centers to verify that modeling
       predictions are correct or to make the necessary adjustments to improve the
       accuracy of predictive models.
   !   Better information on domestic wells, including location data, aquifers utilized,
       and consistent reporting of well abandonment. This could be accomplished by
       improved coordination between MDE and the Counties by developing standard
       methods of data collection, storage, and transfer.
   !   An evaluation of the appropriateness of the 80% management level in aquifers in
       close proximity to their recharge areas. This management strategy may be too
       restrictive in certain areas and may result in unwarranted limits on water
       withdrawals.




                                           24                                Appendix E
References and Data Sources

Achmad, G. and Hansen, H.J., 1997. Hydrogeology, Model Simulation, and Water Supply
Potential of the Aquia and Piney Point-Nanjemoy Aquifers in Calvert and St. Mary’s
Counties, Maryland, Maryland Geological Survey Report of Investigations No. 64, 197
pp.

Achmad, G. and Hansen, H.J., 2001. Simulated Changes in Water Levels of the Aquia
Aquifer Using Revised Water-use Projections to 2025 for Calvert and St. Mary’s
Counties, Maryland, Maryland Geological Supplemental Report S1/RI 64, 58 pp.

Achmad, G. and Hansen, H.J., 2001. Ground-Water Levels and Pumpage Trends in the
Major Coastal Plain Aquifers of Southern Maryland Between 1970 and 1996, Maryland
Geological Survey Open File Report No. 2000-02-12,149 pp.

Andreason, D.C., 1999. Geohydrology and Water Supply Potential of the Lower
Patapsco and Patuxent Aquifers in the Indian Head-Bryans Road Area, Charles County,
Maryland, Maryland Geological Survey Report of Investigations No. 69, 110 pp.

Andreason, D.C., 2002. Hydrogeology, Water Quality, and Water Supply Potential of the
Aquia and Magothy Aquifers in Southern Anne Arundel County, Maryland, Maryland
Geological Survey Report of Investigations No. 74, 119 pp.

Chapelle, F.H. and Drummond, D.D., 1983. Hydrogeology, Digital Simulation, and
Geochemistry of the Aquia and Piney Point-Nanjemoy Aquifer System in Southern
Maryland, Maryland Geological Survey Report of Investigations No. 38,100 pp.

Curtin, S.E., Andreasen, D.C., and Wheeler, J.C., 2002, Potentiometric Surface of the
Aquia Aquifer in Southern Maryland, 1 p., Scale 1:250,000.

Curtin, S.E., Andreasen, D.C., and Wheeler, J.C., 2002, Potentiometric Surface of the
Lower Patapsco Aquifer in Southern Maryland, 1 p., Scale 1:250,000.

Fleck, W.B. and Vroblesky, D.A., 1996. Simulation of Ground-Water Flow of the
Coastal Plain Aquifers in Parts of Maryland, Delaware, and the District of Columbia,
United States Geological Survey Professional Paper 1404-J, 41 pp.

Fleck, W.B. and Wilson, J.M., 1990. Geology and Hydrologic Assessment of Coastal
Plain Aquifers in the Waldorf Area, Charles County, Maryland, Maryland Geological
Survey Report of Investigations No. 53, 137 pp.

Mack, F.K. and Achmad, G, 1986. Evaluation of the Water-Supply Potential of Aquifers
in the Potomac Group of Anne Arundel County, Maryland, Maryland Geological Survey
Report of Investigations No. 46, 111 pp.




                                           25                                Appendix E
Mack, F.K. and Mandle, R.J., 1977. Digital Simulation and Prediction of Water Levels
in the Magothy Aquifer in Southern Maryland. Maryland Geological Survey Report of
Investigations No. 28, 42 pp.




                                         26                               Appendix E

								
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