903R82003
  WATER-QUALITY OF THREE  MAJOR TRIBUTARIES
  TO  THE CHESAPEAKE  BAY,  THE SUSQUEHANNA
            POTOMAC,  AND JAMES  RIVERS,
               JANUARY 1979-APRIL 1981
 U.S.  GEOLOGICAL SURVEY
                                            Ruionffl Library
 Water-Resources Investigations 82-32             Environuwntal Protection
                                     I' xx ,--t-7<
l.l  pared in cooperation with the
j r
   .  ENVIROMENTAL PROTECTION AGENCY
   SAPEAKE BAY PROGRAM

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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
2.
4. Title and Subtitle
Water Quality of the Three Major Tributaries to the
Chesapeake Bay, the Susquehanna, Potomac, and James Rivers,
January 1979 - April 1981
7. Author(s)
David J. Lang
9. Performing Organization Name and Address
U.S. Geological Survey, Water Resources Division
208 Carroll Building
8600 La Salle Road
Towson, Maryland 21204
12. Sponsoring Organization Name and Address
U.S. Geological Survey, Water Resources Division
208 Carroll Building
8600 La Salle Road
Towson, Maryland 21204
3.
5.
6.
8.
10.
11.
(0
(G)
13.
Recipient's Accession No.
Report Date
May 1982

Performing Organization Rept. No.
USGS/WR1-82-32
Project/Task/Work Unit No.
Contract(C) or Grant(G) No.
Type of Report & Period Covered
Final
14.
 IS. Supplementary Notes
   Prepared in cooperation with  the U.S.  Environmental Protection Agency, Chesapeake  Bay
   Program
 16. Abstract (Limit: 200 words)
       Water-quality constituent loads  at  the Fall  Line  stations of  the  Susquehanna,
  Potomac,  and James Rivers,  the three  major tributaries  to the Chesapeake Bay,  can be
  estimated  with reasonable accuracy by  regression techniques, especially  for wet periods
  of 1 year  or more.  Net transport  of  all  nutrient species and most other  constituents is
  dominated  by a few spring  and storm-related, high-flow events.  Atrazine and 2,4-D are
  the two herbicide residues most consistently detected at the Fall Line of  the Susquehanna
  and Potomac  Rivers.   Concentrations  of total residual chlorine  and low-molecular-weight
  halogenated  hydrocarbons  at  selected  sites in estuaries to the upper  Bay are generally at
  or below  detection limits.  Ammonia concentrations  and loads are decreasing at all three
  Fall  Line stations,  as  is orthophosphate in the Susquehanna and Potomac Rivers.   The
  James  River has  the  lowest  average  concentrations of total  nitrogen and  nitrite plus
  nitrate.   Slight  increases in total nitrogen and nitrite plus nitrate in  the Susquehanna
  River  from 1969 to 1980 may warrant  continued monitoring.

       When water discharge of  the Susquehanna River  is below about  400,000 cubic feet per
  second at Conowingo, Maryland, sediments are deposited  behind the  three hydroelectric
  dams  located  between Harrisburg,  Pennsylvania  and  its  mouth.   Peak discharges above
  400,000 cubic  feet per second  resuspend the  sediments and  their  sorbed chemical constitu-
  ents,  carrying them to the Bay.
 17. Document Analysis  a. Descriptors
   *Water Quality, *Nutrients,  *Sediment transport, *Sediments,  Pesticides, Trace metals,
   Stream discharge, Storms,  Chlorine
   b. Identifiers/Open-Ended Terms
   *Chesapeake Bay, *Susquehanna River, *Potomac River, *James  River, Conowingo Dam,
   Fall Line
   c. COSATI Field/Group
18. Availability Statement
No restriction on distribution.
19. Security Class (This Report)
20. Security Class (This Page)
21. No. of Pages
72
22. Price
(See ANSI-Z39.18)
                                       See Instructions on Reverse
OPTIONAL FORM 272 (4-7
(Formerly NTIS-35)
Department of Commerce

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 t
I
         WATER QUALITY OF THE THREE MAJOR TRIBUTARIES


         TO THE CHESAPEAKE BAY, THE SUSQUEHANNA,


         POTOMAC, AND JAMES RIVERS,


         JANUARY 1979 - APRIL 1981


         By David J. Lang
         U.S. GEOLOGICAL SURVEY
         Water-Resources Investigations 82-32
         Prepared in cooperation with the


         U.S.ENVIRONMENTAL PROTECTION AGENCY


         CHESAPEAKE BAY PROGRAM
                                       May 1982

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              UNITED STATES DEPARTMENT OF THE INTERIOR


                         JAMES G. WATT, Secretary



                          GEOLOGICAL SURVEY


                          Dallas L. Peck, Director
For additional information write to:

U.S. Geological Survey
208 Carroll Building
8600 La Salle Road
Towson, Maryland 21204

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                                  CONTENTS
                                                                            Page

Abstract	      1
Introduction	      2
Data collection	      4
Basin land use and its effect on water quality	      4
Hydrologic conditions	      5
Methods of collection and laboratory analysis	      5
Constituent loads	      8
     Load estimation techniques—nutrients and metals	      8
     Load estimation techniques—major cations and anions	     16
     Evaluation and limitation of the load estimates	     18
Examination of selected water-quality constituents    	     20
     Seasonal characterization of pesticides	     20
     Seasonal characterization of chlorophyll a	     23
     Chlorine	     23
     Total recoverable aluminum, iron, and manganese	     27
     Sulfate	     27
     Nutrients and their relationships to suspended
        sediment and discharge	     31
     Seasonal variability of nutrient transport	     36
     Comparison of nutrient data among the three
        Fall Line stations	     42
     Comparison of nutrient data with previous studies	     46
     Comparison of nutrient data at the Susquehanna River
        stations at Harrisburg, Pa., and Conowingo, Md	     51
     Sediment transport characteristics	     54
           Susquehanna River	     54
           Potomac River	     58
           James River    	     58
Summary and conclusions	     61
References	     63

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                               ILLUSTRATIONS
                                                                          Page

Figure 1.  Map of study area showing location of drainage
            basins and sampling sites	      3

       2.  Hydrograph showing mean monthly and long-term
            average monthly discharge for the three Fall
            Line stations	      7

       3.  Hydrograph showing seasonal fluctuations in
            concentrations of 2,4-D at the Susquehanna
            and Potomac Fall Line stations	     21

       4.  Hydrograph showing seasonal fluctuations in concen-
            trations of atrazine at the Susquehanna and
            Potomac Fall Line stations	     22

       5.  Hydrograph showing seasonal fluctuations of concen-
            trations of chlorophyll a  at the three Fall Line
            stations	     24
       6.  Map showing location of chlorine-monitoring stations
            on selected tributaries to Chesapeake Bay	     25
       7.  Hydrograph showing aluminum, iron, and  manganese
            concentrations during February 20-26,  1981, at
            the Susquehanna River Fall Line station	     28

       8.  Hydrograph showing aluminum, iron, and  manganese
            concentrations during September 5-8, 1979, and
            March 21-24, 1980, at the Potomac River Fall
            Line station	     29

       9.  Hydrograph showing aluminum, iron, and  manganese
            concentrations during April 15-17, 1980, at  the
            James River Fall Line station	     30
      10.  Hydrograph showing nutrient concentrations
            during February 20-27,  1981, at the
            Susquehanna River Fall Line station	     33
      11.  Hydrograph showing nutrient concentrations
            during September 5-8, 1979, and
            March 21-24, 1980, at the Potomac River Fall
            Line station	     34

      12.  Hydrograph showing nutrient concentrations
            during April 15-17, 1980,  at the James
            River Fall Line station	     35
      13.  Hydrograph showing nutrient concentrations
            during February 25 -  March 1,  1979, at
            the Potomac River Fall Line station	     37
                                     IV

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                         ILLUSTRATIONS-Continued
Figure 14.  Bar graph showing monthly loads of nitrogen at the
             three Fall Line stations	
           Bar graph showing monthly loads of phosphorous
             at the three Fall Line stations	
       16.
    Hydrographs showing suspended-sediment transport
     for three high flows at the Susquehanna River
     at Harrisburg, Pa., and Conowingo, Md.
       17.  Hydrographs showing suspended-sediment transport
             for three high flows at the Potomac River
             at Chain Bridge at Washington, D.C.   .
Page

 43


 44



 56



 59
                                   TABLES
Table  1.  Average discharge for study period and long-term
             average discharges for the three Fall Line stations
                                                                           Page
       2.
5.

6.


7.
   Least squares regression equations for load calculations
     of selected nutrients and metals with standard
     deviation (s2) and coefficients of determination (r2)

   Monthly load estimates (in hundreds of thousands of
     pounds) for the Susquehanna River at Conowingo, Md.

   Monthly load estimates (in hundreds of thousands of
     pounds) for the Potomac River at Chain Bridge at
     Washington, D.C	
          Monthly load estimates (in hundreds of thousands of
            pounds) for the 3ames River at Cartersville, Va.

          Least squares regression equations for load calculations
            of selected cations and anions with standard deviation
            (s2) and the coefficients of determination (r2) -
          Nutrient loads (in millions of pounds) for the Potomac
             River at Chain Bridge at Washington, D.C., computed
             from the Potomac estuary and Fall Line monitoring
             study data    	
          Schedule of low-molecular-weight, halogenated organic
            compounds analyzed in selected tributaries to the
            Chesapeake Bay  	
  9

 10



 12

 14


 17




 19


 26
                                      v

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                              TABLES—Continued

                                                                           Page
Table  9. Sulfate loads in the Susquehanna, Potomac, and James
           Rivers from May 1980 to April 1981	    32
      10. Annual loads of selected nutrients (in millions of pounds)
           at the three Fall Line stations for calendar years
           1979 and 1980	    38

      11. Seasonal fluctuations of selected nutrients for the
           three Fall Line stations	    39

      12. Total nutrient loads and discharge-weighted average
           nutrient concentrations for the period January 1979
           to December 1980 at the three Fall Line stations	    45

      13. Average  daily loads (in Ibs/d) of selected nutrient
            species for the three Fall Line stations derived
            from different hydrologic investigations	    47

      14. Discharge-weighted average concentrations (in mg/L)
            of selected nutrient species for the  three Fall Line
            stations derived from different hydrologic
            investigations	    48

      15. Estimates of nutrient loads (in Ibs/d) at three
            different discharges for 1969-72 and 1979-81
            data sets for the Susquehanna River at
            Conowingo, Md	    50

      16. Water-quality constituent loads (in millions of
            pounds) for stations on the Susquehanna River
            at Harrisburg, Pa., and Conowingo, Md., from
            April 1980 through March 1981	    52

      17. Relative proportions of orthophosphate, nitrite +
            nitrate, and ammonia + organic nitrogen to
            total phosphorous and nitrogen loads at the
            Susquehanna River at Harrisburg, Pa.,
            and Conowingo,  Md., from April 1980 to
            March  1981	    53

      18. Discharge-weighted average concentrations (in mg/L)
            of water-quality constituents for stations on the
            Susquehanna River at Harrisburg, Pa., and
            Conowingo, Md., from  April 1980 through
            March  1981	    55

      19. Suspended-sediment loads (in tons) at the Harrisburg,  Pa.,
            and Conowingo,  Md., stations on the Susquehanna
            River for three high-flow periods	57

      20. Unit discharge sediment  yields for the Potomac River
            at Chain Bridge at Washington, D.C., for three
            high-flow periods	60
                                      VI

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                    CONVERSION OF MEASUREMENT UNITS
      The following factors may be used to convert the inch-pound units published in
this report to International System (SI) metric units.
Multiply inch-pound unit

inch (in.)

foot (ft)
mile (mi)

square inch (in2)
square mile (mi2)

gallon (gal)

cubic foot  (ft3)
cubic foot per second
      (ft3/s)
gallon per minute (gal/min)
it By To obtain metric unit
Length
25.40
2.54
.3048
1.609
Area
6.452
2.590
Volume
3.785
.003785
.02832
Flow

millimeter (mm)
centimeter (cm)
meter (m)
kilometer (km)

square centimeter (cm2)
square kilometer (km2)

liter (L)
cubic meter (m3)
cubic meter (m3)

degree Fahrenheit (°F)

pound per cubic foot

pound per day (Ib/d)
28.32

  .02832

  .06309
 .00006309

 Temperature
 -32 x 0.555
Concentration
   16055
     Mass
 0.454
liter per second (L/s)
cubic meter per second
      (m 3/s)
liter per second (L/s)
cubic meter per second
      (m 3/s)
degree Celsius (°C)
milligram per liter (mg/L)
kilogram per day (kg/d)
                                      vn

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WATER QUALITY OF THE THREE MAJOR TRIBUTARIES TO THE CHESAPEAKE BAY,

               THE SUSQUEHANNA, POTOMAC, AND 3AMES RIVERS,

                           JANUARY 1979 - APRIL 1981
                                 By David 3. Lang
                                    ABSTRACT


        Water-quality constituent loads at the Fall Line stations of the Susquehanna,
  Potomac, and James Rivers, the three major  tributaries to the Chesapeake Bay,
  can be estimated with reasonable accuracy  by  regression techniques, especially for
  wet periods of 1 year or more.  Net transport of all nutrient species and most other
  constituents, especially  those  found  in  greatest  concentrations associated with
  suspended  material,  is dominated  by a  few  spring  and storm-related  high-flow
  events.  Atrazine and 2,4-D are the  two herbicides most consistently detected at
  the Fall Line of the  Susquehanna and Potomac Rivers.  Concentrations of  total
  residual  chlorine and low-molecular-weight, halogenated hydrocarbons at selected
  sites in estuaries to the upper Bay are generally at or below  detection limits. When
  compared  to the  two other major  tributaries,  the  James River  has the lowest
  discharge-weighted-sulfate concentrations,  presumably because of the lack of coal
  mining  activity in this basin.   This river  also  has lower  total nitrogen concen-
  trations.  Ammonia concentrations  and loads are decreasing at all three Fall Line
  stations, as  is orthophosphate  in the  Susquehanna and Potomac  Rivers.   Slight
  increases  in  total  nitrogen   and   nitrite  plus  nitrate   concentrations  in  the
  Susquehanna River from 1969 to 1980 may warrant continued monitoring.

        Analyses  of  data for this report  confirm the previous suggestion  that when
  water discharge of the Susquehanna River at Conowingo, Maryland,  is below about
  400,000 cubic feet per second, sediment, with  sorbed nutrients and other constitu-
  ents,  is  deposited behind the three  hydroelectric dams   on  this  river  between
  Harrisburg, Pennsylvania, and its mouth.  Discharges above 400,000 cubic feet per
  second resuspend these sediments and transport constituent  loads to the Bay well in
  excess of loads transported by  the Susquehanna River at Harrisburg.  In addition to
  precipitation quantity and intensity, antecedent conditions  and season of the year
  play a  major role in the transport  of  sediments and  their associated chemical
  constituents at all three stations.

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                               INTRODUCTION


     The Chesapeake Bay is the largest estuary in the United States:  200 mi long;
8,000 mi of shoreline;  and  4,400 mi2 of water surface.   It has a drainage area of
64,000 mi2 and is fed by more than 150 tributaries (U.S. Dept. of the Army, Corps
of  Engineers,  1973).   The three major   tributaries of the  Bay (Susquehanna,
Potomac, and James Rivers) drain about 85 percent  of  the  total Chesapeake Bay
drainage basin.

     The Bay supports substantial commercial and sport fishing and recreational
industries. Its water also provides access to two major  shipping ports—Baltimore,
Md., and Hampton Roads, Va. Ship traffic on the Chesapeake Bay is increasing and
is  expected to continue growing as  more coal is  exported from Eastern United
States.

     In  order to  protect and  preserve this  valuable natural  resource, the U.S.
Environmental  Protection Agency  (EPA),  under Congressional directive  (Senate
Report  No. 94-326), conducted an in-depth study of the environmental quality of
the Chesapeake Bay.  As part of  that study, the  U.S.  Geological  Survey (USGS)
assessed  the  water quality of  the   three  major  tributaries  to  the  Bay  [the
Susquehanna, Potomac, and  James Rivers (fig. 1)] at the Fall  Line from January
1979 to April  1981.  (The Fall Line is the boundary between the Coastal  Plain and
Piedmont physiographic provinces.)


     This  report  presents  the  following  water-quality  information   for  the
Susquehanna, Potomac, and James  Rivers:

1.   Estimated loads of major ions,  suspended sediment,  selected nutrient species,
     and selected trace metals for the 2-year, data-collection period.

2.   An assessment of accuracy and limitations inherent in these  estimates.

3.   Seasonal characterization of nutrients,  pesticides, and chlorophyll a  collected
     during the study.

4.   Relationships between discharge,  specific conductance, and suspended sediment
     and selected nutrient and trace  metal concentrations.

5.   Comparisons of nutrient loads with other studies and the detection of trend in
     these loads.


     The cooperation and assistance  received from Mr. Howard Jarmon  and staff
of the  Susquehanna Electric Company at Conowingo  Dam are  gratefully acknowl-
edged.

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          EXPLANTION

   	Drainage Basin boundary

     A    Surface-Water station

     T    Water-Quality station

     |    Surface-Water and Water-
          Quality station

  50           0           50 MILES
   I  '  I   I  I  I	;
                            A-

K
i,
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                                                                        75°
                                                              ^
                                                         ^A ,


                                                     /^-•/r
                                    v         L   >/'
                          )                ,—^\—\ r /
                         r*- -•*- j	^- ^ r V-^N    f ~ 42°

                      ; /  Susquehanna

                              River
                              Basin
                             ^lver'fe/
                             Basin
                            /          i.jii

                                       Cham Bridge
39
     37'
Figure 1.—Study area showing  location of drainage basins and sampling sites,


                                       3

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                             DATA COLLECTION


      Figure 1 shows the location of  the water-quality monitoring stations used in
the study.  The Susquehanna River  station is at Conowingo Dam, Conowingo,  Md.
From January 1979  to  April 1981, if flow  conditions permitted, base-flow  water
quality was measured every 2 weeks.  The James River station is at Cartersville,
Va.,  and  the Potomac River site is at Chain Bridge at Washington, D.C.; during the
study, both were sampled monthly.  Water samples analyzed for both sediment  and
chemical quality  were collected frequently during high flows at all three sites to
better understand the  mechanisms that affect the  water quality  during  these
critical periods of high mass transport.

      The USGS  continuously monitors  stage  and  flow  at the Cartersville  and
Conowingo sites.  Potomac River flow is monitored at Little Falls, Md., half a mile
upstream from Chain Bridge.

      The Susquehanna River contributes almost half of the fresh-water inflow to
the Bay.  It is important to understand the net effects on water quality of the three
hydroelectric dams located in the Susquehanna River between Harrisburg, Pa.,  and
Conowingo, Md.  This report presents only comparisons of  selected  constituent
loads for these two  stations.  A  more detailed analysis of the Harrisburg station
data was made in  another Geological Survey report, now in preparation.

      Because  the monitoring sites  on  the Potomac  and  James Rivers are  not
located at the mouths of these rivers, actual loads to the Chesapeake Bay were not
measured.  However,  the samples collected at  these stations are representative of
constituents available to the Bay.
           BASIN LAND USE AND ITS EFFECT ON WATER QUALITY

     The following table indicates the percentages of each land-use category in
the Susquehanna, Potomac, and James River basins.  Land use in the Susquehanna
and Potomac basins is  similar with slightly more  than half the area covered by
forest.  The James River basin contains 75-percent forest cover.
   Land
   use
Susquehanna River at
  Conowingo, Md.
  drainage area -
   27,100 mi2	
Potomac River at
Chain Bridge at
Washington, D.C.
drainage area  =
  11,360 mi2
 James River at
Cartersville, Va.
 drainage area =
   6,257 mi2
 Agriculture and
  pastureland

 Forest

 Urban
       35%
      60%
     55%
                        22%
    75%

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      Land use has a significant effect on the water quality  of any  river.  Areas
with large forest cover normally have  lower nutrient concentrations  than agricul-
tural  areas.   A study of 473 non-point source  drainage  areas in Eastern  United
States showed that  nutrient concentrations  are generally  proportional   to  the
percentage of agricultural land in  the  watershed  (Omerik,  1976).   In general,
inorganic nitrogen makes up a larger percentage of total nitrogen concentration in
streams  with larger  percentages of agricultural land.   In that study, inorganic
nitrogen  was found to be 27 percent of  the total nitrogen in streams which drained
forested  watersheds and  over  75 percent in streams  draining agricultural areas.
Orthophosphate portion of total phosphorous remained unchanged at approximately
40 percent, regardless of land-use type.   These observations  are fairly consistent
with the  results of this report.

      Coal mining along the tributaries to the  Susquehanna and Potomac  Rivers
influences water quality at the Fall Line.   Major  coal fields are found  in the Tioga,
Juniata (both in  the Susquehanna  watershed), and  North Branch Potomac River
basins. Mining exposes pyritic rock surfaces to weathering and oxidation processes,
which can cause a decrease in pH and  elevate concentrations of iron, manganese,
and sulfate in water emanating from  these areas.  Mine drainage  with  low pH
characteristically  contains  iron  and manganese in solution.  When  this  water is
diluted by inflow and the acids  are neutralized, and if oxidizing conditions exist,
these metals  will  precipitate and sorb onto sediment  particles to  be transported
downstream.  Iron and manganese are carried in this fashion from the  mining areas
into the Susquehanna and Potomac Rivers.
                          HYDROLOGIC CONDITIONS

     Average discharge at each  of  the Fall Line sites for  the  study period was
about 20 percent greater than the long-term averages for the Potomac and James
Rivers,  but 4 percent less  than  the long-term averages for the Susquehanna River
(table 1).  Streamflow  was unevenly distributed over the 28-month study period,
with discharge generally well above normal during the winter and fail of  1979 (fig.
2).  However, from  summer of  1980 to the end of  the data-collection  period  in
April  1981, flow  at all  three stations was well below the long-term averages, with
the exception of a brief period in February 1981.
          METHODS OF COLLECTION AND LABORATORY ANALYSIS

     All water-quality and suspended-sediment samples were collected by USGS
personnel using depth-integrating methods  described  by Guy  and Norman (1970).
All water-quality  samples were preserved  in the  field  according  to  methods
described in the  National Handbook of  Recommended Methods for  Water Data
Acquisition  (U.S.Geological  Survey, 1977)  and  analyzed  at  the  USGS Central
Laboratory  in  Doraville,  Ga.   Pesticide  residues,  low-molecular-weight  halo-
genated  hydrocarbons, and organic carbon were determined according to methods
described by Goerlitz and  Brown (1972), and inorganic constituents were analyzed
according to procedures cited by Skougstad and others (1979).  Samples for analysis
of chlorine were collected and analyzed using methods described in another section
of this report.  Sediment samples were analyzed  in the USGS sediment laboratory
in Harrisburg, Pa., by methods described by Guy (1969).

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   Table  1.—Average  discharge  for study period and long-term average
               discharges for the  three  Fall Line  stations

Period
of
average
Average
discharge
for study
period

Long-term
average
discharge
(ftJ/s)
Percent
difference
from long-
term average
                   SUSQUEHANNA RIVER AT CONOWINGO, MD.
Jan.-Dec. 1979
Jan.-Dec. 1980
Jan.-Apr. 1981

Jan. 1979-Apr. 1981
52,300
28,400
45,900

41,100
'38,900
'38,900
^6,700

L42,900
+ 34
- 27
- 19

-  4
            POTOMAC RIVER AT CHAIN  BRIDGE  AT WASHINGTON,  D.C.
Jan.-Dec. 1979
Jan.-Dec. 1980
Jan.-Apr. 1981

Jan. 1979-Apr. 1981
20,400
11,000
 9,060

14,800
 11,500
 11,500
 15,300

 12,000
+ 79
-  3
- 41

+ 23
                     JAMES RIVER AT CARTERSVILLE, VA.
Jan.-Dec. 1979
Jan.-Dec. 1980
Jan.-Apr. 1981

Jan. 1979-Apr. 1981
12,000
 7,790
 3,180

 8,950
  7,050
  7,050
 10,000

  7,470
+ 70
+ 11
- 68

+ 20
  Based on long-term discharge  record  for  the  Susquehanna  River  at
    Harrisburg,  Pa., and drainage area relationships.

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            SUSQUEHANA RIVER AT CONOWINGO
  Q
  z
  o
  o
  IU
  CO

  cc
  UJ
  Q.
  UJ
  UJ
  O

  CO
  3

  O
  CO
  Q
  Z
  <
  CO
  3
  o
  I
Ul
o
cc

X
o
CO

Q
     200



     100

      80

      60

      40




      20



      10
       8

       6


       4




       2



       1
      60
MEAN  MONTHLY  DISCHARGE


LONG-TERM  AVERAGE MONTHLY DISCHARGE
          IFMAMIJASOND

                     1979
                                         JFMAMIJASONDJFMA
                            1980
                                                                        1981
          POTOMAC  RIVER AT CHAIN BRIDGE, WASHINGTON  D.C.
         2 -
           JFMAMJJASONOj  FMAMJjASONDJFMA

                      1979                          1980                1981


           JAMES RIVER AT CARTERSVILLE , VA
           IFMAMI  JASOND   I  FMAMIJASONDJ  FMA
Figure  2.—Mean monthly and  long-term average monthly discharge  for the  three

                                 Fall  Line stations.
                                           7

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                             CONSTITUENT LOADS

                Load Estimation Techniques—Nutrients and Metals

      Bivariate linear  regression equations were used to  estimate all loads in this
study.  Instantaneous  constituent  concentrations and  discharges were used  to
formulate the equations, which were then used with either mean daily discharges or
daily  sediment loads to obtain daily constituent loads.

      Instantaneous  constituent loads  were computed  for  each  sample collected
using  the following equation:

                           L  = C  x Q x 5.38
where
                L =  nutrient or metal load at time of sample,
                        in Ibs/d;
                C =  nutrient or metal concentration at time of sample,
                        in mg/L;
                Q =  instantaneous discharge at the time of sample, in ft3/s; and
              5.38 = conversion factor.

      The log  of this instantaneous load was regressed against the log of the instan-
taneous discharge  and the log of the instantaneous suspended-sediment load at the
time  of sampling.   Regression equations  were fitted analytically  by the method of
least  squares.
      Three criteria were then used  for  selecting either the discharge  or sediment
regression  to calculate loads: (1) The chosen equation should have a low standard
deviation.  (2)  A large percentage of the variance in the dependent variable (loads)
should be  explained or accounted  for  by the  regression.   The  coefficient  of
determination (r2) is a measure  of this.  The greater r2 is, the better the regression
line fits the observed data points, and the more highly correlated one variable is to
another.  (3)  The signs of all significant regression coefficients should agree with
accepted chemical and physical  principles.

      Table 2  presents  the regression equations and related statistics derived from
the above  regression  analysis  and  used  to  calculate  constituent loads.    Both
equations,   using  either  discharge  or  suspended sediment as  the  independent
variable, are shown.  An asterisk notes the equation selected for determination of
constituent loads found in tables 3, 4, and 5. The selected equation is in the form:

                      Log1Q L  -  a + b(log10 Q)
or
                      Log]0 L  = a + b (log1Q SS)
where
                _L_ =  daily nutrient or metal load, in Ibs/d;
                Q =  mean daily discharge, in ft3/s;
               SS =  daily sediment load, in Ibs;
                a =  constant defining y  intercept;  and
                b =  constant defining slope of regression.

      The mean daily  discharge or  suspended-sediment load is  then substituted to
obtain daily constituent load.  These daily loads are  then summed to obtain the
monthly totals found in tables 3, 4, and 5.

-------






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-------
                Table  3.—Monthly  load  estimates  (in hundreds  of thousands of pounds) for the
                                     Susquehanna  River at Conowingo,  Md.

                                       [ Dashes  indicate missing data  ]
Month
Mean
discharge
(ft3/s)
Aluminum,
total
recoverable
as Al
Calcium,
dissolved
as Ca
Carbon,
organic,
total
as C
Chloride,
dissolved
as Cl
Iron,
total
recoverable
as Fe
Magnesium,
dissolved
as Mg
Manganese,
total
recoverable
as Mn
January 1979
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1980
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1981
February
March
April
101,200
47,600
143,000
65,200
43,900
26,900
13,000
16,140
28,000
48,900
48,300
44,200

52,300
27,200
13,100
70,400
108,000
46,500
17,500
12,300
8,450
4,740
6,270
9,800
16,800

28,400
7,170
104,000
35,500
36,800
57.0
34.5
15.7
4.7
6.7
16.3
45.6
35.9
42.7

-
10.9
2.8
119.3
126.7
44.9
13.5
4.3
3.1
1.8
4.3
5.2
5.3

342
5.1
221.5
20.0
~
-
-
624
688
1,060
1,780
1,710
1,490

-
1,009
614
2,170
2,650
1,480
700
593
438
278
397
685
793

11,800
395
2,800
1,220
~
636
245
969
342
224
120
50.2
65.2
125
256
248
225

3,510
122
47.2
426
648
235
69.5
46.9
29.8
14.5
21.3
35.9
69.4

1,770
24,6
622
174
171
-
-
309
340
530
893
858
748

—
504
304
1,093
1,350
743
349
294
217
137
196
336
393

5,920
195
1,420
615
—
90.0
54.4
24.6
7.4
10.3
25.6
77.0
61.0
72.3

-
18.0
4.4
209.2
219.5
75.7
22.1
6.8
4.9
2.9
6.9
8.4
8.5

587
8.3
394.2
33.2
~
-
-
192
212
317
519
499
426

—
294
188
610
700
420
210
180
135
87
125
219
241

3,410
123
779
352
~"
21.7
13.8
7.0
2.7
3.5
7.3
19.6
15.0
18.0

-
5.9
2.0
38.4
44.3
19.5
7.3
3.0
2.3
1.5
2.9
3.3
3.5

134
3.3
63.0
10.0
~"
Total January 1979
   to   April 1981
6,260
                                                   10

-------
                Table 3.—Monthly load estimates (in hundreds of thousands of pounds) for the
                               Susquehanna River at Conowingo,  Md.—Continued


Month

Nitrogen,
ammonia,
total
as N
Nitrogen,
organic,
total
as N
Nitrogen,
ammonia
+ organic,
total as N
Nitrogen,
nitrite
+ nitrate,
total as N

Nitrogen,
total
as N
Phosphorous,
ortho-
phosphate ,
total as POU

Phosphorous ,
total
as PO^

Sodium,
dissolved
as Na

Sulfate,
dissolved
as SO,,
January 1979
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1980
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1981
February
March
April
18.4
7.3
27.4
10.4
6.9
3.8
1.7
2.2
4.0
7.8
7.6
6.9

104
3.9
1.6
12.4
18.8
7.3
2.3
1.6
1.0
.52
.74
1.2
2.3

53.7
0.9
17.7
5.4
5.4
63.9
25.7
94.0
36.8
24.7
13.9
6.3
8.0
14.5
28.0
26.9
24.9

368
14.3
5.9
43.5
65.6
26.1
8.5
6.0
4.0
2.0
2.8
4.5
8.4

192
3.3
61.0
19.6
19.4
80.7
32.8
117.8
47.3
32.0
18.2
8.4
10.6
18.9
36.1
34.7
32.2

470
18.8
7.9
55.2
83.0
33.8
11.3
7.9
5.3
2.7
3.8
6.0
11.2

247
4.4
76.6
25.5
25.3
201
82.8
291
120
82
47.1
22.3
28.1
49.1
92.1
88.3
83.0

1,190
48.9
21.0
138.0
207
86.7
29.6
21.1
14.1
7.4
10.3
15.9
29.4

629
11.9
189.7
65.5
65.3
285.0
116.8
413.0
169.0
115.0
65.8
31.0
39.0
68.6
129.4
124.1
115.8

1,670
68.3
29.0
195.5
293.5
121.6
41.2
29.2
19.5
10.1
14.3
22.0
40.9

885
16.4
269.3
91.8
91.5
13.2
5.5
19.1
8.0
5.5
3.1
1.5
1.9
3.3
6.1
5.9
5.5

78.6
3.3
1.4
9.1
13.7
5.8
2.0
1.4
1.0
.5
.7
1.0
2.0

41.8
0.8
12.5
4.4
4.4
42.0
15.3
68.7
19.7
12.3
6.1
2.2
2.9
6.3
14.5
14.2
12.4

217
6.0
2.0
27.3
41.9
12.8
3.1
2.0
1.2
.53
.82
1.6
3.2

102
1.0
43.1
9.4
8.9
-
-
-
-
-
-
210
233
350
570
549
470

-
324
206
670
780
460
230
198
148
95
137
239
264

3,751
134
862
388
-
-
-
-
-
-
-
1,210
1,340
2,000
3,280
3,160
2,700

-
1,863
1,190
3,860
4,490
2,650
1,320
1,140
849
549
786
1,370
1,520

21,600
770
4,950
2,230
-
Total January 1979
   to   April 1981  188
663
              848
                       2,150
3,030
                                               143
381
                                                      11

-------
                Table  4.—Monthly  load  estimates  (in hundreds of thousands of pounds) for the
                              Potomac River  at  Chain Bridge at Washington, D.C.

                                       [Dashes  indicate  missing data ]
Month
Mean
discharge
(ft3/s)
Aluminum,
total
recoverable
as Al
Calcium,
dissolved
as Ca
Carbon,
organic,
total
as C
Chloride,
dissolved
as Cl
Iron,
total
recoverable
as Fe
Magnesium,
dissolved
as Mg
Manganese,
total
recoverable
as Mn
January 1979
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1980
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1981
February
March
April
31,100
30,600
38,300
18,900
17,400
14,600
5,960
5,940
21,900
33,700
18,300
13,200

20,400
18,400
8,050
23,300
31,000
25,300
7,910
4,280
3,400
1,670
1,700
3,710
3,550

11,000
1,680
13,700
7,550
13,100
133
138
80.9
24.9
24.6
31.6 -
3.8
7.7
99.8
103
30.8
10.0

689
14.7
4.0
49.7
63.2
63.2
6.2
3.6
2.0
.44
.50
2.7
1.1

211
0.41
42.3
3.8
~
1,045
-
-
-
729
561
317
-
791
1,084
318
604

-
609
341
-
-
65.1
368
259
222
112
138
264
215

-
108
583
359
352
341
255
271
111
114
133
35.6
56.2
274
310
119
56

2,080
76.6
30.3
170
236
217
48
33
20.4
7.6
7.9
21.1
14.3

882
7.3
153
33.3
~
352
-
-
-
277
208
133
-
284
285
126
235

-
227
137
-
-
25.0
149
110
96.2
49.0
62.7
117
91.5

~
49.5
229
141
131
216
237
126
37.2
36.4
47.5
5.1
10.6
161
164
47.2
14.5

1,100
21.4
5.5
77.8
96.4
98.2
8.4
4.7
2.6
.53
.61
3.7
1.4

321
0.49
65.2
5.0
~
219
-
-
-
161
123
73.6
-
170
233
72.0
135

-
133
77.5
-
-
14.5
83.9
60.4
52.3
26.5
33.4
63.0
50.3

~
26.2
131
80.7
77.0
15.9
16.2
9.9
3.1
3.1
3.9
.51
1.0
12.0
12.6
3.8
1.3

83.3
1.9
.52
6.1
7.8
7.8
.81
.47
.27
.06
.07
.35
.15

26.3
0.06
5.2
.50
"
Total January 1979
   to   April 1981
947
3,150
1,490
                                                                          115
                                                 12

-------
                Table 4.—Monthly load estimates (in hundreds of thousands of pounds) for the
                        Potomac  River  at  Chain  Bridge  at  Washington,  B.C.—Continued
Month
Nitrogen,
ammonia,
total
as N
Nitrogen,
organic,
total
as N
Nitrogen,
ammonia
+ organic,
total as N
Nitrogen,
nitrite
+ nitrate,
total as N
Nitrogen,
total
as N
Phosphorous,
ortho-
phosphate ,
total as POi,
Phosphorous ,
total
as PO,,
Sodium,
dissolved
as Na
Sulfate,
dissolved
as SO,,
January 1979
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1980
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1981
February
March
April
4.56
5.53
5.80
2.04
1.87
1.49
.40
.40
2.80
5.00
2.06
1.35

33.3
2.16
.63
3.06
4.12
3.39
.65
.29
.21
.08
.08
.26
.23

15.2
0.09
1.43
.63
1.46
44.2
34.8
33.9
13.3
13.5
16.0
3.8
6.3
35.1
39.4
14.5
6.5

261
8.9
3.3
21.0
29.1
27.0
5.3
3.6
2.1
.74
.78
2.3
1.5

106
0.71
18.8
3.6
11.8
54.3
42.8
41.6
16.3
16.7
19.7
4.7
7.7
43.2
48.5
17.8
7.9

321
11.0
4.1
25.9
35.8
33.2
6.5
4.4
2.6
.91
.96
2.8
1.8

130
0.87
23.2
4.4
-
65.8
68.0
82.9
33.5
31.3
25.1
8.2
8.2
42.3
72.6
33.6
23.4

495
35.1
12.1
47.1
62.1
51.6
12.4
6.2
4.7
1.9
2.1
5.3
5.0

247
2.2
23.3
12.1
24.0
125.0
140.9
158.5
59.3
54.9
43.8
12.8
12.9
78.3
137.5
59.7
40.2

924
62.6
19.7
86.4
115.3
95.2
20.1
9.5
7.1
2.7
2.9
8.4
7.5

438
3.1
41.4
19.6
42.4
6.96
7.20
8.82
3.48
3.24
2.58
.81
.81
4.47
7.68
3.48
2.40

51.9
3.60
1.20
4.95
6.60
5.43
1.23
.60
.45
.18
.21
.54
.48

25.5
0.21
2.40
1.20
2.49
34.2
30.7
23.8
8.3
8.4
10.3
1.82
3.3
26.5
28.9
9.6
3.7

190
5.3
1.7
14.6
19.6
18.7
2.7
1.7
.98
.28
.30
1.2
.61

67.8
0.26
12.8
1.7
—
251
-
-
-
232
170
125
-
221
296
112
202

~
186
123
-
-
21.3
134
104
93.0
47.8
63.1
116
86.8

-
50.1
200
124
107
1,024
-
-
-
1,517
1,219
650
-
1,744
2,403
672
1,289

~
679
-
-
-
1,064
770
528
448
224
198
368
284

-
156
697
430
391
Total January 1979
   to   April 1981
52.1
          402
                       480
                                  804
1,470
                                                         83.7
                                                                      273
                                                       13

-------
               Table 5.—Monthly load estimates  (in hundreds  of  thousands  of  pounds)  for  the
                                      James River at Cartersville, Va.

                                       [Dashes  indicate missing data]
Month
Mean
discharge
(ftVs)
Aluminum,
total
recoverable
as Al
Calcium,
dissolved
as Ca
Carbon,
organic ,
total
as C
Chloride,
dissolved
as Cl
Iron,
total
recoverable
as Fe
Magnesium,
dissolved
as Mg
Manganese,
total
recoverable
as Mn
January 1979
February
March
April
May
June
July
Augu st
September
October
November
December
Calendar year
total
January 1980
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1981
February
March
April
16,400
18,200
20,100
9,690
9,190
13,800
3,580
3,000
16,100
16,000
11,900
7,110

12,000
14,600
6,540
17,900
21,500
8,040
3,590
2,350
1,820
1,420
1,410
2,020
1,860

7,790
1,680
4,760
2,650
3,640
46
115
64.4
12.6
12.1
51.4
1.9
1.5
60.0
40.0
20.0
7.4

432
35.1
5.5
46.6
67.3
9.1
2.0
.9
.5
.3
.3
.7
.6

169
0.51
3.6
1.1
1.9
393.7
-
463.5
264.6
261.4
316.1
122.8
106.4
353.2
391.5
307.0
213.5

~
364.6
188.5
431.3
264.6
236.2
118.3
86.2
69.8
53.5
56.2
73.3
71.0

2,010
65.3
137.1
95.3
120.6
179
207
225
90.1
87.7
149
28.8
23.8
176
171
115
65

1,520
155
54.6
194
234
74.7
28.3
17.7
13.1
9.1
9.7
14.4
13.4

819
11.9
37.2
20.4
28.3
164.5
-
172.4
-
155.7
-
93.3
828
-
172.5
164.0
137.8

~
167.6
126.0
182.2
155.5
147.6
89.0
69.8
58.8
46.7
48.8
60.6
59.6

1,210
55.6
95.8
75.8
91.3
93
261
132
23.1
22.3
110
3.1
2.4
127
79.4
37.6
13.1

904
69.6
9.6
93
138
164
3.4
1.4
.8
.5
.5
1.1
.9

483
0.7
6.2
1.8
3.1
80.6
-
93.7
56.5
55.9
64.4
27.3
23.7
71.1
80.6
64.7
46.1

~
75.4
41.0
88.4
56.4
50.8
26.2
19.3
15.8
12.2
12.8
16.5
16.0

431
14.8
30.0
21.4
26.8
3.5
7.9
4.9
1.1
1.0
3.7
.18
.14
4.4
3.1
1.6
.64

32.2
2.8
.49
3.6
5.1
.78
.19
.09
.05
.03
.03
.07
.06

13.4
0.05
.32
.10
.18
Total January 1979
   to   April 1981
608
                        2,430
1,400
                                                                           46.3
                                                14

-------
                Table 5.—Monthly load estimates (in hundreds of thousands of pounds) for the
                                 James River at Cartersville, Va.—Continued
Month
Nitrogen,
ammonia,
total
as N
Nitrogen,
organic,
total
as N
Nitrogen,
ammonia
+ organic,
total as N
Nitrogen,
nitrite
+ nitrate,
total as N
Nitrogen,
total
as N
Phosphorous,
ortho-
phosphate,
total as P0<,
Phosphorous,
total
as PO,,
Sodium,
dissolved
as Na
Sulfate,
dissolved
as SO,,
January 1979
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1980
February
March
April
May
June
July
August
September
October
November
December
Calendar year
total
January 1981
February
March
April
1.1
1.1
1.4
.61
.59
.90
.22
.18
1.1
1.1
.75
.45

9.5
0.97
.39
1.2
1.4
.52
.21
.14
.11
.08
.08
.12
.11

5.3
0.10
.27
.16
.21
18.0
27.1
23.4
7.3
7.0
16.1
1.8
1.4
19.4
16.7
10.0
4.9

153
14.9
3.9
19.1
24.5
5.8
1.8
.98
.67
.43
.47
.78
.70

74.0
0.60
2.6
1.2
1.8
18.9
28.5
24.7
7.7
7.4
16.9
1.9
1.5
20.3
17.6
10.6
5.2

161
15.7
4.2
20.1
25.8
6.1
1.9
1.0
.7
.5
.5
.8
.7

78
0.6
2.8
1.2
1.9
8.7
9.3
10.8
4.7
4.6
7.2
1.7
1.4
8.4
8.5
5.9
3.5

74.7
7.7
3.0
9.5
11.3
4.0
1.6
1.1
.8
.6
.6
.9
.8

41.9
0.7
2.1
1.2
1.6
29.6
39.3
38.0
13.3
13.0
25.5
3.7
3.0
30.6
28.0
17.8
9.2

251
25.1
7.6
31.9
39.7
10.8
3.7
2.1
1.5
1.0
1.0
1.7
1.6

128
1.4
5.1
2.5
3.7
3.2
2.7
3.7
2.3
2.2
2.6
1.2
1.1
2.9
3.2
2.6
1.9

29.6
3.0
1.7
3.5
3.8
2.1
1.1
.89
.75
.60
.63
.77
.76

19.5
0.71
1.3
.97
1.2
12.4
14.5
15.7
6.2
6.1
10.4
2.0
1.6
12.3
11.9
8.0
4.5

106
10.7
3.8
13.5
16.3
5.2
1.9
1.2
.89
.6
.7
1.0
.9

56.7
0.8
2.6
1.4
1.9
115.4
-
123.9
-
102.6
-
59.5
52.6
-
119.7
110.0
89.8

-
115.4
81.6
127.5
102.7
96.6
56.8
44.2
37.0
29.3
30.7
38.2
37.5

798
35.0
61.7
48.1
58.2
240.0
-
277.3
172.1
170.6
191.3
85.0
74.1
209.8
240.8
195.7
141.8

-
226.0
126.2
263.4
172.1
155.8
81.7
60.7
49.7
38.5
40.4
51.9
50.5

1,320
46.6
92.8
66.8
83.4
Total January 1979
   to   April 1981
15.6
          233
                       246
                                  122
                                             391
                                                         53.3
                                                                      169
                                                       15

-------
              Load Estimation Techniques—Major Cations and Anions

     Because specific conductance is  directly related  to the number of dissolved
ions in water, it is  appropriate  to  use this parameter to predict loads of major
cations and anions in the  three rivers.  The James River specific conductance data
were not sufficient, thus log  Q was substituted as the  independent variable.  The
relationships used were:

                           C = a + b (SC)
or
                           C = a + b (log Q)
where
                C  = major ion concentration at the time of sample, in mg/L;
               SC  = specific conductance at the time  of sample, in ^jmhos/cm2;
                Q  = instantaneous discharge at the time of sample, in ft3/s;
                 a = constant defining y intercept;  and
                 b = constant defining slope of regression.

     Instantaneous  constituent  concentrations were regressed  against  the  daily
specific conductance or  the  log of the  instantaneous discharge and  the above
equations  fitted analytically  by  the  method  of least squares.  By substituting  the
daily specific conductance or log of the mean daily discharge  into  the  equations
instead of  the value at the time of sample, an  average daily concentration C was
calculated:
                           C = a + b (SCd)
or                         _             _
                           C = a + b (log Q).

Then, the daily load was computed by:

                      L  = C x Q x 5.3S,
where            _
                C  = average daily ion concentration, in mg/L;
               SCjj  = daily specific conductance value,  in umhos/cm;
                Q  = mean daily discharge, in ft3/s;
                L  = daily load in Ibs/d;
                a  = constant defining y intercept;
                 b  = constant defining slope  of regression; and
              .5.38  = conversion factor.

     Daily  major cation  and  anion loads are summed to obtain monthly loads  and
are tabulated in tables 3,  4, and 5.  The regression equations used to estimate them
are presented in table 6.
                                      16

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                 Evaluation and Limitation of the Load Estimates

     In tables 3, 4,  and 5, and in subsequent listings,  all constituent loads  are
calculated independently from their regression equations,  regardless of the rela-
tionships  that  are  known  to exist among the parameters.   For  example, total
nitrogen concentration equals the sum of nitrite + nitrate  and ammonia + organic
nitrogen  concentrations for  each  individual  sample.    If  the load  estimation
techniques are accurate, the sums  of monthly or  yearly loads of nitrite + nitrate,
and  ammonia +  organic nitrogen  should  be  nearly  the same as loads for total
nitrogen for the same periods.  Also, the summed loads of ammonia nitrogen and
organic nitrogen should  be  the  same  as  ammonia  + organic  nitrogen.   The
agreement or  disagreement  of the  constituent  loads  and  the  sums  of  their
component species  is  an indication of the ability of the  regression technique to
accurately estimate those constituent loads for the specific period.

     To test  further the  accuracy  of  this  technique,  yearly  constituent  loads
calculated by this regression method were  compared to those obtained by a totally
different  method for Potomac  River at  Chain  Bridge  (table  7).   The USGS's
Potomac  Estuary  Project  personnel  independently  collected  data on  selected
nutrient species at  this site through calendar years 1979 and 1980.  For their load
computations, they  had access to a large data base of which only part was used in
this  report to obtain  regression equations and to  compute  constituent loads.  The
Estuary  Project group  calculated their  loads   using  the  hydrograph  method
(Porterfield, 1972).  In this technique, enough data must be available to estimate a
continuous plot of constituent concentrations. This, along with a continuous plot of
discharge,  is  used to  obtain a continuous measure of  constituent loads,  subdividing
days as necessary.   This is a more direct and, hence, accurate  method  of  load
computation.

     The  comparisons in table 7 show relatively  small differences in annual total
loads.  Month-by-month comparisons do not compare as well because the regression
technique does not  allow for  seasonal- and antecedent-flow  variations, which  are
accounted for in the  hydrograph technique.  Similar results can be expected from
the Susquehanna and James Rivers.

     The  regression load-estimation technique  requires intensive sampling of high
discharges, which carry the majority of most constituent loads.  An inconsistent or
incomplete, high-flow sampling program will not cover the  full range of hydrologic
events and may incorrectly bias the regression equations  to only those high-flow
events that are sampled.

     The   regression  load-estimation  technique  is most  accurate in wet  years
having a wide  range  of  flow.   Factors not  taken into account in the regression
technique, such as  season and time since  the previous  flow  peak,  have a greater
relative effect on constituent loads during sustained low-flow periods.  Based only
on low-flow constituent loads,  the regression line has higher standard deviation,
which leads to a lower coefficient of determination.

     The  basic data  used  in calculating loads for the  Susquehanna  and  Potomac
Rivers are available  in  USGS annual reports titled  "Water Resources Data  for
Maryland  and Delaware;" the James River data is found in  the USGS  publication
titled "Water Resources Data for Virginia."
                                      18

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-------
        EXAMINATION OF SELECTED WATER-QUALITY CONSTITUENTS
                     Seasonal Characterization of Pesticides


     Pesticide residue data (organochlorine and  organophosphorous insecticides
and chlorophenoxy acid herbicides) were collected monthly and during high flows at
each of the Fall  Line stations.  Only 2, 4 dichlorophenoxyacetic acid (2,4-D) and
atrazine were consistently detected at the  Conowingo and Chain Bridge  stations.
Pesticide  concentrations  at the Chain  Bridge  site  were  generally  less than at
Conowingo.  Maximum concentrations detected  at Conowingo were 0.30 and 1.2
ug/L for 2,4-D and  atrazine, respectively.  At Chain Bridge, maximum concen-
trations were 0.14 and 0.4  ug/L for  2,4-D and atrazine, respectively.   Atrazine,
2,4-D,  and silvex were detected at James River at Cartersville several times, but
concentrations were  at the lower limit of detection.


     Both  2,4-D  and atrazine concentrations show strong seasonal patterns in the
Susquehanna  and Potomac  Rivers (figs. 3  and 4).   Both  rivers  have  2,4-D and
atrazine concentration peaks in late spring and summer.  This is reasonable because
herbicides are usually applied just before and during spring planting, and both 2,4-D
and atrazine are readily  soluble in  water.   Therefore, runoff from cropland and
residential  areas in  late  spring and  summer usually carries higher  than normal
concentrations of these  herbicides in solution to nearby tributaries and  streams.
These streams, in turn, carry the herbicides into the estuaries of the Chesapeake
Bay.

     The highest concentrations of 2,4-D in the Susquehanna River occurred during
low-flow periods in  fall  1980  and spring  1981.   As streamflow decreased, the
concentration of 2,4-D in the Susquehanna River increased.  This  trend continued
until high  flows  in  February diluted the  concentration to  much  lower levels.
Following  this high-flow  event, 2,4-D  concentrations again increased in  March
1981.  This type  of  concentration-discharge relationship is  typical of a constant,
continual input of a constituent into a variable flow system; runoff during high
flows dilutes the constituent to low concentrations,  but concentrations  begin to
rise during base flow. Considering 2,4-D is a widely-used domestic herbicide, it is
possible that  input  of 2,4-D to the  Susquehanna River could be  from shallow
ground-water  sources or  point  discharges.  However, more  data  are  needed to
determine  the source  of 2,4-D in  the Susquehanna River which keeps concentra-
tions high (0.20-0.30 ug/L) even during winter  months when herbicide applications
are at a minimum.   In contrast,  the Potomac basin,  which has similar  land-use
practices as the Susquehanna, had  very small concentations (<0.05 pg/L) during the
same low-flow periods in fall 1980 and spring 1981.
                                      20

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         0.15
         0.10 -
         0.05  -
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                                                            T—(—,140,000
                                                               - 120,000
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     IFMAMJJASOND  JFMAMJJASONOJFMA
              1979
                                      1980
                                                           1981
              POTOMAC  RIVER  AT CHAIN BRIDGE ,  WASHINGTON D.C.
                                                    DISCHARGE

                                                    2, 4-D CONCENTRATION
                                        IFMAMJJASOND
0.25 -
         0.20 -
         0.15
         0.10
         0.05 -
                                                                          48,000
                                                               - 40,000
                                                               - 32,000
                                                                       - 24.000
                                                                       - 16,000
                                                                         8,000
         0.00 -
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            1979
                                                1980
                                                                  J F M  A

                                                                   1981
Figure 3.—Seasonal  fluctuations in  concentrations of  2,4-D  at the  Susquehanna

                           and Potomac  Fall Line  stations.
                                           21

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              SUSQUEHANNA  RIVER  AT CONOWINGO, MD.
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                                                                     - 80,000
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                                                           - 40,000
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              1979
                                      1980
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    POTOMAC  RIVER AT CHAIN  BRIDGE , WASHINGTON D.C
          0.0	
              JFMAMJJASONDJFMAMJJASONDJFMA

                      1979                        1980             1981
Figure  4.—Seasonal fluctuations in concentrations  of  atrazine  at the  Susquehanna

                          and  Potomac Fall  Line stations.
                                           22

-------
                   Seasonal Characterization of Chlorophyll A


     Chlorophyll a  is  the  primary pigment of all oxygen-evolving photosynthetic
organisms and  is present in all algae and photosynthetic organisms, except some
photosynthetic  bacteria  (Wetzel,  1975).   Figure  5 presents  the  chlorophyll  a
concentrations  for  each of  the  Fall  Line  stations.    Maximum  chlorophyll  a
concentrations  at all  three sites  occur during  spring  runoff.  Increased spring
concentrations  may be caused by high-velocity runoff carrying  with it fragments of
underdeveloped and emerging  plankton  or  a spring accumulation  of periphytic
chlorophyll.  Concentration  peaks of  lesser magnitude occur during the late spring
and summer months, but these are  generally not related to discharge.  The summer
peaks may be related to increased biological activity which  accompanies warmer
temperatures, increased daylight, and rapid nutrient recycling.
                                   Chlorine


      Because of recent interest in the effects  of chlorine on marine  life, water
samples were collected and field-analyzed for total  residual chlorine at five  sites
on tributaries to the Chesapeake Bay (fig. 6).  At the  same time, additional samples
were  collected and  sent  to the laboratory for  analysis of low-molecular-weight
halogenated hydrocarbons listed  in table 8.  The sites are:  (1) Susquehanna River
at Conowingo, Md.;  (2) Potomac River at Chain Bridge at  Washington, D.C.;  (3)
Potomac River at Woodrow Wilson Bridge at Alexandria, Va.;  CO Patuxent River
near Bowie, Md.;  and (5) Back River at Edgemere, Md.

      The total residual (free  residual and combined)  chlorine analysis employed
(American  Public Health  Association,  1976) was an  amperometric  titration tech-
nique which measures  the total oxidants  in the water.   Therefore,  significant
concentrations of  constituents  such   as  bromine,  iodine,  chlorine  dioxide,  or
permanganate in the sample may produce erroneously high values for total residual
chlorine.

      The five stations  shown in figure 6 were each  sampled in December 1980 or
January  1981 and again  in June or July 1981.  All samples had total  residual
chlorine concentrations of less than or  equal to the lower limit of detection for the
technique,  0.01  mg/L.  In three instances the chemicals listed  in table 8 were
detected.  Trichloroethylene (TCE) concentrations of 0.005 and  0.009  mg/L were
reported for the Back and Patuxent River sites, respectively, on July 1, 1981.  On
June  26,  1981, a benzene concentration  of  0.002  mg/L  was detected  for  the
Potomac River  at  Alexandria, Va.  The  limits of  detection  for  both TCE  and
benzene are 0.001 mg/L.
                                       23

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                      SUSQUEHANNA  RIVER AT CONOWINGO . MD
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          1979             1980       1981



    POTOMAC  RIVER AT CHAIN BRIDGE. WASHINGTON DC
90


80


70


60


50


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                                           CHLOROPHVLL A
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           1979            1980



    JAMES RIVER AT CARTERSVILLE , VA
                                                       1981
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                      N  Oil  F  M  A  M  I  ]  A S  0  H Oil  F  M A

                   1979              1980              1981
Figure 5.--Seasonal fluctuations of concentrations  ol chlorophyll a at  the

                                three Fall Line stations.

-------
          EXPLANATION

  	Drainage  Basin boundary

     S7    Chlorine- Monitoring station
                                        >	NY._.,	l_^T
                                     ;J  Susquehanna
                                            River
                                            Basin
Figure  6.—Location  of  chlorine-monitoring stations on selected tributaries
                                to  Chesapeake Bay.
                                       25

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Table 8.—Schedule of low-molecular-weight,  halogenated organic compounds
          analyzed from selected tributaries to Chesapeake Bay.  All
          samples were collected at base flow and performed on unfiltered,
          water-sediment mixtures.
                       Benzene
                       Bromoform
                       Carbon tetrachloride
                       Chlorobenzene
                       Chlorodibromomethane

                       Chloroethane
                       2-Chloroethyl vinyl ether
                       Chloroform
                       Dichlorobromoethane
                       Dichlorodifuloromethane

                       1,1-Dichloroethane
                       1,2-Dichloroethane
                       1,1-Di chloroethylene
                       1,2-trans-Dichloroethyiene
                       1,2-Dichloropropane

                       1,3-Dichloropropene
                       j'jthylbenzene
                       Methylbromide
                       1,1,2,2-Tetrachlorethane

                       Tetrachloroethylene
                       Toluene
                       1,1,1-Trichloroethane
                       1,1,2-Trichloroethane
                       Trichloroethylene

                       Trichlorofluoromethane
                       Vinyl chloride
                                 26

-------
                Total Recoverable Aluminum, Iron, and Manganese


      The term "total recoverable" refers to the amount of a particular constituent
that is in solution after a  water/suspended-sediment mixture  sample  has  been
digested by  dilute acid.  Complete  dissolution of all particulate  matter  by this
method is not achieved or desirable.   The purpose of the digestion  is to remove
those constituents readily recoverable  from the surfaces of the sediment particles
without breaking down  the crystalline structure of the sediments. Minerals within
this  crystalline  structure are  considered essentially  unavailable  for biological
uptake under normal conditions existing in  the estuaries of the Chesapeake Bay.

      Computed loads for total  recoverable aluminum,  iron,  and  manganese are
presented  in tables  3,  k, and 5.   The greatest loads for each  constituent  were
carried in the Susquehanna  River basin, whereas the  smallest  loads were found in
the James River basin.  Figures  7, 8, and 9 show  aluminum, iron, manganese, and
suspended-sediment  concentrations, and discharge at the three Fall  Line stations
for selected high-flow periods.  Regression data from table 2 for the Susquehanna
River show higher correlations  of aluminum,  iron, and manganese  with suspended
sediment than with discharge. Because of the three dams in the lower Susquehanna
River, this correlation is not  evident in figure 7.

      Aluminum, iron, and manganese correlated very well with suspended sediment
in the Potomac  River  at  Chain Bridge  (table  2 and fig. 8).  As suspended-sediment
concentrations increased, so  did concentrations of  aluminum, iron, and manganese.
All three  metals had peak concentrations that were greater during the high flow in
March than in September.

      Figure  9  shows  slightly different relations  at  the  James  River.   Although
manganese and  suspended-sediment concentrations increased  proportionally  with
discharge,  aluminum  and iron decreased at the peak of both  suspended  sediment
and discharge.  This sag  may be caused by different quality  and arrival times of
water  coming  from  upstream  tributaries.   No  other  storms  were  intensively
sampled to verify whether this phenomenom occurs frequently.
                                    Sulfate


     Sulfate is not a major constituent in the earth's outer crust (Hem,  1970). It is
commonly  derived  from metallic sulfides which  occur in both igneous and sedi-
mentary rocks.  As these sulfides come into contact with aerated water, they are
oxidized to sulfates. The oxidation of sulfur-containing minerals, such as pyrite, is
especially common  in coal areas.

     Sulfate concentrations generally are inversely related to  discharge. Because
rainwater contains  very small concentrations of  sulfate as compared to streams,
sulfate concentrations drop sharply during runoff  events.  During low-flow periods,
streams are fed principally  from ground-water sources, which have relatively high
concentrations of sulfate due to prolong and intimate contact with sulfate-yielding
minerals.
                                      27

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                                                DISCHARGE


                                            O   WATER SAMPLE
                                                TOTAL  Hi-L'JVERABLE  ALUMINUM


                                                TOTAL  RECOVERABLE  MANGANESE
           Figure 7.—Aluminum, iron,  and manganese concentrations during

                       February 20-26,  1981, at  the Susquehanna River

                       Fall  Line station.
                                                  28

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                             MARCH  1980
                             TOTAL RECOVERABLE IRON

                             TOTAL RECOVERABLE ALUMINUM

                             TOTAL RECOVERABLE MANGANESE
  Figure  8.--Aluminum,  iron,  and  manganese concentrations during

              September  5-8,  1979,  and March 21-24,  1980, at the

              Potomac  River  Fall  Line station.

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Figure 9.—Aluminum, iron,  and  manganese concentrations  during  April  15-17,  1980,

                         at  the James River Fall Line  station.
                                            30

-------
     Table 9 compares sulfate loads for the three Fall Line stations for the period
May 1980 to April 1981.  This  period was chosen because it contained the most
complete set of data for each of the stations, primarily during ba. 3-flow  periods.
The  James River  site carried 8.3 percent of the water discharge  for the  three
stations  but  only  3.2 percent  of the  sulfate  load.   Both  the Susquehanna  and
Potomac  Rivers carried  slightly more  than their share of  sulfate loads,  when
compared to their flow contributions for the same period. The discharge-weighted
average concentrations of sulfate also point out that the  Susquehanna and Potomac
Rivers carry greater amounts per unit discharge  of sulfate than the  James River.
The increased  sulfate concentrations may be the result of drainage from coal areas
in the  Susquehanna  and Potomac River  basins.   Very little coal is  mined in the
James  River basin.
                       Nutrients and Their Relationships to
                       Suspended Sediment and Discharge


     Nutrients, chemical  species of phosphorous, nitrogen, and  carbon necessary
for the growth of plant life, are found  in water in the dissolved form associated
with clay particles and  as suspended organic  matter.  Certain nutrient species, such
as orthophosphate, nitrite, and nitrate, are usually found dissolved in water.  Most
of the organic phosphorous and  organic nitrogen is  usually suspended.  Ammonia
and carbon can be found in the  dissolved or suspended phase.

     Generally,  the  highest concentrations  of  all nutrients  occur during  storms
when water discharge and suspended-sediment concentrations are  highest (figs.  10,
11, and  12).   Nitrite + nitrate  and orthophosphate  loads  correlate closely with
discharge at all three Fall Line stations (table 2).  All of the nutrient species data
for the Susquehanna  River at Conowingo correlate  more closely  with discharge;
whereas, for the Potomac River at Chain Bridge, some parameters correlate better
with suspended sediment  while others correlate  better with discharge.  In general,
nutrient  parameters known to  associate  with suspended material relate better to
suspended  sediment,  and  constituents  with greater  solubility  relate  better  to
discharge.

     For the  Susquehanna River site,  the hydroelectric dams between Harrisburg
and Conowingo alter  the natural riverine, sediment-flow patterns.  During most
years,  suspended  sediment becomes trapped behind these dams (Williams and Reed,
1972).  The effect that the dams between Harrisburg and Conowingo have  on the
sediment transport of the lower Susquehanna River is discussed in more detail in a
later section.  However, those nutrients normally in suspension obviously have their
transport regulated by  the dams on  the lower  Susquehanna.  Figure 10 shows the
nutrient  and  suspended-sediment concentrations  at Conowingo for  the largest
storm  during  the  1981  water  year.  None of the water-quality  parameters show
clear relationships with either suspended  sediment or  discharge,  although  both
nitrite-nitrate  and ammonia + organic  nitrogen  both  have their highest concen-
trations occurring at the discharge and suspended-sediment peak.
                                       31

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                               MARCH   1980
                                                  24
             — —  — —   TOTAL AMMONIA + ORGANIC NITROGEN as N

             	  TOTAL NITRITE + NITRATE  as N

              	  TOTAL PHOSPHOROUS as P
Figure 11.—Nutrient concentrations  during September 5-8,  1979,  and

            March 21-24, 1980, at  the  Potomac River Fall  Line station.

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SUSPENDED SEDIMENT

DISCHARGE

WATER SAMPLE

TOTAL AMMONIA + ORGANIC

MiTonrjcw as N

TOTAL NITRITE + NITRATE

as N

TOTAL PHOSPHOROUS as P
                                                                              	1,000
                    15
                                        16

                                       APRIL  1980
                                                                                 -1.200
                                                                                  800
                                                                                          cc
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CC
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                                                                              -- 200
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                                                           17
            Figure 12.—Nutrient concentrations during April 15-17,  1980,  at the
                                James River  Fall Line station.
                                               35

-------
     In figures 11 and  12, ammonia + organic nitrogen is clearly  related  to  the
suspended-sediment hydrograph at both  the  Chain Bridge and Cartersville sites.
Nitrite-nitrate nitrogen relates better  to discharge  at these two sites.  Total
phosphorous shows good correlation with suspended sediment at the Chain  Bridge
station and less correlation with suspended sediment at the Cartersvilie site.

     During  the  high-flow events,  it is critical to  sample  intensively before,
during, and after both the discharge  and  suspended-sediment peaks to provide data
sufficient for  accurate  nutrient  load  estimates.    At the  Chain  Bridge  and
Cartersville  stations,  suspended-sediment  concentration peak precedes  the  dis-
charge peak  by 8  to 40 hours  (figs.  11  and 12).   If  samples are  collected only
between  the  peaks, one  might wrongly conclude that certain nutrient parameters,
such as total phosphorous and organic nitrogen, are inversely related to discharge
during  storm  periods; the loads of these constituents would then be underestimated.

     In only  one instance in the 2-year data-collection period did nutrient concen-
trations decrease  significantly during a high-flow event.  For the Potomac  River at
Chain Bridge in February 1979 (fig. 13), the rise of nutrient concentrations  at  the
beginning of  the flow peak was reversed,  probably because of a  dilution effect from
snowmelt (fig.  13).  However, when  the snow cover had  been melted and  the  rain
came in contact  with  the  land surface, the concentrations  of  nitrite + nitrate,
ammonia + organic nitrogen, and total phosphorous again  increased.

     Table 10  presents annual loads of selected nutrient species  and annual mean
discharges at the three Fall Line stations  for  1979  and  1980.  This table shows that
at each of the stations, mean streamflow during 1980 was approximately  one-half
that of 1979; likewise, all listed nutrient loads are  reduced by about half.  This
suggests  the possibility of using  annual mean  discharges to  approximate  annual
nutrient loads for  past and future years.
                    Seasonal Variability of Nutrient Transport


      Table 11  lists the transported loads  of  selected nutrients at the  three Fall
Line  stations for  2 complete calendar years.  The period of  data collection is
divided into 4-month intervals:  (1) January-April,  which represents the late winter
and early spring high-flow  period; (2)  May-August, the  most intense part of  the
growing season when flows  are low, except during hurricane-related storms; and (3)
September-December, when flows are  low to moderate  (except during  hurricane-
related storms) and biological activity for the year is declining.  Data from January
to April 1981 are not included in order to limit this analysis to two complete yearly
cycles.

      The data in  table  11  show  that for  all  three  stations, the January-through-
April period  transports most of the  loads of these nutrient species.  Sixty-one per-
cent  of  the  total nitrogen and  about two-thirds  of the  total  phosphorous and
organic carbon loads at  the Susquehanna River at Conowingo accompany the high
runoff occurring in late  winter and early spring. At the  Potomac and James  River
Fall Line stations, the January-through-April period contributes 50 to 61  percent of
the loads for these three constituents.
                                      36

-------
O
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UJ
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     220,000-
180,000--3.0  -
 60,000
      20,000--
                                                DISCHARGE
140,000- -     |   /                  ^»TER SAMPLE


                /  SUSPENDED    JX\  *
       --2.0   /   SEDIMENT   ^f  \   \

            -  /         \ f     \  y.  TOTAL  AM

            \' O       J«<^  /      \ v  -(-ORGANIC

100,000--    .,        ^   //°Osv      N

              V    >A        /  /    T>^'W   '
TOTAL  AMMONIA

 ORGANIC NITROGEN

           as N
                                                                                            oc
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                                    FEB.-MAR.   1979
                                           5

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CO
          Figure  13.--Nutrient  concentrations  during February 25  - March  1, 1979,

                               at  the Potomac  River Fall Line station.
                                                37

-------
      Table 10.—Annual loads of selected nutrients (in millions of pounds) at the
                    three Fall Line stations for calendar years 1979 and 1980
Constituent
Susquehanna
at Conowingo
1979 ]
River
, Md.
1980
Potomac River
at Chain Bridge
at feshington, D.C.
1979
1980
James River at
Cartersville, Va.
1979
1980
Nitrogen, nitrite +
nitrate, total as N
   119
 62.9
 49.5
24.7
 7.47
 4.19
Nitrogen, ammonia,
total as N

Nitrogen, ammonia +
organic, total as N

Nitrogen, organic,
total as N
    10.4


    47.0
  5.37
 24.7
    36.8     19.2
  3.33
 32.1
             26.1
 1.52
13.0
            10.6
 0.95
16.1
          15.3
 0.53
 7.80
              7.40
Nitrogen, total
as N
   167
 88.5
 92.4
43.8
25.1
12.8
Phosphorus ,
orthophosphate,
total as PO
     7.86     4.18
              5.19
             2.55
           2.96
              1.95
Phosphorous,
total as PO
    21.7     10.2
             19.0
             6.78     10.6
                        5.67
Carbon, organic,
total as C
   351
177
208
  1.2     152
             81.9
Mean discharge
(ft3/s)
52,300   28,400      20,400     11,000    12,000
                                            7,790
                                          38

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-------
     During  the  May-through-August  period, transport of  nitrogen, phosphorous,
and organic carbon is at a minimum.  StreamfJow is normally  low and biological
uptake of nutrients is high.  During the September-through-December period, while
evapotranspiration,  temperature,   and biological  uptake  of  nutrients  decline,
stream flow and nutrient concentrations show marked increases.

     Figures  14  and 15  graphically present monthly  nitrogen and  phosphorous
species loads from the three Fall Line  stations.  As shown in table  11, much of the
load is delivered during the first few months of each year when streamflow is
above average.  Also worth noting are the very small loads which  were carried by
the three rivers during  the summer and  fall of 1980 when  streamflow  was below
normal.  Nitrogen and phosphorous loads are not evenly distributed throughout the
year, but are delivered mainly during high-flow periods.
                    Comparison of Nutrient Data Among the
                            Three Fall Line Stations

     Of the three stations, the Potomac River at Chain Bridge had  the highest
discharge-weighted averge concentration of total nitrogen,  2.20 mg/L (table  12);
the  Susquehanna  value  had 1.61 mg/L, followed  by the  James River  average
concentration of 0.96 mg/L.

     Most of the  total nitrogen load transported by the Susquehanna and Potomac
Rivers at their Fail Line is in the nitrite  + nitrate form (table 12 and fig.  1^).
Nitrite  +  nitrate comprised 71  and 55 percent of  the  total  nitrogen  at  the
Conowingo and Chain Bridge sites, respectively.  On the other hand, at the James
River at  Cartersville,  nitrite  + nitrate  comprised only 31 percent of  the total
nitrogen load, with the remainder being  mostly  in the form of organic  nitrogen.
Since a much larger  portion  of the Susquehanna and Potomac River  basins  is
involved in agriculture, this agrees  with the  results of Omerik (1976) mentioned
previously.

     The Susquehanna  River at Conowingo has discharge-weighted average con-
centrations of both  total phosphorous and orthophosphate notably lower than the
other two rivers (table 12).

     Orthophosphate comprises  38,  31, and 32  percent of  the total phosphorous
load at the Susquehanna, Potomac,  and James River  stations,  respectively.   The
remainder is in  the  form of organic or  acid hydrolyzable phosphorous. Figure 15
breaks down the transport  loads of each of the  phosphorous  species  for the 28-
month data-collection period.
                                      42

-------
                       SUSQUEHANNA RIVER AT CONOWINGO . MD.
as.o-
40.0-
35.0-

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                         SUSQUEHANNA RIVER  AT CONOWINCO. MD
                   8 0-
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                                         I
                                                           I
                                  Q Orthophosphate as PO4
                                  O Acid Hydrolizable + Organic
                                     Phosphorous  as PC>4
                        JFMAMJJASONDJFMAMJIASOND[JFMA
                             1979              1980         1981
ID|7
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-------
               Comparison of Nutrient Data with Previous Studies


     Tables 13 and 14 compare average nutrient loads and concentrations obtained
from different  hydrologic studies conducted at  the  Fall Line stations since 1966.
At  the  Chain  Bridge  station, the  period of the  Jaworski  (1969) report (January
through December, 1966) was the driest in over  50 years of record.  The loads and
concentrations  of Guide and Villa (1972) were computed for a period (June 1969 to
May 1970)  when Potomac River flow was 4 percent below normal.  The Fall Line
monitoring comparisons  were made during a period (January  1979 to  December
1980) when streamfiow was 38 percent above average.   However, even with these
differences in flow, conclusions can be drawn from the data in tables 13 and 14.

     From 1969 to 1980, average  concentrations and loads of ammonia decreased
at all three Fall Line stations; this is true even  though the mean discharges for the
sampling periods increased in all cases.  The average concentrations and  loads of
orthophosphate at the Susquehanna and Potomac River  sites also declined.  The
average concentration of nitrite + nitrate decreased slightly at  the Potomac River
from 1966  to 1980.  At Conowingo, an increase in nitrate + nitrate concentrations
was noted.

     As another basis for evaluating trends in nutrient loads, the regression equa-
tions for the Susquehanna,  Potomac,  and James Rivers used by Guide and Villa
(1972)  were  applied  to  the mean daily  discharge data from January  1979 to
December  1981.   These  hypothetical loads  and average concentrations  better
reflect  a true  trend in nutrient loads  because the same flow regime is  utilized in
each comparison (Hirsch-1  , oral commun.,  1982).  Tables  13 and 14 show hypo-
thetical  loads and average concentrations which  would have occurred if the 1972
regressions were valid during 1979 and 1980.

     In most cases, the hypothetical  average concentrations for the  Susquehanna
and Potomac Rivers are nearly the same as those derived by Guide and Villa (1972).
In  table  14,   these  data  support  the previous conclusion  that  ammonia  and
orthophosphate concentrations  have  decreased.   The  James  River results are
inconclusive. Examination of the  data used to calculate the 1972 regressions show
that there  were  a significant  number of  high-flow  samples collected  at the
Susquehanna  and Potomac River stations. This  is not true for the James River. In
order to properly predict loads over a  wide  range of stages by  regression, samples
should  be collected  over this  wide  range.  It is extremely difficult to  accurately
extrapolate high-flow loads from  low-flow  data.  The  only trend in James River
water  quality  apparent  from the  data in tables 13 and 14  is a decrease  in the
ammonia loads  and average concentrations.

     Analysis of covariance was applied to the  Guide and Villa (1972) and the Fall
Line data for the nutrients found in tables 13 and 14.  Results indicate  a  significant
difference in all population means at a 5-percent significance level.  There were no
analytical  changes in procedure for determining nitrite + nitrate, orthophosphate,
_i/  Hirsch, R. M., Chief, U.S. Geological Survey Systems Analysis Group,
      Reston, Va.
                                     46

-------
         Table 13.—Average daily loads (in Ibs/d) of selected nutrient species  for  the  three Fall  Line  stations
                                     derived  from different hydrologic investigations
Investigation
and period
of coverage
Average daily
discharge for
sampling period
(fWs)
Phosphorous,
total as POi.
Phosphorous,
ortho-
phosphate ,
total as PCK
Nitrogen,
nitrite +
nitrate ,
total as N
Nitrogen,
ammonia +
organic ,
total as N
Nitrogen,
ammonia,
total as N
Carbon,
organic,
total as C
                                            SUSQu'EHANNA RIVER AT COWOWINGO,  MD
Guide & Villa (1972);
June 1969 - May 1970
Fall Line Monitoring
Study; January 1979 -
December 1980
Hypothetical loads2

'36,000
'40,300
'40,300
POTOMAC
37,800
43,600
46,600
RIVER AT CHAIN
23,300
16,400
30,300
BRIDGE AT
174,000 101,000
249,000 98,600
203,000 110,000
WASHINGTON, B.C.
30,800 568,000
21,600 722,000
32,200 633,000

Jaworski (1969);
January 1966-December 1966

Guide and Villa (1972);
June 1969 - May 1970

Fall Line Monitoring
  Study;  January 1979 -
  December 1980

Hypothetical loads 2
Guide 4 Villa (1972) "
June 1969 - May 1970

Fall Line Monitoring
  Study; January 1979 -
  December 1980

Hypothetical loads
310,500
 15,900
 15,900
                                56,880
24,800


35,300


38,400
                                                              11,000
65,600       37,400
                                                              10,600        102,000        61,700


                                                              18,200        144,000        52,800
             JAMES RIVER AT CARTERSVILLE,  VA.


                 8,670         5,100        18,200
                                 9,910         22,300         6,700         16,000


                                69,910         23,700        13,100         33,900
                                         21,600


                                         32,700


                                         48,600
 6,700      285,000


 6,600      405,000


 9,670      377,000





 5,130      159,000


 2,000      320,000


18,300      229,000
 '  Mean annual discharge for this station is 38,900 ft3/s, based on records at Hamsburg,  Pa.

 2  Based on regressions from Guide and Villa  (1972) and streamflow from Fall Line study.
 3  Mean annual discharge for this station is 11,500 ft3/s.

 *  Station is located at Huguenot Bridge in Richmond, Va., about 40 miles downstream.

 5  Mean annual discharge for this station is 7,610 ftVs.

 6  Mean annual discharge for this station is 7,110 ftVs.
                                                       47

-------
          Table  14.—Discharge-weighted  average  concentrations  (in  mg/L)  of  selected nutrient species for the
                        three Fall Line stations derived from different hydrologic investigations
Investigation
and period
of coverage
Average daily
discharge for
sampling period Phosphorous
(ftVs) total as PO
SUSQUEHANNA
i»
Pho
P
tot
RIVER
sph
ort
hos
al
AT
orous, Nitrogen, Nitrogen,
ho- nitrite + ammonia •*•
as POk total as N total as N
CONOWINGO ,
MD
Nitrogen, Carbon,
ammonia, organic,
total as N total as C

Guide 8, Villa (1972);
June 1969 - May 1970

Fall Line Monitoring
  Study; January 1979
  December 1980

Hypothetical concen-
  trations 2
'40,300


'40,300
.20
                  .21
              .08
                                .14
                           1.14
                            .94
                                                          0.52
                                         .45
                                                            .51
                                                                       0.16
                                                      .10
                                                                         .15
                                                                                    2.92
                                                                  3.32
                                                                  2.92
Jaworski (1969);
January 1966-December 1966

Guide and Villa (1972);
June 1969 - May 1970

Fall Line Monitoring
  Study;  January 1979 -
  December 1980
Hypothetical concen-
  trations 2
     POTOMAC RIVER AT CHAIN BRIDGE AT WASHINGTON, D.C.

 36,740          0.47            -           1.35         0.16


310,500
315,900


'15,900
.44
.42
                                                 .45
              .20
                                .13
                                                                .21
1.16


1.20


1.69
.66


.72


.62
                                                      .12
                                                                         .08
                                                                                                        .11
                                                                  5.06
                                                                                    4.79
                                                                                                                    4.42
Guide S, Villa (1972)"
June 1969 - May 1970
              JAMES  RIVER  AT CARTERSVILLE,  VA.

                 0.23          0.14          0.49
                                                          0.58
  1 Mean annual discharge for this station is 38,900 ftVs,  based  on  records  at  Harrisburg,  Pa.
  2 Based on regressions from Guide and Villa  (1972) and streamflow from  Fall  Line  study.
  3 Mean annual discharge for this station is 11,500 ftVs.
  ** Station is located at Huguenot Bridge in Richmond, Va. ,  about  40  miles  downstream.

  5 Mean annual discharge for this station is 7,610 ft3/s.
  6 Mean annual discharge for this station is 7,110 ft3/s.
                                                                        0.14
                                                                                     4.30
Fall Line Monitoring
Study; January 1979 - 9,910 .41
December 1980
Hypothetical concen- 9,910 .44
trations 2
.12 .30 .61 .04 5.95
.24 .64 .91 .34 4.29
                                                     48

-------
 and total phosphorous that would influence the results of comparisons between the
 two studies (Erdmann- , written commun.,  1981;  and Villa- , written  commun.,
 1981).   Because  of a  more thorough  digestion process, ammonia  concentration
 values recorded during the Fall Line study may actually be higher than during the
 1972 study  by Guide and  Villa.    It  has  been  noted previously that ammonia
 concentrations  apparently  decreased  during  the  Fall Line  study.   This  is  the
 opposite of what  would be expected if  the more thorough digestion influenced the
 results.

      Table 15  compares nutrient loads for  the Susquehanna  River  at Conowingo
 computed by Clark, Donnelly, and Villa (1973) to loads calculated for the period of
 this report.  Both studies use the same load versus discharge  regression  technique
 to  compute loads, although each uses a different regression equation.   Therefore,
 load estimates can be made for any  chosen discharge. In  the table, loads are listed
 for  three  discharges  (10,000, 50,000,  and  100,000  ft 3/s),  which represent  low,
 medium, and high flows at this station.   Because the comparisons of estimated
 loads are made at the same discharges for the  two data periods, differences in the
 loads may  represent trends in water-quality characteristics rather than reflect the
 combined effects of varying amounts of rainfall, runoff,  or ground-water infiltra-
 tion.

      The  comparisons  in  table  15  verify  the apparent reductions in loads  of
 ammonia and orthophosphate at this site,  as previously  noted.  They also reinforce
 the  suggestion  of an  increase in nitrite +  nitrate.   If  nitrogen is the limiting
 nutrient for algal growth  in the  upper  Chesapeake Bay, as  reported by  Clark,
 Donnelly, and Villa (1973). this trend in particular warrants continued  monitoring.

      With  mixed  results,  previous investigations  have  attempted to  correlate
 discharge  with  nutrient concentrations.  In most  instances, there was  either  no
 correlation or discharge directly  related  to  nutrient concentration.   However, in
 several instances, investigators detected  an  inverse correlation of discharge  with
 concentrations  of  certain  nutrient  species.   Guide and Villa  (1972) noted  this
 inverse correlation  for  ammonia + organic nitrogen at the  Susquehanna River  at
 Conowingo; for total phosphorous at the Potomac River at Great  Falls (about 8 mi
 upstream from Chain  Bridge);  and  for nitrite +  nitrate at the  James River  at
 Cartersville.  Clark, Guide, and Pheiffer  (197^) also noted an  inverse relationship
 between concentrations of total  phosphorous or ammonia + organic nitrogen and
 discharge at the Susquehanna River at Conowingo site.  Jaworski (1969) noted a
 similar correlation for total phosphorous  and discharge at the Potomac River Fall
 Line site.
_2/ Erdmann, D. E., Chief, U.S. Geological Survey National Water-Quality
      Laboratory, Alanta, Ga., June 1981.

j/ Villa, Orterio, Chief, U.S. Environmental Protection Agency, Region III
      Laboratory, Annapolis, Md., May 1981.
                                      49

-------
             Table 15.—Estimates of nutrient loads  (in Ib/d) at three
                        different discharges for 1969-72 and  1979-81 data
                        sets for the Susquehanna River at Conowingo, Md.
Constituent
Discharge of Estimate (ft-Vs)
10,000
Data Set
1969-721 1 1979-81
50,000
Data Set
1969-721 1 1979-81
100,
Data
1969-721
000
Set
1979-81
Phosphorus, total
as PO/,
  7,500
             4,370     50,000     43,800   120,000    117,000
Phosphorus,
orthophosphate,
total as PO,
  3,500
             3,360     30,000     20,000    75,000     41,700
Nitrogen, organic, 2
total as N
             14,700   2100,000     90,300  2200,000    197,000
Nitrogen,
inorganic,
total as N
58,000
            359,700    300,000   3330,000   600,000   3694,000
Nitrogen,
nitrite +
nitrate, as N
 40,000       53,700     250,000    301,000   530,000    631,000
Nitrogen,
ammonia +
organic,
total as  N
'40,000
            20,000   4150,000    117,000  4270,000    251,000
Nitrogen,
ammonia,
total as N
'18,000
             3,900    550,000     25,200    570,000     56,200
Nitrogen,
total as N
 80,000      74,100    400,000    423,000   800,000    891,000
'1969-72 data from Clark, Donnelly, and Villa  (1973).
Calculated by (Total nitrogen) - (Total inorganic nitrogen).

Calculated by (Total nitrogen) - (Total organic nitrogen).
^Calculated by (Total nitrogen) - (Nitrite + Nitrate nitrogen).
Calculated by (Total inorganic nitrogen) - (Nitrite + nitrate nitrogen).
                                       50

-------
      Concentrations of all nutrient parameters analyzed  for this  report correlate
directly with discharge including  data  for  total phosphorous, ammonia  + organic
nitrogen, and nitrite + nitrate. Figures 10, 11, and 12 present typical relationships
between  discharge,  suspended sediment,  and nutrient species  for the three Fall
Line  stations during storms.   The direct relationships  between discharge or sus-
pended sediment and nutrient parameters  are clearly apparent for the Potomac and
James River stations. Regulation of the lower Susquehanna River obscures these
relationships somewhat at the Conowingo  station.

      Clark, Donnelly, and Villa (1973) stated that inorganic nitrogen and the  total
nitrogen loads in  the upper Chesapeake Bay were generally constant regardless of
the  Susquehanna  River  flow.  The previous discussion   has  shown  that  in the
Susquehanna, for  calendar  years  1979  and  1980, nitrite  + nitrate (which is the
majority of inorganic nitrogen) and total  nitrogen transport are dependent on  river
discharge;  more than half of  their total  load is transported by spring high  flows
(table 10).   The fate of these nutrients in the water  of  the upper Bay is  crucial to
the development of control strategy and requires further study.
         Comparison of Nutrient Data at the Susquehanna River Stations
                     at Harrisburg, Pa., and Conowingo, Md.


     From April 1980 to March 1981, the water quality of  the Susquehanna River
was intensively monitored at both Conowingo, Md., and Harrisburg, Pa.  The  results
of sampling at these two stations are presented in tables  16 and 17 where  water-
quality constituent loads for the period are compared. All load computations were
by methods previously described in an earlier section.

     The three hydroelectric dams  on the Susquehanna  River between Harrisburg
and Conowingo influence the transport  of many water-quality constituents.  For
the period of concurrent sampling, the suspended-sediment load at the Conowingo
site is 45 percent  lower than the Harrisburg  site, even though the drainage area at
the downstream site is  13 percent greater.  It is reasonable to assume then that
those constituents which  are mainly sorbed to suspended-sediment particles or are
contained in suspended material should also have smaller loads at Conowingo. The
data in  table  16 show that this is indeed true for total  phosphorous,  organic and
ammonia + organic nitrogen, organic carbon,  aluminum,  iron, and  manganese.  A
more  thorough analysis  of the reductions of  the suspended-sediment loads between
the two stations on the Susquehanna River is  presented in a subsequent section.

     The data in table  17 point out that orthophosphate and  nitrite + nitrate make
up  a  greater  percentage of the  total  phosphorous and  nitrogen loads at  the
Conowingo station than at the Harrisburg site. This is also  reasonable since these
constituents  are usually  dissolved in  streams, and  their  concentrations are  not
diminished by the  settling of suspended sediment behind the dams.  There is also a
large  percentage  of  agriculture  in the  area  between  the two stations.   As
previously noted, agricultural areas normally have  higher nitrite + nitrate concen-
trations because of the use of nitrogen based fertilizers.
                                       51

-------
    Table 16.—Water-quality constituent loads (in millions of pounds) for
               stations on the Susquehanna River at Harrisburg, Pa., and
               Conowingo,  Md., from April 1980 through March 1981
      Constituent
Susquehanna River at
 Harrisburg, Pa.1
Susquehanna River at
  Conowingo,  Md.2
 Phosphorous,
 total as PO,
         18.3
          12.1
 Phosphorous,
 orthophosphate,
 total as PO,
          3.14
           4.58
 Nitrogen, organic,
 total as N
         28.2
          21.2
 Nitrogen, nitrite
 + nitrate, total as N

 Nitrogen, ammonia
 + organic, total as N

 Nitrogen, ammonia,
 as N
         53.4
         33.6
          4.23
          68.9
          27.2
           6.00
 Nitrogen,
 total as N
         90.8
          97.0
 Carbon, organic,
 total as C
        237
         199
 Manganese, total
 recoverable as Mn
         20.4
          16.6
 Aluminum, total
 recoverable as Al
         50.5
          46.0
 Iron, total
 recoverable as Fe

 Solids, dissolved

 Sediment, suspended
        162


      5,550

      4,600
          78.8
       7,200

       2,540
JMean daily discharge for the period is 26,500 ft3/s.
2Mean daily discharge for the period is 31,400 ft3/s.
                                    52

-------
    Table 17.—Relative proportions of orthophosphate, nitrite 4- nitrate, and ammonia
               + organic nitrogen to total phosphorous and nitrogen loads at the
               Susquehanna River at Harrisburg, Pa., and Conowingo, Md. , from
               April 1980 to March 1981
Constituent
Susquehanna River at
Harrisburg, Pa.1
Load
(in millions of pounds)
Percent of
total PO,
or N
Susquehanna River at
Conowingo , Md . 2
Load
(in millions of pounds)
Percent of
total PO,
or N
Phosphorous, total
as PO.
     4

Phosphorous,
orthophosphate,
total as PO,
           4

Nitrogen, total
as N

Nitrogen, nitrite
+ nitrate,
total as N

Nitrogen, ammonia
+ organic,
total as N
 18.3
  3.5
534
336
100
 17
                 100
 61
 39
 12.1
  4.56
                 J961
689
272
100
 38
                  100
 72
 28
*Mean daily discharge for the period 26,500 ft /s.

2Mean daily discharge for the period 31,400 ft~Ys.

3Total nitrogen load is the sum of this station's nitrite + nitrate and ammonia + organic
 nitrogen loads (as N)  for the period.
                                             53

-------
     Table 18 presents the  discharge-weighted average concentrations for water-
quality constituents sampled at both Susquehanna River stations.  Reductions in a
downstream direction  are again noted  in the concentration of those parameters
generally associated with suspended sediment. The largest reductions are noted in
total  phosphorous,  organic  nitrogen,  and organic carbon.  Orthophosphate and
nitrite + nitrate concentrations show slight increases at the Conowingo  site  when
compared to  the Susquehanna  River  at  Harrisburg.  Some of these differences are
probably attributed to the large amount of agriculture present between the two
stations.

                       Sediment Transport Characteristics


                              Susquehanna River


     In an average  year,  the Susquehanna  River  transports  1.8 million tons of
sediment to the Chesapeake Bay (Williams and Reed, 1972).   Most  of the load is
carried to the Bay during spring high flows or  hurricane-related  storms.

     According to Williams and Reed (1972), dams  on the lower Susquehanna con-
structed before 1931  reduce  the natural suspended-sediment load by 40 percent.
Between April 1980 and March 1981,  2.3 million  tons of suspended sediment were
measured  at  the Susquehanna River   at Harrisburg,  and 1.3  million tons  at
Conowingo—a 56-percent reduction even though the drainage area at Conowingo is
13 percent greater. The pools behind the dams on the lower Susquehanna River act
as sediment traps during low and medium flows.

     However, at high flow, the dams are  suspended-sediment  sources.  Ritter
(1974)  reports that 7.5 million tons  of  suspended sediment were  measured  at the
Harrisburg site  during Hurricane  Agnes in June  1972.  Gross and  others (1978)
estimate that for the same  period, the river at Conowingo transported 27 million
tons to the Bay, or about a 360-percent increase.  They suggest that during  major
floods  (discharges greater than about 400,000 ft3/s), previously deposited sediment
is eroded from behind  the dams and  transported downstream.  This discharge has a
recurrence interval of approximately 4 years at Conowingo based on 110 years of
streamflow data at Harrisburg and adjusted for drainage-area  difference between
Harrisburg and Conowingo.

     A  comparison   of  recent  suspended-sediment  transport  data  for  the
Susquehanna  River at  the Harrisburg and Conowingo  stations supports the sugges-
tion that above a  discharge of 400,000  ft3/s, sediment is scoured from behind the
dams.  Suspended-sediment  concentrations at the  Harrisburg and  Conowingo sites
during the  three highest discharge peaks from March  1979  to April 1981  are  shown
in figure 16.   The March  5-11,  1979 storm, which  had a peak discharge of  about
500,000  ft 3/s,  transported  67 percent more  sediment  at Conowingo than  at
Harrisburg (table 19).   The other storms in figure 16 had peak discharges of 240,000
and  353,000  ft 3/s.   During  these  storms, the  suspended-sediment transport at
Conowingo was about  50 percent less than that of  Harrisburg. The only time in this
data-collection  period when  suspended-sediment  transport on  the Susquehanna
River at Conowingo exceeded that of the Harrisburg  station was  during the March
5-11, 1979  storm.
                                      54

-------
   Table 18.—Discharge-weighted average concentrations  (in mg/L)  of water-
              quality constituents for stations on  the Susquehanna River at
              Harrisburg, Pa., and Conowingo, Md., from April  1980  through
              March 1981
      Constituent
Susquehanna River at
  Harrisburg, Pa.
Susquehanna River at
                n
  Conowingo, Md.
Phosphorous, total
as PO,
     4

Phosphorous,
orthophosphate,
total as PO,
           4

Nitrogen, organic,
total as N

Nitrogen, inorganic,
total as N

Nitrogen, nitrite +
nitrate, total as N

Nitrogen, ammonia +
organic, total as N

Nitrogen, ammonia,
total as N

Nitrogen, total as N

Carbon, organic,
total as C

Manganese, total
recoverable as Mn

Aluminum, total
recoverable as Al

Iron, total
recoverable as Fe

Solids, dissolved

Sediment, suspended
         0.35


         0.06


         0.54


         1.20


         1.03


         0.65


         0.08

         1.74

         4.54


         0.39


         0.97


         3. 12

       107
         0.20


         0.07


         0.34


         1.22


         1.11


         0.44


         0.10

         1.57

         3.27


         0.27


         0.75


         1.28
       117

        41
 Mean daily discharge for the period is 26,500 ft /s.
2Mean daily discharge for the period is 31,400 ft Vs.

                                    55

-------
        500,000
        300,000
        100,000
              H	£	H
                                    H	7^—I-
                                                                       500
                                                                       400
                                                                       300
                                                                       200
                                                                       100
           5^6'    7       8       9       10      11


                              MARCH  1979
                                                                               cc
                                                                               LU
                                                                               a.

                                                                               en
                                                                               5
                                                                               <
                                                                               cc
                                                                               O
   o
   o
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   03

   CC
   UJ
   Q.
   UJ
   LL

   O

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   z>
   o
   HI
   I
   o
   C/3
500,000
        300,000
        100,000 -'
                                                               500
                                                               400
                                                                       300
                                                               200
                                                                       100
22  '  23       24   '    25   '   26


                   MARCH 1980
                                                          27
                                                                  28
        500,000
        300,000 -
         100,000 -
                                                                       500
                                                                     - 400
                                                                     - 300
                                                                     - 200
                                                                     - 100
                                                                       o

                                                                       !5
                                                                       cc
                                                                       UJ
                                                                       o

                                                                       o
                                                                       o
                                                                       UJ

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                                                                       Q
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                                                                       UJ
                                                                       a.
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                      22
                              23
                                      24   '   25


                                   FEBRUARY   1981
                                                      26
                                                              27
                            DISCHARGE FOR SUSQUEHANNA RIVER AT CONOWINGO MO
                      	   — SUSPENDED SEDIMENT FOR SUSOUEHANNA RIVER AT HARRISBURG  PA


                     	 SUSPENDED SEDIMENT FOR SUSOUEHANNA RIVER AT CONOWINGO  MD
Figure 16.—Suspended-sediment  transport for  three  high flows at  the

              Susquehanna River at  Harrisburg,  Pa., and Conowingo,  Md.
                                           56

-------
Table 19.--Suspended-sediment loads  (in  tons) at  the Harrisburg, Pa.,  and
           Conowingo, Md., stations  on the  Susquehanna  River  for three
           high-flow periods
Date
March 5, 1979
March 6
March 7
March 8
March 9
March 10
March 11
Total load for
high-flow period
March 21, 1980
March 22
March 23
March 24
y.irch 25
March 26
Total load for
high-flow period
February 21, 1981
February 22
February 23
February 24
February 25
February 26
February 27
Susquehanna River at
Harrisburg, Pa.
(Drainage area is 24,100 mi )
32,300
284,000
316,000
149,000
90,100
69,700
30,000

971,100
33,200
152,000
132,000
116,000
55,200
31,600

520,000
196,000
183,000
127,000
199,000
142,000
78,400
30,200
Susquehanna River at
Conowingo , Md .
(Drainage area is 27,100 mi 2)
15,300
] 84, 000
568,000
412,000
236,000
136,000
67,800

1,619,100
13,500
28,000
57,500
63,300
46,900
34,700

243,900
31,600
78,200
76,600
90,800
137,000
70,500
36,200
Total load for
high-flow period
955,600
520,900
                                     57

-------
                                Potomac River


     During the 1979 water year (Oct. 1978 to Sept. 1979), the suspended-sediment
load at  the Potomac River at Chain Bridge at  Washington, D.C.,  was 2.64 million
tons (Lang and Grason, 1980). Water year 1979 had the second highest annual mean
discharge in this station's 86-year  period.  Periods of exceptionally intense runoff
in January, February, March, and September 1979 were the principal causes of the
high yearly  discharge  and sediment  load  (fig.  17).  Feltz  (1976)  estimated  the
average annual  suspended-sediment load to be 1.5 million tons from 1964 to 1975 at
the Potomac River at Great Falls,  8 mi (and 99 percent of the drainage area)
upstream from Chain Bridge.

     Figure 17 shows the importance of antecedent conditions to sediment trans-
port at  the Chain  Bridge station.   Depicted in this figure are the  three highest
discharge peaks occurring during the study period.  Even though the peak and total
discharges for the January 22-21, 1979 storm are very much less than the February
25 -March 1,  1979  storm, suspended sediment reaches higher concentrations during
the January storm.  The most readily  available  sediments  were probably trans-
ported in the January  storm, and  the February storm occurred less  than 1 month
later before  much  more material  was available for transport.   The snow cover
during February also dampened any effect the precipitation had impacting the land
surface  and loosening soil particles. This would also reduce the sediment erosion
rate.

     The September  6-8,  1979 discharge  peak,  which occurred as a  result of
Tropical Storm  David, is  only 51 percent that of the February 25 -  March 1 peak,
but it has a peak suspended-sediment concentration of 1,140  mg/L, nearly twice as
high as that in February. The intensity of the rainfall from the tropical storm  and
the relatively dry period  preceding it greatly increased the unit discharge yields of
suspended sediment during this high-flow  event (table 20).

     The hydrograph and suspended-sediment plots resulting from Tropical Storm
David both show a double peak (fig. 17).  Other  storm hydrographs for this station
do not show  this  double-peak pattern.  Its  cause during the September  5-8,  1979
high flow may be related to  the timing  of  tributary inflow  or  may  have resulted
from two separate periods of  intense precipitation during this storm.
                                 James River


     Because of  problems in establishing and maintaining a daily sediment station
for the James River at Cartersville,  suspended-sediment data  were incomplete and
no storm comparisons or annual totals were available.
                                      58

-------
                   180,000
                   140,000
                   too,ooo
                    60,000
                    20,000-
                     „ SUSPENDED SEDIMENT

                    :V
                                               DISCHARGE
                            24
                                     25       26

                                     JAN.  1979
                                                           800
                                                           600
                                                           400
                                                           200
                                                      27
                                                           OC
                                                           UJ
                                                           QC
                                                           UJ
                                                           a

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        UJ
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200,000
180.000
               140,000
               100,000
 60,000
                20,000
                                                 1000
                                                800
                                                               600
                                                               400
                                                               200
                                                           cc
                                                           O
          25  '    26       27      28

                   FEB -MAR  1979
                   220,000
                   180,000
                   140.OOO
                   100,000
                    60.000
                   20 000
                                   / I  SUSPENDED  SEDIMENT
                                  /    M

                                 I     I
                         -   /  / DISCHARGE

                            i
                                                           1000
                                                           800
                                                           600
                                                           400
                                                           200
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                             5       6   '    7

                                     SEP.  1979
Figure 17.—Suspended-sediment  transport for  three high flows at  the

              Potomac  River at  Chain  Bridge at  Washington, D.C.
                                       59

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                      SUMMARY AND CONCLUSIONS

 1.  Loads of water-quality constituents estimated in this report were using linear
    regression relations and  daily values of either  streamflow, suspended-sedi-
    ment concentration, or specific conductance.  Comparison of these estimates
    to  loads  calculated  by  a  more  data-intensive  and  accurate  technique
    (Porterfield, 1972) for  selected constituents at the Potomac River Fall  Line
    station showed good agreement (within 10.5 percent), when considering the 2-
    year  data  set  as  a whole.   The  regression technique is more  accurate for
    years when precipitation and streamflow are above average.

2. The only two pesticide  residues consistently detected at  the Susquehanna and
    Potomac  River Fall  Line stations were 2,4-D and atrazine.   The concen-
    trations of both  generally peak at  these  stations in  the late  spring  and
    summer, although  2,4-D  concentrations  at the  Susquehanna  River site re-
    mained high during the fall and winter of  1980-81.  In this case, 2,4-D  may
    have entered the stream in ground-water inflow.

3.  Generally, the highest  concentrations of  chlorophyll a  occurred at the three
    Fall Line stations during  spring high flows.  These peak concentrations  may
    have  been  caused by  high  velocity runoff carrying  fragments  of  under-
    developed  and  emerging  plankton  or  spring  accumulation  of  periphytic
    chlorophyll.

4.  Samples collected  at  five  sites in tributaries  to  the northern part  of
    Chesapeake Bay were analyzed for  total residual chlorine and selected  low-
    molecular-weight  hydrocarbons.  The results of all the chlorine analyses were
    less than  or  equal to the detection limit of 0.01  mg/L.  There were three
    instances when those organic compounds  listed  in table 8 were detected.
    Trichloroethylene (TCE)  was  detected at low levels  at Back and Patuxent
    River  sites on  3uly  1, 1981;  a  0.002 mg/L concentration  of benzene  was
    found in the Potomac River at  Alexandria, Va., on June 26, 1981.

5.  For the Susquehanna and  Potomac River Fall Line  stations, concentrations of
    total  recoverable aluminum,  iron,  and manganese correlated  closely  with
    suspended sediment.  However, the character of this correlation differs for
    the two sites and  from one storm to the next at each site.   For the  James
    River  at Cartersville, there  was  lesser correlation between suspended sedi-
    ment and these metals.

6. When measured at their  Fall  Line  stations, the Susquehanna and Potomac
    Rivers had significantly greater discharge-weighted-average sulfate concen-
    trations than the James River.  Significant areas of active coal mining in the
    Susquehanna  and Potomac basins may account for this.

7.  Concentrations and loads of all nutrient species were  highest during spring
    and storm-related high flows for the three Fall Line stations.

8.  At each of the Fall Line stations,  there was a close correlation between mean
    annual  water discharge and  the corresponding annual nutrient  loads.   This
    relationship  may  provide a basis for estimating  specific nutrient loads in
    years for which load estimates  are not now available.

                                     61

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9.  Of the  three Fall Line stations, the Potomac River at Chain Bridge had the
   highest  discharge-weighted average  concentration of  total nitrogen, 2.20
   mg/L, and the  James River station had the lowest, 0.96 mg/L.  Most  of the
   total  nitrogen load at the Susquehanna (71 percent) and Potomac River (5.5
   percent) sites was in the form of nitrite and nitrate. However, 69 percent of
   the total  nitrogen at  the James River  station  was  ammonia  +  organic
   nitrogen, and only 31 percent is nitrite + nitrate nitrogen.

10. Of the three rivers sampled, the Susquehanna River had the lowest discharge-
   weighted  average concentrations of total phosphorous and orthophosphate,
   0.20 and 0.08 mg/L, respectively.

11. Based  on  comparisons with previous  studies,  ammonia concentrations and
   loads  decreased at all three Fall  Line stations from  1969 to  1981.   Ortho-
   phosphate  concentrations and loads in the Susquehanna and Potomac  Rivers
   also declined.

12. If nitrogen is the limiting nutrient for algal growth in the upper Chesapeake
   Bay, as  suggested by Clark, Donnelly,  and  Villa  (1973), the slight increases in
   total  nitrogen, principally as nitrite  + nitrate,  at  the Susquehanna River at
   Conowingo may signal the need for further monitoring.

13. Generally, nutrient  concentrations were proportional  to streamflow.  The
   data  in  this report do not support suggestions  from  some previous investi-
   gations  that certain  nutrient species are inversely proportional to  stream-
   flow.   The majority  of the nutrient  loads transported by the  three  rivers
   occurred during spring storm events.  This is particularly significant in light
   of the conclusions of  Clark, Donnelly, and Villa (1973), who suggested that
   total  and inorganic nitrogen loads in the upper  Chesapeake Bay are generally
   constant regardless of Susquehanna River flow.

14. Comparison of data for the Susquehanna River at  Harrisburg and Conowingo
   indicated that loads  of dissolved constituents such  as  orthophosphate and
   nitrite + nitrate, increased in the downstream direction. Both orthophosphate
   and nitrite + nitrate comprised a larger fraction of the total phosphorous and
   nitrogen loads at Conowingo than at Harrisburg.

15. The data in this report support the suggestion by Gross and others (1978) that
   at  discharges  below  about 400,000   ft 3/s  at the  Susquehanna  River at
   Conowingo,  sediment accumulates  behind the  three  hydroelectric  dams
   between Harrisburg and the mouth.  Above that peak discharge, sediment is
   scoured and resuspended for transport to  the Bay.  The recurrence interval
   for this flow is approximately 4 years.

16. Sediment transported by the  Potomac  River at  Chain Bridge is  heavily
   influenced by seasonal variations, type of precipitation, rainfall  intensity, and
   antecedent conditions.   Peak  concentrations  of suspended sediment  for a
   late-winter flow peak were half that of a late-summer high flow, although
   the winter storm peak discharge was twice that  of the summer storm.
                                     62

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                                REFERENCES


American Public Health Association, 1976, Standard methods for  the examination
      of  water and  wastewater, Part 409  C.,  Amperometric  Titration Method,
      fourtheenth edition, p. 322-325.

Clark, L. J., Donnelly, D. K., and Villa, Orterio,  1973, Nutrient enrichment and
      control requirements  in  the  upper Chesapeake Bay:   Environmental Pro-
      tection Agency, Region III, Annapolis Field Office, Technical  Report 56, 58 p.

Clark, L. J., Guide, Victor, and Pheiffer, I.  H.,  1974, Summary and conclusion-
      nutrient transport and accountability in the lower Susquehanna River basin:
      U.S. Environmental  Protection  Agency, Region III, Annapolis Field  Office,
      Technical Report 60, 97 p.

Feltz, H. R., 1976, Sedimentation in the Potomac River basin: Presented before
      Subcommittee  on the  Bicentennial, the Environment and the International
      Community, House Committee  on  the District of  Columbia, June 17, 1976,
      28 p.

Gross, M. G., Kariverit, M., Cronin, W.  B., and  Schubel, 3.  R., 1978, Suspended-
      sediment  discharge of the Susquehanna River to northern Chesapeake Bay,
      1966 to 1976: Estuaries, v. 1, no. 2, p. 106-110, June 1978.

Goerlitz,  D. F.,  and Brown,  Eugene,  1972,  Methods  for  analysis  of  organic
      substances in water:  U.S. Geological Survey Techniques of Water-Resources
      Investigations, Book 5, Chapter A3,  40 p.

Guide, Victor, and Villa, Orterio, 1972, Chesapeake Bay nutrient input study: U.S.
      Environmental  Protection Agency,  Region III, Annapolis Field office, Tech-
      nical Report 47, 120 p.

Guy,  H.  P.,  1969, Laboratory theory and methods for  sediment  analysis:  U.S.
      Geological  Survey  Techniques of  Water-Resources Investigations, Book  5,
      Chapter CJ, 58 p.

Guy,  H. P.,  and Norman, U. W.,  1970, Field methods for measurement of fluvial
      sediment:   U.S. Geological Survey Techniques of  Water-Resources  Investi-
      gations, Book 3, Chapter C2, 59 p.

Hem, J.  D., 1970, Study and interpretation  of the  chemical characteristics  of
      natural waters, U.S. Geological Survey Water-Supply Paper 1473, 363  p.

Jaworski, N. A., 1969, Nutrients in the upper Potomac River  basin: Federal Water
      Pollution Control Administration, U.S.  Department  of the Interior,  Technical
      Report No.  15, 98 p.

Lang, D.  J.,  and Grason, David, 1980, Water-quality monitoring of three  tributaries
      to the  Chesapeake Bay—interim data report:  U.S.  Geological Survey Water-
      Resources Investigations 80-78, 66 p.
                                       63

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Omerik,  3.  M.,  1976, Influence  of land  use  on stream  nutrient  levels:   U.S.
     Environmental  Protection  Agency  Office of  Research and  Development,
     Corvallis, Oregon, EPA-600/3-76-014, 106 p.

	 1977, Nonpoint source—stream nutrient level relationships:   A nationwide
     study:    U.S.  Environmental  Protection  Agency  Office of  Research  and
     Development, Corvallis, Oregon, EPA-600/3-77-105, 151 p.

Porterfield,  George,  1972,  Computation  of  fluvial-sediment discharge, Book 3,
     Chapter C3:  U.S. Geological Survey Techniques of  Water-Resources Investi-
     gations, 66 p.

Ritter, 1. R., 1974, The effects of the Hurricane Agnes Flood on channel geometry
     and sediment discharge of selected streams in  the Susquehanna River basin:
     Pennsylvania Journal Research, U.S. Geological  Survey, v. 2, p. 753-761.

Skougstad, M. W., Fishman, M. 3.,  Friedman, L.  C., Erdmann, D. E., and Duncan, S.
     S.,  1979,  Methods for  determination of  inorganic  substances  in water  and
     fluvial sediments:  U.S. Geological  Survey Techniques of Water-Resources
     Investigations, Book 5, Chapter Al, 626 p.

U.S. Department of the Army, Corps of Engineers, 1973, Chesapeake Bay—existing
     conditions  report,  summary:   U.S.  Department  of  the  Army,  Corps  of
     Engineers,  126 p.

U.S. Geological  Survey,  1977, National  handbook of recommended  methods for
     water-data acquisition, Chapter 5,  Chemical and physical quality  of water
     and sediment:  U.S. Geological Survey, Office of Water-Data  Coordination,
     196 p.

Wetzel, R. G., 1975, Limnology: New York, W. B. Saunders, 743 p.

Williams, K. F.,  and  Reed, L. A., 1972,  Appraisal of stream  sedimentation in the
     Susquehanna  River basin: U.S. Geological Survey Water-Supply Paper 1532F,
     24 p.
                                      64

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