vvEPA
United States
Environmental Protection
Agency
Chesapeake Bay
Program
Annapolis MD 21403
Research and Development
EPA-600/S3-82-081 Dec. 1982
Project Summary
Water Quality of the
Three Major Tributaries to the
Chesapeake Bay, the
Susquehanna, Potomac, and
James Rivers, January 1979 -
April 1981
David J. Lang and David Grason
This project characterizes the inputs
from the Susquehanna, Potomac, and
James Rivers — the major sources of
fresh water to Chesapeake Bay. The
rivers were monitored for inorganic
and organic chemical and physical
components.
The Susquehanna was monitored at
Conowingo, Maryland; the Potomac
was monitored at the Chain Bridge in
Washington, D.C.; and the James was
monitored at Cartersville, Virginia.
Measurements were made for sus-
pended sediment, nutrients, carbon,
trace metals, pesticides, major ions,
chlorophyll a, total solids, and dis-
charge. Scheduled frequencies of
measurement vary from daily to
monthly depending upon the type of
measurement. Supplemental sampling
was used to assess the impact of
extreme events (e.g., storms).
Study results provide estimates of
pollutant loadings for use in evaluating
the effects of existing and future land
use, water use, and regional economic
developments in the freshwater por-
tions of the Susquehanna, Potomac,
and James River Basins.
This Project Summary was devel-
oped by EPA's Chesapeake Bay Pro-
gram, Annapolis, MD, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
The ultimate objectives of this project
are to provide four categories of water
information:
1) Estimated loadings of major ions,
suspended sediment, selected
nutrient species, and major trace
metals for the two-year data
collection period.
2) An assessment of accuracy and
limitations inherent in these
estimates.
3) Seasonal characteristics of nu-
trients, pesticides, and chlorophyll
a collected during the study.
4) Relationships, comparisons,
correlations, and trends detected
in selected water quality constit-
uents.
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Procedure
Water quality data were collected
from the three sites at intervals during
base flow, and at more frequent
intervals during high flow. The other
parameters collected were daily or
continuous discharge, suspended sedi-
ment, specific conductance, and water
temperature. Water quality, suspended
sediment, and chlorine samples were
collected, preserved, and analyzed
according to scientifically accepted
procedures.
Bivariate linear regression equations
were used to estimate all loads in this
study. Logarithmic transformations of
constituent loads (computed from in-
stantaneous concentrations, discharges,
and a factor to yield loads in pounds per
day) were regressed against logarithmic
transformations of concurrent mea-
surements of discharge, suspended
sediment, and specific conductance.
The regression lines were fitted analyti-
cally by the method of least squares.
Results
Month-by-month comparisons of
loads do not compare as well as annual
total loads. This is because the regres-
sion technique does not allow for
seasonal and antecedent-flow varia-
tions. The regression load estimations
technique is most accurate in wetter
years having a wide range of flow.
Two pesticides were consistently
detected at the Conowingo and Chain
Bridge stations — 2,4-dichlorophen-
oxyacetic acid (2,4D) and atrazine,
primarily in late spring and summer.
Maximum chlorophyll a concentra-
tions at all three sites occur during the
high spring runoff. Concentration peaks
of lesser magnitude occur during the
late spring and summer and are possibly
related to high velocity runoff in the
spring and warmer temperatures in the
summer.
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"1.
Aluminum, iron, and manganese
concentrations correlate more closely
with suspended sediment totals than
with discharge totals at the Potomac
and Susquehanna Rivers. Correlations
for the James River station are not as
high.
According to discharge-weighted
concentrations of sulfate concentra-
tions, the Susquehanna and Potomac
Rivers carry greater sulfate loadings
than the James River, possibly due to
coal mining activities within their
drainage basins.
All the nutrient parameters at the
Susquehanna River station correlate
more closely with discharge; for the
Potomac River site, however, some
parameters correlate better with sus-
pended sediment while others correlate
better with discharge. In general,
nutrient parameters associated with
suspended material relate better to
suspended sediment, while constituents
with large solubilities relate better to
discharge.
The Potomac River at Chain Bridge
has the highest discharge-weighted
average concentration of total nitrogen
(2.20 mg L"1), primarily in the form of
nitrite-nitrate. The James River at
Cartersville has the highest discharge-
weighted concentration of both total
phosphorus (.42 mg L~1)andorthopnos-
phate (.13 mg L"1).
The data in this report do not support
suggestions from some previous invest-
igations which state that certain nutrient
species are inversely proportional to
streamflow.
Comparisons of data for the Susque-
hanna River at Harrisburg and Cono-
wingo indicate that loads of those
parameters more associated with the
water phase (dissolved), such as ortho-
phosphate and nitrite plus nitrate,
increase in the downstream direction.
However, for total phosphorus, organic
and Kjeldahl nitrogen, organic carbon,
aluminum, iron, and manganese (those
parameters more closely associated
with the suspended sediments), loads
near the mouth of the Susquehanna
River are less than those at Harrisburg,
presumably because of the effects of the
intervening hydroelectric dams.
High-flow sediment transport for the
Potomac River at Chain Bridge is heavily
influenced by seasonal variations.form
of precipitation, and antecedent condi-
tions.
Conclusions
Water quality loadings can be esti-
mated reasonably by regression tech-
niques, especially for wetter periods of
one year or more.
Net transport of nutrient species and
adsorbed constituents is dominated by a
relatively few spring and storm-related
high flow events.
Atrazine and 2,4D are the two most
consistently detected pesticides at the
Susquehanna and Potomac sites.
The sparsity of coal mining activity in
the James River may be responsible for
the River's lower sulfate concentrations.
Phosphorus loads are increasing in the
James and concentrations for both total
phosphorus and orthophosphate are
higher than in the other two tributaries.
Peak discharges above 400,000 ft3
sec"1 at the Susquehanna River at
Conowingo resuspend sediments and
related water quality constituents
which had been deposited behind the
three hydroelectric dams and transport
constituents to the Bay in excess of
those transported 40 miles upstream at
Harrisburg.
Sediment transport at the Potomac
River site is heavily influenced by
antecedent and seasonal conditions in
addition to precipitation quality and
quantity.
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David J. Lang and David Grason are with the U.S. Department of the Interior,
Harrisburg Subdistrict Office, Harrisburg, PA 17108.
James T. Smullen was the EPA Project Officer (for information, see contact
below).
The complete report, entitled "Water Quality of the Three Major Tributaries to
the Chesapeake Bay, the Susquehanna, Potomac, and James Rivers, January
1979-April 1981, "(Order No. PB 82-238 593; Cost: $9.00, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
For information contact David Flemer at:
Chesapeake Bay Program
2083 West Street, Suite 5G
Annapolis. MD 21403
U.S. GOVERNMENT PRINTING OFFICE: 1982—659-O17/O873
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
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Penalty for Private Use $300
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