United States
Environmental Protection
Agency
Water Engineering Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-85/043 June 1985
&EPA Project Summary
Characterization of the Water
Quality of the Lower
Mississippi River
W. M. Grayman
•
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is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The water quality characteristics of
surface water used as a source of drinking
water is important information for water
utilities. This characterization may be
used to make decisions about modifying
the water treatment process, to design
water quality monitoring programs, or to
identify desirable reduction in pollutant
discharges to the surface water.
Characterization of water quality takes
several forms. When available, in-stream
water quality samples may be analyzed to
identify spatial and temporal trends and
to define the movement and transforma-
tion of pollutants in surf ace water. Mathe-
matical models operating at a wide range
of detail may be applied to address a
range of scenarios or what-if questions.
For example, the impact of alternative
discharge limitation policies or varying
hydrologic conditions may be studied with
such models
A recent study (Conceptual Develop-
ment of a Toxic Screening Model, EPA/
600/9-84/018, September 1984, U.S.
Environmental Protection Agency, Cincin-
nati, Ohio) demonstrated the application
of a water quality model linked to the
Reach File System, a nationwide com-
puterized data base of stream related
information and application programs
maintained by the U.S. Environmental
Protection Agency (EPA). This screening
model was applied to the lower Missis-
sippi River to characterize the concentra-
tions of organics in the river resulting
from point source discharges. This study
concluded that the joint use of the Reach
File System and a water quality model
provided an economic and feasible means
of performing such characterization.
Another study demonstrated the applica-
bility of water quality models to predict
toxic pollutant concentrations resulting
from upstream industrial discharges.
The present study was conducted as a
natural extension of the toxic screening
application to the lower Mississippi River.
Specific areas investigated in this study
include further statistical analysis of the
water quality data on the lower Missis-
sippi River, identification of additional
sources of data for characterizing the
water quality of the lower Mississippi
River, and a review of models and methods
that may be used in this further character-
ization. This information is intended as a
source document for future water quality
management studies with specific appli-
cation to the lower Mississippi River
Data Base
Application of mathematical models
requires a data base both as a means of
defining parameters for the model and
verifying the results of the modeling.
Within the context of the present study,
the required data base must include
information in three major areas: In-situ
water quality, stream flow and flow
dynamics, and point discharge data. Also
required is general, geographically refer-
enced information on the river and its
environs.
The specific area of interest in this
study is the mamstem of the Mississippi
River between Baton Rouge and New
Orleans, Louisiana.
In-situ water quality data on the lower
Mississippi River is routinely collected by
several government agencies and water
utilities. Additional data have been col-
lected for special studies or for industries
using the river as a source of water supply
or as a discharge location. The primary
sources of data on the level of organics
concentrations in the lower Mississippi
River arethe Jefferson Parish Department
of Public Utilities, the Sewerage and
Water Board of New Orleans, and the
Louisiana Department of Environmental
Quality (formerly Louisiana Department
of Natural Resources). Jefferson Parish
and New Orleans perform weekly and
daily sampling, respectively, for volatile
and nonvolatile organics. Louisiana col-
lects samples and analyzes for 29 con-
stituents on a weekly to bi-weekly basis at
12 stations on the lower M ississippi River.
The major source of streamflow infor-
mation is the elevation and discharge
measurements made at the Tarbert
Landing, Mississippi, gage located approx-
imately 75 miles upstream of Baton
Rouge This gage is 8.2 miles downstream
of the inlet channel to the Old River
Control Structure, where approximately
30% of the streamflow in the Mississippi
River is diverted to the Atchafalaya River
Basin. The gage is maintained bytheU.S
Army Corps of Engineers, and elevation
measurements are taken every 3 days.
Daily flow is estimated from these meas-
urements and published by the U.S.
Geological Survey (USGS) on a yearly
basis. Continuous flow records have been
published by the USGS since 1972, and
they are available in Corps of Engineers
reports dating back to 1936.
The USGS has cooperated with the
Louisiana Department of Public Works to
perform several studies aimed at identi-
fying the time-of-travel and dispersion
characteristics of solutes in the lower
Mississippi River. Based on dye tracer
studies performed in 1965, 1974, and
1975, the USGS has estimated travel
time and dispersion characteristics under
varying flow conditions from the Arkan-
sas-Louisiana state line to below New
Orleans.
The primary source of discharge infor-
mation is data collected by EPA in the
process of issuing or monitoring permits
for the National Pollutant Discharge
Elimination System (NPDES). For the
State of Louisiana, permits are issued
and monitored by EPA Region VI in Dallas.
Currently, 93 major dischargers are lo-
cated on the lower Mississippi River.
These dischargers are required to submit
quarterly Discharge Monitoring Reports
(DMR) based on the sampling require-
ments in their permit. This report will
become a monthly requirement m the
near future. Information from the DMR is
put into the computerized Permit Compli-
ance System (PCS), and various reports
are generated.
In the past, few industries have been
required to sample for specific organic
compounds, which has resulted in rela-
tively few discharge data on organics. In
the past few years, many of the permits
written for the organic chemical indus-
tries have required the industries to report
organic concentrations in terms of aggre-
gate organic indices such as total purge-
able halocarbons and total purgeable
aromatics. In calculating such aggregate
indices, measurements of the individual
compounds are made and mathematically
summed. The industries are required to
save those individual measurements, and
EPA may request them for a period of up
to 3 years. Thus, though an extensive
data base on organic chemicals in dis-
charges is not currently available, a
mechanism for obtaining the data is in
place.
No information on minor permits is
stored in the PCS. These data are stored
in hard copy files along with monitoring
results.
The present study assembled a compu-
terized data base of currently available
information on organics in the lower
Mississippi River. The sources of these
data, sampling stations, period of sam-
pling, and pollutants sampled are sum-
marized in Table 1. The sampling data
have been organized in a common format
with the following information stored for
each observation.
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Table 1. Summary of Data Stored in Computerized Project Data Base
Data Source
Jefferson Parish
Jefferson Parish
New Orleans
Louisiana Dept. of
Natural Resources
uses
No. of
Sampling
Stations
1 Feb.
1 Oct.
1 Sept.
12 Dec.
1
Period of
Sampling
1977
1979
1980
1982
1977
- Oct. 1979
-Nov. 1983
- Dec. 1983
-Sept. 1983
-Sept. 1981
No. of
Parameters
153
74f
fit
29
Suspended
Total No. of
Observations*
34.455
1.830
5.190
1 1,339
1.734
U.S. Army Corps of
Engineers
1977 - 1982
solids
Streamflow
2.191
*An observation corresponds to a sample analyzed for a single pollutant.
^Additional routine sampling was performed but was not inserted into the project data base.
• Source code (source of data)
• Observation number (unique number
for each sample)
• Station number (code for each sam-
pling location)
• Substation number (lateral location of
sample within the river)
• Year
• Day
• Constituent number (unique number
for each constituent)
• River mile
• "Less than" code (code indicating
whether sample concentration has
been given as less than given value)
• Value (concentration for pollutants,
flow rate for Streamflow)
Water Quality of the Lower
Mississippi River
Though no in-depth study of the water
quality of the lower Mississippi River has
been performed previously, there have
been several studies aimed at specific
aspects of the problem. Studies by Region
VI, the State of Louisiana, and EPA's
Drinking Water Research Division have
been reviewed. The Region VI studies
indicated the prevalence of selected
organics in the river and a substantial
reduction in total organic concentrations
from 1977 to 1979. A study by the State
of Louisiana identified significant fluctua-
tions in the levels of 1,2-dichloroethane
in the river and attempted to correlate the
peaks with occurrences of known spills.
The Drinking Water Research Division
used a large data base on organics in the
•iver collected at Jefferson Parish,
Louisiana. That study noted a significant
variation in concentrations, with little
apparent correlation to Streamflow or
sediment.
In the present study, long-term and
short-term temporal and spatial variations
were investigated. Graphical and statis-
tical analyses indicated a significant
short-term, high-frequency variation in
concentrations. Concentration variations
of 500% to 1000% in samples taken a few
days or a week apart were not uncommon.
The significant variation is reinforced by
statistics derived from information pre-
sented in Table 2. For the six constituents
sampled at New Orleans, the ratio of
standard deviation to mean (a normalized
measure of variation known as the coef-
ficient of variation) ranges from 1.47 to
8.21, and the ratio of maximum values to
mean values varies from 16.31 to 181.16.
A third statistic is the percentage of
samples in which the constituent is not
detected (i.e., when the concentration is
equal to zero or belowthe detection limit).
This figure varies from 96% to 19%. All
three statistics indicated significant vari-
ations in the observed values of the
constituents. The results are similar for
the data collected at Jefferson Parish.
Analysis of the data at Jefferson Parish
indicated a moderate, general, long-term
trend toward decreasing concentrations.
However, exceptions to this trend do
occur. For example, the average concen-
trations for bromodichloromethane are
increasing, and those for other constitu-
ents such as chloroform and trichloro-
ethylene show significant random vari-
ation between years rather than a general
trend.
Spatial variation in water quality may
be characterized by differences in any of
three dimensions: the longitudinal (in the
direction of primary advective flow), the
lateral (horizontally perpendicular to the
direction of primary advective flow, and
the vertical. In a river environment,
primary emphasis is generally placed on
longitudinal variation—namely, the
changes in concentration at different
river miles. The sampling data collected
and analyzed by the Louisiana Depart-
ment of Natural Resources provides a
potential resource of analyzing the longi-
tudinal and lateral variations in water
quality of the Mississippi River. These
data indicate increased concentrations,
occurrence of detectable levels of pollu-
tants, and greater lateral variations in
concentration in the vicinity of major
industrial dischargers. However, defini-
tive statements on longitudinal and lateral
variations are limited by the relatively
short history of water quality data that is
availableflessthan 10 months) and by the
reporting precision, which measures only
to the nearest microgram per liter (//g/L).
Several means are available for deter-
mining whether sets of constituents are
correlated. If correlation exists, sampling
requirements may be minimized by re-
quiring only samples of the independent
constituent. In addition, other inferences
may be drawn concerning the source and
transformations of correlated constitu-
ents. Pollutant constituents were com-
pared in pairs using both graphical and
statistical methods. Little or no correlation
was detected. Values of the correlation
coefficient(R)varyfromahighof0.56toa
low of essentially zero, with nearly 80% of
the absolute values of R less 0.1. The data
were further investigated to identify
whether any relationship existed between
the joint occurrence of detectable levels
of constituents. For each sample, a de-
tected presence in a sample was assigned
a value of 1, and an undetected value was
assigned a value of 0. The correlation
analysis applied to this transformed data
set indicated no significant improvement
in correlation.
Available Models and Methods
Over the past 25 years, the develop-
ment and use of computer-based math-
ematical models of the movement and
transformation of pollutants in streams,
lakes, and estuaries has been extensive.
In more recent years, models have been
developed for tracing organics, pesticides,
and other toxics. These models form the
pool of currently available tools that may
serve as the basis for modeling of the
lower Mississippi River.
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Table 2. Statistical Characteristics of Selected Pollutants at New Orleans and Jefferson Parish. September 1980 to November 1983
Concentrations
Sample
No.
Constituent Name
No. of
Observations
No. of
Non-Zero
Observations
Average
(fJ9/LJ
Standard
Deviation
(W/L)
Minimum
Value
Maximum
Value
tfjg/Lj
Jefferson Parish samp/ing data:
7 Chloroform
11 Bromodichloromethane
15 Chlorodibromomethane
19 Bromoform
23 1.2-Dichloroethane
35 Trichloroethylene
39 1,1,2-Tnchloroethane
43 Carbon Tetrachloride
47 Dichloromethane
50 Bromochloromethane
54 Dichloroethylene
58 Chlorobenzene
126 Tetrachloroethylene
134 1,1,2.2-Tetrachloroethane
New Orleans sampling data.
118
118
118
58
118
118
58
118
58
58
58
58
58
58
117
76
14
1
111
67
17
39
29
0
0
0
0
0
4946
192.0
16.7
0.3
1144.6
65.6
56.0
18.8
66.9
00
00
0.0
0.0
0.0
554.5
3085
66.2
2.6
1801.6
179.0
218.2
61.2
130.7
00
00
0.0
0.0
0.0
0.0
0.0
00
00
0.0
00
00
00
00
0.0
0.0
0.0
00
00
3850.0
1850.0
470.0
20.0
101200
1491 0
1570.0
6000
740.0
0.0
0.0
0.0
0.0
0.0
7
11
15
23
35
43
Chloroform
Bromodichloromethane
Chlorodibromethane
1 ,2-Dichloroethane
Trichloroethylene
Carbon Tetrachloride
847
847
847
847
847
847
600
241
37
687
32
93
300.4
91 3
138
1363.0
138
27 1
4409
3940
959
2788.8
113.3
1307
0.0
0.0
0.0
0.0
0.0
0.0
49000
7100.0
2000.0
34800 0
2500.0
17000
Models used in studying the movement
and transformation of pollutants in a
water body are generally composed of
two components: a hydraulic component
and a water quality component. The
hydraulic component is used to calculate
the spatial and temporal variation of
discharge and depth within the water
body. The water quality component is
used to determine the spatial and tem-
poral variation of pollutant concentrations
in the water body. The following models
were reviewed in terms of their potential
application to water quality modeling of
the lower Mississippi River.
The Routing and Graphical
Display System
The Routing and Graphical Display
System (RGDS) is a modular set of
computer-based files and programs de-
veloped for EPA. The RGDS uses files of
the EPA Reach File System and performs
routing of pollutants through a stream
network using simplified first-order decay
functions. This system can produce a
variety of graphical displays of informa-
tion generated by the routing process or
other information stored in EPA-main-
tained data files.
Water Quality Analysis
Simulation Program
The Water Quality Analysis Simulation
Program (WASP) is a general-purpose
water quality model developed for EPA.
Water bodies are represented in WASP
by interconnecting compartments. These
compartments may be linked to permit
one-, two-, or three-dimensional models.
WASP is a time-varying model in terms of
both loading conditions, flow, and ex-
change coefficients. The kinetic/reactive
equations governing pollutant transfor-
mations and interactions may be repre-
sented by simple linear relationships,
interactive linear relationships, or a wide
range of nonlinear interactive relation-
ships.
Exposure Analysis
Modeling System
The Exposure Analysis Modeling Sys-
tem (EXAMS) was developed by EPA to
evaluate the ultimate (steady-state) be-
havior of synthetic organic chemicals in
aquatic ecosystems. The system was
designed to provide information on
chemical exposure (ultimate expected
environmental concentrations), fate (dis-
tribution of the chemical in the system),
and persistence (time required for effec-
tive purification of the system). A system
is represented by a series of compart-
ments that correspond to levels within
the water column (littoral and benthic ma
river, and epilimnion and hypohmnion in
a lake) or to different two-dimensional
locations. A wide range of transforma-
tions is represented, including ionization,
sorption, photolysis, hydrolysis, biolysis,
oxidation, and volatilization Hydraulic
transport between compartments is
through advection and dispersion
Chemical Transport and
Fate Model
The Chemical Transport and Fate Model
(TOXIWASP) was developed by EPA's
Environmental Research Laboratory in
Athens, Georgia, as a means of simula-
ting the transport and fate of toxic
chemicals in water bodies. The model
combines the chemical transformation
processes adapted for the EXAMS model,
the transport and program structure of
the WASP model, and a simple sediment
balance algorithm. Like WASP, it is a
dynamic model designed to operate in
conjunction with a hydraulic model or
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other source of advective/diffusive flow
information.
Sediment- Contaminant
Transport Model
The Sediment-Cohtaminant Transport
Model (SERATRA) is an unsteady-state,
two-dimensional (longitudinal and verti-
cal), finite element, sediment-contami-
nant transport model. The sediment-
contaminant interaction is represented
bythree sub-models: a sediment transport
sub-model; a dissolved contaminant
transport sub-model; and a particulate
contaminant transport sub-model.
Adjusting Parameters for
Specific Situations
To apply a water quality model to a
specific situation, the parameters of the
model must be adjusted so the model will
represent, to the degree possible, the
results of the actual processes occurring
within the water body. The fine tuning of
parameters generally encompasses both
the selection of some parameters based
on past experience or commonly accepted
literature values and their further ad-
justment to match field data for the
specific situation being modeled.
Recommendations
The lower Mississippi River provides a
good framework for demonstrating water
quality management, with particular
emphasis on the use of surface water as a
source of drinking water. The availability
of a significant data base and applicable
models, and the general interest in identi-
fying water quality problems and pro-
posing mitigating solutions contribute to
this area's applicability for further study
in this field.
To support future efforts in the area of
water quality management, the following
actions are recommended to augment the
present data base:
• The data base on discharge data for
the lower Mississippi River should be
expanded by requesting EPA Region VI
to secure supplemental specific organic
discharge data from industries on the
river.
• Scheduling and quality control should
be coordinated among the monitoring
programs of Louisiana, New Orleans,
Jefferson Parish, and others to assure
a comparable and compatible water
quality data base for modeling efforts.
The State should consider modifying
its monitoring program to provide
greater precision in reporting organic
concentrations and to stagger the time
of sampling to correspond with the
approximate travel time between
stations.
• Industries along the river conducting
water quality monitoring studies should
be requested to provide this informa-
tion as part of an overall water quality
data base for the lower Mississippi
River.
The full report was submitted in fulfill-
ment of Contract No. 2211NAST by
Walter M. Grayman under the sponsor-
ship of the U.S. Environmental Protection
Agency.
Walter Grayman is with Walter M. Grayman Consulting Engineers. Cincinnati,
OH 45229.
'Richard G. Eilers is the EPA Project Officer fsee below).
The complete report, entitled "Characterization of the Water Quality of the Lower
Mississippi River," (Order No. PB 85-190 981 /AS; Cost: $13.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
*U.S.Government Printing Office: 1985 - 559-111/10860
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