SOURCES AND QUANTITIES OF NUTRIENTS
ENTERING THE GULF OF MEXICO
FROM SURFACE WATERS OF
THE UNITED STATES
Prepared by Professor Stephen B. Lovejoy
Department of Agricultural Economics
Purdue University
West Lafayette, IN 47907
Prepared for the U.S. Environmental Protection Agency
Gulf of Mexico Program
Nutrient Enrichment Subcommittee
Under Cooperative Agreement Number 68-3A75-1-16
Between Purdue University and
The U.S. Department of Agriculture,
Soil Conservation Service
Partial Funding Supplied By
The Gulf of Mexico Program Office
Through Interagency Agreement Number DW12934260-01-0
Between The U.S. Environmental Protection Agency and
The U.S. Department of Agriculture
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TABLE OF CONTENTS
Nutrient Enrichment Subcommittee v
Preface vii
Executive Summary viii
Introduction 1
The Purdue University Water Quality Model 3
Description 3
Model Results 5
Summary of Water Quality Model Estimates 20
STORET Data: Quantities of Nitrogen and Phosphorus at Monitoring Stations 21
STORET Data for Gulf of Mexico Drainage Area 24
Concentrations .24
Loadings 32
Summary of Discussion 48
Data Discussion 49
Appendix A: Subregional Analysis of Ambient and Nonambient Concentrations Al
Appendix B: Subregional Analysis of Ambient Concentrations Bl
Appendix C: Regional Estimates of Gulf Coast Loadings Cl
Appendix D: Regional Comparisons of Geographic Areas in USGS and
Purdue Water Quality Model Dl
Appendix E: Summary Estimates of Concentrations from Purdue Water
Quality Model El
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LIST OF TABLES
Table 1 1982 Model Base: Nonurban Nonpoint, Urban Nonpoint, Point
and Total Loadings: Total Phosphorus (TP) 11
Table 2 1982 Model Base: Nonurban Nonpoint, Urban Nonpoint, Point
and Total Loadings: Total Kjeldahl Nitrogen (TKN) 12
Table 3 Changes in Nonurban, Nonpoint and Total Phosphorus Loadings:
90 Base (40 Million Acre CRP) 16
Table 4 Changes in Cropland, Nonurban Nonpoint and Total Nitrogen (TKN)
Loadings: 90 Base (40 Million Acre CRP) 17
Table 5 USGS Region Summaries: Mean Nitrogen and Phosphorus Concentrations
by Region 26
Table 6 USGS Region Summaries: Mean Ambient Nitrogen and Phosphorus
Concentrations by Region 30
Table 7 USGS Region Summaries: Mean Ambient Phosphorus and Nitrogen
Loadings by Region 36
Table 8 "Lowest Subregions": Mean Ambient Phosphorus and Nitrogen Loadings
of USGS Subregions Adjacent to the Gulf of Mexico 39
Table 9 Regional Summary of Nutrient Loadings for "Lowest Subregions":
Subregions Adjacent to the Gulf of Mexico 43
Table 10 Relative Contributions of Mississippi River System Components to Nutrient
Loadings Entering the Gulf of Mexico from the Lower Mississippi River
and Atchafalaya River 46
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LIST OF FIGURES
Figure 1 Water Quality Model Description
Figure 2 Sediment and Related Pollutants Models for Water Quality Model
Figure 3 Livestock Runoff Models for Water Quality Model
Figure 4 Cropland Nutrient Runoff Models for Water Quality Model
Figure 5 USDA Crop Reporting Regions
10
Figure 6 Continental U.S. Map of USGS Water Resource Regions..
23
111
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IV
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MEMBERS
Nutrient Enrichment Subcommittee
Gulf of Mexico Program
Mr. L. Pete Heard, Federal Co-Chair, U.S. Dept. of Agriculture, Soil Conservation
Service, Jackson, Mississippi
Mr. Dugan S. Sabins, State Co-Chair, Louisiana Dept. of Environmental Quality, Baton
Rouge, Louisiana
Ms. Jan R. Boydstun, Louisiana Dept. of Environmental Quality, Baton Rouge, Louisiana
Dr. C. Fred Bryan, Lousiana State University, Baton Rouge, Louisiana
Mr. Charles Demas, U.S. Geological Survey, Baton Rouge, Louisiana
Mr. Mike J. Dowgiallo, National Oceanic and Atmospheric Administration, Coastal Ocean
Program Office, Washington, D.C.
Mr. Daniel Farrow, National Oceanic and Atmospheric Administration, National Ocean
Service, Rockville, Maryland
Dr. David A. Flemer, U.S. Environmental Protection Agency, Environmental Research
Laboratory, Gulf Breeze, Florida
Mr. Tim Forester, Alabama Dept. of Environmental Management, Montgomery, Alabama
Mr. Douglas J. Prague', Gulf Coast Fisheries Coordination Office, Ocean Springs,
Mississippi (Johnny French, alternate)
Dr. Eddie Funderberg, Louisiana State University Extension Service, Baton Rouge,
Louisiana
Mr. Brian Grantham, Citizen's Advisory Committee, Foley, Alabama (James Fogarty,
alternate)
Dr. Churchill Grimes, National Oceanic and Atmospheric Administration, National Marine
Fisheries Service, Panama City, Florida
Mr. Vince Guillory, Louisiana Department of Wildlife and Fisheries, Bourg, Louisiana
Dr. Peter J. Kuch, U.S. Environmental Protection Agency, Washington, D.C.
Mr. Ira H. Linville, U.S. Environmental Protection Agency, Region 4, Atlanta, Georgia
Dr. Stephen R. Lovejoy, Purdue University, West Lafayette, Indiana
Gale Martin, Mississippi Soil and Water Conservation Commission, Jackson, Mississippi
(Mark Gilber, alternate)
Dr. David Moffitt, U.S. Dept. of Agriculture, Soil Conservation Service, Fort Worth,
Texas
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Mr. James M. Moore, Texas State Soil and Water Conservation Board, Temple, Texas
fMel Davis, alternate)
James Patek, Lower Colorado River Authority, Austin, Texas (Charles Dvorsky
. -nate)
Mr. Edward J. Pullen, U.S. Army Corps of Engineers, Waterways Experiment Station,
Vicksburg, Mississippi
Mr. Dale Rapin, U.S. Dept of Agriculture, Forest Service, Atlanta, Georgia
Ms. Stephanie Sanzone, U.S. Environmental Protection Agency, Washington, D.C.
Dr. Alan M. Shiller, Center for Marine Science, University of Southern Mississippi,
S tennis Space Center, Mississippi
Dr. Bob Thompson, Jr., Potash & Phosphate Institute, Starkville, Mississippi
Dr. Terry E. Whitledge, The University of Texas, Marine Science Institute, Port Aransas
Texas
Dr. John W. Day, Jr., advisor, Louisiana State University, Baton Rouge, Louisiana
Dr. Nancy N. Rabalais, advisor, Louisiana Universities Marine Consortium, Chauvin,
Louisiana
VI
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PREFACE
This report was prepared for the Nutrient Enrichment Subcommittee of the U.S.
Environmental Protection Agency's Gulf of Mexico Program. Because nearly 60% of the
continental United States drains into the Gulf of Mexico, a large and diverse amount of data are
available that could potentially be used to assess the sources and quantities of nutrients entering
the Gulf. Unfortunately, data from these studies often are not comparable in their timeframes,
methods employed, or the water quality parameters reported. In addition, data on nutrient
concentrations in rivers often are not accompanied by data on water flow, therefore pollutant
loadings cannot be ascertained. As this report indicates, there is no shortage of appropriate data
of documented quality upon which to base decisions about protection of the water of the Gulf of
Mexico.
This report is not intended to be a complete examination of the sources of nutrients in the
Gulf of Mexico. Rather, it represents an effort to examine the data for one specific year—1989.
Funding was inadequate to include analysis of additional years. While care was used in selecting
this year, 1989 may not represent a typical year for nutrient inflow into the Gulf. The
examination of only one specific year also means that no trend analysis over a multiyear
timeframe was performed. It is hoped that future reports will address these and other questions
concerning the relationship between nutrient enrichment and the ecological integrity of the Gulf
of Mexico.
After reviewing this document, the members of the Nutrient Enrichment Subcommittee
caution readers to bear these aforementioned limitations of the report in mind.
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Executive Summary:
Sources and Q ntities of Nutrients Entering
the Gulf of Mexico from Surface Waters of
the United States
The Gulf of Mexico is one of our nation's premier natural resources. A vital habitat for both aquatic and
terrestrial species, it is a major supplier of seafood production and recreational opportunities. However,
this marine ecosystem is now threatened by a variety of contaminants resulting from man's activities. This
degradation of the Gulf is caused by activities in the coastal areas as well as from freshwaters flowing into
the Gulf from the entire drainage area. One specific area of concern is the potential overenrichment of
Gulf waters by excessive nutrients, particularly nitrogen and phosphorus.
At the beginning of the Gulf of Mexico project, some felt that we needed to concentrate on the activities
in the Gulf Coast states but others felt that we needed to include the entire drainage basin in any analysis
or particularly in management plans. We quickly arrived at the point where we were uncertain from
where these excessive nutrients were originating. On farms in Louisiana or Texas or ranches in Montana?
From industries in Florida or municipalities in Indiana or Minnesota?
We knew that nationally nonpoint sources of nitrogen and phosphorus accounted for about 80% of total
loadings into U.S. rivers and streams. But there was a great deal of variance across regions of the country.
For nitrogen, in the Northeast, less than 50% came from nonpoint sources, while in the Northern Plains
over 96% came from nonpoint sources.1 For phosphorus, in the Southeast only 45% came from nonpoint
sources while nonpoint sources accounted for 90% or more in the northern Great Plains, Pacific and
Mountain states.2 In order to answer these questions, we decided to initiate a study to examine the sources
and quantities of nutrients entering the Gulf of Mexico.
The drainage area into the Gulf is quite extensive, it covers roughly from the Appalachians to the Rockies
plus the Florida Gulf Coast The Gulfs drainage basin extends up into New York state in the east to
nearly all of Montana on the west or nearly 60% of the land area of the continental United States. Nearly
half of the population of the United States lives in the drainage area.3 Three-fourths of our land in farms
and ranches is in the drainage basin and almost 80% of our cropland. The basin produces nearly 90% of
the com and soybeans in the United States and 70% or more of our wheat and hay.*
This is obviously a vast, agriculturally productive area with major population centers and extensive
industry including much of what we have called the rust belt So, we have extensive agriculture with high
levels of nutrient application; we have hundreds of cities discharging nutrients; and thousands of industries
discharging pollutants. All of these are putting nutrients into water that eventually flows into the Gulf of
Mexico.
With such diversity of sources in the geographic dispersion, the issue became how to simplify in order
to begin the analysis and to discover the data that was available. We found data that was comparable and
Vlll
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covered the entire drainage area in both the Purdue University Water Quality Model and in EPA/s
STORET data base. Both of these are described in detail in the final report. Here we will point out some
difficulties and general results of that investigation.
Attempting the study of the sources and quantities of pollutants in all of the major waterways comprising
an area as large as the Gulf of Mexico drainage basin severely limits the data sources which one can
utilize effectively. We believed it necessary to collect or estimate data from one recent time span, with
a strong preference for a very recent and fairly typical year. While there is a plethora of studies on
various segments of waterways in river systems flowing into the Gulf, most are of value to this particular
study only for general background information rather than as actual data sources.
For example, research on the Galveston Bay Entrance Channel, the Mississippi River near St. Cloud MN,
Lake Austin in Texas and the Tampa Harbor is all within the geographic scope of this project However,
these and other studies are not comparable in their time frames or in the methods employed and chemical
elements reported. Data collected from 1973 to 1979 may differ from that collected in 1981 or 1987 for
many reasons, none of which may be relevant to our current study. Some individual states in the Gulf
drainage area publish comprehensive data on water quality every few years; some others publish, for
example, data on concentrations but no data on water flow or pollutant loadings. And the sum total of
all of these reports for the relevant area was far from complete geographically.
With such a large geographic dispersion, the issue became one of simplifying in order to begin the
analysis from the large databases available. We considered using the National Stream Quality Accounting
Network (NASQAN) data, established in 1972. Its data includes streamfiow, concentrations of major
inorganic and trace constituents, presence or absence of bacterial indicators, and pesticide concentrations.
However, NASQAN only has approximately 500 stations in the entire United States, all located at the
mouths of major river systems and therefore not obtaining measurements from upstream reaches of many
waterways. Furthermore, federal budget constraints have led to bimonthly and quarterly sampling, leading
to a very low number of measurements even from fairly large geographic areas in a particular season or
even over the course of a year. For these reasons we decided to use primarily the two data sources
mentioned below.
We found data that was comparable and which covered the entire Gulf of Mexico drainage area in both
the Purdue University Water Quality Model and in the U.S. Environmental Protection Agency's STORET
database. The Purdue Model, described in detail on pages 5-7 of this report, has more than 1300 nodal
points around the nation both at the mouths of rivers and upstream on major tributaries, with an average
distance of 66 miles- between nodal points. For this report we updated the original 1982 database with
estimates for 1990.
The Environmental Protection Agency's STORET system is the only national database which we located
that provides data comparable to that in Purdue's Water Quality Model for the Gulf of Mexico drainage
basin. STORET contains water quality data for more than 700,000 sampling sites throughout the United
States and Canada, including several measures of phosphorus and nitrogen, though some are reported in
IX
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only one or a few surface water subsystems. A package of analytical programs allows access and some
analysis of water quality data, with the ability to restrict the analysis to data which were collected and
stored using certain quality control standards.
We made several decisions regarding which data to select, to maintain as high a degree of-quality control
as possible. Only "active" data, for which an individual currently with the agency that entered the data
is willing to be responsible for the accuracy and collection methods used, was retrieved; "retired" data was
not. We used only actual grab samples from surface waters, excluding such categories as underground
aquifers, wells or springs. Several "remark" codes may cast doubt on the accuracy of a particular sample;
we excluded all such samples except those consisting of the mean of samples collected on the same date,
calculations from actual samples, field measurements and those after any amount of recent rainfall, to
retrieve a cross section of all accurate data.
As noted in the report, we occasionally ended up with less data than desired for a specific subregion and
season. We did not attempt to pad these gaps with nearby or less accurate data, as this could reduce the
credibility of comparisons among subregions or seasons. We also attempted to run a "lowest station"
analysis using the most-downstream data collection stations' data to confirm the "lowest subregions"
analysis for Gulf-adjacent subregions and the Mississippi River system. After a lengthy attempt, the
decision was made that sufficient data was not available for several subregions, negating the ability to
confirm the data in others.
The lack of data for 1990 also led to our decision to analyze 1989 data, as it is the most recent year for
which consistently sufficient data was generally available at the time of the analysis. With all of these
restrictions we believe we have reduced any quality control variability which was formerly sometimes
associated with the STORET system.
We began by examining the 1989 seasonal concentrations in each of the USGS regions and subregions
which form the Gulf of Mexico drainage basin. This includes the Upper and Lower Mississippi regions
the Ohio, Tennessee, Missouri, Arkansas and Texas Gulf regions as well as part of the South Atlantic-Gulf
or "Southeast" region.
One of the more surprising observations about nutrient concentrations was the lack of any consistent
seasonal trend in any of the regions or subregions. Nonpoint sources of nutrients such as cropland runoff,
urban lawn runoff and large construction projects would be expected to be somewhat seasonal.
A second finding is- that concentrations of nutrients do not generally increase as a river system flows
downstream. While in some stream reaches in some seasons, we found a trend, it was not consistent
across regions or across seasons. This may be the result of nutrient degradation or plant uptake of
nutrients, lags from sediment attached nutrients or simply that volumes of water increase more quickly
than volumes of nutrients.
For instance, if we begin in the Upper Mississippi region we find average concentrations of phosphorus
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and nitrogen at A mg/L and 1.6 mg/L. As we go south toward the Gulf, the Missouri comes in with
higher average concentrations in its system of 1 mg/L of phosphorus and 2.4 mg/L of nitrogen, the Ohio
system inflow has average concentrations of .2 and .6 and the Tennessee, which flows into the lower Ohio
shortly before it reaches the Mississippi, has concentrations of .1 and .4. By the time all this water
reaches the Lower Mississippi, the average daily concentrations including lower Mississippi tributaries are
.2 mg/L of phosphorus and .8 mg/L of nitrogen. Therefore, the concentrations in the lower Mississippi
are lower than most of the major regions of its drainage basia However, since the amount of water being
contributed to the Mississippi from its tributaries is so vastly different, the next step was to examine
loadings of nutrients.
The mean concentrations throughout each of the USGS regions discussed above, and the average daily
flows, are used to calculate nutrient loadings. Regional mean loadings are useful primarily as a basis for
comparisons between regions, as they represent a cross section of data from the largest rivers to the
smaller tributaries. Our estimates of mean daily loadings of phosphorus are highest in the Ohio River
region over the entire year, with the Lower Mississippi region's mean loadings second highest. The lowest
average daily phosphorus loadings are found in the Rio Grande region. Average daily Kjeldahl nitrogen
loadings were highest in the Lower Mississippi region in 1989; the Ohio system is a fairly distant second
for nitrogen. Several other regions report fairly low average daily Kjeldahl nitrogen loadings, with the
Rio Grande region again the lowest throughout the entire year.
Based on analysis later in the report of only the "lowest subregion" data, which studies only those
subregions closest to the Gulf of Mexico, much higher daily loadings of nutrients actually flowing into
the Gulf are likely. From this analysis we estimate that more than 379,000 pounds of phosphorus and
over 1,872,600 pounds of Kjeldahl nitrogen are discharged into the Gulf on an average day.
Approximately 94% of the phosphorus and 91% of the Kjeldahl nitrogen from these gulfside subregions
comes from the Mississippi River system.
Because of the high proportion of nutrients clearly coming from the Mississippi system using either
method, we should examine it more closely. When we looked at concentrations, remember mat the waters
from the Missouri system and the Upper Mississippi were the most heavily nutrient laden. However, we
know that the Ohio discharges considerably more water into the Mississippi than the Missouri. If we look
at the data available for average daily loadings into the Mississippi system, specifically those systems
above the lower Mississippi region, we find for example that the relatively "nutrient rich" Missouri
accounts for only approximately 10% of average daily loadings of phosphorus and Kjeldahl nitrogen near
the mouth of the Mississippi. The largest amounts of water flowing into the Lower Mississippi come from
the Upper Mississippi and the Ohio regions, both of which also have many large population centers and
large amounts of agricultural activity. The Upper Mississippi then contributes roughly one-third of the
phosphorus and Kjeldahl nitrogen discharged into the Gulf from the Mississippi system, and the Ohio
River system (including relatively small loadings from the Tennessee region) which contributes more than
half of the phosphorus and more than a quarter of the Kjeldahl nitrogen.
We must remember that these are averages across the entire year, there is considerable seasonal variation
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within the huge Mississippi drainage basin. For instance, the Ohio River System contributes over 60%
of the phosphorus in the spring but well under 20% in the summer. The Upper Mississippi and its
tributaries contribute only roughly 10% of the phosphorus in the spring but well over four-fifths in the
summer.
Overenrichment of the Gulf of Mexico, then, is caused by not only activities along the Coast but also by
the behaviors of Iowa farmers, Pennsylvania steel magnates and urban residents in cities like Indianapolis,
Louisville, SL Louis, Minneapolis and Rising Sun, Indiana. If we are to develop plans to protect the Gulf,
we must examine methods for influencing those behaviors. In addition, we need to identify which nutrient
is the most important to control or which is the most troublesome for the Gulf ecosystem. The
contributions of regions vary by nutrient and by season. In addition, the proportion of various nutrients
from point sources and nonpoint sources varies across regions and nutrients. Attempting to protect and
preserve the Gulf of Mexico ecosystem will require consideration of the activities throughout the entire
drainage basin as well as along the Gulf coast.
See Table 2 of report
See Table 1 of report
United States Department of Commerce, Bureau of the Census, Statistical Abstract of the United
States: 1990. 110th Edition, Washington, D.C., 1990. ~~~
United States Department of Commerce, Bureau of the Census, 1987 Census of Agriculture. Volume
1: Geographic Area Series, Part 51: United States Summary and State Data, 1989.
XII
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Sources and Quantities of Nutrients Entering
the Gulf of Mexico from Surface Waters of
the United States
Introduction.
The Gulf of Mexico is one of our nation's premier natural resources. A vital habitat for both aquatic
and terrestrial species, it is a major supplier of seafood production and recreational opportunities.
However, this marine ecosystem is now threatened by a variety of contaminants resulting from man's
activities. This degradation of the Gulf is caused by activities in the coastal areas as well as from
freshwaters flowing into the Gulf from the entire drainage area. One specific area of concern is the
potential overenrichment of Gulf waters by excessive nutrients, particularly nitrogen and phosphorus.
Before a strategy to manage and protect the resources of the Gulf can be established, the sources and
quantities of these nutrients entering it from major United States river systems must be identified.
This paper reports on efforts to. gather the available information and data to accomplish such
identification. The report utilizes primarily a combination of data from the U.S. Environmental Protection
Agency's STORET database and analysis from Purdue University's Water Quality Model. The geographic
area studied covers the entire U.S. drainage area into the Gulf, roughly from the Appalachians to the
Rockies plus the Florida Gulf Coast
Many people do not realize the extent of this drainage area; it extends even to a small portion of
New York state and nearly all of Montana, covering nearly 60% of the continental United States' area.
A little less than half of the U.S. population lives in this area,1 but it includes approximately three-quarters
of all U.S. land in farms and nearly 80% of our cropland. Approximately 90% of the soybeans produced
in this country (a source of nitrogen in soils) comes from this area, and nearly 90% of our com, one of
the more heavily fertilized crops. More than 70% of our wheat is produced in the region, and
approximately 70% of U.S. acres in hay production (about 65% of dry tons produced) are located in this
vast drainage area.2
This vast area, then, includes extensive agricultural regions with high levels of nutrient application,
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major population centers discharging nutrients and other pollutants, and many varied industries also
discharging a multitude of pollutants. Eventually many of these pollutants must flow into the Gulf of
Mexico.
This report contains first, a description of Purdue's Water Quality Model and the analysis of results
obtained through its use for the river systems in the Gulf of Mexico drainage area. Next, the
Environmental Protection Agency's STORET database is described and the general results of studying
1989 data from it are presented. Comparisons of data from USGS regions on nutrient concentrations and
loadings follow, again using the STORET database. Loadings entering the Gulf from its coastal (USGS)
subregions, and some further analysis of the vast Mississippi River system, complete the main body of
the report, along with the summary and conclusions.
Five important appendices follow the main report. Appendices A and B analyze STORET's USGS
subregional data on concentrations of phosphorus and nitrogen within regions; the data in Appendix A
include some non-ambient observations, while Appendix B includes strictly ambient data. Appendix C
contains nutrient loadings for USGS subregions within each region, from STORET. These three
appendices provide the means of locating more specific geographic problem areas regarding sources of
nutrients and Appendix D provides a cross-reference between USGS subregion or region numbers and the
Purdue Water Quality Model river system numbers and Appendix E provides a concentration of pollutants
for each river mode in the Purdue Water Quality Model.
United States Department of Commerce, Bureau of the Census Statistical Abstract of the United
States: 1990. 110th Edition, Washington, D.C., 1990.
United States Department of Commerce, Bureau of the Census, 1987 Census of Agriculture,
Volume 1: Geographic Area Series, Part 51: United States Summary and State Data, 1989.
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The Purdue University Water Quality Model
Description
In recent years, the issue of water quality has achieved a much more important focus. The general
public, as well as their representatives in Washington, are increasingly suggesting that the country needs
clean water as well as food and fiber production. It should be the goal of the government as well as both
agricultural and environmental groups to provide these desired commodities and amenities. The
Environmental Protection Agency has concentrated their water quality efforts on assisting municipalities
in construction and operation of sewage treatment plants and in regulating and assisting industries in
reducing the discharge of pollutants into pur nation's surface waters. However, recent investigation
suggests that reducing point sources of pollution will be inadequate for achieving society's water quality
goals. The role of agriculture in nonpoint source water pollution has been well documented.
The U.S. Department of Agriculture has also been responding to the social forces which are
suggesting that agricultural practices should be less environmentally degrading. Their work on the
National Program for Soil and Water Conservation for 1988 through 1997 illustrates the department's
concern over water quality and, in general, the offsite impacts of agricultural production practices. While
their first priority remains reducing the damage caused by excessive soil erosion, the damages mentioned
include offsite damages as well as onsite damages. In addition, their number two priority for their ten year.
program is to "protect the quality of surface and groundwater against harmful contamination from nonpoint
sources."3
All of this interest in the water quality impacts of agricultural production practices suggests that as
a sector, agriculture will be increasingly called upon to estimate the water quality impacts of alternative
agricultural program's and policies. However, unlike estimating changes in gross soil erosion resulting
from agricultural policies, the tools for estimating the water quality impacts of agricultural policies are not
3 United States Department of Agriculture. 1988. "National Conservation Program." In Journal of
Soil and Water Conservation. 43(3) :243.
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as refined. In the 1970's and early 1980's, a group of researchers at Resources for the Future in
Washington, D.C., began construction of a model to estimate the water quality impact of various point
and nonpoint sources. This model has been used in several procedures, such as the RCA process, to
provide some baseline information on the impact of cropland production practices upon nutrient loadings
into the nation's surface waters. This type of national model for estimating the water quality impacts
associated with alternative policies is absolutely essential. While Americans desire cleaner water, they
also want the most efficient and effective policies for achieving their water quality goals.
This concern about water quality impacts of agricultural practices led the Soil Conservation Service
and the U.S. EPA, in cooperation with Purdue University, to revive and renew the development of the
Water Quality Model which was originally constructed by Leonard Gianessi and Henry Peskin at
Resources for the Future. This Water Quality Model (WQM) is utilized to provide directional estimates
of water quality impacts to decision makers for use in policy deliberations.
While there are many water quality models oriented toward small watersheds (ANSWERS, AGNPS,
CREAMS, etc.), there has been much less work done on regional or national water quality models. In
considering the degradation of surface water quality by agricultural production at the national level, it is
useful to take one or two steps back from the water quality problem and examine the endowment of the
United States in terms of surface water. The United States has thousands of rivers, lakes, reservoirs,
creeks, etc., into which flow billions of gallons of water per day. Obviously, some method for
representing these hundreds of thousands of water bodies is essential for wise use of the resources. The
Water Quality Model, as originally developed by Resources for the Future and now adapted by Purdue
University, attempts to represent an aggregate picture of the nation's water resource by concentrating on
the major rivers, streams and lakes in the nation. In order to do this, the Water Quality Model establishes
nodal points at the mouths of rivers, the entrances to reservoirs, forks of major tributaries, major
population centers and the beginning of estuaries. This method yields 1,300 nodal points around the
nation which are used in 44 distinct subnetworks and then aggregated for national estimates. For instance,
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the Mississippi River subnetwork (the largest) has a total of 124 different rivers as well as 78 lakes and
reservoirs. Nationwide, the average distance between nodal points is 66 miles.
A first question in the analysis of water quality is determining the sources of various pollutants.
Data developed by Leonard Gianessi at Resources for the Future suggests that sediment, phosphorus and
nitrogen are generated in large quantities by rural land uses including cropland. Nearly all suspended
sediments come from rural land uses, and over 80% of total phosphorus and nitrogen comes from rural
land uses. This suggests that when these are the pollutants of concern, the loadings emanating from rural
lands must be considered in any policies or proposals to reduce the amount of degradation of our water
resources.
The Water Quality Model is unique in its ability to examine the issues surrounding the sources of
t
pollutants into our surface waters. The Water Quality Model is very data intensive in the sense that
substantial information on point source pollution, rural land uses, urban nonpoint source pollution and
technical coefficients are necessary. The Water Quality Model is illustrated in Figure 1. Figure 1 shows
that the point sources of pollution consist of industrial discharges as well as municipal treatment plants.
The nonpoint sources can be divided into the rural and urban. The rural pollutants can best be described
by separating out sediment originating from various rural land uses, nutrient from animal agricultural
practices and nutrient runoff from cropland. These various sources are described in more detail in figures
2 through 4. Figure 5 consists of a map showing the USDA Crop Reporting Regions .for the continental
U.S. Note that some part or all of every region except the Pacific Region is included in the Gulf of
Mexico drainage area.
Model Results
Data from the-original 1982 base of the Model is shown in Table 1 for Total Phosphorus and in
Table 2 for Total Kjeldahl Nitrogen, for nonurban nonpoint, urban nonpoint and point sources, and the
total from all sources. The Pacific Region is included for comparison only.
Note the very wide differences between regions in both phosphorus and nitrogen loadings. In the
Northeast (little of which is in the Gulf of Mexico drainage area, see Figure 6 on page 23) and the
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TABLE 1: 1982 Model Base: Nonurban Nonpoint, Urban Nonpoint, Point
and Total Loadings: Total Phosphorus (TP)
All data: 1000 tons/year
Region
Northeast
Appalachian
Southeast
Delta States
Cornbelt
Lake States
Northern Plains
Southern Plains
Mountain States
Pacific
Nonurban
Nonpoint
TP
64.4
119.8
22.3
40.5
306.0
33.1
183.7
53.2
247.1
356.8
Urban
Nonpoint
TP
5.8
0.7
0.9
0.2
2.1
1.5
0.1
0.4
0.1
0.7
Point
Source
TP
68.0
31.3
23.9
20.2
39.8
18.6
6.6
23.5
11.8
39.6
Total: All
Sources
Phosphorus
138.2
151.8
47.2
61.0
348.0
53.2
190.4
77.1
259.0
397.2
Continental U.S.
1427.0
12.6
283.5
1723.0
11
-------
TABLE 2: 1982 Model Base: Nonurban Nonpoint, Urban Nonpoint, Point
and Total Loadings: Total Kjeldahl Nitrogen (TKN)
All data: 1000 tons/year
Region
Northeast
Appalachian
Southeast
Delta States
Cornbelt
Lake States
Northern Plains
Southern Plains
Mountain States
Pacific
Nonurban
Nonpoint
TKN
256.5
563.2
182.6
202.0
1848.7
334.1
827.1
353.8
844.4
569.5
Urban
Nonpoint
TKN
21.5
4.3
6.4
2.1
8.3
5.1
0.8
3.9
0.6
4.3
Point
Source
.TKN
339.0
118.5
90.0
80.6
216.5
123.8
29.1
104.0
40.0
146.0
Total: All
Sources
TKN
617.0
686.0
279.0
284.7
2073.5
463.0
857.0
461.6
885.1
719.8
Continental U.S.
5981.8
57.2
1287.4
' 7326.5
12
-------
Southeast (approximately half of whose waters flow to the Gulf) about half of all phosphorus is from point
sources such as industries and municipal sewage plants. In the Northeast more than half of the Total
Kjeldahl Nitrogen is from point sources. These data are in sharp contrast with many other regions, which
receive most of their nutrients from nonpoint sources, primarily from agriculture. For example in the
Northern Plains, nearly all draining to the Gulf, over 96% of both nitrogen and phosphorus comes from
nonpoint sources. Agriculture is clearly a primary source of nutrients which eventually enter the Gulf of
Mexico.
With the assistance of the Center for Agricultural and Rural Development at Iowa State University
in providing us with estimates of changes in land use and changes in erosion, we were able to estimate
the impacts of specific policies or programs upon water quality parameters (e.g. loadings of total
phosphorus and TKN). The 1982 NRI was utilized as the baseline with the changes in cropping and
erosion estimated for government policies by CARD. These results are then used to estimate an updated
"base" for 1990, and the model is run for this 1990 base (Table 1, Appendix E).
One part of the solution to erosion and water quality problems which has already been implemented,
is the Conservation Reserve Program (CRP) of the Food Security Act of 1985. Farmers are encouraged ,
to set aside highly erodible cropland and to plant permanent vegetative cover on such land through a ten
year contract, with USDA making annual "rental payments" on the land. Assuming that 40 million acres
of agricultural land are enrolled in the Conservation Reserve Program in 1990 (34 million acres were
enrolled by 1989), there has been a dramatic reduction in pollution in most regions of the United States
since 1982.4
Over the past several years we have seen tremendous changes in the Conservation Reserve Program
including dramatic changes in eligibility requirements. These changes have resulted in changes in the
definition of highly erodible land as well as broadening of eligibility criteria to include filter strips,
Lovejoy, S.B., J.J. Jones, B.B. Dunkelberg, J.J. Fletcher and P.J. Kuch. 1990. "Water Quality and
the Conservation Title." In Implementing the Conservation Title of the Food Security Act of 1985.
Ted L. Napier (editor): Soil and Water Conservation Society, Ankeny, Iowa, pp. 122-132.
13
-------
cropped wetlands and other acres that are not highly credible but are deemed worthy of protection for
some other environmental amenity. We have accounted for these changes in the 1990 base.
Tables 3 and 4 show the percentage changes from the 1982 base in phosphorus and nitrogen loadings
for the "90 base," along with the estimated loadings for all sources. Note that only changes from
agricultural programs such as the Conservation Reserve Program are accounted for, changes for urban
nonpoint sources and point sources are not estimated at this time. Again, the regional variations are
noteworthy.
The Northeast (hardly relevant to Gulf studies) and the Southern Plains (all flowing to the Gulf) are
estimated to have higher water pollution from nutrients in 1990 than in 1982, as more land is put into
production and cropping patterns may change to require more fertilization. The Cornbelt (nearly all
eventually draining into the Gulf) and Lake States (slightly over half draining to the Gulf) show very large
decreases in nutrient pollution from croplands, which in turn lead to decreases of more than 30% in these
pollutants from all sources in the Cornbelt, and more than 20% in the Lake States.
Policies which result in a reduction in nutrient pollution from agriculture, then, may have a large
impact on some regions but lead to little or no reduction of nutrients in water systems in other areas. The
discussion which follows summarizes the 1990 estimated concentrations for the major river systems
flowing into the Gulf, from the Purdue Water Quality Model data.
Table 1. Appendix E: Purdue University Water Quality Model Summary For Gulf of Mexico Drainage
Area
As a very general rule, the concentrations of nitrogen and phosphorus estimated in the Model's
summary are slightly lower than the subregion summaries reported later from the STORET database. One
possible explanation is that STORET data includes samples which were taken by an agency specifically
because a problem was known to exist at or near a particular station; some of the STORET means, then,
may overstate the degree of nitrogen or phosphorus pollution over an entire region or subregion. It should
be noted again that the Water Quality Model's 1990 "base" is updated from 1982 only for agricultural
14
-------
changes in cropland and its erosion; no changes in point sources of pollution since 1982 are included.
15
-------
TABLE 3:
Changes in Nonurban, Nonpoint & Total Phosphorus Loadings: 90 Base
(40 Million Acre CRP)
% Change From 1982 NRI Base
Region
Northeast
Appalachian
Southeast
Delta States
Cornbelt
Lake States
Northern Plains
Southern Plains
Mountain States
Pacific
National Total
Cropland
TP
4
+28%
-23
-31
-19
-45
-43
-13
+15
-17
-26
-29%
Nonurban
Nonpoint
TP
+15%
-8
-17
-12
-36
-36
-6
+5
-3
-3
-12%
All Sources:
Change
+7%
-6
-8
-8
-32
-22
-6
+3
-3
-2
-10%
Total
Phosphorus
Estimated
Loadings1
147.7
142.8
43.4
56.0
236.5
41.4
178.5
79.6
252.1
387.5
1558.1
1 1000 tons/year
16
-------
TABLE 4: Changes in Cropland, Nonurban Nonpoint & Total Nitrogen
(TKN) Loadings: 90 Base (40 Million Acre CRP)
% Change From 1982 NRI Base
Region
Northeast
Appalachian
Southeast
Delta States
Cornbelt
Lake States
Northern Plains
Southern Plains
Mountain States
Pacific
National Total
Cropland
TKN
+28%
-23
-31
-19
-45
-43
-13
+15
-17
-26
-29%
Nonurban
Nonpoint
TKN
+14%
-10
-15
-13
-35
-33
-7
+5
-3
-3
-15%
All Sources:
Change
+6%
-8
-10
-9
-32
-24
-7
+4
-3
-3
-12%
Total Nitrogen
Estimated
Loadings1
652.7
632.5
251.1
257.7
1417.4
351.8
799.0
478.1
860.6
700.5
6438.4
1 1000 tons/year
17
-------
"River System 12" is comprised of the Kissimmee-Okeechobee-Caloosahatchie subsystem and the
Peace (FL)-Tampa Bay subsystem. (See Appendix D for a list of the USGS subregions comprising each
of the Model's River Systems.) Using an arbitrary standard of 0.2 mg/L for total phosphorus in surface
waters (used throughout the remainder of this section), all of the river miles in the Gulf river systems of
South Florida and the Peace River-Tampa Bay area of Florida, Subregions 0309 and 0310 respectively,
are estimated to be above the limit in phosphorus pollution. Note mat phosphate production does take
place in some of these areas. See the summary for River System 12, Table 1, Appendix E. Using an
arbitrary standard of 1.5 mg/L for TKN (also used for the remainder of this section), the percent of river
system miles in these subregions with TKN above this standard decreases steadily through the seasons
from 100% in winter to 42% in the fall.
River System 13 encompasses USGS Subregions 0311,0312 and 0313: the Suwanee, Ochlockonee
and Apalachicola systems. Using the 0.2 mg/L standard for phosphorus, the percent of river miles not
meeting the standard increase steadily through the year from 12% in winter to 57% in the fall. A 1.5
mg/L standard for TKN appears easier to meet in these subregions: 7% of river miles are estimated to
be above the limit in winter, increasing seasonally to 24% in the fall in these subregions. See summary
for River System 13.
The Choctawhatchee-Escambia, Coosa-Alabama, Tombigbee-Mobile Bay, Pascagoula and Pearl River
systems (USGS Subregions 0314-0318) comprise the Water Quality Model's River System 14. A large
seasonal change in meeting the phosphorus standard is found, with 2% and 4% of river miles exceeding
the standard in winter and spring, respectively, but 42% and 44% in the summer and fall, respectively.
The TKN standard is estimated to be met by all miles of these rivers in the winter, but 13% of river miles
in Subregions 03144)318 do not meet the TKN standard by the fall season. See summary for River
System 14. Note that diversion of some water from the Tennessee River system to the Tombigbee after
1982 is not accounted for in the Model.
The Model's "River System 18" includes most of Appendix E, Table 1's data: The entire
Mississippi River system. All of USGS Regions 05,06,07,08,10, and 11 (the Ohio, Tennessee, Upper
18
-------
Mississippi, Lower Mississippi, Missouri and Arkansas-White-Red Regions) are part of the Mississippi
system. For the whole Mississippi system stretching from western New York State and Pennsylvania to
western Montana to Louisiana, the 0.2 mg/L total phosphorus standard is not met in 32% of all river miles
in winter, 19% in spring, 24% in summer and 27% in fall. The 1.5 mg/L TKN standard is by our
estimation not met for 23% of all river miles in winter, 13% in spring, 16% in summer and 18% in the
fall season. See summary for River System 18.
A further perusal of the 1990 estimated concentrations for the nodes in the Mississippi system
("River System 18" in Appendix E) indicates tendencies similar to the 1989 data from STORET. The
Upper Mississippi generally shows slightly higher concentrations of phosphorus (TP) and TKN than the
Lower Mississippi. Some of the largest groups of nodes with very high estimated concentrations are in
the Missouri and Arkansas-White-Red systems, especially in a wide range of their middle reaches.
Compared to average concentrations for the entire Gulf drainage area, the Ohio system shows generally
lower concentrations, especially for TP; and the Tennessee system's estimated concentrations are generally
lower man average for both TP and TKN. These results are generally consistent with data from the EPA
STORET data base, discussed later in this paper.
Four of the eastern subregions of the USGS Texas Gulf Region comprise the Water Quality Model's
"River System 19". These are the Sabine, Neches, Trinity and Galveston Bay-San Jacinto Subregions
(1201-1204). In this combination of rivers it is estimated that 39% of the river miles do not meet the 0.2
mg/L standard for phosphorus in winter, but in summer 100% of the river miles are above that limit In
summer many of these miles may be nearly dry, increasing the concentrations of phosphorus from
previous runoff or from point sources. The percent of river miles failing to meet a 1.5 mg/L standard for
TKN is 17% in winter rising to 74% in summer, possibly for the same reason. See "Summary for River
System 19."
The Model's "River System 20" consists of the seven western subregions of USGS Region 12.
Included are all three Brazos River Subregions, both Colorado River of Texas Subregions including the
San Bernard Coastal area, the Central Texas Coastal and Nueces-Southwestem Texas Coastal Subregions
19
-------
(1205-1211). The Guadalupe and San Antonio Rivers and Corpus Christi Bay are also part of this system.
There is less seasonal variation in mid- to western Texas: 24% of river miles are estimated to exceed the
0.2 mg/L standard for phosphorus in winter, rising to 41% in the fall. 20% of river miles in this area are
estimated to fail a 1.5 mg/L standard for TKN in spring (21% in winter) with the highest percent of river
miles exceeding the standard at only 29% in the fall season. See "Summary for River System 20."
The Rio Grande system, USGS Region 13, is the Model's River System 21. While some high
individual concentrations are estimated, notably in the Pecos River and at a few Rio Grande nodes, only
13% of river miles are estimated to exceed the 0.2 mg/L phosphorus standard in the summer. In this
system the winter months are estimated to have the most phosphorus, with 46% of river miles failing to
jraeet the standard. (This does not appear to be consistent with 1989 STORET data, but means are not
necessarily consistent with miles meeting a particular standard, and 1989 data during a drought in that
region may not be consistent with a 1990 estimation based on "average" years.) The TKN proposed
standard of 1.5 mg/L is exceeded by only 4% of river miles in the summer, rising to 42% in winter. See
"Summary for River System 21."
Summary of Water Quality Model Estimates
The Water Quality Model's estimations of total phosphorus (TP) concentrations for 1990 show that
nearly every major river system or group of smaller rivers would have at least one season of the year in
which at least 40% of its river miles exceed a 0.2 mg/L standard. The exception is the huge Mississippi
system, whose estimates of percent of river miles exceeding this standard range from 19% in the spring
to 32% in the winter season. The rivers and lakes of the western Florida peninsula (River System 12)
show the highest percentages, with 100% of their river miles, exceeding the 0.2 mg/L standard in all
seasons.
With regard to Total Kjeldahl Nitrogen (TKN), all river systems have lower estimates of the percent
of river miles exceeding a 1.5 mg/L standard for TKN in most seasons. The Florida peninsula again is
20
-------
estimated to have a large percentage of river miles exceeding the standard, ranging from 24% of river
miles in summer to 100% in winter. The Gulf of Mexico rivers in Mississippi and Alabama (River
System 14), on the other hand, are estimated to have few miles above the 1.5 mg/L standard, ranging from
0% in winter to only a 13% maximum in fall. The other river systems (except the eastern Texas Gulf
rivers which have higher percentages), have much lower percentages of river miles exceeding the TKN
standard, less than 50% in their highest-percentage season. The Mississippi system's percent of river miles
not meeting the standard ranges from 13% in spring to 23% in winter.
STORET Data: Quantities of Nitrogen and Phosphorus at Monitoring Stations
The Environmental Protection Agency's STORET database and computerized management
information system provides thorough and timely water quality data for the U.S It includes data which
is comparable to that in the Water Quality Model. With nearly 200 million parametric observations from
more than 700,000 monitoring sites, sampled primarily over the last twenty years, it includes data from
the U.S. Geological Society, EPA, state public health and environmental agencies, U.S. Forest Service,
TVA, Army Corps of Engineers, and other interstate agencies. STORET includes data on many metals
and nutrients, including several different measures of phosphorus and nitrogen, some of which are
measured in only one or a few small surface water systems. We used only that data which is from an
actual sample, and is not "retired," i.e. a specific person at the reporting agency will vouch for its accuracy
at the time of the sample.
The most recent time period for which there is currently and consistently sufficient data to analyze
in STORET is the year 1989, which is analyzed by calendar quarters, closely equivalent to our seasons.
The terms "quarterly" and "seasonal" are used interchangeably in this report. Table 5 on pages 26-27,
Table 6 on pages 30-31, Table 7 on pages 36-37 and Tables A1-A10, B1-B10 and C1-C10 in Appendices
A, B and C represent summaries of the 1989 quarterly data for nitrogen and phosphorus by region and
subregion for USGS Water Resource Regions 05,06,07,08,10,11,12,13, and part of 03, whose waters
21
-------
eventually flow into the Gulf of Mexico. See Figure 6, which consists of a continental U.S. map of USGS
Water Resource Regions.
22
-------
I
I
1
tt
y
I
•L
Figure 6: Continental U.S. Map of USGS Water Resource Regions.
23
-------
1989 STORET Data for Gulf of Mexico Drainage Area
Concentration
One of the more surprising observations about the 1989 STORET data on nitrogen and phosphorus
concentrations is the lack of any consistent seasonal trend, either among the Water Resource Regions or
in the subregions of most regions. Nonpoint sources of nutrients such as agricultural cropland runoff and
even urban runoff from streets and large construction projects would be expected to be seasonal, with
more fertilizer applied in the spring ?as an example. It is possible that point sources of pollution from
industrial and municipal plants still have the most' influence on overall nitrogen and particularly
; ;, -; • "''.. - " •'' ' :/ ;
phosphorus pollution, at least in many smaller areas and even groups of subregions. Further analysis of;
*• " .. • y ,• • "••'• ' ' ,•• -• ( •'••;' y -^ \
seasonal trends"tor lac^ thereof) is recommended." , •' ;/, ^
"> ,- - --rt - - * ''.' ' k
A second finding is that samples in surface waters do not show increasing concentrations as the river •
system flows downstream in several regions, and in most seasons. In some regions such as the Missouri ,
--•'-• ' " ~ ....'.,, , ^ _ *•„ >. ' Sl
River system (Region 10) and the Lower Mississippi River (Region 08) there is a slight increase in
'f • • %. ?T "••
phosphorus or nitrogen when traveling downstream along some reaches, but it is not consistent throughout,
<> " " "v ••• ' >- ; , , ''
the system. In no region does 'the most downstream subregion report the highest concentrations of i
\
nitrogen and phosphorus in the region in even two seasons.
^' . f: t
i • ' •
The'Lower Mississippi Region (08) reports lower nutrient concentrations than most of its constituent
* * U % ; '
parts. It shows generally consistently lower nutrient pollution than the Upper Mississippi (Region 07),
i -•* . .,..'.
the Missouri (Region 10) and the •Arkansas-White-Red Rivers (Region 11). The degradation of both
*vi ,. • ,. ' '• .t,,t, .'••'".
nitrogen and phosphorus as they are transported downstream could provide an explanation of this. At least
f "*
in some seasons, sediment-attached phosphorus, and nitrogen to a lesser degree, may have settled to the
riverbed as it flows downsjtream. And, the large water volume with input from cleaner tributaries, arid
" '. l!
wide surface of the lower Mississippi River itself with higher plant growth, may be factors in decreasing
* - - , v .i , \ .*
.-, •«, ' • ••- - ,.' ,. ' :: '•' "-.i
nutrient concentrations. * - J " '
Ah interesting regional comparison is found among the .Ohio River system (Region 05), the
24
-------
Tennessee system (Region 06), and the Lower Mississippi (Region 08). The Lower Mississippi has
slightly higher concentrations of Total KjeldaM Nitrogen (TKN) than the Ohio Region in all four seasons;
compared to the Tennessee Region which Hows into the Ohio just before they reach the Mississippi, the
Lower Mississippi shows approximately double the concentrations of TKN in all seasons, with even more
difference in the fall. For phosphorus, however, the situation is generally reversed: the Lower Mississippi
has lower concentrations than the Ohio in winter, summer and fall and is lower in phosphorus than the
Tennessee in winter and fall. The higher concentration downstream only in the spring (or spring and
summer, for the Tennessee tributary system) appears reasonable: phosphorus attached to sediment may
be deposited soon after entering upstream waters in the summer, fall and winter in the Ohio, then picked
up and taken downstream to the Lower Mississippi during spring storms. For the Tennessee, the timing
of storms and transport time may extend the time for nutrients to reach the Lower Mississippi.
The Southeast and Texas Gulf Regions (03 and 12, respectively) are more difficult to analyze in
terms of upstream-downstream trends. Neither of these regions, nor the Rio Grande system (Region 13)
reports a consistent seasonal or downstream trend, though many subregions in Regions 03 and 12 consist
of one smaller river system. The lack of trends may be the most important finding of this part of the
study.
Brief Interpretation of Table 5 - The Gulf of Mexico Drainage Area: Regional Comparison of
Ambient and Some Nonambient Concentrations*
The geographic area covered by the Gulf of Mexico drainage area extends approximately from the
Appalachians to the Rockies. South of the Appalachians, many rivers from Florida and Georgia also flow
west or southwest into the Gulf. In the northern states, the Great Lakes system (USGS Region 04) and
the Souris-Red-Rainy area of northern Minnesota and North Dakota (Region 05) eventually flow north
to Canada and are not part of the Gulf systems. The data is presented quarterly for the year 1989, the
most recent time period with complete data. Means are weighted by the number of observations in each
Nonambient samples are drawn directly downstream from a pollution source while ambient
samples should not be influenced by a particular source.
25
-------
Table 5
USGS Region Summaries: Mean Nitrogen and Phosphorus Concentrations
by Region
1989: All data in mg/L
Subregion
03
Southeast (Gulf
of Mexico River
Systems Only)
05
Ohio River
System
06
Tennessee
07
Upper Miss
08
Lower Miss
10
Missouri River
System
11
Arkansas -
Red -White
River System
12
Texas Gulf
Nutrient
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
Winter
.336 (756)
1.111 (625)
.808 (214)
1.062 (98)
.290 (847)
.674 (582)
#
.451 (130)
.450 (72)
1.690 (44)
.414(1168)
1.771 (551)
1.033 (53)
.196 (1016)
.856 (681)
*
1.665 (955)
1.929 (434)
.889 (9)
.728 (911)
3.256 (553)
5.335 (134)
8.244 (242)
.730 (572)
1.003 (403)
*
Spring
.306 (713)
1.301 (699)
.888 (197)
1.311 (46)
.135 (1395)
.618 (1259)
*
.130 (385)
.471 (146)
.325 (302)
.347 (2575)
1.429 (1347)
1.576 (194)
.187 (1014)
.901 (699)
*
.358 (1359)
1.398 (642)
*
.631 (1064)
2.391 (589)
2.817 (197)
6.261 (223)
.279 .(453)
.747 (358)
*
Summer
.222 (607)
1.138 (641)
.982 (177)
*
.255 (2074)
.682 (1847)
*
.081 (572)
.421 (136)
.239 (490)
.484 (3089)
1.623 (1421)
1.413 (235)
.188 (988)
.850 (637)
*
1.697 (1600)
5.328 (881)
*
.535 (1205)
1.889 (654)
3.118 (120)
3.345 (203)
.436 (391)
.911 (438)
*
Fall1
.176 (420)
.745 (366)
.780(112)
*
.331 (896)
.706 (645)
*
.250 (54)
.282 (94)
1,268 (5)
.444 (1022)
1.105 (588)
.638 (46)
.182 (626)
.763 (531)
*
.407 (587)
1.526 (201)
*
1.305 (520)
3.505 (343)
4.235 (120)
8.815 (144)
.755 (148)
.809 (148)
*
26
-------
Table 5 (continued)
Subregion
Nutrient
Winter
Soring
Summer
Fall1
13
Rio Grande
System
Entire U.S.
Gulf of Mexico
Drainage
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
.158 (88)
.678 (61)
.240 (21)
1.656 (17)
.609 (6443)
1.454 (3962)
2.169 (475)
.288 (188)
1.231 (183)
.630 (150)
1.695 (140)
.315 (9146)
1.201 (5922)
1.181 (1040)
.557 (101)
1.185 (99)
.418 (57)
2.022 (57)
.562 (10627)
1.679 (6754)
.946 (1079)
.337 (29)
.672 (29)
.328 (6)
.513 (6)
.463 (4302)
1.174 (2945)
2.191 (289)
* No samples taken
() = Number of samples
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
27
-------
quarter, for each region or subregioa As expected, nutrient concentrations are highly variable among the
regions; however, no consistent seasonal trends appear.
Total Kjeldahl Nitrogen is measured by the Kjeldahl method, one most commonly used for
converting combined forms of nitrogen to ammonia. The majority of nitrogen compounds are amenable
to the Kjeldahl method, except such ring structures as pyrazolones, diazines and triazoles (H.D. Drew,
"Determination of Total Nitrogen"). Organic nitrogen is generally those compounds which are degraded
from nitrogen-containing living organisms including urea, uric acid, amino acids and others; it may include
some ammonia, but excludes such compounds as nitrites and nitrates.
The mean for total phosphorus varied from a low of .081 milligrams per liter (mg/L) in the summer,
in the Tennessee River Region, to a high of 1.697 mg/L in summer in the Missouri River system. Total
Kjeldahl Nitrogen (TKN) regional means ranged from .282 mg/L in the fall season in the Tennessee
system, to 5.328 in the summer in the Missouri Region. Organic nitrogen means were found as low as
.24 mg/L in both the Tennessee Region in the summer and the Rio Grande Region in the winter. The
high mean for organic nitrogen was 5.335 mg/L in winter in the Arkansas-White-Red tributary system of
the Mississippi River*.
It should be noted that not all regions measure organic nitrogen, and in many regions both TKN and
organic nitrogen are not measured in all subregions. Attention should also be called to the fact that some
regional and subregional means may be influenced by one or a few extremely high readings from
individual samples, as will be noted in the descriptions of each region's data.
Brief Interpretation of Table 6 - The Gulf of Mexico Drainage Area: Regional Comparison of
Ambient Concentrations Only
When data samples are strictly limited to ambient data only, mean seasonal concentrations change
very little in many USGS regions. A few regions, however, show large decreases in nutrient
concentrations or some individual quarterly means which are much lower than the corresponding means
Measurements of total nitrogen are made in too few regions to provide a basis for comparison, though
the means are shown in the tables for those regions in which some subregions reported it.
28
-------
in Table 5. Region 03 (partial Southeast Region) means are generally very slightly lower for total
phosphorus and Total Kjeldahl Nitrogen, while organic nitrogen means, where data are available, are
identical. In regions 05,07,08 and 10 the seasonal means generally show small decreases when compared
with Table 5, with some nitrogen means showing no change. Ambient data excludes any data collected
at waterway points such as those near industrial or municipal outlet pipes.
In the Tennessee River system (Region 06), the winter means for phosphorus and organic nitrogen
and the fall mean for organic nitrogen, are much lower than those which included some non-ambient
sampling. All seasonal TKN means in the Tennessee area are identical to those in Table 5, and all other
means are slightly lower than those which included some nonambient data. All Region 11 (Arkansas-Red-
White) seasonal means are much lower when all nonambient data are excluded; this region's waters still
have somewhat higher concentrations of nutrients than those of several other regions, but these differences
are much smaller. In Region 12, the Texas Gulf Region, all quarterly means are identical to those in the
previous table; in other words, no nonambient samples were included before. The Rio Grande system's
data show large decreases from those in Table 5 in all spring and summer means, with fall means showing
no change and winter means slightly lower for phosphorus and TKN and much lower for organic nitrogen.
Across the Gulf of Mexico drainage area, ambient mean concentrations for total phosphorus ranged
from .070 mg/L in the Tennessee River system in the summer, to 1.641 mg/L in the Missouri River
system, again in the summer. Regional TKN means varied from a low of .282 mg/L in the fall in the
Tennessee Region, to 4.853 mg/L in the Missouri Region in summer. The lowest organic nitrogen mean
was .155 in winter in the Rio Grande Region; the highest was 1.576 mg/L in the Upper Mississippi system
in the spring. Again, we must point out that organic nitrogen measurements were not reported in some
entire regions.
It is interesting to compare annual average ambient concentrations of the two most widely reported
nutrients, computed as an arithmetic average of the four seasonal means. (These averages are not shown
in the table.) The Tennessee Region still appears to have the lowest concentrations, with annual average
phosphorus of .128 mg/L and TKN of .406 mg/L. The Lower Mississippi Region is not far behind in
29
-------
Table 6
USGS Region Summaries: Mean Ambient Nitrogen and Phosphorus
Concentrations by Region
1989: All data in mg/L
Subregion
03
Southeast (Gulf
of Mexico River
Systems Only)
05
Ohio River
System
06
Tennessee
07
Upper Miss
08
Lower Miss
10
Missouri River
System
11
Arkansas -
Red - White
River System
12
Texas Gulf
Nutrient
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
Winter
.337 (766)
1.106 (630)
.808 (214)
1.062 (98)
.268 (845)
.599 (585)
*
.187(113)
.450 (72)
.385 (33)
.396(1160)
1.758 (549)
1.033 (53)
.196 (1016)
.856 (681)
*
1.630 (953)
1.929 (434)
.543 (7)
.301 (794)
1.129 (435)
.486 (20)
2.016 (124)
.730 (572)
1.003 (403)
*
Spring
.305 (713)
1.298 (704)
.888 (197)
1.311 (46)
.130 (1404)
.549 (1278)
*
.084 (381)
.471 (146)
.260 (298)
.286 (2566)
1.419 (1344)
1.576 (194)
.187 (1014)
.901 (699)
*
.335 (1346)
1.341 (635)
*
.274 (964)
1.007 (499)
.464(112)
1.031 (132)
.279 (453)
.747(358)
*
Summer
.219 (615)
1.131 (641)
.982 (177)
*
.206 (2068)
.649 (1843)
*
.070 (569)
.421 (136)
.228 (488)
.350 (3074)
1.587 (1408)
1.418 (234)
.186 (1021)
.828 (669)
*
1.641 (1569)
4.853 (856)
*
.429 (1153)
1.296 (619)
1.342 (89)
1.434 (176)
.436 (391)
.911 (438)
*
Fall1
.180 (427)
.739 (371)
.780(112)
*
.309 (916)
.697 (670)
*
.172 (85)
.282 (94)
.380 (12)
.394 (1012)
1.104 (591)
.638 (46)
.179 (714)
.711 (606)
*
.418 (562)
1.526 (201)
*
.526 (423)
1.433 (248)
.496 (32)
1.597 (49)
.755 (148)
.809 (148)
*
30
-------
Table 6 (continued)
Subregion
Nutrient
Winter
Soring
Summer
* No samples taken
() = Number of samples
Fall1
13 .
Rio Grande
System
TP2
TKN
OrgN
TOTN
.154 (86)
.580 (59)
.155 (19)
.637 (15)
.126 (180)
.553 (175)
.294 (142)
.687 (132)
.259 (92)
.783 (90)
.305 (48)
.644 (48)
.337 (29)
.672 (29)
.328 (6)
.513 (6)
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
31
-------
phosphorus with an annual average of .187 rag/L, and most regions' annual average phosphoms is below
.5 mg/L. The highest annual average phosphorus mean is clearly in the Missouri Region, at 1.006 mg/L;
the second highest is far lower, at .550 in the Texas Gulf Region. For Total Kjeldahl Nitrogen the next
lowest annual average concentrations are .624 mg/L in the Ohio Region and .647 mg/L in the Rio Grande
Region. The highest annual average TKN concentrations are 2.412 mg/L, again in the Missouri system,
and 1.556 mg/L in the Upper Mississippi system. As expected, annual averages have somewhat less
variation than seasonal means though concentrations measured in the Missouri system are still at least six
times as high as those in the Tennessee Region.
We have seen the areas of the Gulf of Mexico drainage basin which have higher or lower
concentrations of nutrients in their waterways. This information is important for determining regions or
smaller subregions (see Appendices A and B), perhaps far upstream of the Gulf itself, which merit closer
scrutiny. The specific causes of high concentrations will eventually need to be located; these are the
places most likely to be able to be "cleaned up" to reduce nutrient pollution in waterways flowing into
the Gulf. Those areas with very low concentrations may be close to "background levels" or naturally
occurring levels of nitrogen and phosphorus, where further reductions in nutrients will be difficult to
achieve.
While concentrations of a pollutant indicate the water quality in a specific region relative to other
regions, they do not account for different quantities of water and pollutants which are transported to
downstream regions and ultimately to the Gulf of Mexico. To discover how much nitrogen or phosphorus
actually flows into the Gulf of Mexico from the many waterways feeding into it, we now turn to the data
from Table 7 on nutrient loadings, which account for not only the nutrient concentrations but the amount
of water flowing downstream.
Loadings
These loadings were calculated from STORET data showing the average record concentration and
average record flow rates for each hydroUzed unit. However, the flow and concentration parameters often
came from different samples. There were relatively few STORET data points containing both flow and
32
-------
concentration values. While this would certainly raise questions about the loading estimates, the purpose
of this analysis is not to furnish point estimates, but rather to compare regions relative to each other.
Table 7 - The Gulf of Mexico Drainage ArM- n^ona! Comparison of Ambient Nutrient Loadings
When we analyze data on loadings of specific nutrients we see a somewhat different picture from
that which appeared in the analysis of concentrations. There is soil considerable variation between regions
and in some cases, among the subregions of a given region (see Appendix Q. However, those regions
and subregions which had the higher concentrations in the previous discussions do not necessarily
contribute the largest loadings or actual amounts of nutrients to the waterways flowing into the Gulf of
Mexico.
Among all of the USGS regions whose waters eventually flow into the Gulf, the highest mean
loadings of total phosphorus in 1989 are found in the Ohio River system (Region 05): mean phosphorus
loadings of 84856 pounds per day (Ibs/day) in the winter season. The next highest seasonal means are
50621 Ibs/day in spring, again in the Ohio Region, and 41987 Ibs/day in the fell in the Lower Mississippi
Region. The lowest quarterly mean phosphorus loadings come from the Rio Grande system (Region 13):
176 Ibs/day in the fall season. The next lowest phosphorus means are 229 Ibs/day in spring, again in the
Rio Grande, and 237 Ibs/day in the spring in the Tennessee River system, Region 06.
We must note that the Missouri River system (Region 10) and the Arkansas-Red-White system
(Region 11), which generally had some of the highest concentrations of phosphorus, have relatively low
loadings of the same nutrient once the flow of water is taken into account. An annual arithmetic average
of the seasonal phosphorus means in the Missouri system is only 1436 Ibs/day, and that for the Arkansas-
Red-White system is 4007 Ibs/day. Their contribution to loadings in the Lower Mississippi and the Gulf
is quite small; see the later discussion of the Mississippi system. The Tennessee system (Region 06) still
does average very small amounts of loadings in most seasons (note the very small number of samples in
the fall season throughout the entire region). And even the Upper Mississippi and its tributaries (Region
07) average relatively small actual amounts of phosphorus heading to the lower Mississippi River and the
33
-------
Gulf of Mexico. The Southeast (Region 03) waterways flowing into the Gulf, and the Texas Gulf river
systems (Region 12), also have relatively small mean daily loadings of phosphorus.
Regarding Total Kjeldahl Nitrogen (TKN), the mean seasonal loadings for entire regions in 1989
ranged from a low of 627 Ibs/day in the fall in the Rio Grande (Region 13) to a high of 904,023 Ibs/day
in the winter in the Lower Mississippi (Region 08). Other very low seasonal means are 756 Ibs/day in
the summer in the Tennessee River system (Region 06) and 902 Ibs/day in the fall in the Texas Gulf
Region. Additional very high mean loadings of TKN are 329,792 Ibs/day in the spring, again in theLower
Mississippi region, and 153,703 Ibs/day and 152,129 Ibs/day in winter and spring, respectively, both in
the Ohio River system (Region 05).
Organic nitrogen loadings are measured in relatively few regions and seasons, particularly when one
considers the low number of samples, (shown in parentheses in Table 7), included in many of the means.
The highest seasonal "mean" of 67,798 Ibs/day is based on only one measurement, in the fall in the
Tennessee River system (Region 06). The lowest seasonal mean of .5 Ibs/day is for only four
measurements, in the fall in the Southeast (Region 03) rivers flowing to the Gulf of Mexico.
The loading measurements detailed above in Table 7 are means for entire USGS regions, useful for
determining the broad areas producing higher amounts of nutrient pollution. Appendix C details the
variations among subregions within these regions, from which one can point to more specific areas of
concern. To see how much phosphorus and nitrogen are actually entering the Gulf of Mexico, however,
we must turn to the "Lowest Subregions" analysis in Table 8 and Table 9. These are the subregions which
actually border on the Gulf, and whose nutrients are presumably being input into the Gulf during the same
season of record or very soon thereafter. The "Lowest Subregions" were chosen because, as much as one
would be interested in further study of the most downstream Accounting Unit or Catalog Unit, there
simply is not a consistent amount of data available for these smaller units across four seasons. Subregions
are the smallest units for which data for all seasons in nearly every subregion exists. Total phosphorus
and Total Kjeldahl Nitrogen loadings data are analyzed. The apparent difference between Table 7 and
Table 8 result from Table 7 utilizing all samples within a hydrologic region whereas Table 8 reports data
34
-------
only from the lowest sampling point. There are also differences in the number of samples. Some points
in Table 8 have very few samples.
35
-------
Table?
USGS Region Summaries: Mean Ambient Phosphorus and Nitrogen
Loadings by Region
1989: All data in Ibs/day
Region
03
Southeast (Gulf
of Mexico River
Systems Only)
05
Ohio River
System
06
Tennessee
07
Upper
Mississippi
08
Lower
Mississippi
10
Missouri River
System
11
Arkansas -
Red - White
River System
12
Texas Gulf
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
4315 (180)
13197 (90)
*
84856 (281)
153703 (249)
*
2816 (8)
9502 (4)
14025 (2)
5670 (276)
40311 (199)
250 (1)
5158 (192)
904023 (26)
*
2148 (426)
5606 (311)
111 (3)
5775 (196)
26267 (117)
*
1845 (199)
3598 (171)
*
Soring
2295 (170)
11345 (100)
8 (14)
50621 (311)
152129 (270)
*
237 (37)
1169(33)
107 (3)
5017 (440)
61588 (218)
6161 (10)
19097 (246)
329792 (37)
*
1006 (541)
5288 (401)
*
5488 (187)
32327 (124)
*
2409 (183)
12000 (160)
*
Summer
1364 (169)
3983 (92)
6 (22)
9806 (333)
37560 (312)
*
777 (22)
756 (20)
20581 (5)
7451 (293)
44435 (195)
40 (9)
15455 (185)
144973 (25)
*
2209 (339)
10671 (216)
*
3687 (118)
14924 (128)
*
1689 (168)
6736 (171)
*
Fall1
1538(111)
5829 (28)
.5 (4)
10742 (128)
48096(118)
*
14070 (4)
5717 (1)
67798 (1)
1450 (133)
8823 (109)
86 (3)
41987 (16)
133620 (15)
*
379 (146)
1760 (103)
*
1078 (30)
3963 (54)
*
696 (90)
902 (74)
*
36
-------
Table 7 (continued)
Reeion
13
Rio Grande
System
Nutrient
TP2
TKN
OrgN
Winter
345 (37)
1243 (31)
*
Spring
229 (30)
1231 (30)
*
Summer
829 (38)
2554 (38)
*
Fall1
176 (26)
627 (24)
*
* No samples taken
() = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
37
-------
Tables 8-9; Lowest Subregions* Mean Loadings of Phosphorus and Nitrogen
There is a huge variation in nutrient loadings for those subregions adjacent to the Gulf of Mexico,
as we found across regions and across subregions even within the same USGS region. As one would
expect, by far the highest loadings of both phosphorus and nitrogen are found in the waters of the Lower
Mississippi and the Atchafalaya. Each of these subregions has higher nutrient loadings than the sum of
all others.
The highest mean seasonal phosphorus loadings are found in the Lower Mississippi River in winter
and spring at 308,804 Ibs/day and 301,958 Ibs/day respectively. The Atchafalaya's loadings are not far
behind in some seasons. Subregions which apparently send very little phosphorus into the Gulf from their
river systems, at least in most seasons, include the river systems of South Florida (Partial Subregion 0309)
which flow into the Gulf, with a maximum of 102 Ibs/day in summer (though it should be noted that no
data was collected in the fall); Subregion 1211 in the Nueces area of Southwestern Texas, with a
maximum seasonal mean of 83 Ibs/day in the fall; and the Lower Rio Grande with a maximum quarterly
mean of 271 Ibs/day in winter. Many other river systems consistently send far less than 1,000 Ibs/day of
phosphorus to the Gulf. The highest seasonal phosphorus loadings into the Gulf from outside the
Mississippi system are found in the wintertime in the Tombigbee-Mobile Bay area at 30,551 Ibs/day.
For Total Kjeldahl Nitrogen the highest seasonal means are also in the Lower Mississippi River in
the winter and the spring, with loadings of 1,715,000 Ibs/day and 1,632,000 Ibs/day respectively. Again
the Atchafalaya River, with some flow from the Mississippi diverted to it above these two subregions, also
has TKN loadings far exceeding the sum of the loadings from all Gulf-adjacent subregions east and west
of Region 08. Subregions which sent very low amounts of TKN into the Gulf from their river systems
in 1989 include the Peace River-Tampa Bay area (subregion 0310) with maximum mean loadings of 557
Ibs/day in the winter, subregion 1210 on the Central Texas Coast with a maximum seasonal mean of
1,205 Ibs/day, also in winter; and once again the Nueces River area of Southwestern Texas with maximum
seasonal mean loadings of 1,421 Ibs/day in the fall. The highest mean seasonal TKN loadings outside of
the Mississippi-Atchafalaya region were 82,949 Ibs/day in the Sabine River outlet in Eastern Texas
38
-------
Table 8
"Lowest Subregions": Mean Ambient Phosphorus and Nitrogen Loadings
for USGS Subregions Adjacent to the
Gulf' of Mexico
1989: All data in Ibs/day
East-to-West
USGS
Subregion
0309 (Partial)
South Florida
0310
Peace -
Tampa Bay
0311
Suwanee
0312
Ochlockonee
0313
Apalachicola
0314
Choctawhatchee
- Escambia
03 153
Coosa-Alabama
0316
Tombigbee -
Mobile Bay
0317
Pascagoula
Nutrient
TP2
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
Winter
51(3)
1854 (3)
297 (38)
557 (39)
343 (23)
1796 (6)
350 (11)
1417 (3)
2283 (35)
13038 (8)
973 (4)
11261 (4)
3792 (47)3
23896 (14)
30551 (16)
71003 (9)
1209 (2)
6881 (3)
Spring
57 (4)
1355 (4)
136(26)
143 (24)
444 (22)
3401 (5)
1040(11)
6220 (2)
3944 (35)
28226 .(9)
1 (6)
50 (13)
3192 (46)3
19459 (27)
5360(14)
25965 (10)
1047(4)
11387 (4)
Summer
,102 (4)
747 (4)
353 (17)
399 (16)
477 (22)
4979 (4)
881 (11)
379 (2)
2659 (37)
8416 (7)
373 (4)
1433 (10)
1620 (56)3
6621 (31)
770 (16)
3377 (15)
822 (1)
2941 (2)
Fall1
*
*
5 (2)
122(2)
387(19)
5018(3)
396(9)
670 (2)
3536 (36)
19830 . (6)
690 (4)
8344(3)
846 (35)3
265 (9)
11(6)
64(3)
*
*
39
-------
Table 8 (continued)
Subregion
0318
Pearl
Total:
Region 03
Gulf River
Systems
0809: Lower
Mississippi R.
0808: Louisiana
Coastal incl.
Atchafalaya
Total:
Region 08
Flow to Gulf
1201
Sabine
1202
Neches
1204
Galveston Bay -
San Jacinto
1207
Lower Brazos
1209: Lower
Colorado - San
Bernard Coastal
1210
Central Texas
Coastal
NNutrie
nt
TP2
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
Winter
250 (1)
1877 (1)
36307
109684
308804 (2)
1715000 (2)
200640 (10)
1031000 (5)
509444
2746000
1418 (5)
13560 (5)
3724 (10)
16282 (8)
1309 (51)
3710 (34)
148(8)
214 (7)
861 (31)
2921 (32)
1793 (28)
1205 (28)
Spring
548 (2)
5483 (2)
12577
82230
301958 (3)
1632000 (3)
130900 (12)
570777 (6)
432858
2202777
2786 (4)
22156 (4)
1526 (7)
59510 (7)
2465 (11)
6595 (9)
442 (9)
3892 (10)
517 (43)
3339 (42)
1221 (39)
1014 (30)
Summer
231 (1)
1384 (1)
6668
24055
114467 (2)
572763 (2)
76923 (10)
204154 C5)
191390
776917
4705 (4)
82949 (4)
2918 (5)
50844 (5)
368 (50)
520 (50)
845 (9)
. 3853 (8)
293 (12)
1006(19)
751 (33)
260 (34)
Fall1
*
*
[5025]4
[34048]
191674 (3)
774006 (2)
95470 (1)
445525 (1)
287144
1219531
282 (3)
1586 (3)
3908 (4)
5426 (3)
496 (4)
664(4)
666(4)
1157(3)
536 (19)
1318 (19)
870 (24)
258 (19)
40
-------
Table 8 (continued)
Subregion
1211: Nueces-
Southwestern
Texas Coastal
Nutrient
TP2
TKN
Winter
11(3)
55(7)
Soring
52(11)
1170 (5)
Summer
56(3)
301 (5)
Fall1
83(4)
1421 (2)
Total:
Region 12
Flow to Gulf
1309
Lower Rio
Grande
TP
TKN
TP
TKN
9264
37947
271 (2)
5630 (2)
9009
97676
47(3)
592 (3)
9936
139733
53(1)
740 (1)
6841
11830
171 (2)
1248 (2)
* No samples taken
() = Number of samples
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
Subregion 0315 does not flow directly into the Gulf of Mexico; it flows into the Tdmbigbee
system (subregion 16) a short distance north of Mobile Bay. This data is not included in the
total for Region 03. It is included in Table 8 only because it obviously contributes the major
proportion of the nutrient pollution to subregion 0316 in most seasons.
The total for the fall is incomplete, as some subregions had no measurements in the fall. It
is included and should be interpreted as a minimum amount.
41
-------
Table 9
Regional Summary of Nutrient Loadings for "Lowest Subregions":
Subregjons Adjacent to the Gulf of Mexico
1989: All data in Ibs/day; % of total loadings
Region/Primary
States or Rivers
03/FL/AL/
MS Coast
08/LA:
Mississippi R7
Atchafalaya
12/TX
Coast
13/Rio
Grande
Total: All USGS
subregions
adjacent to Gulf
of Mexico
1 Winter runoff:
Spring
Summer
Fall
Nutrient
TP2
TKN
TP
TKN
TP
TKN
TP
TKN
TP
TKN
January
April 1
July 1 -
October
Winter
36307: 7%
109684: 4%
509444: 92%
2746000: 95%
9264: 2%
37947: 1%
271: 0%
5630: 0%
555286: 100%*
2899261: 100%
1 -March 31
- June 30
September 30
1 -December 31
Spring
12577: 3%
82230: 3%
432858: 95%
2202777: 92%
9009:2%
97676: 4%
47:0%
592:0%
454491: 100%
2383275: 100%
2
Summer
6668:3%
24055: 3%
191390: 92%
776917: 83%
9936: 5%
139733: 15%
53:0%
740:0%
208047: 100%
941445: 100%
TP = Total
TKN = Total
Fall1
[5025: 2%]
[34048: 3%]
287144: [96%]
1219531: [96%]
6841: [2%]
11830: [1%]
171: 0%
1248: 0%
[299181: 100%]3
[1266657: 100%]
Phosphorus
Kjeldahl Nitrogen
3 The total for Region 03 in the fall season is incomplete, as no data was collected for a few subregions.
Columns may not add to exactly 100% due to rounding.
42
-------
(subrcgion 1201) in the summer and 71,003 Ibs/day in the winter in the Tombigbee-Mobile Bay area. The
Neches River area (subregion 1202) also had some high TKN loadings.
Table 9 presents the summary of loadings from Gulf-adjacent subregions by region, and their estimated
percentage contributions to the total loadings of phosphorus and nitrogen into the Gulf of Mexico. Even
a
with this degree of summation it is apparent that while there are wide seasonal variations, these seasonal
variations are not consistent across regions.
As was previously indicated, the Mississippi River-Atchafalaya system accounts for the vast majority
of nutrients entering the Gulf. More than ninety percent of total phosphorus loadings are attributable to
it in each season of 1989. (As noted in footnote 3 of Table 9, the fall season totals for Region 03 should
be interpreted as minimum amounts; the percentages for other regions in the fall season should therefore
be interpreted as maxima. However, it is extremely unlikely that the addition of data from these few
subregions of Region 03, all of which had very small phosphorus loadings in the other three seasons,
would lower the Mississippi-Atchafalaya contribution to loadings into the Gulf to 90% or less.)
The seasonal loadings from the Florida/Alabama/state of Mississippi coast contribute seven percent
or less of the phosphorus entering the Gulf of Mexico, the maximum being in the winter. The annual
average is less than 4%. The Texas coast subregions contribute no more than five percent of phosphorus
loadings to the Gulf in any one season; its annual average is less than 3%. The Rio Grande's seasonal
mean phosphorus loadings never approached one-half of one percent in 1989. Unless authorities along
the Rio Grande were to decide to lower water levels in its reservoirs all at the same time, these reservoirs
appearing to trap somewhat higher nutrient levels from upper reaches, the Rio Grande does not at this time
present a nutrient threat to the Gulf.
Total Kjeldahl'Nitrogen loadings into the Gulf of Mexico also enter largely from the Mississippi and
Atchafalaya rivers. Approximately five-sixths of the TKN entered from these subregions in the summer
of 1989, and more than ninety percent in all other seasons. (The comment regarding Region OS's missing
data in a few subregions for the fall season applies to TKN as well as to phosphorus.) Outside of Region
43
-------
08, only the summer TKN loadings from part of the Texas coast would appear to warrant further study,
as will be discussed below.
TKN loadings from the Gulf coastline of the states of Florida, Alabama, and Mississippi contributed
a maximum of four percent of the total Gulf loadings in any season of 1989, the maximum being during
ii
the winter season. The annual average was only three percent. Seasonal TKN loadings from the Texas
coast varied greatly, from 11,830 Ibs/day or one percent of the total loadings in the fall to 139,733 Ibs/day
in the summer, or fifteen percent of total Gulf loadings during this season. Nearly all of the Texas coast
loadings of TKN in summer came from only the two easternmost subregions in Texas: the Sabine and
Neches valleys. Each of these two means, it should be noted, is based on few measurements. The annual
average TKN loadings from the Texas coast still contribute only five percent of all Gulf loadings, as they
are quite a small percentage in all other seasons. The Rio Grande's TKN loadings into the Gulf are again
insignificant relative to those from other areas.
Total loadings of phosphorus into the Gulf of Mexico from all subregions adjacent to the coast
ranged from a seasonal low of 208,047 Ibs/day in the summer to 555,286 Ibs/day in the winter, for an
average of more than 379,000 Ibs/day in 1989. Total seasonal mean TKN loadings into the Gulf varied
from 941,445 Ibs/day in the summer to a high of 2,899,261 Ibs/day in the winter in 1989; the annual
average was more than 1,872,600 Ibs/day. These annual averages can be translated to 190 tons per day
of phosphorus and 1,450 tons per day of Kjeldahl Nitrogen entering the Gulf of Mexico from the surface
waters of the United States.
We have now looked at the total loadings into the Gulf of Mexico, and their immediate sources
along its coast. Since such a high proportion of nutrients comes from the Mississippi system, its
components obviously deserve some further analysis. Unfortunately, complete data for all of the most
downstream subregions of each tributary river system comprising this vast system is available for only the
spring and summer seasons.
44
-------
Table 10; Relative Contributions of Mississippi River System Tributary Systems or Regions
Table 10 summarizes the relative contributions to the Lower Mississippi- Atchafalaya Rivers' loadings
of total phosphorus and TKN, for the various systems comprising the entire Mississippi system. It should
be noted first that the proportional contributions do not add to 100%, for a variety Of reasons. The Upper
Mississippi loadings include those from the Missouri system, and the Ohio system's loadings include the
Tennessee's contribution, small though, it may be. Some of the phosphorus or TKN dissipates as it flows
downstream, at potentially widely varying rate due to temperatures, turbulence and flow rates. There are
time lags from sediment attached nutrients, and plant uptake of nutrients varies seasonally. And additional
nutrients enter the surface waters in the Lower Mississippi region itself; this factor was especially apparent
for the spring season in 1989. Many operations involving various chemicals are located along or near the
lower Mississippi River.
Nevertheless, seasonal differences in the relative contributions of Mississippi "tributary" systems are
of interest The greatest flows of water into the Lower Mississippi come from the Upper Mississippi and
the Ohio regions, each of which has large amounts of agricultural activity as well as many large
population centers. In the spring the Upper Mississippi contributes only approximately 10% of the
phosphorus and 21% of the TKN found near the mouths of the Mississippi-Atchafalaya outlets, but in the
summer season this rises to approximately 88% and 76% respectively. Conversely, the Ohio system has
larger contributions in the spring: approximately 62% of the phosphorus and 28% of the TKN falling to
about 17% for phosphorus and 14% for TKN in the summer. The Tennessee subsystem of the Ohio, and
the Arkansas-Red-White river systems, contribute very low proportions of nutrients to the Lower
Mississippi in any season. The Missouri system contributes very little of either nutrient in the spring, but
about a quarter of the phosphorus and of the TKN in the summer.
45
-------
Table 10
Relative Contributions of Mississippi River System Components to Nutrient
Loadings Entering the Gulf of Mexico from the Lower Mississippi River and
the Atchafalaya River
All Proportions Calculated from 1989 Data
Spring
River
System
Missouri
Tennessee
Ohio
Upper Mississippi4
Arkansas-Red-
White
Most-
Downstream
Subregion #
1030
06043
0514
0714
1114
IE
.03
.003
.62
.10
.02
TKN
.04
.001
.28
.21
.01
Summer1
TP TKN2
.26 .24
* *
.17 .14
.88 .76
.03 .005
* Less than .0005
1 Spring runoff: April 1 - June 30
Summer runoff: July 1 - September 30
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
Subregion 0604 flows into the Ohio River in the downstream reaches of subregion 0514.
Includes flow from Missouri River system.
46
-------
Summary and Discussion
Data from both the Purdue Water Quality Model and the U.S. Environmental Protection Agency's
STORET database confirm the lack of any consistent seasonal trend in nutrient concentrations or loadings,
among the overall regional means and among the subregions within a given region. A priori theories
would suggest that nutrient sources such as cropland runoff, construction runoff and urban gardening
runoff would be seasonal, but at least in 1989 these sources are apparently negated by opposite seasonal
trends in other sources in many regions and subregions. There are wide variations in nutrient
concentrations and loadings within most subregions, but these variations are quite inconsistent across
subregions.
Secondly, nutrient concentrations do not generally increase as a river system flows downstream.
Some slight trends appear for a few subregions within one region, but the trend then disappears farther
downstream. Several possible explanations of this observation are noted in the report. Nutrient loadings
do increase somewhat as they move downstream, in some river systems. Once again, however, the trend
is not consistent across all relevant regions, nor does it appear all of the way from upstream to
downstream in any given region.
From our analysis we estimate that on an average day in 1989 more than 379,000 pounds (190 tons)
of phosphorus and more than 1,872,(500 pounds (1450 tons) of Kjeldahl nitrogen were discharged into the
Gulf of Mexico from the surface waters of the United States. More than 90% of each nutrient comes from
the Mississippi River system alone, but most of this originates far from the Gulf itself.
It is clear that the regions which are the major sources of both Kjeldahl nitrogen and phosphorus
during much of the year are the Ohio River basin and the Upper Mississippi River basin. In both of these
regions, nonurban nonpoint sources provide by far the largest sources of nutrient pollution in waterways.
It would seem, then, that continuation and expansion of policies directed toward decreasing nutrient runoff
from nonurban lands in these upstream regions could have the biggest impact on programs to reduce
nutrient pollution in the Gulf.
47
-------
Several questions arise which will, of course, need further study. One is that of possible spatial
variations within the Gulf of Mexico. For example: is a pound of phosphorus or nitrogen from southern
Florida or the Rio Grande equivalent, in terms of ecosystem damage, to a pound of phosphorus or nitrogen
from the Mississippi-Atchafalaya Gulf Coast which is much farther north? Does a pound of a nutrient
discharged into the Gulf in winter have the same impact on the ecosystem as in the summer? Many such
questions will be answered by other groups in the Gulf of Mexico Project, and the answers will help to
determine which potential policies will have the greatest favorable impact.
Nutrient overenrichment in the Gulf of Mexico is caused by the practices of rural and urban residents
far from the Gulf Coast as well as those living near the coast. Plans to protect the Gulf must examine
ways of influencing these practices. The particular nutrient which is the limiting factor in the Gulf
ecosystem must also be determined. The contributions of the various regions whose waterways flow to
the Gulf vary widely, both by season and by nutrient, though there is not much consistency in these
variations. The proportion of nutrients coming from point sources and nonpoint sources also varies,
though nonpoint sources appear to be the larger factor in those regions which provide the majority of the
nutrients in most seasons. Protecting the Gulf ecosystem requires that we consider the full range of
activities throughout the entire drainage area of river systems flowing into the Gulf of Mexico.
Data Discussion
This analysis clearly illustrates a major problem in environmental programs and policies, insufficient
data of reasonable quality. The measurements of actual concentrations of pollutants and flows were
nonexistent, both temporally and spatially. In addition, this project found that there is relatively little
known about the transport of pollutants through a large river basin. While laboratory or small watershed
models have been developed and calibrated, refocusing these micro-level models on meso- or micro-scale
basins is a major research need.
If we expect better discussions regarding protection of Gulf of Mexico waters, or other environmental
resources, we need better data that is consistent, spatially and temporally, which can be utilized to
structure research efforts.
48
-------
One major finding of this study is the poor quality of the data upon which to base decisions about
protection of the water of the Gulf of Mexico.
49
-------
-------
APPENDIX A
Subregional Analysis of Ambient
and Nonambient Concentrations
-------
-------
Appendix A: Brief Interpretation of Tables A2-A10:
»
(Table Al is included for easy reference only. It is identical to Table 5.)
Table A2 • Region 03 (Partial): The Gulf Coast River Systems of the Southeast Region
Region 03 is the only region whose flow is divided, between the Atlantic Ocean and the Gulf of
Mexico (though there is no definitive line dividing these two bodies of water). Subregions 01 through
08 and part of 09 flow directly into the Atlantic, while part of 09 and all of 10 through 18 flow into the
Gulf. The half (approximately) of Region 03 flowing into the Gulf of Mexico covers the geographic area
from southwestern Florida through a small part of eastern Louisiana.
The quarterly means presented by subregions show a wide range of nutrient concentrations (all data
is in milligrams per liter), as is true of most regions. Mean total phosphorus ranged from .05 mg/L in the
•
spring in subregion 17, the Pascagoula River system, to .89 mg/L in the winter in subregion 12, the
Ochlockonee system, though a few very high readings may dominate the latter, as is the case in several
regions. The highest individual sample readings include 6.6 mg/L in the summer in the Peace River
system in Florida (Subregion 10), 5.6 mg/L in both the Peace River system (FL) in winter and the
Ochlockonee system (Subregion 12), also in winter, and 5.42 mg/L in the Kissimmee-Okeechobee
(Subregion 09) in winter.
Mean TKN ranged from .416 mg/L in the fall in Subregion 13, the Apalachicola River system, to
2.927 mg/L in Subregion 14, the Choctawhatchee-Peace (Alabama) system in spring. Maximum individual
samples were an extremely high 98.8 mg/L in the summer in Subregion 15, the Coosa River system (the
mean was still 1.47 mg/L), 18.8 mg/L in summer in the Choctawhatchee-Peace (Alabama) system and 18.4
mg/L in spring in Subregion 16, the Tombigbee system. Many subregions had single samples of TKN
of 11 mg/L or higher in the Gulf rivera of Region 03.
Organic Nitrogen is not reported in every subregion. Mean Organic N ranged from .083 mg/L in
spring in the Suwanee River system (Subregion 11) to 2.962 mg/L in spring in the Tombigbee system,
the latter strongly influenced by the highest individual sampling in the region in 1989 of 13.6 mg/L. The
second highest concentration reported was 6.50 mg/L in spring in the Peace River system in Florida.
Al
-------
For Region 03's gulf coast river systems overall, quarterly means of total phosphorus ranged from
.176 mg/L for the fall season to .336 mg/L in winter. TKN varied from a low of .745 mg/L in fall to
1.301 mg/L during the spring. Organic nitrogen means (with many subregions not reporting) were lowest
in fall (.780 mg/L) and highest in summer (.982 mg/L). Many of the nitrogen means in some Gulf of
Mexico river systems of the Southeast Region are above generally accepted safe upper limits.
A2
-------
Table A-l
USGS Region Summaries: Mean Nitrogen and Phosphorus Concentrations
by Region
1989: All data in mg/L
Subregion
03
Southeast (Gulf
of Mexico River
Systems Only)
05
Ohio River
System
06
Tennessee
07
Upper Miss
08
Lower Miss
10
Missouri River
System
11
Arkansas -
Red - White
River System
12
Texas Gulf
Nutrient
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
Winter
.336 (756)
1.111 (625)
.808 (214)
1.062 (98)
.290 (847)
.674 (582)
*
.451 (130)
.450 (72)
1.690 (44)
.414(1168)
1.771 (551)
1.033 (53)
.196 (1016)
.856 (681)
*
1.665 (955)
1.929 (434)
.889 (9)
.728(911)
3.256 (553)
5.335 (134)
8.244 (242)
.730 (572)
1.003 (403)
*
Soring
.306 (713)
1.301 (699)
.888 (197)
1.311 (46)
.135 (1395)
.618 (1259)
*
.130(385)
.471 (146)
.325 (302)
.347 (2575)
1.429 (1347)
1.576 (194)
.187 (1014)
.901 (699)
*
.358 (1359)
1.398 (642)
*
.631 (1064)
2.391 (589)
2.817 (197)
6.261 (223)
.279 (453)
.747 (358)
*
Summer
.222 (607)
1.138 (641)
.982(177)
*
.255 (2074)
.682(1847)
*
.081 (572)
.421 (136)
.239 (490)
.484 (3089)
1.623 (1421)
1.413 (235)
.188 (988)
.850 (637)
*
1.697 (1600)
5.328 (881)
*
.535 (1205)
1.889 (654)
3.118 (120)
3.345 (203)
.436 (391)
.911 (438)
*
Fall1
.176 (420)
.745 (366)
.780 (112)
*
.331 (896)
.706 (645)
*
.250 (54)
.282 (94)
1.268 (5)
.444 (1022)
1.105 (588)
.638 (46)
.182 (626)
.763 (531)
*
.407 (587)
.1.526(201)
*
1.305 (520)
3.505 (343)
4.235 (120)
8.815 (144)
.755 (148)
.809 (148)
*
A3
-------
Table A-l (continued)
Subregion
Nutrient
Winter
Soring
Summer
Fall1
13
Rio Grande
System
Entire U.S.
Gulf of Mexico
Drainage
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
.158 (88)
.678 (61)
.240 (21)
1.656 (17)
.609 (6443)
1.454 (3962)
2.169 (475)
.288 (188)
1.231 (183)
.630 (150)
1.695 (140)
.315 (9146)
1.201 (5922)
1.181 (1040)
.557 (101)
1.185 (99)
.418 (57)
2.022 (57)
.562 (10627)
1.679 (6754)
.946 (1079)
.337 (29)
.672 (29)
.328 (6)
.513 (6)
.463 (4302)
1.174(2945)
2.191 (289)
* No samples taken
() = Number of samples
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
A4
-------
Table A-2
Partial USGS Region 03:
Southeast Gulf Coast River Systems
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
09 Partial
Caloosahatchee
L. Okeechobee
10
Peace (FL) -
Tampa Bay
11
Suwanee
12
Ochlockonee
13
Apalachicola
14
Choctawhatchee
- Escambia
15
Coosa - Alabama
16
Tombigbee -
Mobile Bay
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.227 (90)
1.171 (96)
.946 (64)
.371 (158)
1.070 (159)
.842 (103)
1.062 (98)
.667 (61)
.555 (26)
.446 (7)
.897 (27)
2.877 (7)
.651 (19)
.275 (185)
.816 (29)
.193 (11)
.505 (68)
1.454 (98)
.812 (10)
.178(96)
1.104 (49)
*
.133 (26)
.786 (106)
*
Spring
.298 (105)
1.230 (106)
1.102 (60)
.549 (118)
1.118(115)
.944 (50)
1.311 (46)
.364 (58)
.791 (35)
.083 (7)
.599 (17)
1.886 (5)
.782 (19)
.191 (190)
.700 (47)
.440 (11)
.542 (73)
2.927(110)
.650 (13)
.106 (93)
.746 (80)
.317 (29)
.098 (22)
1.056 (159)
2.962 (8)
Summer
.251 (96)
1.530 (93)
1.153 (61)
.664 (43)
1.388 (42)
2.474 (7)
*
.488 (34)
.779 (22)
.431 (7)
.439(17)
.661 (8)
.572 (16)
.150 (195)
.602 (48)
.356 (10)
.252 (42)
1.015 (70)
.693 (20)
.107 (89)
1.468(118)
.295 (37)
.074 (25)
1.034 (170)
2.401 (19)
Fall1
.086 (67)
1.153 (66)
1.006 (57)
.306 (34)
.955 (34)
2.864 (5)
*
.603 (29)
.783 (9)
.255 (4)
.438 (12)
.607 (3)
.338 (20)
.142(117)
.416 (23)
.145 (11)
.060 (52)
.583 (60)
.544(11)
.087 (51)
.422 (52)
.087 (4)
.085 (22)
.550 (79)
*
A5
-------
Table A-2 (continued)
Subregion
Nutrient
Winter
Soring
Summer
* No samples taken
() = Number of samples
Fall1
17
Pascagoula
18
Pearl
Region 03
(Partial)
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
.Q65 (16)
1.713 (24)
*
.111 (29)
1.044 (31)
*
.336 (756)
1.111 (625)
.808 (214)
1.062 (98)
.054 (10)
.613 (15)
*
.096 (27)
.814 (27)
*
.306 (713)
1.301 (699)
.888 (197)
1.311 (46)
.107 (35)
.768 (39)
*
.099 (31)
.892 (31)
*
.222 (607)
1.138 (641)
.982 (177)
*
.739 (8)
2.060 (12)
*
.113 (28)
.730 (28)
*
.176 (420)
.745 (366)
.780(112)
*
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
A6
-------
Table A3 • Region 05; The Ohio River System*
The Ohio River and its tributaries comprise one of the larger tributary systems of the Mississippi
River system, particularly in terms of the amount of water flowing into the Mississippi. Consequently the
Tennessee River system, which joins the Ohio shortly before it flows into the Mississippi, has been given
its own separate region (06) by the USGS. Geographically, Region 05 extends from a small part of
southwestern New York State through West Virginia to western Kentucky and eastern Illinois.
For the rest of the Ohio system, Region 05, quarterly mean concentrations of total phosphorus in the
subregions varied from a low of .032 mg/L in the fall in the Kentucky-Licking rivers area (several other
subregions also had seasonal means below .1 mg/L) to 1.578 mg/L, also in the fall, in the Middle Ohio
Subregion (09). The maximum individual samples were 35.7 mg/L in the fall in the Middle Ohio area,
16.0 mg/L in the fall in Subregion 06, the Scioto River area, and 15.36 mg/L in winter in the Wabash
River Subregion (12).
Mean TKN in Region 05 ranged on a seasonal basis from a low of .160 mg/L in the springtime in
the Monongahela area (Subregion 02), to 1.448 mg/L in the fall in Subregion 12 (Wabash). Maximum
single readings of TKN were 44.4 mg/L in spring, 37.0 mg/L in spring and 34.0 mg/L in the fall in
Subregions 09 (Kentucky-Licking), 05 (Kanawha River) and 12 (Wabash), respectively.
Organic nitrogen was not measured in Region 05 in 1989.
For the region as a whole, mean total phosphorus in the Ohio Region varied from a low of .135
mg/L in spring to .331 mg/L in the fall. TKN was steady overall, though not in all subregions: it ranged
from .618 mg/L in the spring to a high of .706 mg/L in the fall.
Excluding the Tennessee tributary system (Region 06).
A7
-------
Table A-3
USGS Region 05: Ohio River System
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Allegheny
02
Monongahela
03
Upper Ohio
04
Muskingum
05
Kanawha
06
Scioto
07
Big Sandy -
Guyandotte
08
Great Miami
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.045 (73)
.217 (3)
*
.075 (64)
.240 (26)
*
.185 (98)
.786 (50)
*
.476 (39)
1.167 (51)
*
.098 (67)
.363 (70)
*
.205 (45)
1.030 (36)
*
.082 (51)
.258 (75)
*
.297 (23)
.910 (31)
*
Spring
.066 (74)
.242 (4)
*
.093 (61)
.160 (24)
*
.133 (96)
.461 (60)
*
.088 (129)
.397 (164)
*
.099 (97)
.604 (135)
*
.148 (85)
.759 (75)
*
.055 (74)
.207(111)
*
.220 (66)
.845 (106)
*
Summer
.060 (79)
.330 (3)
*
.076 (69)
.371 (27)
*
.128 (120)
.491 (78)
*
.428 (383)
.754 (391)
*
.109 (134)
.367 (147)
*
.500(111)
.596 (124)
*
.059 (105)
.255 (124)
*
.312 (224)
.667 (238)
*
Fall1
.052 (79)
.330 (3)
*
.113 (60)
.301 (18)
*
.136(110)
.453 (64)
*
.169 (60)
.429 (68)
*
.091 (93)
.470 (100)
*
1.083 (59)
.851 (70)
*
.042 (33)
.217 (58)
*
.323 (19)
.561 (18)
*
A8
-------
Table A-3 (continued)
Subreglon
09
Middle Ohio
10
Kentucky -
Licking
11
Green
12
Wabash
13
Cumberland
14
Lower Ohio
Region 05
Nutrient Winter
TP2 .162(23)
TKN .468 (36)
OrgN *
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
.193 (43)
.495 (44)
*
.064 (25)
.436 (26)
*
.682 (197)
1.550 (52)
*
.059 (23)
.228 (19)
*
.324 (76)
.664 (63)
*
.290(847)
.674 (582)
*
Spring
.160 (92)
1.024 (108)
*
.121 (73)
.407 (87)
*
.085 (34)
.451 (53)
*
.189 (298)
1.032 (144)
*
.132 (37)
.584 (30)
*
.144 (179)
.593 (158)
*
.135 (1395)
.618 (1259)
*
Summer
.345 (124)
.800 (162)
*
.154 (66)
.424 (78)
*
.042 (46)
.379 (51)
*
.232 (400)
1.098 (239)
*
.071 (39)
.353 (33)
*
.224 (169)
.932 (144)
*
.255 (2074)
.682 (1847)
*
Fall1
1.578 (43)
.560 (49)
*
.032 (13)
.582 (15)
*
*
*
*
.305 (259)
1.448(118)
.078 (2)
.441 (5)
*
.264 (44)
.820 (29)
*
.331 (896)
.706 (645)
*
* No samples taken
( ) = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
2
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
A9
-------
Table A4 - Region 06: Tennessee River System
Bowing into the Ohio and thence to the Mississippi, the Tennessee River and its tributaries comprise
one of the smaller USGS hydrologic Regions. It extends geographically from western Virginia and North
Carolina to the Ohio River at Kentucky and Illinois. Small or not, the Tennessee Valley was one of the
less polluted areas in 1989, in terms of both nitrogen and phosphorus.
Mean total phosphorus presented quarterly for the four subregions ranged from .07 mg/L in the
spring and summer in the Middle Tennessee-Hiwassee Subregion, with several seasonal means below 1.0
mg/L, to 1.5 mg/L in the fall in the Middle Tennessee-Elk Subregion. The highest individual 1989
measurement of TP (total phosphorus) was 9.0 mg/L in the Middle Tennessee-Elk area, in the spring
season.
Quarterly TKN means varied from a low of .16 mg/L in the spring in the Middle Tennessee-
Hiwassee Subregion, to 1.76 mg/L in the Middle Tennessee-Elk Region, also in the spring. The maximum
sample readings were 4.0 mg/L and 3.9 mg/L in spring and winter, respectively, in the Middle Tennessee-
Elk area.
Seasonal mean organic nitrogen, reported in most subregions and seasons, ranged from .19 mg/L in
the Middle Tennessee-Hiwassee area in summer (for data with sufficient observations), to 4.97 mg/L in
winter in the Middle Tennessee-Elk subsystem.
In the entire Tennessee Valley, total phosphorus varied from a low of .08 mg/L in summer to a high
of .45 mg/L in winter, TKN from .28 mg/L in fall to .47 mg/L in spring; and Organic Nitrogen from .24
mg/L in summer to 1.69 mg/L in winter.
A10
-------
Table A-4
USGS Region 06: Tennessee River System
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Upper Tennessee
02
Middle Tennessee
- Hiwassee
03
Middle Tennessee
-Elk
04
Lower
Tennessee
Region 06
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.353 (79)
.322 (57)
.814 (28)
.314 (29)
.465 (6)
.310 (4)
1.281 (14)
1.717 (6)
4.971 (10)
.468 (8)
.320 (3)
.310 (2)
.451 (130)
.450 (72)
1.690 (44)
Spring
.082 (82)
.347 (106)
*
.072 (209)
.164 (20)
.198 (196)
.321 (77)
1.762 (14)
.560 (106)
.219 (17)
.668 (6)
*
.130 (385)
.471 (146)
.325 (302)
Summer
.086 (97)
.315 (110)
.292 (15)
.066 (223)
.500 (1)
.190 (209)
.079 (235)
1.007 (19)
.274 (264)
.292 (17)
.486 (6)
.180 (2)
.081 (572)
.421 (136)
.239 (490)
Fall1
.115 (35)
.278 (85)
*
.274(11)
*
*
1.522 (4)
.320 (6)
1.535 (4)
.100 (3)
.343 (3)
*
.250 (54)
.282 (94)
1.268 (5)
* No samples taken
() = Number of samples
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
All
-------
Table AS • Region 07: Upper Mississippi River System
The Upper Mississippi system includes the upper reaches of the mighty river which eventually drains
nearly two-thirds of the surface water in the 48 contiguous states, and all of its tributaries in Minnesota,
Wisconsin, Iowa, northern Missouri and Illinois which join it upstream of the Missouri River (Region 10)
on the western bank and the Ohio River (Region 05) on the eastern bank.
Nutrient concentrations are highly variable in the Upper Mississippi Region, again without a
consistent trend either seasonally or from upstream to downstream. Mean total phosphorus in each
subregion ranged in 1989 from .05 mg/L in winter in the St. Croix River Subregion (03) to a high of 2.74
mg/L in the summer in the Wisconsin River area (Subregion 07). The highest individual phosphorus
samples were a rather extreme measurement of 170.0 mg/L in the Wisconsin River Subregion in summer
and 29.8 mg/L in the Minnesota River system, also in summer.
Mean TKN among the subregions ranged from .57 mg/L in the fall season in the Upper Mississippi-
Black-Root system (Subregion 04) to 3.69 mg/L in winter in the lowa-Skunk-Wapsipinicon area
(Subregion 08). There was a slight trend of increasing concentrations from upstream to downstream in
some seasons. Maximum concentrations were found at 48.0 mg/L in the summer in the Wisconsin River
area, and several 25 to 28 mg/L readings in various seasons and subregions.
The means for organic nitrogen, reported in fewer than half of the subregions, varied from a low of
.4 mg/L in the St. Croix River area in winter to 3.77 mg/L in the Des Moines River subsystem, Subregion
10, in spring. The highest individual concentrations were 27.3 mg/L in summer in the Minnesota River
area and 26.5 mg/L in the spring in Subregion 04, the Upper Mississippi-Black-Root.
For Region 07 the mean total phosphorus was fairly steady, ranging from .35 mg/L in spring to .48
mg/L in summer. Mean TKN varied only from 1.1 mg/L in the fall to 1.77 mg/L in winter. Seasonal
means for organic nitrogen (for those snbregions reporting) ranged from a low of .64 mg/L in the fall to
1.58 mg/L in the spring.
A12
-------
Table A-5
USGS Region 07: Upper Mississippi River System
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Mississippi
Headwaters
02
Minnesota R.
03
St. Croix R.
04
Upper Miss.-
Black-Root
05
Chippewa
06
Upper Mississippi
-Maquaketa-Plum
-Escambia
07
Wisconsin R.
08
Upper Miss.-Iowa
Skunk-
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.318 (103)
2.196 (74)
.946 (15)
.299 (70)
2.316 (26)
1.396 (20)
.051 (73)
.895(11)
.397 (3)
.367 (34)
1.191 (34)
.653 (12)
.950 (85)
.778 (46)
*
.410 (21)
1.860 (15)
*
.528 (68)
1.588 (34)
*
.785 (55)
3.692 (26)
1.193 (3)
Spring
.210 (343)
.929 (132)
.964 (50)
.185 (155)
1.819 (74)
1.244 (51)
.152(169)
1.526 (104)
.888 (12)
.714 (146)
2.611 (146)
2.195 (43)
.632 (197)
.791 (131)
*
.222 (30)
.844 (16)
*
1.468 (124)
1.240 (60)
*
.366 (94)
1.896 (34)
1.602 (25)
Summer
.347 (422)
1.248 (182)
.947 (49)
.524 (176)
2.617 (100)
2.078 (51)
.306 (151)
2.116 (69)
.745 (11)
.321 (131)
1.381 (129)
.823 (44)
.858 (213)
1.083 (105)
*
.703 (36)
2.583 (30)
*
2.741 (160)
2.480 (45)
*
.491 (158)
1.508 (51)
1.384 (62)
Fall1
.215 (49)
1.168 (19)
.615 (13)
.813 (23)
1.352 (13)
.852 (13)
.645 (38)
1.011 (26)
.483 (3)
.180 (56)
.570 (54)
.512 (13)
.347 (73)
.679 (32)
*
.184 (24)
.733 (18)
*
.329 (46)
.770 (46)
*
.623 (57)
1.189 (28)
.550 (4)
Wapsipinicon
A13
-------
Table A-5 (continued)
Subregion
09
RockR.
10
DcsMoines R.
11
Upper Miss.
-Salt
12
Upper Illinois
13
Lower Illinois
14
Upper Miss.-
Kaskaskia-
Meramcc
Region 07
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.349 (162)
3.053 (32)
*
.725 (13)
1.750 (14)
*
.129 (14)
1.180 (5)
*
.419 (198)
1.939 (128)
*
.419 (136)
1.200 (35)
*
.280 (136)
.996 (71)
*
.414(1168)
1.771 (551)
1.033 (53)
Spring
,134(227)
1.213 (62)
*
.599 (36)
1.454 (13)
3.769 (13)
.451 (25)
1.088 (8)
*
.298 (383)
1.545 (231)
. *
.230 (322)
1.318(128)
*
.195 (324)
1.171 (208)
*
.347 (2575)
1.429 (1347)
1.576 (194)
Summer
.223 (427)
2.481 (21)
*
.538 (51)
1.848 (14)
2.744 (18)
.177 (18)
.925 (8)
*
.238 (493)
1.464 (276)
*
.324 (294)
1.561 (140)
*
.292 (359)
1.614 (251)
*
.484 (3089)
1.623 (1421)
1.413 (235)
Fall1
.280 (90)
1.433 (21)
*
.898 (12)
1.500 (12)
*
136 (9)
.900(1)
*
.576 (183)
1.397 (143)
*
.542 (182)
1.436 (61)
*
.380 (180)
.990(114)
*
.444 (1022)
1.105 (588)
.638 (46)
* No samples taken
( ) = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer 'July 1 - September 30
Fall October 1 - December 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
A14
-------
Table A6 - Region 08: Lower Mississippi River System Excluding
the Arkansas-White-Red System
The Mississippi and its tributaries below the Missouri and Ohio systems (minus the Arkansas-White-
Red Region) comprise this region which extends from southern Missouri and Kentucky through the
Mississippi delta in southern Louisiana. Region 08 has few individual samples with high phosphorus or
nitrogen, and the means are perhaps lower than some might expect from the river draining our nation's
entire heartland.
Seasonal means for the nine subregions for total phosphorus ranged from .07 mg/L in the spring
season in the Lower Mississippi-Big Black-Escambia Subregion (06) to a high of only .47 mg/L in the
fall in the Lower Mississippi-Yazoo area (Subregion 03). The highest individual sample had a 4.6 mg/L
concentration of phosphorus, in the summer in the Lower Mississippi-St. Francis Subregion (02).
TKN subregion means in 1989 varied from a low of .44 mg/L in the summer in Subregion 06 to a
high of 2.346 mg/L in Subregion 03 in the fall, for subregions and seasons with at least three observations.
The maximum single samples had concentrations of 11.26 mg/L TKN in the Louisiana Coastal area
(Subregion 08) in the summer, and 10.8 mg/L in the fall in the Lower Red-Ouachita Subregion (04).
For Region 08 as a whole, mean total phosphorus was seasonally steady, varying only from a low
of .182 in the fall to .196 in the winter. TKN ranged only from .763 in the fall to .9 in the spring. These
and the subregion means are generally lower than those for the measurements taken upstream, particularly
from the Missouri River system (Region 10) and the Arkansas-White-Red rivers system (Region 11), and
even somewhat lower in general than those for the Upper Mississippi Region. This suggests several
possible interpretations including either (1) There is considerable degradation of nutrient pollutants as
they travel downstream in surface waters, applicable to both phosphorus and nitrogen; (2) there is
considerable settling out of sediment-attached chemicals and nutrients, particularly applicable to
phosphorus; or (3) 'the increased volume of water in the Lower Mississippi has additional input from
smaller, cleaner tributaries leading to dilution of nutrients; and (4) its large surface expanse and therefore
increased plant growth which utilizes nitrogen and phosphorus, contribute to a lowering of concentrations.
A combination of these processes and possibly others is most likely.
A15
-------
Table A-6
USGS Region 08:
Lower Mississippi River System Excluding Arkansas-
White-Red (Region 11)
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Lower Mississippi
R. - Hatchie
02
Lower Miss.-
St. Francis
03
Lower Miss.-
Yazoo
04
Lower Red -
Ouachita
05
Boeuf -
Tensas
06
Lower Miss.-
Big Black
- Escambia
07
Lower Miss.-
Lake Maurepas
08
Louisiana
Coastal
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.161 (23)
1.100 (1)
*
.188 (87)
.815 (13)
*
.262 (243)
.483 (138)
He
.089 (294)
.526 (199)
*
.286 (94)
1.373 (91)
*
.193 (7)
1.257 (7)
*
.198 (66)
1.005 (58)
*
.274 (103)
1.303 (89)
*
Spring
.114(43)
.684 (13)
*
.259 (60)
.797 (21)
*
.190(292)
.507 (125)
• *
.097 (279)
.621 (226)
*
.330 (86)
1.320 (85)
*
.073 (6)
.517 (6)
*
.218 (56)
1.127 (49)
*
.277 (103)
1.460 (91)
*
Summer
.147 (32)
.892 (18)
*
.398 (100)
.872 (17)
*
.191 (177)
.459 (75)
*
.132 (325)
.726 (204)
*
.205 (91)
1.131 (91)
*
.110(4)
.443 (3)
*
.184 (65)
.945 (57)
*
.178 (97)
1.009 (89)
*
Fall1
.170 (1)
.500 (1)
*
.446 (43)
.713(11)
*
.470 (7)
2.346 (7)
*
.131 (229)
.569 (197)
*
.159 (92)
1.014 (91)
*
*
6.340 (1)
*
.176 (64)
.640 (52)
*
.174 (101)
.721 (90)
*
A16
-------
Table A-6 (continued)
Subregion
09
Lower
Mississippi R.
Region 8
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
Winter
.199 (99)
1.081 (85)
*
.196(1016)
.856 (681)
*
Spring
.193 (89)
1.172(83)
*
.187 (1014)
.901 (699)
*
Summer
.174(97)
.963 (83)
*
.188 (988)
.850(637)
*
Fall1
.198 (89)
.883 (81)
*
.182 (626)
.763 (531)
*
* No samples taken
( ) = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
A17
-------
Table A7 - Region 10: The Missouri River System
The Missouri River system is the largest geographic USGS Region, covering an area from western
Montana through eastern Colorado and southwestern Minnesota to most of Missouri. Its thirty subregions
have the highest individual sample concentrations in the study, and some of the higher subregion means.
Its upper reaches are frozen and therefore not sampled in the winter and fall seasons.
The lowest subregion mean concentration for total phosphorus in 1989 was .024 mg/L in Subregion
06, the Missouri-Poplar area, in the fall, for subregions and seasons with sufficient observations. The
highest means were 18.12 mg/L and 11.15 mg/L in the summer and winter, respectively, in the Cheyenne
River subsystem (Subregion 12). Both of these high means were dominated by extremely high individual
samples with 830.0 mg/L summer and 1102.0 mg/L winter concentrations, the maximum observations for
the region. The next highest single sample was 30.9 mg/L in summer in the Missouri-White Subregion
(14).
Seasonal means for TKN in Region 10 ranged from a low of .20 mg/L in the fall in the Gasconade-
Osage Subregion (29) to 153.76 mg/L in the Cheyenne Subregion in summer, the latter again dominated
by a single sample measurement, of 1300.0 mg/L, the maximum for the region. The second highest
individual sample concentration was 28.0, in the summer in the Nebraska Subregion (15).
Organic nitrogen was measured in only one subregion of the thirty, and in only one season.
For the entire Missouri Region as a whole, the seasonal mean total phosphorus varied from .36 mg/L
in the spring to a high of 1.70 mg/L in summer; TKN seasonal means ranged from 1.40 mg/L in the
spring to 5.33 mg/L in the summer.
A18
-------
Table A-7
USGS Region 10: Missouri River System
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Saskatchewan
02
Missouri
Headwaters
03
Missouri -
Marias
04
Missouri -
Musselshell
05
Milk
06
Missouri -
Poplar -
Escambia
07
Upper
Yellowstone
08
Big Horn
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
*
*
*
*
*
*
.030 (3)
.367 (3)
*
.040 (5)
.520 (5)
*
.698 (5)
2.640 (5)
*
.079 (8)
1.225 (8)
*
.035 (2)
.400 (2)
*
.112(22)
.589 (19)
*
Spring
.020 (1)
.300 (1)
*
.097 (4)
*
*
.036 (12)
.420 (10)
*
.046 (9)
.432 (8)
*
.075 (4)
.700 (4)
*
.057(11)
.736(11)
*
.063 (6)
.550 (2)
*
.097 (48)
2.413 (23)
*
Summer
.020 (1)
.200 (1)
*
.135 (2)
*
*
.052 (8)
.367 (6)
* .
.037 (10)
.472 (9)
*
.053 (3)
.833 (3)
*
.051 (12)
.873 (15)
*
.028 (5)
.450 (2)
*
.057 (39)
.695 (22)
*
Fall1
*
*
*
*
*
*
.030 (3)
.300 (2)
*
.040(4)
.360 (5)
*
.033 (6)
.600(4)
*
.024 (8)
.700 (8)
*
.030 (2)
1.900 (1)
*
.075 (15)
.350 (6)
*
A19
-------
Table A-7 (continued)
Subregion
09
Powder -
Tongue
10
Lower
Yellowstone
11
Missouri -
Little Missouri
12
Cheyenne
13
Missouri - Oahe
14
Missouri -
White
15
Niobrara
16
James
17
Missouri -
Big Sioux
18
North Plane
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
. TKN
OrgN
Winter
.084 (28)'
.500(11)
*
.893 (3)
1.533 (3)
*
.510 (1)
2.600 (1)
*
11.150(102)
1.155 (11)
*
.254 (62)
1.993 (26)
*
.458 (20)
.625 (4)
*
.168 (34)
1.167 (3)
*
.543 (41)
2.798 (30)
*
.798 (41)
1.133 (3)
*
.160 (37)
1.066 (15)
*
Spring
.179 (69)
.557 (23)
*
.038 (4)
1.050 (2)
*
.454 (6)
1.318 (5)
*
.195 (138)
.647 (42)
*
.243 (87)
1.624 (30)
*
.945 (30)
.899 (7)
*
.145 (47)
1.237 (18)
*
.369 (75)
1.798 (44)
*
.380 (48)
.718 (9)
*
.122 (72)
1.484 (37)
*
Summer
.654 (31)
.514 (7)
*
.046 (5)
.720 (5)
*
.079 (7)
.850 (2)
*
18.120(100)
153.760 (17)
*
.169 (109)
2.097 (23)
*
3.201 (25)
1.484 (8)
*
1.269 (142)
5.399(113)
*
.820 (155)
2.878 (136)
*
.584 (51)
1.149 (8)
*
.235 (70)
1.269 (45)
*
Fall1
.859 (19)
.860 (10)
*
.037 (3)
.425 (4)
*
.038 (5)
.600(3)
*
.238 (81)
.555 (5)
*
.090 (24)
.725 (8)
*
.316 (14)
.540 (2)
*
.138 (22)
2.286 (12)
*
.724 (17)
1.750 (3)
*
.923 (38)
.815 (4)
*
.167 (22)
2.779 (15)
*
A20
-------
Table A-7 (continued)
Subreeion
19
South Plane
20
Plane
21
Loup
22
Elkhorn
23
Missouri -
Little Sioux
24
Missouri -
Nishnabotna
25
Republican
26
Smoky Hill
27
Kansas
28
Chariton -
Grand
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
1.133 (87)
5.162 (55)
*
.692 (25)
2.216 (19)
*
.240 (41)
1.056 (8)
*
.426 (17)
1.334 (14)
*
1.784 (28)
1.354 (19)
.889 (9)
.215 (30)
1.220(11)
*
.159 (26)
.853 (3)
*
.373 (39)
.625 (4)
*
.536 (197)
1.523 (133)
*
.144 (7)
.829 (7)
*
Spring
.785 (130)
1.982 (79)
*
.723 (33)
2.035 (32)
*
.256 (43)
.895 (11)
*
.353 (18)
1.269 (18)
*
.540 (24)
1.574(24)
*
.310 (43)
2.096 (13)
*
.298 (35)
1.110 (9)
*
.360 (61)
1.167 (6)
*
.408 (190)
1.383 (125)
*
.177 (24)
1.241 (19)
*
Summer
.293 (181)
1.734 (127)
*
.618 (24)
1.987 (22)
*
.395 (44)
2.032 (13)
*
.744 (19)
2.621 (18)
*
1.487 (26)
2.036 (26)
*
.277 (72)
1.340 (9)
*
.684(51)
1.261 (25)
*
1.119(80)
1.270 (15)
*
.539 (181)
1.505 (88)
*
.393 (35)
1.039 (36)
*
Fall1
.620(111)
2.162 (67)
*
.427(11)
1.799(11)
*
.182 (4)
.397 (3)
*
.197(3)
1.303 (3)
*
.688(8)
1.600(7)
*
.186 (16)
.300 (4)
*
.211 (11)
1.040 (1)
*
.231 (24)
*
*
.446 (51)
.867 (9)
*
.100 (3)
.600(3)
*
A21
-------
Table A-7 (continued)
Subregion
29
Gasconade
Osage
30
Lower
Missouri
Region 10
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.091 (27)
.489 (9)
1.814(17)
.567 (3)
1.165 (955)
1.929 (434)
.889 (9)
Spring
.099 (58)
.674 (16)
1.245 (29)
.874 (14)
.358 (1359)
1.398 (642)
Summer
.149 (94)
3.758 (74)
.976 (18)
.663 (6)
1.697 (1600)
5.328 (881)
Fall'
.166(37)
.200 (1)
1.387 (14)
*
.407 (587)
1.526 (201)
*
* No samples taken
() = Number of samples
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
A22
-------
Tabte A8 - Region 11: The Arlwnsas-White-Red System
The Arkansas-White-Red River Region is the last (and farthest downstream) of the great tributary
systems flowing into the Mississippi. Geographically, it stretches from eastern Colorado to" Arkansas and
Louisiana. It also appears to be one of the regions with higher nutrient concentrations, with several
individual samples measuring very high, especially in nitrogen.
Total phosphorus seasonal means for Region 11 's subregions ranged from a low of .03 mg/L in the
Upper Cimarron Subregion (04) in the winter, to a high of 5.01 mg/L in the Red-Washita Rivers area,
Subregion 13, in the fall. The highest individual measurement of TP in 1989 was 18.6 mg/L in the
summertime in Subregion 07, the Neosho-Verdigris area; several subregions also had one or more
measurements over 12 mg/L.
Seasonal means of TKN varied from a low of .50 mg/L in the Upper Cimarron Subregion in the
spring, to reports of 10.95 mg/L in winter in Subregion 09, the Lower Canadian, 9.86 mg/L in winter in
the Arkansas-Keystone Subregion (06), and 9.53 mg/L in the fall in the Red-Washita Subregion. The
maximum single observations of TKN in 1989 were 82.0 mg/L in winter in the Lower Canadian area, 80.7
mg/L in spring in the Neosho-Verdigris Subregion, and 70.6 mg/L in winter in the Red-Washita area.
There were many other individual measurements higher than 40 mg/L in Region 11, making some of its
waters higher in nitrogen concentrations than any others flowing to the Gulf of Mexico (with the Missouri
River system a close second in some of its subregions).
Organic nitrogen is measured in ten subregions and most seasons for Region 11. The lowest mean
subregion organic N was .46 mg/L in spring for the Upper Canadian Subregion (08), for subregions and
seasons with sufficient observations; this is unusually low for most subregions in this region. The highest
subregion means were 21.68 mg/L in Subregion 14 (Red-Sulphur), 10.83 mg/L in Subregion 06 (Arkansas-
Keystone) and 9.78 mg/L in Subregion 13 (Red-Washita). Many subregions and seasons appear to be high
in organic nitrogen as well as TKN; maximum individual organic N readings were 58.14 mg/L in winter
in the Red-Washita area and 48.28 mg/L in winter in the North Canadian Subregion (10).
A23
-------
Total nitrogen was also measured in a majority of subregions and seasons in Region 11. Subregion
varied from lows of .9 mg/L in summer in the North Canadian area (10) and the Arkansas-
Keystone area (06), to highs of 17.9 mg/L in winter in the Lower Canadian, 16.0 mg/L in fall in the Red-
Sulphur, 15.8 mg/L in spring in the Neosho-Verdigris and 15.1 mg/L in winter in the Red-Washita. Many
subregions had seasonal mean total nitrogen readings over 10 mg/L; data mentioned are from those with
a sufficient number of observations.
For the entire Region 11, mean total phosphorus ranged from a low of .535 in summer to 1.305 in
the fall; TKN varied from 1.889 in summer to 3.505 in the fall; organic nitrogen ranged from a low of
2.817 in spring to 5.335 in winter; and total nitrogen ranged from 3.345 in summer to 8.815 in the fall
season.
A24
-------
Table A-8
USGS Region 11: Arkansas-White-Red System
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Upper White
02
Upper
Arkansas
03
Middle
Arkansas
04
Upper
Cimarron
05
Lower
Cimarron
06
Arkansas -
Keystone
07
Neosho -
Verdigris
08
Upper
Canadian
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
Winter
.1.17(154)
1.057 (60)
*
1.081 (14)
3.974 (35)
*
.624 (60)
1.500 (1)
*
.026 (5)
.533 (6)
*
2.894 (16)
5.246 (17)
4.257 (9)
9.971 (14)
2.512 (9)
9.865 (9)
10.832 (4)
13.141 (7)
.635 (108)
1.874 (43)
3.087 (10)
4.276 (19)
.015 (2)
.300 (2)
*
*
Spring
.153(181)
.714 (72)
*
.429 (27)
1.676(41)
*
.675(72)
.900 (1)
*
.058 (10)
.500 (6)
*
.187 (3)
.867 (3)
*
*
1.934 (6)
4.712 (6)
3.940 (4)
12.367 (4)
1.269 (160)
8.488 (44)
5.536 (34)
15.804 (32)
.225 (92)
.743 (79)
.465 (93)
1.031 (93)
Summer
.296(135)
.742 (65)
*
.342 (28)
1.868 (73)
*
.327(113)
2.600 (1)
*
.146 (20)
.500 (2)
*
.700 (5)
.560 (7)
*
.902 (5)
.347 (7)
.787 (4)
*
.920 (3)
.961 (169)
6.681 (37)
4.645 (19)
11.545 (25)
.408 (42)
1.789 (42)
1.755 (38)
2.022 (38)
Fall1
.773 (43)
.941 (31)
*
.082 (5)
4.155 (33)
*
.409 (41)
*
*
.070 (2)
.400(2)
*
8.070 (1)
1.546 (1)
.870 (1)
3.550 (1)
*
*
*
*
1.508 (79)
5.409 (24)
2.789 (19)
11.674 (17)
.010 (1)
.400 (1)
*
*
A25
-------
Table A-8 (continued)
Subregion
09
Lower
Canadian
10
North
Canadian
11
Lower
Arkansas
12
Red
Headwaters
13
Red-Washita
14
Red-Sulphur
Region 11
Nutrient
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
Winter
2.338 (21)
10.955 (19)
9.060 (8)
17.943 (13)
2.632 (35)
6.617 (33)
6.083 (21)
11.910(28)
.729 (283)
2.704 (203)
3.894 (62)
5.802 (131)
.133 (8)
.635 (6)
*
3.010 (1)
2.237 (33)
8.636 (28)
9.781 (14)
15.110(19)
.198 (163)
1.245 (91)
3.970 (6)
6.520 (10)
.728(911)
3.256 (553)
5.335 (134)
8.244 (242)
Spring Summer Fall1
3.146(17) 2.057(55) 2.796(33)
5.127(18) 4.214(53) 7.847(34)
3.060 (15) 2.817 (41) 5.539 (32)
9.073 (15) 2.001 (13) 10.306 (32)
.657 (42) .198 (40) 4.872 (15)
2.230 (33) 1.048 (24) 5.880 (15)
5.310 (5) * 5.019 (14)
10.014 (5) .929 (7) 10.943 (14)
.834 (255) .570 (322) 1.105 (168)
2.831(157) 1.172(185) 2.329(113)
4.685 (40) 1.111 (15) 2.528 (33)
6.847 (68) 1.588 (95) 4.617 (59)
1.723(7) .192(6) .476(2)
4.436 (7) .826 (8) 3.904 (2)
6.480 (2) * 7.080 (1)
16.825 (2) .700 (1) 9.010 (1)
2.176(7) .505(15) 5.011(17)
7.966 (7) 2.586 (15) 9.532 (16)
8.247 (4) 10.185 (2) 5.977 (13)
14.920(4) 4.872 (8) 14.824(14)
.139(185) .197(246) .566(113)
1.081(115) 1.474(136) 1.758 (71)
* 21.677 (3) 6.423 (6)
* 10.410 (8) 15.978 (6)
.631 (1064) .535 (1205) 1.305 (520)
2.391 (589) 1.889 (654) 3.505(343)
2.817 (197) 3.118 (120) 4.235(120)
6.261 (223) 3.345 (203) 8.815(144)
* No samples taken
( ) = Number of samples
1 Winter runoff : January
Spring April 1
Summer July 1 -
Fall October
1 - March 31
- June 30
September 30
1 - December 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
A26
-------
Table A9 - Region 12: The Texas Gulf Region
The Texas Gulf Region consists of several individual river systems flowing into the Gulf of Mexico,
from the Sabine River on the Texas-Louisiana state line westward to the Nueces near the southern tip of
Texas.
Subregion seasonal mean concentrations for total phosphorus ranged from .02 mg/L in summer in
Subregion 11, the Nueces-Southwestem Texas Coastal area, to the highest mean of 1.5 mg/L in the
summer in the Central Texas Coastal Subregion (10). Several quarterly means were below .1 mg/L in this
region. Maximum individual measurements in 1989 were 8.2 mg/L in the Central Texas Coastal area in
winter, 7.7 mg/L in the Galveston Bay-San Jacinto Subregion (04) in spring and 7.6 mg/L in winter in
the same subregion.
Quarterly TKN means varied from a low of .37 mg/L in summer in the Nueces-Southwestem Texas
Coastal Subregion to 1.63 mg/L in Subregion 05, the Brazos Headwaters, for subregions and seasons with
sufficient data. The highest individual samples had TKN concentrations of 17.0 mg/L in winter in the
Galveston Bay-San Jacinto Subregion, 16.0 mg/L in winter in Subregion 09, the Lower Colorado-San
Bernard Coastal Subregion, and 14.0 mg/L in summer in the Middle Brazos Subregion (06).
Organic total and total inorganic nitrogen were not reported in Region 12. For the entire Texas Gulf
Region seasonal means of total phosphorus varied from a low of .28 in spring to .76 in the fall; TKN
means ranged from .75 in the spring to 1.0 in the winter.
A27
-------
Table A-9
USGS Region 12: Texas Gulf Region
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Sabine
02
Neches
03
Trinity
04
Galveston
Bay - San Jacinto
05
Brazos
Headwaters
06
Middle
Brazos
07
Lower Brazos
08
Upper Colorado
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.109(18)
.905 (14)
*
.492 (12)
.640 (10)
*
.772 (95)
1.019 (76)
*
1.325 (149)
1.241 (81)
*
.045 (5)
.675 (4)
*
.440 (63)
.865 (57)
*
.127 (59)
.691 (54)
*
.060(2)
1.000 (2)
*
Spring
.125 (17)
.851 (14)
*
.252 (10)
1.557 (7)
*
.301 (62)
.910 (59)
*
.670 (70)
1.126 (43)
*
.063 (5)
.500 (2)
*
.183 (56)
.663 (49)
*
.082 (50)
.580 (56)
* •
.080 (1)
.600(1)
*
Summer
.066(11)
.849 (13)
*
.068 (5)
.760 (5)
*
.255 (72)
.826 (74)
*
.527(139)
1.088 (139)
*
.037 (3)
1.633 (3)
*
.434 (53)
1.112(65)
*
.064 (48)
.735 (60)
*
.145(2)
2.150 (2)
*
Fall1
.110(11)
.736(11)
*
.055 (4)
.500 (4)
*
2.231 (17)
1.118 (17)
*
.689 (49)
.829 (49)
*
.010(1)
.400(1)
*
1.334 (8)
1.150(8)
*
1.030 (3)
.700 (3)
*
.060(1)
.500 (1)
*
A28
-------
Table A-9 (continued)
Subregion
09
Lower Colorado
San Bernard
Coastal
10
Central Texas
Coastal
11
Nueces -
Southwestern
Texas Coastal
Region 12
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.426 (68)
1.264 (66)
.811 (73)
.919 (32)
.547 (28)
.414 (7)
.730 (572)
1.003(403)
Spring
.105 (99)
.509 (87)
.464 (56)
.809 (33)
.188 (27)
.714 (7)
.279 (453)
.747 (358)
Summer
.099 (22)
.557 (35)
1.491 (33)
.682 (36)
.020 (3)
.367 (6)
Fall'
.290 (25)
.711 (28)
.646 (27)
.687 (24)
.075 (2)
.750 (2)
.436 (391) .755 (148)
.911(438) .809(148)
* No samples taken
() = Number of samples
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
A29
-------
Table A10 - Region 13; The Rio Grande System
Geographically, the Rio Grande system extends from its headwaters in southern Colorado through
the heart of New Mexico and southwestern Texas. The Rio Grande Region has a few subregions
(especially the Rio Grande-Elephant Butte and Mimbres areas near its headwaters) with a large number
of samples in some seasons of 1989, while some other subregions have very few observations for some
nutrients as noted in Table 9. The quarterly means for subregions do not have as much variability in
nutrient concentrations as some other regions.
Mean total phosphorus ranged from a low of .026 mg/L in the lower Rio Grande valley in the winter
to .752 mg/L in summer in the intensively sampled Rio Grande-Elephant Butte Subregion, for those
subregions with several observations per season. The maximum individual sample in 1989 was 6.54 mg/L
in the spring in the Elephant Butte area (Subregion 02).
Mean TKN by subregion varied from .300 mg/L in the Rio Grande Headwaters Subregion in
wintertime to 1.825 mg/L in summer in Subregion 04, the Rio Grande-Armistad area, again for those
subregions and seasons with sufficient sampling. The highest single sample was again in the spring in
the Rio Grande-Elephant Butte Subregion: 28.0 mg/L.
Organic nitrogen is measured in only a few subregions. The lowest mean for a subregion and season
with sufficient sampling was .244 mg/L in winter in the Elephant Butte area; the highest such mean was
.670 in spring in the same subregion. A 13.99 mg/L reading was the maximum single measurement, in
the same Elephant Butte Subregion in spring.
Total nitrogen is reported in the Rio Grande Region, but sparsely. A fairly high mean of 2.022 mg/L
in summer was found in the Elephant Butte area. The highest reading was 28.95 mg/L in spring for total
N in the Elephant Butte Subregion.
For the entire Rio Grande system, 1989 total phosphorus means ranged from a low of .158 mg/L
in winter to a high of .557 mg/L in summer. TKN means were .672 mg/L in fall and .678 mg/L in
winter, with a seasonal high of 1.231 in spring. Organic nitrogen, for all of the subregions reporting,
ranged from .240 in winter to .630 in die spring.
A30
-------
Table A-10
USGS Region 13: Rio Grande System
Mean Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Rio Grande
Headwaters
02
Rio Grande -
Elephant Butte
03
Rio Grande -
Mimbres
04
Rio Grande -
Armistad
05
Rio Grande
Closed Basins
06
Upper
Pecos
07
Lower Pecos
08
Rio Grande -
Falcon
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.084(11)
.300 (1)
*
.210 (27)
.705 (25)
.244 (19)
1.656 (17)
.489 (9)
1.317 (6)
*
*
.147 (12)
.667 (12)
*
.025 (2)
.400(2)
*
.050 (9)
.381 (8)
.205 (2)
*
.025 (2)
.500 (2)
*
.050 (8)
.350 (2)
*
Spring
.082 (8)
.550 (2)
*
.409 (114)
1.555 (121)
.670(115)
1.993 (105)
.091 (36)
.614 (35)
.507 (34)
.812(34)
.305 (2)
.600(3)
*
*
.400 (1)
*
.069(11)
.526 (13)
.240 (1)
.460 (1)
.010 (1)
.400(1)
*
.147 (7)
.825 (4)
*
Summer
.075 (10)
.600 (1)
*
.752 (69)
1.242 (77)
.418 (57)
2.022 (57)
.155 (2)
1.000 (2)
*
*
.590 (3)
1.825 (4)
*
.030 (2)
.400(2)
*
.120 (12)
.800(10)
*
*
.010 (2)
1.150 (2)
*
*
*
*
Fall1
.107 (3)
.600(2)
*
.514 (14)
.756 (13)
.352 (4)
.560 (4)
.310(1)
.400(1)
*
*
.720 (2)
.933 (3)
*
.040(1)
.200 (1)
*
.042 (6)
.527 (6)
.280 (2)
.420 (2)
*
.200 (1)
*
*
*
*
A31
-------
Table A-10 (continued)
Subregion
Nutrient
Winter
Soring
Summer
* No samples taken
() = Number of samples
Fall1
09
Lower
Rio Grande
Region 13
TP2
TKN
OrgN
TP
TKN
OrgN
TOTN
.026 (7)
.750 (2)
*
.158 (88)
.678 (61)
.240 (21)
1.656 (17)
.132(9)
.567 (3)
*
.288 (188)
1.231 (183)
.630 (150)
1.695 (140)
.050 (1)
.700 (1)
*
.557 (101)
1.185 (99)
.418 (57)
2.022 (57)
.110(2)
.850 .(2)
*
.337 (29)
.672 (29)
.328 (6)
.513 (6)
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
A32
-------
APPENDIX B
Subregional Analysis of Ambient Concentrations
-------
-------
Appendix B: Brief Interpretation of Tables B2-B10: Ambient Concentrations
(Table B1 is included for easy reference only. It is identical to Table 6.)
Table B2 • Region 03 (Partial): The Gulf Coast River Systems of the Southeast Region
Region 03, we must remember, is the only region whose data is for approximately half of its
subregions only. Subregions 01 through 08 and part of 09 flow directly into the Atlantic, while part of
09 and all of 10 through 18 flow into the Gulf. The half of Region 03 flowing into the Gulf of Mexico
covers the geographic area from southwestern Florida through a small part of eastern Louisiana.
The quarterly ambient means presented by subregion again show a wide range of nutrient
concentrations (all data is in milligrams per liter). Mean total phosphorus ranged from .05 mg/L in the
spring in Subregion 17, the Pascagoula River system, to .89 mg/L in the winter in Subregion 12, the
Ochlockonee system, though a few very high readings may dominate the latter, as is the case in several
regions. The means generally show a very slight decrease from Table A2; organic and total nitrogen
means, where data exist, are identical. The highest individual sample readings in 1989 include 6.6 mg/L
in the summer in the Peace River system in Florida (Subregion 10), 5.6 mg/L in both the Peace River
system (FL) in winter and the Ochlockonee system (Subregion 12), also in winter, and 5.42 mg/L in the
Kissimmee-Okeechobee (Subregion 09) in winter.
Mean ambient TKN ranged from .416 mg/L in the fall in Subregion 13, the Apalachicola River
system, to 2.927 mg/L in Subregion 14, me Choctawhatchee-Escambia-Peace (Alabama) system in spring.
Maximum individual samples were an extremely high 98.8 mg/L in the summer in Subregion 15, the
Coosa-Alabama River system (the mean was still 1.45 mg/L) and 3.04 mg/L in spring in the
Choctawhatchee-Escambia-Peace (Alabama) system. Many subregions had one or more samples of TKN
of 11 mg/L or higher in the Gulf rivers of Region 03.
Organic Nitrogen is not reported in every subregion. Mean ambient Organic N ranged from .083
mg/L in spring in the Suwanee River system (Subregion 11) to 2.962 mg/L in spring in the Tombigbee
system, the latter strongly influenced by the highest individual sampling in the region in 1989 of
Bl
-------
13.6 mg/L. The second highest concentration reported was 9.85 mg/L in summer, also in the Tombigbee
system.
For Region OS's gulf coast river systems overall, quarterly means of ambient total phosphorus ranged
from .180 mg/L for the fall season to .337 mg/L in winter. Ambient TKN varied from a low of .739
mg/L in fall to 1.298 mg/L during the spring. Organic nitrogen means (with many subregions not
reporting) were lowest in fall (.780 mg/L) and highest in summer (.982 mg/L). Again, the general trend
shows a very slight decrease from Table A2, which included some nonambient samples.
B2
-------
Table B-l
USGS Region Summaries: Mean Ambient Nitrogen and Phosphorus
Concentrations by Region
1989: All data in mg/L
Subregion.
03
Southeast (Gulf
of Mexico River
Systems Only)
05
Ohio River
System
06
Tennessee
07
Upper Miss
08
Lower Miss
10
Missouri River
System
11
Arkansas -
Red - White
River System
12
Texas Gulf
Nutrient
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
Winter
.337 (766)
1.106 (630)
.808 (214)
1.062 (98)
.268 (845)
.599 (585)
*
.187 (113)
.450 (72)
.385 (33)
.396(1160)
1.758 (549)
1.033 (53)
.196(1016)
.856 (681)
*
1.630 (953)
1.929 (434)
.543 (7)
.301 (794)
1.129 (435)
.486 (20)
2.016 (124)
.730 (572)
1.003 (403)
*
Spring
.305 (713)
1.298 (704)
.888 (197)
1.311 (46)
.130(1404)
.549 (1278)
*
.084 (381)
.471 (146)
.260 (298)
.286 (2566)
1.419 (1344)
1.576 (194)
.187 (1014)
.901 (699)
*
.335 (1346)
1.341 (635)
*
.274 (964)
1.007 (499)
.464 (112)
1.031 (132)
.279 (453)
.747 (358)
*
Summer
.219 (615)
1.131 (641)
.982 (177)
*
.206 (2068)
.649 (1843)
*
.070 (569)
.421 (136)
.228 (488)
.350 (3074)
1.587 (1408)
1.418 (234)
.186 (1021)
.828 (669)
*
1.641 (1569)
4.853 (856)
*
.429 (1153)
1.296 (619)
1.342 (89)
1.434 (176)
.436 (391)
.911 (438)
*
Fall'
.180 (427)
.739 (371)
.780(112)
*
.309 (916)
.697 (670)
*
.172 (85)
.282 (94)
.380 (12)
.394 (1012)
1.104 (591)
.638 (46)
.179 (714)
.711 (606)
*
.418 (562)
1.526 (201)
*
.526 (423)
1.433 (248)
.496 (32)
1.597 (49)
.755 (148)
.809 (148)
*
B3
-------
Table B-l (continued)
Subregion
Nutrient
Winter
Soring
Summer
* No samples taken
() = Number of samples
Fall1
13
Rio Grande
System
TP2
TKN
OrgN
TOTN
.154 (86)
.580 (59)
.155 (19)
.637 (15)
.126(180)
.553 (175)
.294 (142)
.687 (132)
.259 (92)
.783 (90)
.305 (48)
.644 (48)
.337 (29)
.672 (29)
.328 (6)
.513 (6)
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
B4
-------
Table B-2
Partial USGS Region 03: Southeast Gulf Coast River Systems
Mean Ambient Nitrogen and Phosphorus
Concentrations by Subregion
1989: All data in mg/L
Subregion
09 Partial
Caloosahatchee
L. Okeechobee
10
Peace (FL) -
Tampa Bay
11
Suwanee
12
Ochlockonee
13
Apalachicola
14
Choctawhatchee
- Escambia
15
Coosa - Alabama
16
Tombigbee -
Mobile Bay
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.227 (90)
1.171 (96)
.946 (64)
.371 (168)
1.055 (164)
.842 (103)
1.062 (98)
.667 (61)
.555 (26)
.446 (7)
.897 (27)
2.877 (7)
.651 (19)
.275 (185)
.816 (29)
.193 (11)
.505 (68)
1.454 (98)
.812 (10)
.178 (96)
1.104 (49)
*
.133 (26)
.786 (106)
*
Spring
.298 (105)
1.230 (106)
1.102 (60)
.549 (118)
1.101 (120)
.944 (50)
1.311 (46)
.351 (57)
.787(34)
.083 (7)
.599 (17)
1.886 (5)
.782 (19)
.191 (190)
.700 (47)
.440 (11)
.542 (73)
2.927 (110)
.650 (13)
.106 (93)
.746 (80)
.317 (29)
.098 (22)
1.056 (159)
2.962 (8)
Summer
.251 (96)
1.530 (93)
1.153 (61)
.664 (43)
1.388 (42)
2.474 (7)
*
.494 (32)
.745 (20)
.431 (7)
.352 (22)
.661 (8)
.572 (16)
.148 (198)
.602 (48)
.356 (10)
.252 (42)
1.015 (70)
.693 (20)
.107 (89)
1.450(110)
.295 (37)
.074 (25)
1.034 (170)
2.401 (19)
Fall1
.086(67)
1.153 (66)
1.006 (57)
.342 (39)
.909 (39)
2.864 (5)
*
.594 (29)
.577 (7)
.255 (4)
.438 (12)
.607 (3)
.338 (20)
.142 (117)
.416 (23)
.145 (1.1)
.060 (52)
.583 (60)
.544(11)
.087 (51)
.422 (52)
.087 (4)
.085 (22)
.550 (79)
*
B5
-------
Table B-2 (continued)
Subregion
Nutrient
Soring
Summer
* No samples taken
() = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
Fall1
17
Pascagoula
18
Pearl
Region 03
(Partial)
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
.065 (16)
1.713 (24)
*
.111 (29)
1.044 (31)
*
.337 (766)
1.106 (630)
.808 (214)
1.062 (98)
.054 (10)
.613 (15)
*
.096 (27)
.814 (27)
*
.305 (713)
1.298 (704)
.888 (197)
1.311 (46)
.107 (35)
.768 (39)
*
.099 (31)
.892 (31)
*
.219 (615)
1.131 (641)
.982 (177)
*
.739 (8)
2.060 (12)
*
.113(28)
.730 (28)
*
.180 (427)
.739 (371)
.780(112)
*
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
B6
-------
Table B3 - Region OS: The Ohio River System*
Again we should point out that the Tennessee River system, which joins the Ohio shortly before it
flows into the Mississippi, has been given its own separate region (06) by the USGS. For the rest of the
Ohio system, Region 05, quarterly mean concentrations for ambient total phosphorus in the subregions
varied from a low of .032 mg/L in the fall in the Kentucky-Licking rivers area (several other subregions
again also had seasonal means below .1 mg/L) to 1.147 mg/L, also in the fall, in the Middle Ohio
Subregion (09). The maximum individual samples were 35.7 mg/L in the fall in the Middle Ohio area,
16.0 mg/L in the fall in Subregion 06, the Scioto River area, and 15.36 mg/L in winter in the Wabash
River Subregion (12).
Mean ambient TKN in Region 05 in 1989 ranged on a seasonal basis from a low of .16 mg/L in the
springtime in the Monongahela area (Subregion 02), to 1.55 mg/L in the winter in Subregion 12 (Wabash).
Maximum single readings of TKN were 37.0 mg/L in spring, 34.0 mg/L in the fall, and 20.0 mg/L in
summer in Subregions 05 (Kanawha River), 12 (Wabash), and 09 (Middle Ohio), respectively.
Organic nitrogen was not measured in Region 05 in 1989.
For the region as a whole, mean ambient total phosphorus in the Ohio Region varied from a low of
.130 mg/L in spring to .309 mg/L in the fall. TKN was steady overall, though not in all subregions: it
ranged from .549 mg/L in the spring to a high of .697 mg/L in the fall.
Excluding the Tennessee tributary system (Region 06).
B7
-------
Table B-3
USGS Region
Subregion
01
Allegheny
02
Monongahela
03
Upper Ohio
04
Muskingum
05
Kanawha
06
Scioto
07
Big Sandy -
Guyandotte
08
Great Miami
05: Ohio River System
Mean Ambient Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.045 (73)
.217 (3)
*
.075 (64)
.240 (26)
*
.152 (97)
.585 (49)
*
.182 (36)
.644 (48)
*
.098 (71)
.349 (79)
*
.205 (45)
1.033 (36)
*
.082 (51)
.258(75).
*
.128 (21)
.797 (29)
*
Spring
.066 (74)
.242 (4)
*
.093(61)
.160 (24)
*
.133 (95)
.463 (59)
*
.088 (129)
.397 (164)
*
.093 (108)
.558 (159)
*
.148 (85)
.689 (74)
*
.055 (74)
.207(111)
*
.220 (66)
.835 (105)
*
Summer
.060 (79)
.330 (3)
*
.076 (69)
.371 (27)
*
.128 (120)
.491 (78)
*
.273 (367)
.679 (372)
*
.107 (156)
.377 (174)
*
.402(112)
.585 (127)
*
.059 (105)
.255 (124)
*
.300 (221)
.656 (233)
*
Fall1
.052 (79)
.330 (3)
*
.113 (60)
.301 (18)
*
.136(110)
.453 (64)
*
.169 (60)
.429 (68)
*
.087 (109)
.442(119)
*
1.102 (84)
.901 (104)
*
.042 (33)
.217 (58)
*
.313 (17)
.537 (16)
*
B8
-------
Table B-3 (continued)
Subregion
09
Middle Ohio
10
Kentucky -
Licking
11
Green
12
Wabash
13
Cumberland
14
Lower Ohio
Region 05
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.162(23)
.468 (36)
*
.193 (43)
.495 (44)
*
.064 (25)
.436 (26)
.682 (197)
1.550 (52)
*
.059 (23)
.228 (19)
*
.324 (76)
.664 (63)
*
.268 (845)
.599 (585)
Soring
.088 (91)
.332 (106)
*
.121 (73)
.407 (87).
*
.085 (34)
.451 (53)
*
.189 (298)
1.032 (144)
*
.132 (37)
.584 (30)
*
.144 (179)
.593 (158)
*
.130 (1404)
.549 (1278)
Summer
.173(119)
.678 (160)
*
.154 (66)
.424 (78)
*
.042 (46)
.379 (51)
.232 (400)
1.098 (239)
*
.071 (39)
.353 (33)
.224 (169)
.932 (144)
.206 (2068)
.649 (1843)
*
Fall1
1.147 (40)
.557 (53)
*
.032 (13)
.582 (15)
*
*
*
.305 (259)
1.448(118)
.144(8)
.441 (5)
.264 (44)
.820 (29)
*
.309 (916)
.697 (670)
*
* No samples taken
( ) = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogei
OrgN - Organic Nitrogen
Fall October 1 - December 31
B9
-------
Table B4 - Region 06: Tennessee River System
Flowing into the Ohio and thence to the Mississippi, the Tennessee River and its tributaries comprise
one of the smaller USGS hydrologic Regions. The Tennessee River system was one of the less polluted
areas in 1989, in terms of nitrogen and phosphorus, when samples are limited strictly to ambient
observations, as before in Appendix A which included some nonambient data.
Mean ambient total phosphorus concentrations presented quarterly for the four subregions ranged
from .05 mg/L in the summer in the Middle Tennessee-Elk Subrcgion (03), with several seasonal means
below .1 mg/L, to .47 mg/L in the winter in the Lower Tennessee Subregion (04). The highest individual
1989 measurements of TP (total phosphorus) were 2.4 mg/L in the Middle Tennessee-Hiwassee area
(Subregion 02), in the spring season, and 2.34 mg/L in the Lower Tennessee area in winter.
Quarterly ambient TKN means varied from a low of. 16 mg/L in the spring in the Middle Tennessee-
Hiwassee Subregion, to 1.76 mg/L in the Middle Tennessee-Elk Subregion, also in the spring. The
maximum sample readings were 4.0 mg/L and 3.9 mg/L in spring and winter, respectively, in the Middle
Tennessee-Elk area.
Seasonal ambient mean organic nitrogen, reported in most subregions and seasons, ranged from .19
mg/L in the Middle Tennessee-Hiwassee area in summer (for data with sufficient observations), to .54
mg/L in fall in the Middle Tennessee-Elk subsystem. The highest individual concentration was 4.0 mg/L
in the Middle Tennessee-Elk area in the spring.
For the entire Tennessee Valley, ambient total phosphorus varied from a low of .07 mg/L in summer
to a high of .19 mg/L in winter, TKN from .28 mg/L in fall to .47 mg/L in spring; and Organic Nitrogen
from .23 mg/L in summer to .385 mg/L in winter.
BIO
-------
Table B-4
USGS Region 06: Tennessee River System
Mean Ambient Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Upper Tennessee
02
Middle Tennessee
- Hiwassee
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
03 TP
Middle Tennessee TKN
- Elk OrgN
04
Lower
Tennessee
Region 06
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.110(69)
.322 (57)
.396(23)
.314 (29)
.465 (6)
.310 (4)
.097 (7)
1.717 (6)
.438 (4)
.468 (8)
.320 (3)
.310 (2)
.187(113)
.450 (72)
.385 (33)
Spring
.082 (82)
.347 (106)
*
.072 (209)
.164 (20)
.198(196)
.089 (73)
1.762 (14)
.380 (102)
.219(17)
.668 (6)
*
.084 (381)
.471 (146)
.260 (298)
Summer Fall1
.086 (97) .100(47)
.315 (110) .278 (85)
.292 (15) .307 (7)
.066 (223) .182 (21)
.500 (1) *
.190(209) .095 (2)
.051 (232) .172 (12)
1.007 (19) .320 (6)
.255 (262) .537 (10)
.292 (17) .336 (13)
.486 (6) .343 (3)
.180 (2) .420 (1)
.070 (569) .172 (85)
.421 (136) .282 (94)
.228 (488) .380 (12)
* No samples taken
( ) = Number of samples
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
2 Tp
TKN
OrgN
= Total Phosphorus
= Total Kjeldahl Nitrogen
= Organic Nitrogen
Bll
-------
Table BS - Region 07: Upper Mississippi River System
Again, the Upper Mississippi system includes the upper reaches of the mighty river which eventually
drains nearly two-thirds of the surface water in the 48 contiguous states, and all of its tributaries in
Minnesota, Wisconsin, Iowa, northern Missouri and Illinois which join it upstream of the Missouri River
(Region 10) on the western bank and the Ohio River (Region 05) on the eastern bank.
Ambient nutrient concentrations are also highly variable in the Upper Mississippi Region, still
without a consistent trend either seasonally or from upstream to downstream. Mean ambient total
phosphorus in each subregion ranged in 1989 from .05 mg/L in winter in the St. Croix River Subregion
(03) and in the fall in the Wisconsin Subregion (07) to a high of .95 mg/L in the winter in the Chippewa
area (Subregion 05). The highest individual phosphorus sample was 29.8 mg/L in the Minnesota River
system (Subregion 02), in the summer, with several samples at or above 10 mg/L in various subregions.
Mean ambient TKN among the subregions ranged from .57 mg/L in the fall season in the Upper
Mississippi-Black-Root system (Subregion 04) to 3.69 mg/L in winter in the Iowa-Skunk-Wapsipinicon
area (Subregion 08). There was a slight trend of increasing concentrations from upstream to downstream
in some seasons. Maximum concentrations were found at 28 mg/L in the spring in the Upper Mississippi-
Blackroot area (04) and the Minnesota system in summer, 27 mg/L in the fall in the Lower Illinois River
(13), and 25 mg/L in summer in the Kaskaskia-Meramec area (14).
The means for organic nitrogen, reported in fewer than half of the subregions, varied from a low of
.4 mg/L in the St. Croix River area in winter to 3.77 mg/L in the Des Moines River subsystem (Subregion
10) in spring. The highest individual ambient concentrations were 27.3 mg/L in summer in the Minnesota
River area, 26.5 mg/L in the spring in Subregion 04, the Upper Mississippi-Black-Root, and 24.0 mg/L
in spring in the DCS, Moines River Subregion (10).
For Region 07 overall the mean ambient total phosphorus was fairly steady, ranging from .286 mg/L
in spring to .396 mg/L in winter. Mean TKN varied only from 1.1 mg/L in the fall to 1.76 mg/L in
winter. Seasonal means for ambient organic nitrogen (for those subregions reporting) ranged from a low
of .64 mg/L in the fall to 1.58 mg/L in the spring.
B12
-------
Table B-5
USGS Region 07: Upper Mississippi River System
Mean Ambient Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Mississippi
Headwaters
02
Minnesota R.
03
St. Croix R.
04
Upper Miss.-
Black-Root
05
Chippewa
06
Upper Mississippi
-Maquaketa-
Plum-Escambia
07
Wisconsin R.
08
Upper
Mississippi-Iowa-
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.318 (103)
2.196 (74)
.946 (15)
.299 (70)
2.316 (26)
1.396 (20)
.051 (73)
.895(11)
.397 (3)
.367 (34)
1.191 (34)
.653 (12)
.950 (85)
.778 (46)
*
.410 (21)
1.860 (15)
*
.190 (63)
1.353 (32)
*
.785 (55)
3.692 (26)
1.193 (3)
Spring
.210 (343)
.929 (132)
.964 (50)
.185 (155)
1.819 (74)
1.244 (51)
.152 (169)
1.526 (104)
.888 (12)
.714 (146)
2.611 (146)
2.195 (43)
.617 (196)
.768 (130)
*
.222 (30)
.844 (16)
*
.234(118)
1.029 (58)
*
.366 (94)
1.896(34)
1.602 (25)
Summer
.347 (422)
1.248 (182)
.947 (49)
.524 (176)
2.617 (100)
2.078 (51)
.306 (151)
2.116 (69)
.745 (11)
.321 (131)
1.381 (129)
.823 (44)
.647 (207)
1.033 (93)
*
.703 (36)
2.583 (30)
*
.488 (153)
1.307 (41)
*
.464 (157)
1.508 (51)
1.402 (61)
Fall1
.215 (49)
1.168 (19)
.615 (13)
.813 (23)
1.352 (13)
.852 (13)
.083 (36)
1.011 (26)
.483 (3)
.180 (56)
.570 (54)
.512 (13)
.072 (65).
.679 (32)
*
.184 (24)
.733 (18)
*
.050 (43)
.770 (46)
*
.623 (57)
1.189 (28)
.550 (4)
Skunk-
Wapsipinicon
B13
-------
Table B-5 (continued)
Subregion
09
RockR.
10
DesMoines R.
11
Upper Miss.
-Salt
12
Upper Illinois
13
Lower Illinois
14
Upper Miss.-
Kaskaskia-
Meramec
Region 07
Nutrient Winter
TP2 .349 (162)
TKN 3.053 (32)
OrgN *
TP .725 (13)
TKN 1.750 (14)
OrgN *
TP .129 (14)
TKN 1.180 (5)
OrgN *
TP .424 (195)
TKN 1.939 (128)
OrgN *
TP .419 (136)
TKN 1.200 (35)
OrgN *
TP .280 (136)
TKN .996 (71)
OrgN *
TP .396(1160)
TKN 1.758 (549)
OrgN 1.033 (53)
Spring Summer Fall1
.134 (227) .223 (427) .280 (90)
1.213 (62) 2.481 (21) 1.433 (21)
* * *
.599(36) .538(51) .898(12)
1.454 (13) 1.848 (14) 1.500 (12)
3.769 (13) 2.744 (18) *
.451 (25) .177 (18) 136 (9)
1.088 (8) .925 (8) .900(1)
* * *
.298 (381) .238 (492) .576 (183)
1.545 (231) 1.461 (279) 1.397 (143)
* * *
.230 (322) .324 (294) .542 (182)
1.318 (128) 1.561 (140) 1.436 (61)
* * *
.195 (324) .292 (359) .375 (183)
1.171(208) 1.614(251) .987(117)
* * *
,
.286 (2566) .350 (3074) .394 (1012)
1.419 (1344) 1.587 (1408) 1.104 (591)
1.576 (194) 1.418 (234) .638 (46)
* No samples taken
() - Number of samples
1 Winter runoff: January 1 - March 31
Spring .April 1 -June 30
Summer July 1 - September 30
Fall October 1 - December 31
B14
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
-------
Table B6 - Region 08: Lower Mississippi River System Excluding
the Arkansas-White-Red System
Remembering that Region 08, the Mississippi and its tributaries below the Missouri and Ohio
systems, excludes the Aricansas-White-Red (Region 11), ambient concentrations again show few individual
samples with high phosphorus or nitrogen, and the mean concentrations are perhaps lower than some
might expect from the river draining our nation's entire heartland.
Seasonal ambient mean concentrations for the nine subregions for total phosphorus ranged from .07
mg/L in the spring season in the Lower Mississippi-Big Black-Escambia Subregion (06) to a high of only
.446 mg/L in the fall in the Lower Mississippi-St. Francis area (Subregion 02). The highest individual
sample in 1989 had a 6.3 mg/L concentration of phosphorus, in the fall in the Lower Red-Ouachita
Subregion (04).
Ambient TKN subregion means varied from a low of .44 mg/L in the summer in Subregions 03
(Lower Miss-Yazoo) and 06 (Lower Miss-Big Black) to a high of 1.46 mg/L in Subregion 08 in the
spring, for subregions and seasons with at least three observations. The maximum single ambient samples
had concentrations of 11.26 mg/L TKN in the Louisiana Coastal area (Subregion 08) in the summer, and
10.8 mg/L in the fall in the Lower Red-Ouachita Subregion (04).
Organic nitrogen was not measured in Region 08 in 1989.
For Region 08 as a whole, mean ambient total phosphorus was seasonally steady, varying only from
a low of .179 in the fall to .196 in the 'winter. TKN ranged only from .711 in the fall to .9 in the spring.
These and the subregion means are generally lower than those for the measurements taken upstream,
particularly from the Missouri River system (Region 10) and the Arkansas-White-Red rivers system
(Region 11), and even somewhat lower in general than those for the Upper Mississippi Region. Several
possible interpretations are suggested in Appendix A, with a combination of processes most likely.
B15
-------
Table B-6
USGS Region 08: Lower
White-]
Mean i
by Sub
Subregion
01
Lower Mississippi
R. - Hatchie
02
Lower Miss.-
St. Francis
03
Lower Miss.-
Yazoo
04
Lower Red -
Ouachita
05
Boeuf-
Tensas
06
Lower Miss.-
Big Black
- Escambia
07
Lower Miss.-
Lake Maurepas
08
Louisiana
Coastal
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Mississippi F
*ed (Region
Ambient Nitre
region
1989: All da
Winter
.161 (23)
1.100 (1)
.188 (87)
.815 (13)
.262 (243)
.483 (138)
*
.089 (294)
.526 (199)
*
.286 (94)
1.373 (91)
.193 (7)
1.257 (7)
.198 (66)
1.005 (58)
.274 (103)
1.303 (89)
B16
Liver System Excluding Arkansas-
ID
)gen and Phosphorus Concentrations
ta in mg/L
Spring
.114(43)
.684 (13)
.259 (60)
.797 (21)
.190 (292)
.507 (125)
*
.097 (279)
.621 (226)
*
.330 (86)
1.320 (85)
*
.073(6)
.517 (6)
*
.218 (56)
1.127 (49)
.277 (103)
1.460 (91)
*
Summer
.143 (33)
.892 (18)
*
.398 (100)
.872 (17)
*
.181 (209)
.440 (107)
.132 (325)
.726 (204)
*
.205 (91)
1.131 (91)
.110(4)
.44-3 (3)
*
.184 (65)
.945 (57)
*
.178 (97)
1.009 (89)
*
Fall1
.105 (14)
.500 (1)
.446 (43)
.713(11)
* *
.192 (82)
.513 (82)
*
.131 (229)
.569 (197)
.159 (92)
1.014 (91)
6.340 (1)
*
.176 (64)
.640 (52)
.174 (101)
.721 (90)
-------
Table B-6 (continued)
Subregion
09
Lower
Mississippi R.
Region 8
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
Winter
.199 (99)
1.081 (83)
*
.196 (1016)
.856 (681)
*
Soring
.193 (89)
1.172(83)
.187 (1014)
.901 (699)
*
Summer
.174 (97)
.963 (83)
*
.186 (1021)
.828 (669)
*
Fall1
.198 (89)
.883 (81)
*
.179 (714)
.711 (606)
*
* No samples taken
() = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
B17
-------
Table B7 - Region 10: The Missouri River System
The thirty subrcgions of the Missouri system have some of the highest individual ambient sample
concentrations in the study, and some of the higher subregion means. Its upper reaches are frozen and
therefore not sampled in the winter and fall seasons. Though it is the largest geographic USGS Region,
the smaller flow of water from the Missouri system than the Ohio means that less impact is actually felt
in the Gulf of Mexico.
The lowest ambient subregion mean concentration in Region 10 for total phosphorus in 1989 was
.024 mg/L in Subregion 06, the Missouri-Poplar area, in the fall, for those subregions and seasons with
sufficient observations. The highest means were 18.12 mg/L and 11.16 mg/L in the summer and winter,
respectively, in the Cheyenne River subsystem (Subregion 12). Both of these high means were dominated
by extremely high individual samples with 830.0 mg/L summer and 1102.0 mg/L winter concentrations,
the maximum observations for the region. The next highest single sample was 30.9 mg/L in summer in
the Missouri-White Subregion (14).
Seasonal ambient means for TKN in Region 10 ranged from a low of .30 mg/L in the fall in the
Missouri-Nishnabotna Subregion (24) to 153.76 mg/L in the Cheyenne Subregion in summer, the latter
again dominated by a single sample measurement, of 1300.0 mg/L, the maximum for the region. The next
highest individual sample concentrations were 39.0 mg/L in the summer and 32.0 mg/L in the fall, both
in the South Platte Subregion (19). Means quoted are for subregions and seasons with sufficient
observations.
Organic nitrogen was measured in only one subregion of the thirty, and in only one season.
For the entire Missouri Region as a whole, the seasonal ambient mean total phosphorus varied from
.335 mg/L in the spring to a high of 1.641 mg/L in summer, TKN seasonal means ranged from 1.341
mg/L in the spring to 4.853 mg/L in the summer.
B18
-------
Table B-7
USGS Region 10: Missouri River System
Mean Ambient Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Saskatchewan
02
Missouri
Headwaters
03
Missouri -
Marias
04
Missouri -
Musselshell
05
Milk
06
Missouri-
Poplar-
Escambia
07
Upper
Yellowstone
08
Big Horn
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
*
*
*
*
*
*
.030 (3)
.367 (3)
*
.040(5)
.520 (5)
*
.698 (5)
2.640 (5)
*
.079 (8)
1.225 (8)
*
.035 (2)
.400 (2)
*
.112 (22)
.589(19)
*
Soring
.020 (1)
.300 (1)
*
.097 (4)
*
*
.036 (12)
.420 (10)
*
.046 (9)
.432 (8)
*
.075 (4)
.700 (4)
*
.057(11)
.736(11)
*
.063 (6)
.550 (2)
*
.097 (48)
2.413 (23)
*
Summer
.020 (1)
.200 (1)
*
.135 (2)
*
*
.052 (8)
.367 (6)
*
.037 (10)
.472 (9)
*
.053 (3)
.833 (3)
*
.051 (12)
.873 (15)
*
.028 (5)
.450 (2)
*
.057 (39)
.695 (22)
*
Fall1
*
*
*
*
*
*
.030(3)
.300 (2)
*
.040(4)
.360 (5)
*
.033 (6)
.600(4)
*
.024 (8)
.700 (8)
*
.030 (2)
1.900 (1)
*
.075 (15)
.350 (6)
*
B19
-------
Table B-7 (continued)
Subregion
09
Powder -
Tongue
10
Lower
Yellowstone
11
Missouri -
Little Missouri
12
Cheyenne
13
Missouri -
Oahe
14
Missouri -
White
15
Niobrara
16
James
17
Missouri -
Big Sioux
18
North Platte
Nutrient .
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.084 (28)
.500(11)
*
.893 (3)
1.533 (3)
*
.510(1)
2.600 (1)
*
11.159 (102)
1.155 (11)
.254 (62)
1.993 (26)
*
.458 (20)
.625 (4)
*
.168 (34)
1.167 (3)
*
.543 (41)
2.798 (30)
*
.798 (41)
1.133 (3)
4i
.160 (37)
1.066 (15)
Spring
.179(69)
.557 (23)
*
.038 (4)
1.050 (2)
*
.454 (6)
1.318 (5)
.195 (138)
.647 (42)
.243 (87)
1.624 (30)
» .945 (30)
.899 (7)
*
.145(47)
1.237 (18)
*
.369 (75)
1.798 (44)
*
.380 (48)
.718 (9)
*
.122 (72)
1.484 (37)
*
Summer
.654 (31)
.514 (7)
*
.046 (5)
.720 (5)
*
.079(7)
.850 (2)
18.120 (100)
153.760 (17)
*
.169 (109)
2.097 (23)
*
3.201 (25)
1.484 (8)
.351 (119)
1.201 (90)
*
.820 (155)
2.878 (136)
*
.584 (51)
1.149 (8)
*
.235 (70)
1.269 (45)
*
Fall1
.859 (19)
.860 (10)
.037(3)
.425 (4)
*
.036 (6)
.600(3)
.222 (87)
.555 (5)
.084 (26)
.725 (8)
*
.316 (14)
.540 (2)
*
.138 (22)
2.286 (12)
*
.664 (19)
1.750 (3)
*
.923 (38)
.815 (4)
*
.167 (22)
2.779 (15)
B20
-------
Table B-7 (continued)
Subreeion
19
South Platte
20
Platte
21
Loup
22
Elkhorn
23
Missouri -
Little Sioux
24
Missouri -
Nishnabotna
25
Republican
26
Smoky Hill
27
Kansas
28
Chariton -
Grand
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
1.133 (87)
5.162 (55)
*
.692 (25)
2.216 (19)
*
.240 (41)
1.056 (8)
*
.426 (17)
1.334 (14)
ik
.498 (26)
1.354 (19)
.543 (7)
.215 (30)
1.220(11)
*
.159 (26)
.853 (3)
*
.373 (39)
.625 (4)
*
.536 (197)
1.523 (133)
*
.144(7)
.829 (7)
*
Soring
.591 (126)
1.514 (75)
*
.723 (33)
2.035 (32)
*
.256 (43)
.895 (11)
*
.353 (18)
1.269 (18)
*
.540 (24)
1.574 (24)
*
.310 (43)
2.096 (13)
*
.298 (35)
1.110 (9)
*
.360 (61)
1.167 (6)
*
.408 (190)
1.383 (125)
*
.177 (24)
1.241 (19)
*
Summer
.293 (181)
1.734 (127)
*
.618 (24)
1.987 (22)
*
.395 (44)
2:032 (13)
*
.744 (19)
2.621 (18)
*
1.487 (26)
2.036 (26)
*
.277 (72)
1.340 (9)
* •
.689 (49)
1.261 (25)
*
1.119(80)
1.270 (15)
*
.553 (175)
1.505 (88)
*
.393(35)
1.039 (36)
*
Fall1
.620(111)
2.162 (67)
*
.427(11)
1.799(11)
*
.182(4)
.397 (3)
*
.197 (3)
1.303 (3)
*
.688 (8)
1.600 (7)
*
.186 (16)
.300 (4)
*
.211 (11)
1.040 (1)
*
.231 (24)
*
*
.449 (45)
.867 (9)
*
.100 (3)
.600 (3)
*
B21
-------
Table B-7 (continued)
Subregion
29
Gasconade -
Osagc
30
Lower
Missouri
Region 10
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.091 (27)
.489 (9)
*
1.814 (17)
.567 (3)
*
1.630 (953)
1.929 (434)
.543 (7)
Soring
.107 (52)
.674 (16)
*
1.093 (26)
.800(11)
*
.335 (1346)
1.341 (635)
*
Summer
.149 (94)
3.335 (72)
*
.976 (18)
.663 (6)
*
1.641 (1569)
4.853 (856)
id
Fall1
.288 (18)
.200 (1)
*
1.387 (14)
*
*
.418 (562)
1.526 (201)
*
* No samples taken
() ~ Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
B22
-------
Table B8 - Region 11; The Arkansas-White-Red System
When only ambient nutrient samples are included, the Arkansas-White-Red River Region still
appears to be one of the regions with higher nutrient concentrations, with some individual samples
measuring very high.
Total ambient phosphorus seasonal means for Region 11 's subregions ranged from a low of .03 mg/L
in the Upper Cimarron Subregion (04) in the winter, to a high of 1.622 mg/L in the Lower Canadian area,
Subregion 09, in the fall. The highest individual measurement of TP in 1989 was 12.4 mg/L in the
summertime in Subregion 11, the Lower Arkansas area.
Seasonal means of ambient TKN varied from a low of .374 mg/L in the Lower Canadian Subregion
in the spring, to reports of 3.974 mg/L in winter in Subregion 02, the Upper Arkansas, for subregions with
a Sufficient number of samples per season. The maximum single observation of TKN in 1989 was 31.0
mg/L in summer in the Upper Arkansas area, with many individual samples having concentrations over
10 mg/L.
Organic nitrogen was measured in four subregions in Region 11. The lowest mean ambient
subregion organic N was .065 mg/L in spring for the Lower Canadian Subregion (09). The highest
subregion mean was 1.755 mg/L in Subregion 08 (Upper Canadian). Many samples were quite high in
organic nitrogen as well as TKN; the maximum individual organic N reading was 26.28 mg/L in summer
in the Upper Canadian area.
For the entire Region 11, mean ambient total phosphorus concentrations for 1989 ranged from a low
of .274 in spring to .526 in the fall; TKN varied from 1.007 in spring to 1.433 in the fall; and organic
nitrogen ranged from a low of .464 in spring to 1.342 in summer.
Subregion 11 (Lower Arkansas) had the highest individual total nitrogen concentrations in all four
seasons, with a maximum of 21.68 in the summer.
B23
-------
Table B-8
USGS Region 11: Arkansas-White-Red System
Mean Ambient Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Upper White
02
Upper
Arkansas
03
Middle
Arkansas
04
Upper
Cimarron
05
Lower
Cimarron
06
Arkansas -
Keystone
07
Neosho -
Verdigris
08
Upper
Canadian
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
Winter
.117 (154)
1.057 (60)
*
1.081 (14)
3.974(35)
*
.624 (60)
1.500 (1)
*
.026 (5)
.533 (6)
*
.367 (7)
1.286 (8)
*
1.898 (5)
.160 (5)
.846 (5)
*
1.147 (3)
.588 (100)
.683 (34)
.360 (1)
.980 (10)
.015 (2)
.300 (2)
*
*
Spring
.153(181)
.714 (72)
*
.429 (27)
1.676 (41)
*
.708 (68)
.900 (1)
*
.058 (10)
.500 (6)
*
.187 (3)
.867 (3)
*
*
.105 (2)
1.000 (2)
*
*
.412 (123)
.687 (12)
.515 (2)
*
.126 (90)
.684 (77)
.441 (91)
.682 (91)
Summer
.296 (135)
.742 (65)
*
.342 (28)
1.868 (73)
*
.306 (107)
2.600 (1)
*
.044 (16)
.500 (2)
*
.700 (5)
.560 (7)
*
.902 (5)
.347 (7)
.787 (4)
*
.920 (3)
.568 (148)
.702 (21)
.470 (3)
.530 (9)
.408(42)
1.789 (42)
1.755 (38)
2.022 (38)
Fall1
.773 (43)
.941 (31)
*
.082 (5)
4.155 (33)
*
.409 (41)
*
" *
.070 (2)
.400(2)
*
*
*
*
*
*
*
*
*
.534 (60)
.893 (7)
.395 (2)
*
.010 (1)
.400(1)
*
*
B24
-------
Table B-8 (continued)
Subregion
09
Lower
Canadian
10
North
Canadian
11
Lower
Arkansas
12
Red Headwaters
13
Red-Washita
14
Red-Sulphur
Region 11
Nutrient
TP2
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
Winter
.599 (13)
1.435 (11)
*
2.698 (5)
.450(14)
1.093 (12)
*
2.357 (7)
.265 (236)
.800 (156)
.493 (19)
2.091 (84)
.133 (8)
.635 (6)
*
3.010 (1)
.450 (19)
1.459 (14)
*
2.526 (5)
.126 (157)
.793 (85)
*
1.488 (4)
TP .301 (794)
TKN 1.129 (435)
OrgN .486 (20)
TOTN 2.016(124)
Spring Summer Fall1
.204 (6) 1.622 (48) .197 (13)
.374 (7) 3.240 (46) .821 (14)
.065 (4) 1.302 (34) .619 (12)
1.080 (4) .992 (12) .851 (12)
.116(37) .198(40) .120(1)
1.344 (28) 1.048 (24) .400 (1)
* * *
* .929 (7) *
.361 (224) .560 (315) .776 (146)
1.112(127) 1.093(180) 1.276(91)
.705 (15) .507 (14) .451 (17)
1.886 (37) 1.438 (90) 1.839 (37)
.114(5) .192(6) .020(1)
1.020(5) .826(8) .500(1)
* * *
* .700(1) *
.083 (3) .231 (13) .377 (3)
.733 (3) .882 (13) .650 (2)
* ' * *
* 1.677 (6) *
.139 (185) .157 (243) .213 (107)
1.081 (115) .964(133) .800 (65)
* * *
* 1.000 (5) *
.274(964) .429(1153) .526(423)
1.007(499) 1.296 (619) 1.433(248)
.464(112) 1.342 (89) .496 (32)
1.031 (132) 1.434 (176) 1.597 (49)
* No samples taken
( ) = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
2 TP SB Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
B25
-------
Table B9 - Region 12: The Texas Gulf Region
Again, the Texas Gulf Region consists of several individual river systems flowing into the Gulf of
Mexico, from the Sabine River on the Texas-Louisiana state line westward to the Nueces ndar the southern
tip of Texas. Though all quarterly means are identical to those in Table A9, we present them again for
continuity.
Subregion seasonal mean concentrations for ambient total phosphorus ranged from .02 mg/L in
summer in Subregion 11, the Nueces-Southwestem Texas Coastal area, to the highest mean of 1.5 mg/L
in the summer in the Central Texas Coastal Subregion (10), for subregions and seasons with three or more
observations. Several quarterly means were below .1 mg/L in this region. Maximum individual
measurements in 1989 were 8.2 mg/L in the Central Texas Coastal area in winter, 7.7 mg/L in the
Galveston Bay-San Jacinto Subregion (04) in spring and 7.6 mg/L in winter in the same Subregion.
Quarterly ambient TKN means varied from a low of .37 mg/L in summer in the Nueces-
Southwestem Texas Coastal Subregion to 1.63 mg/L in Subregion 05, the Brazos Headwaters, for
subregions and seasons with sufficient data. The highest individual samples had TKN concentrations of
17.0 mg/L in winter in the Galveston Bay-San Jacinto Subregion, 16.0 mg/L in winter in Subregion 09,
the Lower Colorado-San Bernard Coastal Subregion, and 14.0 mg/L in summer in the Middle Brazos
Subregion (06).
Organic nitrogen was not reported in Region 12. For the entire Texas Gulf Region seasonal means
of ambient total phosphorus varied from a low of .28 in spring to .76 in the fall; TKN means ranged from
.75 in the spring to 1.0 in the winter.
B26
-------
Table B-9
USGS Region 12: Texas Gulf Region
Mean Ambient Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Sabine
02
Neches
03
Trinity
04
Galveston
Bay - San Jacinto
05
Brazos
Headwaters
06
Middle
Brazos
07
Lower Brazos
08
Upper Colorado
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.109 (18)
.905 (14)
*
.492(12)
.640 (10)
*
.772 (95)
1.019 (76)
*
1.325 (149)
1.241 (81)
*
.045 (5)
.675 (4)
*
.440 (63)
.865 (57)
*
.127 (59)
.691 (54)
*
.060(2)
l.OOQ (2)
*
Spring
.125 (17)
.851 (14)
*
.252 (10)
1.557 (7)
*
.301 (62)
.910 (59)
*
.670 (70)
1.126(43)
*
.063 (5)
.500 (2)
*
.183 (56)
.663 (49)
*
.082 (50)
.580 (56)
*
.080 (1)
.600(1)
*
Summer
.066(11)
.849 (13)
*
.068 (5)
.760 (5)
*
.255 (72)
.826 (74)
*
.527 (139)
1.088 (139)
*
.037 (3)
1.633 (3)
*
.434 (53)
1.112(65)
*
.064 (48)
.735 (60)
*
.145 (2)
2.150 (2)
*
Fall1
.110(11)
.736(11)
*
.055(4)
.500 (4)
*
2.231 (17)
1.118(17)
*
.689 (49)
.829 (49)
*
.010 (1)
.400(1)
*
1.334 (8)
1.150 (8)
' *
1.030 (3)
.700 (3)
' ' , *
.060(1)
.500 (1)
*
B27
-------
Table B-9 (continued)
Subregion
09
Lower Colorado -
San Bernard
Coastal
Nutrient
TP2
TKN
OrgN
Winter
.426 (68)
1.264 (66)
Soring
.105 (99)
.509 (87)
Summer
.099 (22)
.557 (35)
Fall1
.290 (25)
.711 (28)
10
Central Texas
Coastal
11
Nueces -
Southwestern
Texas Coastal
Region 12
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
.811 (73)
.919 (32)
.547 (28)
.414 (7)
.730 (572)
1.003 (403)
.464 (56)
.809 (33)
.188 (27)
.714 (7)
.279 (453)
.747 (358)
1.491 (33)
.682 (36)
*
.020 (3)
.367 (6)
*
.436 (391)
.911 (438)
.646 (27)
.687 (24)
.075 (2)
.750 (2)
.755 (148)
.809 (148)
* No samples taken
() = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - JJecember 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
B28
-------
Table BIO - Region 13: The Rio Grande System
The Rio Grande Region has a few subregions (especially the Rio Grande-Elephant Butte and
Mimbres areas near its headwaters), we should remember, with a large number of samples in some seasons
of 1989, while some other subregions have very few observations for some nutrients as noted in Table
9. The quarterly means for subregions again do not have as much variability in nutrient concentrations
as some other regions.
Mean ambient total phosphorus ranged from a low of .026 mg/L in the Lower Rio Grande valley
in the winter to .59 mg/L in summer in the Rio Grande-Armistad Subregion (04), for those subregions
with several observations per season. The maximum individual sample in 1989 was 4.7 mg/L in the fall
in the Elephant Butte area (Subregion 02).
Mean ambient TKN concentrations by subregion varied from .381 mg/L in the Upper Pecos
Subregion in wintertime to 1.825 mg/L in summer in Subregion 04, the Rio Grande-Armistad area, again
for those subregions and seasons with sufficient sampling. The highest single sample was in the spring
in the Rio Grande-Elephant Butte Subregion (02):. 17.2 mg/L.
Organic nitrogen is measured in only a few subregions. The lowest mean of ambient samples for
a subregion and season with sufficient sampling was .149 mg/L in winter in the Elephant Butte area; the
highest such mean was .507 in spring in the Rio Grande-Mimbres Subregion (03). A 3.7 mg/L reading
was the maximum single measurement, in the same Elephant Butte Subregion in spring.
For the entire Rio Grande system, 1989 total phosphorus means ranged from a low of .126 mg/L
in spring to a high of .337 mg/L in fall. Ambient TKN means varied from .553 mg/L in spring to a
seasonal high of .783 in summer. Ambient organic nitrogen, for those subregions reporting, ranged from
.155 in winter to .328 in the fall.
B29
-------
Table B-10
USGS Region 13: Rio Grande System
Mean Ambient Nitrogen and Phosphorus Concentrations
by Subregion
1989: All data in mg/L
Subregion
01
Rio Grande
Headwaters
02
Rio Grande -
Elephant Butte
03
Rio Grande -
Mimbrcs
04
Rio Grande -
Armistad
05
Rio Grande
Closed Basins
06
Upper
Pecos
07
Lower Pecos
08
Rio Grande -
Falcon
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TOTN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
.084(11)
.300 (1)
*
.201 (25)
.455 (23)
.149 (17)
.637 (15)
.489 (9)
1.317 (6)
*
*
.147 (12)
.667 (12)
*
.025 (2)
.400(2)
*
.050 (9)
.381 (8)
.205 (2)
*
.025 (2)
.500 (2)
*
.050 (8)
.350 (2)
*
Spring
.082 (8)
.550 (2)
*
.142 (106)
.529(113)
.227 (107)
.645 (97)
.091 (36)
.614 (35)
.507 (34)
.812 (34)
.305 (2)
.600(3)
*
*
.400 (1)
*
.069(11)
.526 (13)
.240 (1)
.460 (1)
.010 (1)
.400(1)
*
.147 (7)
.825 (4)
*
Summer
.075 (10)
.600 (1)
*
.324 (60)
.717 (68)
.305 (48)
.644 (48)
.155 (2)
1.000 (2)
*
*
.590 (3)
1.825 (4)
*
.030(2)
.400(2)
*
.120(12)
.800 (10)
*
*
.010 (2)
1.150 (2)
*
*
*
*
Fall1
.107 (3)
.600(2)
*
.514 (14)
.756 (13)
.352 (4)
.560 (4)
.310(1)
.400(1)
*
*
.720 (2)
.933 (3)
*
.040(1)
.200 (1)
*
.042 (6)
.527 (6)
.280 (2)
.420 (2)
*
.200 (1)
*
*
*
*
B30
-------
Table B-10 (continued)
Subreeion
Nutrient
Winter
Soring
Summer
* No samples taken
() = Number of samples
Fall1
09
Lower
Rio Grande
Region 13
TP2
TKN
OrgN
TP
TKN
OrgN
TOTN
.026 (7)
.750 (2)
*
.154 (86)
.580 (59)
.155 (19)
.637 (15)
.132(9)
.567 (3)
*
.126 (180)
.553 (175)
.294 (142)
.687 (132)
.050 (1)
.700 (1)
*
.259 (92)
.783 (90)
.305 (48)
.644 (48)
.110(2)
.850 (2)
*
.337 (29)
.672 (29)
.328 (6)
.513 (6)
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
TOTN = Total Nitrogen
B31
-------
-------
APPENDIX C
Regional Estimates of Gulf Coast Loadings
-------
-------
Appendix C: Brief Interpretation of Tables C2-C10: Ambient Loadings
(Table Cl is included for easy reference only. It is identical to Table 7.)
Table C2 - Region 03 (Partial): Nutrient Loadings in the Gulf Coast River Systems
of the Southeast Region
Again we must point out that analysis of Region 03 for the Gulf of Mexico Project includes only
part of subregion 09 and all of subregions 10-18, those whose waterways flow into the Gulf of Mexico.
As was the case with nutrient concentrations, there is a wide range of nutrient loadings in this part of the
Southeast Region. All data is in pounds per day (Ibs/day).
Mean total phosphorus loadings ranged from a seasonal low of 1 (one) Ib/day in the spring in
subregion 14, the Choctawhatchee-Escambia system, to a high of 30,551 Ibs/day in subregion 16, the
Tombigbee-Mobile Bay system. The second and third highest quarterly phosphorus means, however, are
5,360 Ibs/day in spring, again in the Tombigbee-Mobile Bay subregion, and 3,944 Ibs/day in subregion
13, the Apalachicola River system, again in the spring. The highest individual samples found in this
region were 180,147 Ibs/day in subregion 16, the Tombigbee-Mobile Bay area in winter, 54,477 Ibs/day
in the spring and 29,660 Ibs/day in winter, both in subregion 15, the Coosa-Alabama Rivers system. Note
that the Coosa-Alabama system feeds into the Tombigbee not far upstream of Mobile Bay, and apparently
accounts for much of the higher nutrient pollution in subregion 16.
Quarterly ambient mean Total Kjeldahl Nitrogen (TKN) loadings varied from a low of 50 Ibs/day
in the spring in subregion 14, the Choctawhatchee-Escambia system, to 71,003 Ibs/day in the winter in
the Tombigbee-Mobile Bay subregion. The highest individual measurements were 359,225 Ibs/day in the
winter in the Tombigbee-Mobile Bay subregion; 217,908 Ibs/day in spring and 197,736 Ibs/day in winter
in the Coosa-Alabama system. This pattern is similar to that for phosphorus loadings.
Organic nitrogen loadings were measured in too few subregions and seasons of the partial Region
03 to provide a meaningful comparison.
For Region 03 's Gulf Coast river systems in total, seasonal means of ambient total phosphorus
loadings ranged from a low of 1,364 Ibs/day in the summer to 4,315 Ibs/day in the winter. Ambient TKN
mean loadings varied from 3,983 Ibs/day in the summer to 13,197 Ibs/day in the winter. Organic nitrogen
Cl
-------
was not measured in all seasons.
C2
-------
Table C-l
USGS Region Summaries: Mean Ambient Nitrogen and Phosphorus
Loadings by Region
1989: All data in Ibs/day
Region
03
Southeast (Gulf
of Mexico River
Systems Only)
05
Ohio River
System
06
Tennessee
07
Upper
Mississippi
08
Lower
Mississippi
10
Missouri River
System
11
Arkansas -
Red - White
River System
12
Texas Gulf
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
4315 (180)
13197 (90)
*
84856 (281)
153703 (249)
*
2816 (8)
9502 (4)
14025 (2)
5670 (276)
40311 (199)
250 (1)
5158 (192)
904023 (26)
*
2148 (426)
5606(311)
111 (3)
5775 (196)
26267(117)
*
1845 (199)
3598 (171)
*
Soring
2295 (170)
11345 (100)
8 (14)
50621 (311)
152129 (270)
*
237 (37)
1169(33)
107 (3)
5017 (440)
61588 (218)
6161 (10)
19097 (246)
329792 (37)
*
1006 (541)
5288 (401)
*
5488 (187)
32327 (124)
*
2409 (183)
12000 (160)
*
Summer
1364 (169)
3983 (92)
6 (22)
9806 (333)
37560 (312)
*
111 (22)
756 (20)
20581 (5)
7451 (293)
44435 (195)
40 (9)
15455 (185)
144973 (25)
*
2209 (339)
10671 (216)
*
3687 (118)
14924(128)
*
1689 (168)
6736 (171)
*
Fall1
1538 (111)
5829 (28)
.5 (4)
10742 (128)
48096(118)
*
14070 (4)
5717 (1)
67798 (1)
1450 (133)
8823 (109)
86 (3)
41987 (16)
133620 (15)
*
379 (146)
1760 (103)
*
1078 (30)
3963 (54)
*
696 (90)
902 (74)
*
C3
-------
Table C-l (continued)
Region
13
Rio Grande
System
Nutrient
TP2
TKN
OrgN
Winter
345 (37)
1243 (31)
*
Spring
229 (30)
1231 (30)
*
Summer
829 (38)
2554 (38)
*
Fall1
176 (26)
627 (24)
*
* No samples taken
( ) = Number of samples
1 Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
C4
-------
Table C-2
Partial USGS Region 03: Southeast Gulf Coast River Systems
Mean Ambient Nitrogen and Phosphorus
Loadings by Subregion
1989: All data in Ibs/day
Subregion
09 Partial
Caloosahatchee
L. Okeechobee
10
Peace (FL) -
Tampa Bay
11
Suwanee
12
Ochlockonee
13
Apalachicola
14
Choctawhatchee
- Escambia
15
Coosa - Alabama
16
Tombigbee -
Mobile Bay
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
51 (3)
1854 (3)
*
297 (38)
557 (39)
*
343. (23)
1796 (6)
*
350(11)
1417 (3)
*
2283 (35)
13038 (8)
*
973 (4)
11261 (4)
*
3792 (47)
23896 (14)
*
30551 (16)
71003 (9)
*
Spring
57(4)
1355 (4)
*
136 (26)
143 (24)
*
444 (22)
3401 (5)
*
1040(11)
6220 (2)
*
3944 (35)
28226 (9)
*
1 (6)
50 (13)
1 (4)
• 3192 (46)
19459 (27)
7 .(6)
5360(14)
25965 (10)
14 (4)
Summer
102 (4)
747 (4)
*
353 (17)
399 (16)
*
477 (22)
4979 (4)
*
881 (11)
379 (2)
*
2659 (37)
8416 (7)
*
373 (4)
1433 (10)
3 (5)
1620 (56)
6621 (31)
5(12)
770 (16)
3377 (15)
9 (5)
Fall1
*
*
*
5(2)
122 (2)
*
387 (19)
5018 (3)
*
396 (9)
670 (2)
*
3536 (36)
19830 (6)
*
690(4)
8344 (3)
*
846 (35)
265 (9)
.5 (4)
11(6)
64(3)
• *
C5
-------
Table C-2 (continued)
Subregion
Nutrient
Winter
Soring
Summer
* No samples taken
() = Number of measurements
1 Winter runoff:
Spring
Summer
Fall
Fall1
17
Pascagoula
18
Pearl
Region 03
(Partial)
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
1209 (2)
6881 (3)
*
250 (1)
1877 (1)
*
4315 (180)
13197 (90)
*
1047 (4)
11387 (4)
*
548 (2)
5483 (2)
*
2295 (170)
11345 (100)
8 (14)
822 (1)
2941 (2)
*
231 (1)
1384 (1)
*
1364 (169)
3983 (92)
6 (22)
*
*
*
*
*
*
1538(111)
5829 (28)
.5 (4)
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December. 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
C6
-------
Table C3 - Region 05: Nutrient Loadings in the Ohio River System*
Region 05, extending from far southwestern New York State through West Virginia to western
Kentucky and eastern Illinois. Even without its tributary Tennessee River system, which flows into the
western most part of the Ohio and encompasses Region 06, the Ohio River system has some of the largest
flows of water contributing to some of the higher nutrient loadings flowing toward the Gulf of Mexico.
The nutrient concentrations were not generally high, but the loadings certainly are.
For Region 05, seasonal means for ambient total phosphorus loadings ranged from a low of 161
Ibs/day in the summer in the Cumberland subregion (13) to 843,190 Ibs/day in the Lower Ohio River area
(subregion 14), which carries the waters of all of the Ohio's tributaries. Other high means include 267,766
Ibs/day in the spring, again in the Lower Ohio, and 143,031 Ibs/day in the spring in the Middle Ohio area,
subregion 09. The highest individual measurements were 11,030,000 Ibs/day in the winter and 1,023,000
Ibs/day in spring both in the Lower Ohio subregion.
The mean quarterly ambient TKN loadings in 1989 for Region OS's subregions varied from lows of
896 Ibs/day in the fall in the Wabash River area (subregion 12), based on only three measurements, and
1280 Ibs/day in the summer in subregion 10, the Kentucky-Lickings Rivers area, to highs of 1,010,000
Ibs/day in the winter and 626,217 Ibs/day in the spring, both in the Lower Ohio area. The Middle Ohio
subregion also had some very high loadings of TKN. The highest individual measurements of TKN in
the Ohio River region in 1989 were 4,989,000 Ibs/day in winter and 2,669,000 Ibs/day in spring, both
again in the Lower Ohio, or most downstream, subregion of USGS Region 05.
Organic nitrogen loadings were not measured in Region 05 in 1989.
For the region overall, mean quarterly ambient total phosphorus loadings ranged from 9,806 Ibs/day
in the summer to 84,856 Ibs/day in the winter. Comparable mean TKN loadings varied from a low of
37,560 Ibs/day in the summer to 153,703 Ibs/day in the winter. Spring loadings were nearly as high,
averaging 152,129 Ibs/day.
Excluding the Tennessee tributary system (Region 06)
C7
-------
Table C-3
USGS Region 05: Ohio River System
Mean Ambient Nitrogen and Phosphorus Loadings
by Subregion
1989: All data in Ibs/day
Subregion
01
Allegheny
02
Monongahela
03
Upper Ohio
04
Muskingum
05
Kanawha
06
Scioto
07
Big Sandy -
Guyandotte
08
Great Miami
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
3285 (2)
27069 (2)
*
2188 (19)
12927 (19)
*
27849 (31)
112720(30)
*
2892 (18)
6786(16)
*
5676 (23)
27049 (23)
*
2243 (4)
18475 (4)
*
6224 (15)
14293 (18)
*
12848 (2)
111349(2)
*
Spring
12273 (3)
54612 (3)
*
1304 (20)
5393 (19)
*
27967 (34)
104911 (34)
*
4956 (19)
34744(11)
*
5717 (26)
28363 (24)
*
4289 (6)
16758 (6)
*
1823 (16)
5746 (16)
*
16239 (3)
71259 (3)
*
Summer
1397 (3)
14971 (3)
*
1650 (10)
12278 (10)
*
5099 (28)
32487 (31)
*
1461 (16)
6407 (8)
*
2524 (25)
13641 (25)
*
2199 (8)
6575 (8)
*
2433 (17)
6322 (18)
*
5939 (31)
13689 (32)
*
Fall1
1778 (3)
20867 (3)
*
715 (13)
4238 (13)
*
5359 (31)
39743 (29)
*
1017 (12)
1573 (6)
*
1157 (23)
7248 (22)
*
1892 (2)
2738 (2)
*
194 (8)
1488 (7)
*
2494 (5)
4268 (5)
*
C8
-------
Table C-3 (continued)
Subregion
09
Middle Ohio
10
Kentucky -
Licking
11
Green
12
Wabash
13
Cumberland
14
Lower Ohio
Region 05
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
90446 (21)
241053 (22)
*
25680 (41)
38952 (42)
*
6267 (18)
33910(19)
*
2560 (51)
18274 (12)
*
2629 (13)
15787 (15)
*
843190 (23)
1010000 (25)
*
84856 (281)
153703 (249)
*
Spring
143031 (30)
324903 (32)
*
3013 (38)
12434 (40)
*
2123 (15)
10333 (19)
*
5142 (53)
54153 (12)
*
2807 (12)
18209 (13)
*
267766 (36)
626217 (38)
*
50621 (311)
152129 (270)
*
Summer
34260(36)
121295 (37)
*
509(44)
1280 (48)
*
547 (20)
3182 (20)
*
4596 (42)
24321 (18)
*
161 (13)
7774 (15)
*
32770 (40)
112307 (39)
*
9806 (333)
37560 (312)
*
Falll
35243 (15)
129833 (15)
*
701 (3)
2273 (3)
*
*
*
*
172 (3)
896 (3)
*
*
*
*
60640 (10)
224193 (10)
*
10742(128)
48096(118)
*
* No samples taken
( ) = Number of measurements
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
G9
-------
Table C4 - Region 06: Nutrient Loadings in the Tennessee River System
The relatively small (geographically) Tennessee Region, whose waters eventually flow into the Gulf
of Mexico via the Mississippi, had lower nutrient concentrations than most other regions under study.
Loadings of phosphorus and nitrogen are also lower in many cases, but we are hampered by the -lack of
abundant data for 1989 in its four subregions.
The lowest mean ambient total phosphorus loading for a season and subregion with more than three
measurements (see numbers in parentheses) was 142 Ibs/day in the spring in the Upper Tennessee valley,
subregion 01. Most seasonal means were below 1000 Ibs/day, but many are calculated from very few
measurements. The highest such mean phosphorus loading was 808 Ibs/day in winter in the Middle
Tennessee-Hiwassee area (subregion 02); the highest means are all calculated from very few
measurements. The highest individual readings were 55,085 Ibs/day in the fall and 11,927 Ibs/day in the
summer, both in the Middle Tennessee-Elk subregion, and 9,348 Ibs/day in the winter in the Upper
Tennessee.
Quarterly means for ambient TKN loadings ranged (for seasons and subregions with sufficient data)
from 1,088 Ibs/day in summer in the Upper Tennessee subregion to a high of 2,0581 Ibs/day in summer
in the Middle Tennessee-Elk area (subregion 03). Again the highest and lowest means are based on few
cases. The highest individual measurements were 33,512 Ibs/day in winter and 15,615 Ibs/day in spring,
both in the Upper Tennessee, and 9,288 Ibs/day in the spring in the Lower Tennessee.
Organic nitrogen loadings were measured in only one subregion of Region 06 in 1989. Again, the
lack of sufficient data -- no nutrient loadings at all were measured in some of the four subregions and
seasons in 1989, for all of the nutrient measurements studied - make analysis of loadings in this region
difficult The lack of data in the Lower Tennessee (subregion 04) is especially important and unfortunate.
For Region 06 as a whole, mean ambient total phosphorus loadings varied from 237 Ibs/day in the
spring to 14070 Ibs/day in winter, the latter based on only four measurements. Mean TKN loadings
ranged from 756 Ibs/day in the summer to 9502 Ibs/day in winter, the latter again calculated from only
four measurements. Organic nitrogen means are entirely from one subregion.
CIO
-------
Table C-4
USGS Region 06
Subreeion
01
Upper Tennessee
02
Middle Tennessee
- Hiwassee
03
Middle Tennessee
-Elk
"04
Lower
Tennessee
Region 06
: Tennessee River System
Mean Ambient Nitrogen and Phosphoms Loadings
by Subregion
1989: All data in Ibs/day
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
5261 (2)
18387 (2)
*
808 (4)
618 (2)
*
4389 (2)
*
14025 (2)
*
*
*
2816 (8)
9502 (4)
14025 (2)
Soring
142 (32)
1107 (25)
*
231 (2)
526 (1)
*
*
130 (4)
107 (3)
1255 (3)
3287 (3)
*
237 (37)
1169 (33)
107 (3)
Summer
233 (13)
1088 (13)
*
428 (4)
485 (1)
*
6137 (2)
98(4)
20581 (5)
30(3)
54(2)
*
777 (22)
756 (20)
20581 (5)
Fall1
800(1)
5717 (1)
*
197 (2)
*
*
55086 (1)
*
67798 (1)
*
*
*
14070 (4)
5717 (1)
67798 (1)
* No samples taken
() = Number of measurements
'. Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
2 TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
Cll
-------
Table CS - Region 07: Nutrient Loadings in the Upper Mississippi River System
The Upper Mississippi and its tributaries have loadings measurements of phosphorus and TKN for
most of the 14 subregions of Region 07, with abundant data in most seasons and subregions south of
Minnesota and Wisconsin.
The lowest mean seasonal ambient loadings of total phosphorus were 1 (one) Ib/day in spring,
summer and fall in the St. Croix River area (subregion 03). Many very low means are found in the upper
reaches of Region 07. The highest such mean phosphorus loadings were 168,700 Ibs/day in summer,
41,852 Ibs/day in spring, and 39,010 Ibs/day in winter, all in subregion 14, the Upper Mississippi-
Kaskaskia-Meramec area. This is the most downstream subregion of the Upper Mississippi Region. The
highest individual measurements in this region in 1989 were 757,986 Ibs/day in summer, 214,079 Ibs/day
in winter and 213,593 Ibs/day in spring, all in subregion 14, the area farthest downstream in the Upper
Mississippi Region.
For seasons and subregions with sufficient data, mean seasonal ambient loadings of TKN ranged
from lows of 5 Ibs/day in the spring in the St. Croix River subregion (based on 7 measurements) and
13 Ibs/day in winter in the same subregion (9 measurements) to high means of 592,921 Ibs/day (5
measurements) in summer, 468,096 Ibs/day (6 measurements) and 385,236 Ibs/day (7 measurements) in
winter, all in subregion 14. Several other seasonal mean loadings of TKN were over 40,000 Ibs/day
through much of the region, notably in subregion 11, the Upper-Mississippi-Salt River area. The highest
single measurements in 1989 were 938,732 Ibs/day in the spring in the Upper Mississippi-Maquaketa-
Plum-Escambia subregion (06); 850,489 Ibs/day in the winter in the Upper Mississippi-Salt subregion (11);
and 689,054 Ibs/day in the Upper Mississippi-Iowa-Skunk-Wapsipinicon subregion (08).
Organic nitrogen loadings were measured too infrequently in Region 07 in 1989 to allow for seasonal
comparisons.
For the entire Region 07 mean total phosphorus loadings ranged from a low of 1,450 Ibs/day in the
fall to 7,451 Ibs/day in the summer. TKN means varied from 8,823 Ibs/day in the fall to a high of
61,588 Ibs/day in the spring. Organic nitrogen loadings were sparsely measured in 1989.
C12
-------
Table C-5
USGS Region 07: Upper Mississippi River System
Mean Ambient Nitrogen and Phosphorus Loadings
by Subregion
1989: All data in Ibs/day
Subregion
01
Mississippi
Headwaters
02
Minnesota R.
03
St. Croix R.
04
Upper Miss.-
Black-Root
05
Chippewa
06
Upper Mississippi
- Maquaketa - Plum
- Escambia
07
Wisconsin R.
08
Upper Miss.-Iowa-
Skunk-Wapsipinicon
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
6(48)
32 (39)
*
*
*
*
4(11)
*
*
4521 (6)
24088 (6)
250 (1)
365 (5)
9178 (3)
*
5992 (15)
38408 (15)
*
3700 (3)
60534 (2)
*
4239 (48)
46742 (23)
*
Spring
10 (163)
311 (3)
*
*
*
*
1 (8)
5(7)
*
6767 (38)
44804 (38)
6161 (10)
4810 (5)
94796 (2)
*
22112(19)
193737 (16)
*
1490 (3)
20855 (3)
*
5853 (41)
43123 (25)
*
Summer
9(33)
69 (3)
19 (2)
15(2)
66(2)
.1(1)
1(10)
*
*
10308 (10)
47399 (10)
80 (4)
1459 (3)
36370 (1)
*
7238 (20)
44589 (17)
*
743 (2)
11542(2)
*
1897 (26)
11897(27)
.7 (2)
Fall1
2(4)
*
$
3(1)
9(1)
8(1)
1(11)
13 (9)
*
5529 (8)
28435 (8)
22(1)
251 (6)
6375 (1)
*
3973 (16)
25024 (18)
#
459 (2)
3945 (2)
*
262 (16)
848 (22)
227 (1)
C13
-------
Table C-5 (continued)
Subregion
09
RockR.
10
DesMoines R.
11
Upper Miss.
-Salt
12
Upper Illinois
13
Lower Illinois
14
Upper Miss.-
Kaskaskia-Meramec
Region 07
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
2181 (13)
16701 (11)
*
331 (12)
1222 (13)
*
32076 (5)
284790 (5)
*
5079 (81)
24650 (71)
*
9358 (17)
1514 (4)
*
39010 (12)
385236 (7)
*
5670 (276)
40311 (199)
250 (1)
Spring
1307 (17)
34536 (6)
*
549 (13)
1658 (13)
*
22208 (9)
168821 (8)
*
4203 (96)
24977 (82)
*
7820 (16)
95190 (9)
*
41852 (12)
468096 (6)
*
5017 (440)
61588 (218)
6161 (10)
Summer
2299 (35)
37463 (12)
*
161 (13)
1232 (13)
*
38095 (8)
188262 (8)
*
3518 (106)
16332 (84)
*
13805 (20)
67615 (11)
*
168700 (5)
592921 (5)
*
7451 (293)
44435 (195)
40 (9)
^—
Fall1
192 (17)
17039 (1)
*
111(12)
1024 (12)
*
32(1)
359 (1)
*
2386 (30)
7301 (30)
*
360(6)
540(3)
*
106(1)
441 (1)
*
1450 (133)
8823 (109)
86 (3)
* No samples taken
() = Number of measurements
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
• July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
C14
-------
Table C6 - Region 08: Nutrient Loadings in the Lower Mississippi Region
While the concentrations of nutrients in the Lower Mississippi may have been lower than some
would expect, the nutrient loadings, as expected, include some of the highest in the Gulf of Mexico
drainage area. This is particularly true in the vast expanse of flowing water which comprises the
downstream portions of Region 08. Unfortunately, one subregion, the Boeuf-Tensas subregion (05) has
no nutrient loadings measurements for 1989, and several show no data for the fall season.
The lowest quarterly means of ambient total phosphorus loadings, for subregions and seasons with
more than three observations, were 124 Ibs/day in the fall in the Lower Mississippi-St Francis area
(subregion 02) and 197 Ibs/day in the summer in the Lower Mississippi-Yazoo area (subregion 03). The
highest such means are found in the Lower Mississippi-Lake Maurepas area (subregion 07), just
downstream from the point where the Mississippi and Atchafalaya Rivers split: 809,535 Ibs/day in winter,
519,710 Ibs/day in spring with only 3 measurements, and 432,527 Ibs/day in summer. The highest
individual measurements of phosphorus loadings were 1,753,000 Ibs/day in subregion 07 in the winter,
1,062,000 Ibs/day in the winter in subregion 06, the Lower Mississippi-Big Black-Escambia area which
is mostly just upstream of the Mississippi-Atchafalaya split; and 1,047,000 Ibs/day in the summer in
subregion 07,
The TKN measurements in the lower readies of Region 08 are very high in general. Through the
entire region they are highly variable. The lowest seasonal mean is 16 Ibs/day in the spring in the Lower
Mississippi-St. Francis subregion. The highest seasonal subregion TKN means are in subregions with a
low number of measurements, but these are consistently high: 2,143,000 Ibs/day in the winter in the
Lower Mississippi-Lake Maurepas subregion (3 measurements); 1,880,000 Ibs/day in winter in the Lower
Mississippi-Big Black-Escambia area (4 measurements-subregion 06) and 1,715,000 Ibs/day in winter in
the Lower Mississippi River (2 measurements -subregion 09) which includes its huge delta. The highest
single measurements of TKN in 1989 were 4,047,000 Ibs/day in subregion 06; 3,536,000 Ibs/day in
subregion 07; and 3,430,000 Ibs/day in subregion 09, all in winter.
C15
-------
Organic nitrogen loadings were not measured in the Lower Mississippi Region.
The seasonal means for total phosphorus for Region 08 as a whole varied from a low of 15,455
Ibs/day in the summer to 51,518 Ibs/day in the winter. For TKN, mean seasonal loadings throughout the
region ranged from 133,620 Ibs/day in the fall to 944,023 Ibs/day in the winter. Winter appears to be the
season with the highest nutrient pollutant loadings for the Lower Mississippi, in terms of both seasonal
means and extremely high individual measurements.
C16
-------
Table C-6
USGS Region 08: Lower Mississippi River System Excluding Arkansas-
White-Red (Region 11)
Mean Ambient Nitrogen and Phosphorus Loadings
by Subregion
1989: All data in Ibs/day
Subregion
01
Lower
Mississippi
R. - Hatchie
02
Lower
Mississippi-
St. Francis
03
Lower
Mississippi-
Yazoo
04
Lower Red -
Ouachita
05
Boeuf -
Tensas
06
Lower
Mississippi-Big
Black-Escambia
07
Lower
Mississippi-
Nutrient
TP2
TKN
OrgN
•.
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
*
*
*
22042 (32)
96790 (4)
*
5849 (94)
167746 (3)
*
1491 (45)
14721 (5)
*
*
*
*
474423 (4)
1880000 (4)
*
809535 (5)
2143000 (3)
*
Spring
698 (3)
2252 (3)
*
6806 (25)
16 (9)
*
1441 (164)
110572 (2)
*
1747 (32)
10807 (8)
*
*
*
*
49376 (4)
484683 (4)
*
519710 (3)
814123 (2)
*
Summer
5(3)
51 (2)
*
2814 (28)
2195 (4)
*
197 (96)
45577 (1)
*
804(40)
10203 (8)
*
*
*
*
497 (2)
2132 (1)
*
432527 (4)
659917 (2)
*
Fall1
*
*
*
124 (8)
587 (8)
*
*
*
*
152 (2)
3035 (2)
*
*
*
*
*
*
*
*
*
*
Lake Maurepas
C17
-------
Table C-6 (continued)
Subregion
08
Louisiana
Coastal (incl.
Atchafalaya)
Nutrient
Winter
Soring
Summer
Fall1
TP2
TKN
OrgN
200640 (10)
1031000 (5)
*
130900 (12)
570777 (6)
76923 (10)
204154 (5)
*
95470 (1)
445525 (1)
09
Lower
Mississippi R.
Region 8
TP
TKN
OrgN
TP
TKN
OrgN
308804 (2)
1715000 (2)
*
51518 (192)
904023 (26)
*
301958 (3)
1632000 (3)
*
19097 (246)
329792 (37)
*
114467 (2)
572763 (2)
*
15455 (185)
144973 (25)
*
191674 (3)
774006 (2)
41987 (16)
133620 (15)
*
* No samples taken
( ) = Number of measurements
1
Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
CIS
-------
Table C7 - Region 10; Nutrient Loadings in the Missouri River System
We found the concentrations of nutrients in the Missouri River system to be generally quite high.
However, with smaller and slower flows of water than in some other regions the nutrient loadings are
nearly all quite slow. We should note again that the uppermost reaches of this region are rarely sampled,
particularly in fall and winter when they may be frozen. Some other subregions have no loadings
measured in the fall.
For subregions and seasons with a sufficient number of measurements, the lowest total phosphorus
loadings means were found in subregion 6, the Missouri-Poplar-Escambia area: .25 Ibs/day in winter,
.45 Ibs/day in summer and 3 Ibs/day in the spring. Many of the Missouri system's 30 subregions had
seasonal phosphorus means lower than 100 Ibs/day, and the majority were below 1,000 Ibs/day on average.
A few high mean phosphorus loadings push up the regional averages, however 117,623 Ibs/day based
on 3 measurements in winter in the Lower Yellowstone subregion (10), 49,482 Ibs/day (2 observations)
in the most downstream Lower Missouri subregion (30) in the summer, and 10,289 Ibs/day (18
observations) in the winter in the Missouri-Nishnabotna area, subregion 24. The highest single
measurements of phosphorus loadings in Region 10 were 352,429 Ibs/day in the winter in subregion 10;
90,917 Ibs/day in the summer in the Kansas River area, subregion 27; and 64,466 Ibs/day in subregion
30, the farthest downstream, also in the summer.
Generally, seasonal mean ambient TKN loadings were also quite low in the Missouri system. The
lowest mean loadings for subregions and seasons with sufficient data for 1989 were 9 Ibs/day in the
summer and 22 Ibs/day in the fall, both in subregion 06, and 24 Ibs/day in the summer in the James River
area, subregion 16. The highest such mean seasonal TKN loadings were 81,123 Ibs/day in spring in
subregion 30, and 32,071 Ibs/day in spring, 30,671 Ibs/day in winter and 28,081 Ibs/day in summer, all
in subregion 24. Note, however, the highest seasonal means: 187,056 Ibs/day in summer (2
measurements) and 101,960 Ibs/day in winter (3 measurements), both in the Lower Missouri subregion
30. The highest individual measurements of TKN were 359,441 Ibs/day in subregion 27, the Kansas River
C19
-------
area in summer, 266,452 Ibs/day in the spring in subregion 30, the Lower Missouri; and 223,302 Ibs/day
in the winter in subregion 24, the Missouri-Nishnabotna area.
Organic nitrogen loadings were measured in only one season and subregion in the Missouri system
in 1989.
For all of Region 10 the seasonal mean total phosphorus loadings varied from 379 Ibs/day in the fall
to 2,209 Ibs/day in the summer. Mean TKN loadings ranged from 1,760 Ibs/day in the fall to 10,671
Ibs/day in the summer. Many individual subregions, however, had their high or low means in other
seasons.
C20
-------
Table C-7
USGS Region 10: Missouri River System
Mean Ambient Nitrogen and Phosphorus Loadings
by Subregion
1989: All data in Ibs/day
Subregion
01
Saskatchewan
02
Missouri
Headwaters
03
Missouri -
Marias
04
Missouri -
Musselshell
05
Milk
06
Missouri -
Poplar - Escambia
07
Upper Yellowstone
08
Big Horn
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
*
*
*
*
291 (3)
2986 (3)
294 (4)
3845 (4)
*
5867 (5)
,19822 (5)
*
163 (8)
1051 (8)
*
360 (2)
3844 (2)
*
89 (22)
1299 (19)
Spring
375 (1)
257 (1)
*
265 (4)
*
128 (12)
2531 (10)
*
621 (7)
6667 (7)
*
49(4)
232 (4)
3(11)
52 (11)
*
2318 (6)
17934(2)
*
163 (42)
6934 (23)
*
Summer
50(1)
497 (1)
*
104(2)
*
57(8)
1137 (6)
*
1001 (5)
5327 (7)
19(3)
240(3)
.45 (12)
9(15)
843 (5)
18150 (2)
*
180 (39)
2689 (22)
*
Fall1
*
814 (1)
*
*
367 (3)
4045(2)
918 (4)
4659 (5)
*
13(6)
164 (4)
*
.25 (8)
22(8)
*
332 (2)
25620 (1)
*
116(21)
1673 (6)
*
C21
-------
Table C-7 (continued)
Subregion
09
Powder -
Tongue
10
Lower
Yellowstone
11
Missouri -
Little Missouri
12
Cheyenne
13
Missouri - Oahe
14
Missouri -
White
15
Niobrara
16
James
17
Missouri -
Big Sioux
18
North Platte
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
25 (28)
236(11)
*
117623 (3)
32914 (3)
*
131 (1)
670 (1)
*
273 (16)
809 (10)
*
75(4)
490(4)
*
114(4)
405(2)
*
647 (17)
9380 (2)
*
1592 (4)
5640(4)
*
3994 (3)
14116(2)
*
335 (17)
1692 (14)
*
Spring
232 (69)
338 (23)
*
1779 (4)
183 (2)
*
105 (4)
399 (4)
*
11 (47)
45 (41)
*
65 (7)
509 (7)
*
727 (7)
1295 (3)
*
793 (13)
4944 (5)
*
772 (21)
3673 (21)
*
192 (5)
1713 (2)
*
371 (23)
3250 (19)
*
Summer
686 (31)
267 (7)
*
157 (5)
2623 (5)
*
3(2)
26(2)
*
12 (10)
279 (7)
*
1910 (4)
410 (4)
*
733 (5)
741 (3)
*
281 (13)
4776 (6)
*
6(6)
24(6)
*
186 (2)
1909(2)
*
619 (17)
3231 (18)
*
Fall1
1022 (16)
540 (10)
*
489 (3)
4891 (4)
*
.2(3)
3(3)
*
16 (8)
129 (3)
*
3(7)
33(7)
*
49(3)
337 (1)
*
278 (10)
4045 (1)
*
4(2)
36(2)
*
151 (2)
423 (1)
*
91(7)
1712 (5)
*
C22
-------
Table C-7 (continued)
Subregion
19
South Platte
«
20
Platte
21
Loup
22
Elkhom
23
Missouri -
Little Sioux
24
Missouri -
Nishnabotna
25
Republican
26
Smoky Hill
27
Kansas
28
Chariton -
Grand
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
2018 (13)
6194 (13)
*
4795 (18)
19616 (14)
*
657 (26)
918 (7)
*
1544- (15)
4931 (12)
*
145 (11)
397 (8)
111 (3)
10289 (18)
30671 (11)
*
97(8)
928 (2)
*
84(4)
394 (4)
*
548 (146)
1973 (27)
*
66(7)
422 (7)
*
Soring
415 (11)
1779(11)
*
3289 (19)
16430 (17)
*
324 (15)
397 (7)
*
865 (15)
3403 (15)
*
367 (8)
840 (8)
*
9268 (16)
32071 (13)
*
43(9)
410 (7)
*
233 (6)
1773 (6)
*
635 (127)
2545 (111)
*
373 (9)
1636 (7)
*
Summer
385 (17)
1636 (20)
*
6347 (17)
23182 (17)
*
528 (10)
1623 (9)
*
2025 (15)
13350 (14)
*
244(8)
767 (8)
*
5463(12)
28081 (9)
*
257 (8)
1257 (7)
*
1284 (3)
7102 (3)
' *
5493 (65)
23758 (58)
*
17(6)
190(5)
*
Fall1
491 (10)
2436 (8)
*
2454 (4)
8065 (4)
*
472 (3)
432 (2)
*
1301 (1)
1752 (1)
*
491 (7)
1207 (7)
*
136 (4)
272 (4)
*
*
*
*
*
*
*
453 (9)
1053 (9)
*
11 (2)
60(3)
*
C23
-------
Table C-7 (continued)
Subregion
Nutrient
Winter
Soring
Summer
Fall1
29
Gasconade -
Osage
30
Lower
Missouri
Region 10
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
365 (14)
5468 (9)
*
11906(5)
101960 (3)
*
2148 (426)
5606(311)
111 (3)
129 (10)
1973 (7)
*
14133 (9)
81123 (7)
*
1006 (541)
5288 (401)
*
719 (6)
2817 (8)
*
49482 (2)
187056 (2)
*
2209 (339)
10671 (276)
*
•2(1),
1 (1)
*
*
*
*
379 (146)
1760 (103)
*
* No samples taken
() = Number of measurements
i
Winter runoff: January 1 - March 31
Spring April 1 - June 30
Summer July 1 - September 30
Fall October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
C24
-------
Table C8 - Region 11: Nutrient Loadings in the Arkansas-White-Red System
The Arkansas-White-Red system of rivers flowing from eastern Colorado through southern Kansas,
Oklahoma and Texas to the lower Mississippi is another system which had relatively high concentrations
of nutrients in 1989. Again, however, the loadings which account for flow of water, as well as
concentrations of nutrients, are generally fairly low. The lack of abundant data in some subregions is
again a problem in analyzing the data, particularly in the fall season, as a perusal of Table C8 shows.
The lowest ambient total phosphorus mean loadings in Region 11 were 6 Ibs/day in the fall season
in the Upper Cimarron area (subregion 04) and 17 Ibs/day in the winter in the Red River Headwaters
(subregion 12), for those subregions and seasons with more than three measurements. The highest such
phosphorus loadings were 12,061 Ibs/day in the winter and 11,246 Ibs/day in the spring, both in the Lower
Arkansas (subregion 11). The highest individual measurements of phosphorus in 1989 were
95,362 Ibs/day in the spring in subregion 11; 77,298 Ibs/day in the spring in subregion 14, the Missouri-
White rivers area; and 64,725 Ibs/day in the winter, again in subregion 11.
For TKN, the lowest ambient mean loadings for subregions and seasons with more than three
measurements were 31 Ibs/day in the fall and 60 Ibs/day in winter, bosh in the Upper Cimarron subregion.
The highest mean TKN loadings are all. found in the Lower Arkansas subregion: 115,933 Ibs/day in the
spring, 104,942 Ibs/day in the winter and 61,345 Ibs/day in the summer. All of these means are for those
subregions and seasons with more than three measurements. The highest individual measurements of TKN
loadings in 1989 were 513,487 Ibs/day in the spring, 392,677 Ibs/day in winter and 267,963 Ibs/day in the
summer, all in subregion 11, the Lower Arkansas River area.
Ambient organic nitrogen loadings were not measured in Region 11 in 1989.
For all of Region 11 mean ambient total phosphorus loadings varied from a low of 1,078 Ibs/day
in the fall to 5,775 Ibs/day in the winter. Mean TKN loadings ranged from a low of 3,963 Ibs/day in the
fall to 32,327 Ibs/day in the spring. It should be noted that some subregions, especially the Upper White
(subregion 01), the Upper Arkansas (subregion 02), the Neosho-Verdigris (subregion 07), the Lower
Arkansas (subregion 11) and the Red-Sulphur (subregion 14) were more often measured for total
C25
-------
phosphorus and/or TKN in 1989. Region means are therefore heavily influenced by those in some of
these subregions.
C26
-------
Table C-8
USGS Region
Subregion
01
Upper White
02
Upper
Arkansas
03
Middle
Arkansas
04
Upper
Cimarron
05
Lower
Cimarron
06
Arkansas -
Keystone
07
Neosho -
Verdigris
08
Upper
Canadian
09
Lower
Canadian
11: Arkansas- White-Red System
Mean Ambient Nitrogen and Phosphorus Loadings
by Subregion
1989: All data in Ibs/day
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
1198(44)
15821 (13)
*
59 (2)
1302 (28)
*
54 (1)
1359 (1)
*
3(5)
60(6)
*
10736 (2)
41028 (3)
*
1052 (2)
11227 (2)
*
374 (17)
3277 (6)
*
6(2)
113(2)
*
154 (5)
487 (4)
*
Spring
1255 (40)
20136 (19)
*
201 (4)
827 (29)
*
51(1)
1141 (1)
*
5(6)
96(6)
*
4199 (2)
16063 (3)
*
2443 (2)
35362 (2)
*
718 (19)
16350 (4)
*
5(1)
145 (1)
*
83(4)
295 (4)
*
Summer
289 (32)
1986 (13)
*
102 (2)
430 (50)
*
498 (1)
4796 (1)
*
2(2)
29(2)
*
1030 (2)
1535 (2)
*
27670 (1)
202914 (1)
*
536(11)
40142 (4)
0 (1)
28(3)
182 (3)
*
4766 (7)
11066 (7)
*
Fall1
433 (2)
1571 (1)
*
109 (3)
1187(30)
. 0
*
*
*
. 6(4)
31(4)
*
*
*
*
*
*
*
82(1)
*
He
.5(1)
91(1)
*
1209 (2)
1887 (2)
*
C27
-------
Table C-8 (continued)
Subregion
10
North
Canadian
11
Lower
Arkansas
12
Red Headwaters
13
Red-Washita
14
Red-Sulphur
Region 11
••
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
=^=
Winter
1245 (5)
10678 (5)
*
12061 (63)
104942 (20)
*
17(5)
167 (5)
*
208 (10)
1442 (5)
*
8487 (33)
29518 (17)
*
5775 (196)
26267(117)
*
=====
Soring
500(3)
1000(3)
*
11246(63)
115933(25)
*
41(5)
313 (5)
*
162 (4)
1027 (4)
*
7275 (32)
28203 (18)
*
5488 (187)
32327 (124)
*
Summer
1719 (2)
5537 (2)
*
5847 (66)
61345 (22)
*
43(6)
247 (7)
*
464(8)
3409(7)
*
5895 (25)
3898 (7)
*
3689 (168)
14924 (128)
*
— — ~— Ml
Fall1
98(1)
328 (1)
*
4508 (4)
22928 (4)
*
4(1)
89(1)
*
91(3)
575 (2)
*
1278 (8)
9949 (8)
*
1078 (30)
3963 (54)
*
g-i1- —
* No samples taken
( ) =* Number of measurements
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
C28
-------
Table C9 - Region 12: Nutrient Loadings in the Texas Gulf Rivers
In the Texas Gulf rivers we generally found relatively low concentrations of nutrients; in this region
the same pattern holds true for nutrient loadings, though it should be noted that some subregions had a
limited number of measurements.
The lowest quarterly mean ambient total phosphorus loadings, for those subregions and seasons with
more than three measurements, were 2 Ibs/day in winter and 3 Ibs/day in summer, both in the Brazos
Headwaters, subregion 05. The highest such total phosphorus loadings were 8,307 Ibs/day in the spring
and 6,694 Ibs/day in the summer, both in the Trinity River area (subregion 03), and 4,705 Ibs/day in the
summer in the Sabine River area, subregion 01. The highest individual measurements of total phosphorus
in 1989 were 51,694 Ibs/day in the summer, 41,403 Ibs/day in the spring, and 37,224 Ibs/day in the winter,
all in Trinity River subregion (03).
Ambient TKN loadings in the Texas Gulf Region were almost as highly variable in 1989. The
lowest seasonal mean TKN loadings were 18 Ibs/day in the winter in the Brazos Headwaters; 55 Ibs/day
in subregion 11, the Nueces-Southwestem Texas Coastal subregion, also in winter, and 59 Ibs/day in the
fall in subregion 06, the Middle Brazos River area. (Other low means were from three or fewer
measurements.) The highest mean TKN loadings were 82,949 Ibs/day in the summer in the Sabine River
area, subregion 01; 59,510 Ibs/day in the spring, and 50,844 Ibs/day in the summer, both in the Neches
River subergion (02). The highest single measurements of TKN in 1989 were 344,388 Ibs/day in the
spring in the Trinity River subregion; 329,381 Ibs/day in the spring and 226,538 Ibs/day in the summer,
both in the Neches River subregion.
Organic nitrogen loadings were not measured in Region 12 in 1989.
For the Texas'Gulf region as a whole, seasonal mean total phosphorus loadings varied from 696
Ibs/day in the fall to 2,409 Ibs/day in the spring. TKN loadings ranged from 902 Ibs/day in the fall to
12,000 Ibs/day in the spring. Again, some subregions and seasons had more measurements than others,
but the differences are not as great as in a few other regions.
C29
-------
Table C-9
USGS Region 12: Texas Gulf Region
Mean Ambient Nitrogen and Phosphorus Loadings
by Subregion
1989: All data in Ibs/day
Subregion
01
Sabine
02
Neches
03
Trinity
04
Galveston
Bay - San Jacinto
05
Brazos
Headwaters
06
Middle
Brazos
07
Lower Brazos
08
Upper Colorado
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
1418 (5)
13560 (5)
*
3724 (10)
16282 (8)
*
4197 (42)
5170 (31)
*
1309 (51)
3710 (34)
*
2(5)
18(4)
*
115(14)
106(13)
*
148 (8)
214(7)
*
3(2)
131 (2)
*
C30
Spring
2786 (4)
22156 (4)
*
1526 (7)
59510 (7)
*
8307 (38)
29923 (38)
*
2465 (11)
6595 (9)
*
47(2)
159 (2)
*
99(18)
219 (12)
*
442 (9)
3892 (10)
*
11 (1)
84(1)
*
Summer
4705 (4)
82949 (4)
*
2918 (5)
50844 (5)
*
6694 (29)
15952 (30)
*
368 (50)
520 (50)
*
3(6)
19(3)
*
119 (15)
90(11)
*
845 (9)
3853 (8)
*
.3(2)
5(2)
*
Fall1
282 (3)
1586 (3)
*
3908 (4)
5426 (3)
*
640(13)
764 (8)
*
496 (4)
664 (4)
*
.01 (1)
.5(1)
*
139 (13)
59(11)
*
666(4)
1157 (3)
*
2(1)
15(1)
*
-------
Table C-9 (continued)
Subregion
09
Lower Colorado -
San Bernard-
Coastal
Nutrient
TP2
TKN
OrgN
Winter
861 (31)
2921 (32)
Spring
517 (43)
3339 (42)
Summer
293 (12)
1006 (19)
Fall1
535 (19)
1318 (19)
10
Central Texas
Coastal
11
Nueces -
Southwestern
Texas Coastal
Region 12
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
* No samples taken
() = Number of measurements
1793 (28)
1205 (28)
11 (3)
55(7)
1845 (199)
3598 (171)
1221 (39)
1014 (30)
52(11)
1170 (5)
2409 (183)
12000 (160)
1 Winter runoff:
Spring
Summer
Fall
January 1 - March 31
April 1 - June 30
July 1 - September 30
October 1 - December 31
751 (33)
260 (34)
56(3)
301 (5)
1689 (168)
6736 (171)
870 (24)
258 (19)
83(4)
1421 (2)
696 (90)
902 (74)
TP = Total Phosphorus
TKN = Total Kjeldahl Nitrogen
OrgN = Organic Nitrogen
C31
-------
Table CIO - Region 13: Ambient Nutrient Loadings in the Rio Grande System
Several of the nine subregions in the Rio Grande region had very sparse measurements of
phosphorus and nitrogen in 1989. The Rio Grande-Elephant Butte and Upper Pecos subregions, both
upstream reaches, have higher numbers of measurements.
The lowest mean ambient total phosphorus loadings were 12 Ibs/day in the fall and 27 Ibs/day in
the winter, both in the Upper Pecos River system, subregion 06. This data is for subregions and seasons
with more than three measurements. The highest such mean phosphorus loadings in 1989 were
1,209 Ibs/day in the summer and 612 Ibs/day in the winter, both in subregion 2, the Rio Grande-Elephant
Butte area, and 543 Ibs/day in the winter in the Rio Grande-Mimbres subregion (03), again for those
means based on more than three measurements. The highest individual measurements of ambient total
phosphorus loadings were 15,534 Ibs/day in the summer in the Rio Grande-Elephant Butte subregion;
5,874 Ibs/day in the summer in subregion 04, the Rio Grande-Armistead area; and 2,662 Ibs/day in the
winter, again in the Rio Grande-Elephant Butte area.
Mean ambient TKN loadings were also relatively low in 1989. For subregions and seasons with
sufficient data the lowest mean TKN loadings were 173 Ibs/day in the winter, 224 Ibs/day in the fall and
388 Ibs/day in the summer, all in the Upper Pecos subregion. The highest such mean TKN loadings were
6,657 Ibs/day in the summer in the Rio Grande-Armistad subregion and 2,935 Ibs/day in the Rio Grande-
Elephant Butte subregion, again the summer. The highest single measurements of TKN in Region 13 in
1989 were 35,599 Ibs/day in the summer in the Rio Grande-Elephant Butte subregion; 17,621 Ibs/day in
summer in the Rio Grande-Armistad subregion; and 10,469 Ibs/day in the winter in subregion 09, the
Lower Rio Grande River as it nears the Gulf of Mexico.
Ambient organic nitrogen loadings were not measured in the Rio Grande region in 1989.
In 1989 seasonal mean total phosphorus loadings for the entire Rio Grande system varied from a low
of 176 Ibs/day in the fall to 829 Ibs/day in the summer. Mean TKN loadings ranged from 627 Ibs/day
in the fall to a high of 2,554 Ibs/day in the summer. We must again caution mat all data analysis of this
region is hampered by the lack of ample data in many subregions.
C32
-------
Table C-10
USGS Region 13: Rio Grande System
Mean Ambient Nitrogen and Phosphorus Loadings
by Subregion
1989: All data in Ibs/day
Subregion
01
Rio Grande
Headwaters
02
Rio Grande -
Elephant Butte
03
Rio Grande -
Mimbres
04
Rio Grande -
Armistad
05
Rio Grande
Closed Basins
06
Upper
Pecos
07
Lower Pecos
08 ,
Rio Grande -
Falcon
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
TP
TKN
OrgN
Winter
167 (1)
626 (1)
*
612 (10)
1350 (8)
*
543 (7)
1051 (6)
*
349 (4)
1857 (4)
*
3(2)
52(2)
27(6)
173 (5)
*
25(2)
483 (2)
250 (2)
*
Spring
298 (2)
1429 (2)
*
346 (8)
2114(8)
391 (1)
2932 (1)
*
556 (2)
1430 (3)
50(1)
*
123 (9)
713(11)
*
15(2)
265 (1)
243 (3)
*
Summer
26(1)
139 (1)
1209 (17)
2935 (18)
795 (2)
6144 (2)
*
2869 (3)
6657 (4)
3(2)
40(2)
*
67 (10)
388 (8)
5(2)
617 (2)
*
*
*
*
Fall1
58(2):
269 (2)
*
114(10)
465 (9)
*
140 (1)
180 (1)
1222 (2)
2116(3)
*
4(1)
20(1)
12(6)
224 (5)
*
145 (1)
*
155 (2)
*
*
C33
-------
Table C-10 (continued)
Subregion
09
Lower
Rio Grande
Region 13
Nutrient
TP2
TKN
OrgN
TP
TKN
OrgN
Winter
271 (2)
5630 (2)
*
345 (37)
1243 (31)
*
SprinE
47(3)
592 (3)
*
229 (30)
1231 (30)
*
Summer Fall1
53 (1) 171 (2)
740 (1) 1248 (2)
* *
829 (38) 176 (26)
2554 (38) 627 (24)
* *
* No samples taken
( ) ~ Number of measurements
1 Winter runoff:
Spring
Summer
Fall
January 1 - March
April 1 - June 30
July 1 - September
October 1 - Decem
31
30
ber 31
2 TP
TKN
OrgN
= Total Phosphorus
= Total Kjeldahl Nitrogen
= Organic Nitrogen
C34
-------
APPENDIX D
Regional Comparisons of Geographic Areas
in USGS and Purdue Water Quality Model
-------
-------
Appendix D: USGS Regions/Subregions Comprising Purdue Water Quality Model
River Systems1
USGS Regions (2-digit)
or Subreeions (4-digit)
Purdue Water Quality
Model River System #
0309 - Partial, 0310
0311,0312,0313
0314, 0315, 0316, 0317, 0318
05, 06, 07, 08, 10, 11 - All Subrcgions
1201, 1202, 1203, 1204
1205, 1206, 1207, 1208, 1209, 1210, 1211
13 - All Subregions
12
13
14
18
19
20
21
1 See Table 1, Appendix E of report for names of rivers, lakes and reservoirs included in each.
Dl
-------
-------
APPENDIX E
Summary Estimates of Concentrations
from Purdue Water Quality Model
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