Cover photo:The Mad River at Dayton,Ohio. Photo by Richard Baumer,

published with permission.
U.S. Department of the Interior

U.S. Geological Survey

Nitrogen and Phosphorus in Streams of 

the Great Miami River Basin, Ohio, 

1998–2000 

By David C. Reutter

Water-Resources Investigations Report 02–4297 

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM
U.S. Department of the Interior 

GALE A. NORTON, Secretary 

U.S. Geological Survey 

Charles G. Groat, Director 

Any use of trade, product, or firm names is for 

descriptive purposes only and does not imply

endorsement by the U.S. Government.

For additional information write to:

District Chief

U.S. Geological Survey

6480 Doubletree Avenue

Columbus, OH 43229-1111

Copies of this report can be purchased from:

U.S.Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225-0286

2003 
Foreword III

FOREWORD 

The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and 

timely scientific information that helps enhance and protect the overall quality of life, and 

facilitates effective management of water, biological, energy, and mineral resources. 

Information on the quality of the Nation’s water resources is of critical interest to the 

USGS because it is so integrally linked to the long-term availability of water that is clean 

and safe for drinking and recreation and that is suitable for industry, irrigation, and 

habitat for fish and wildlife. Escalating population growth and increasing demands for the 

multiple water uses make water availability, now measured in terms of quantity and

quality, even more critical to the long-term sustainability of our communities and 

ecosystems. 

The USGS implemented the National Water-Quality Assessment (NAWQA) Program to 

support national, regional, and local information needs and decisions related to waterquality management and policy. Shaped by and coordinated with ongoing efforts of other 

Federal, State, and local agencies, the NAWQA Program is designed to answer: What is 

the condition of our Nation’s streams and ground water? How are the conditions 

changing over time? How do natural features and human activities affect the quality of 

streams and ground water, and where are those effects most pronounced? By combining 

information on water chemistry, physical characteristics, stream habitat, and aquatic life, 

the NAWQA Program aims to provide science-based insights for current and emerging 

water issues. NAWQA results can contribute to informed decisions that result in 

practical and effective water-resource management and strategies that protect and restore 

water quality. 

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in 

more than 50 of the Nation’s most important river basins and aquifers, referred to as 

Study Units. Collectively, these Study Units account for more than 60 percent of the 

overall water use and population served by public water supply, and are representative of 

the Nation’s major hydrologic landscapes, priority ecological resources, and agricultural, 

urban, and natural sources of contamination.

Each assessment is guided by a nationally consistent study design and methods of 

sampling and analysis. The assessments thereby build local knowledge about waterquality issues and trends in a particular stream or aquifer while providing an 

understanding of how and why water quality varies regionally and nationally. The 

consistent, multi-scale approach helps to determine if certain types of water-quality issues 

are isolated or pervasive, and allows direct comparisons of how human activities and 

natural processes affect water quality and ecological health in the Nation’s diverse 

geographic and environmental settings. Comprehensive assessments on pesticides, 

nutrients, volatile organic compounds, trace metals, and aquatic ecology are developed at 

the national scale through comparative analysis of the Study-Unit findings.

The USGS places high value on the communication and dissemination of credible, 

timely, and relevant science so that the most recent and available knowledge about water 
IV Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998—2000

resources can be applied in management and policy decisions. We hope this NAWQA 

publication will provide you the needed insights and information to meet your needs, and 

thereby foster increased awareness and involvement in the protection and restoration of 

our Nation’s waters.

The NAWQA Program recognizes that a national assessment by a single program cannot 

address all water-resource issues of interest. External coordination at all levels is critical 

for a fully integrated understanding of watersheds and for cost-effective management, 

regulation, and conservation of our Nation’s water resources. The Program, therefore, 

depends extensively on the advice, cooperation, and information from other Federal, 

State, interstate, Tribal, and local agencies, non-government organizations, industry, 

academia, and other stakeholder groups. The assistance and suggestions of all are greatly 

appreciated.

 Robert M. Hirsch 

 Associate Director for Water 
Contents V

CONTENTS

Abstract ................................................................................................................................................................................. 1

Introduction .......................................................................................................................................................................... 2

Purpose and Scope ...................................................................................................................................................... 2

Acknowledgments........................................................................................................................................................ 2

Description of the Study Area .............................................................................................................................................. 4

Physiography and Geology .......................................................................................................................................... 4

Climate......................................................................................................................................................................... 4

Land Use ...................................................................................................................................................................... 4

Sampling Sites ............................................................................................................................................................. 6

Sampling and Analytical Methods ........................................................................................................................................ 6

Sampling Frequency .................................................................................................................................................... 6

Sample Collection and Laboratory Methods ............................................................................................................... 9

Quality-Control Sampling............................................................................................................................................ 9

Computation of Instream Loads................................................................................................................................... 10

Sources of Nitrogen and Phosphorus..................................................................................................................................... 10

Nonpoint Sources......................................................................................................................................................... 10

Commercial Fertilizer and Manure.................................................................................................................... 10

Nitrogen Fixation by Soybeans ......................................................................................................................... 11

Atmospheric Deposition.................................................................................................................................... 11

Nonpoint-Source Distribution of Nutrients in the Study Area.......................................................................... 12

Point Sources ............................................................................................................................................................... 15

Nitrogen and Phosphorus in Streams..................................................................................................................................... 15

Forms of Nitrogen and Phosphorus ............................................................................................................................. 15

Relation of Nitrogen and Phosphorus Concentrations to Season ................................................................................ 20

Relation of Nitrogen and Phosphorus Concentrations to Land Use ............................................................................ 20

Estimated Nitrogen and Phosphorus Loads ................................................................................................................. 23

Monthly Loads................................................................................................................................................... 23

Loads Computed from U.S. Environmental Protection Agency Data............................................................... 27

Historical Trends of Nitrogen and Phosphorus Loads for the Great Miami River............................................ 30

Nitrogen and Phosphorus Yields.................................................................................................................................. 33

Comparison of Nitrogen and Phosphorus Inputs and Instream Loads......................................................................... 36

Suggestions for Further Work................................................................................................................................................ 38

Summary and Conclusions ................................................................................................................................................... 38

References ............................................................................................................................................................................ 39

Glossary ................................................................................................................................................................................ 41

Appendix A

Quality-control data ..................................................................................................................................................... 43

Appendix B

Coefficients B0 through B6 used in the ESTIMATOR concentration models.............................................................. 44

Appendix C

 Statistical summary of nitrogen and phosphorus concentrations in the Great Miami River Basin, October 1998 – 

September 2000. .................................................................................................................................................... 45

Appendix D

Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total phosphorus. .. 47

Appendix E

Annual loads and confidence intervals for total nitrogen and total phosphorus.......................................................... 67
VI Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

FIGURES

1. Map showing location of U.S. Geological Survey and U.S. Environmental Protection Agency watersampling sites and the atmospheric-deposition sampling site for the Great Miami River Basin. ........................ 3

2. Graph showing difference in monthly precipitation recorded for the study area for water years 1998 

through 2001 as compared to the mean monthly precipitation for 1971 through 2000. ..................................... 4

3. Map showing land use of the Great and Little Miami River Basins. ..................................................................... 5

4. Graphs showing daily mean streamflow, 30-year median daily streamflow, and sample collections for 

 Stillwater River near Union, Great Miami River near Vandalia, Mad River near Eagle City, 

 Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 and 2000............... 8

5. Pie charts showing estimated nonpoint-source inputs of nitrogen to the Stillwater River, Upper

 Great Miami River, Mad River, and Lower Great Miami River Basins. ............................................................ 13

6. Pie charts showing the estimated nonpoint-source inputs of phosphorus to the Stillwater River, 

 Upper Great Miami River, Mad River, and Lower Great Miami River Basins. .................................................. 14

7. Map showing location of dischargers used in estimating the point-source inputs to the study area....................... 18

8. Graphs showing mean concentration distribution of nitrogen and phosphorus species computed 

 from samples collected at Stillwater River near Union, Great Miami River near Vandalia, Mad River 

 near Eagle City, Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 

 1999 and 2000. ..................................................................................................................................................... 19

9. Boxplots showing seasonal distribution of total nitrogen and dissolved nitrate concentrations for

 Stillwater River near Union, Great Miami River near Vandalia, Mad River near Eagle City, Holes 

 Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 and 2000. ......................... 21

10. Boxplots showing the seasonal distribution of total phosphorus and dissolved orthophosphate 

concentrations for Stillwater River near Union, Great Miami River near Vandalia, Mad River near 

 Eagle City, Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 

 and 2000. .............................................................................................................................................................. 22

11. Graphs showing relation between the percentage of drainage basin in row crops and the median 

concentrations of total nitrogen and total phosphorus for sites in the Great Miami and Little Miami 

 River Basins, Lake Erie-Lake Saint Clair Drainages, and the White River Basin study units. ........................... 24

12. Pie charts showing the load distribution of nitrogen species based on ESTIMATOR means for 

 Stillwater River near Union, Great Miami River near Vandalia, Mad River near Eagle City, Holes 

 Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 and 2000. ........................ 25

13. Pie charts showing the load distribution of phosphorus species based on ESTIMATOR means 

 for Stillwater River near Union, Great Miami River near Vandalia, Mad River near Eagle City, Holes 

 Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 and 2000. ......................... 26

14–21. Graphs showing:

14. Instream loads and point-source inputs of nitrate for Stillwater River near Union, Great Miami River 

 near Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great Miami River at 

 Hamilton, Ohio, water years 1999 and 2000....................................................................................................... 28

15. Instream loads and point-source inputs of total phosphorus for Stillwater River near Union, Great 

 Miami River near Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great Miami 

 River at Hamilton, Ohio, water years 1999 and 2000. ....................................................................................... 29

16. Percentage of stream load from point-source contributions for total nitrogen and total phosphorus at 

 Great Miami River at Hamilton, Ohio, water years 1999 and 2000. ................................................................... 31

17. Monthly loads of total nitrogen and total phosphorus for the three sites above Dayton, Ohio, and 

 Great Miami River at Hamilton, Ohio, water years 1999 and 2000.................................................................... 31

18. Comparison of nitrate, total nitrogen, and total phosphorus concentrations from samples collected 

 on the same day by the U.S. Environmental Protection Agency and the U.S. Geological Survey .................... 32

19. Monthly loads of nitrate, total nitrogen, and total phosphorus computed from U.S. Environmental 

 Protection Agency and U.S. Geological Survey data, December 1999 through September 2000...................... 32

20. Annual loads of total nitrogen and total phosphorus for the Great Miami River at Miamisburg, 

 Hamilton, Ohio, water years 1974 through 2000................................................................................................ 33
Contents VII

21. Daily mean yields of ammonia, nitrate, total nitrogen, orthophosphate, and total phosphorus for 

 Stillwater River near Union, Great Miami River near Vandalia, Mad River near Eagle City, and 

 Holes Creek near Kettering, Ohio, water years 1999–2000, and Great Miami River at Hamilton, 

Ohio, water years 1974–93 and 1999-2000. ....................................................................................................... 35

TABLES

1. Description of the water-quality, streamflow, and atmospheric stations used in the study ........................................... 7

2. Nutrients determined by the National Water Quality Laboratory.................................................................................. 9

3. Estimated 1997 amounts of nitrogen and phosphorus from manure and commercial fertilizer applications 

and nitrogen from nitrogen fixation. ...........................................................................................................................11

4. Atmospheric deposition of inorganic nitrogen and precipitation measured at Oxford, Ohio...................................... 12

5. Estimated atmospheric deposition of inorganic nitrogen to the basins and study area ................................................ 12

6. Description of dischargers used in point-source input calculations ............................................................................. 16

7. Percentage contribution to mean total nitrogen and total phosphorus loads by species, October 1998–

 September 2000......................................................................................................................................................... 23

8. Statistical summary of the monthly nutrient loads for sites in the Great Miami River Basin, October 1998– 

 September 2000..........................................................................................................................................................30

9. Statistical summary of the monthly nutrient yields for sites in the Great Miami River Basin, October 1998– 

 September 2000.......................................................................................................................................................... 34

10. Estimated daily point- and nonpoint-source inputs of total nitrogen and total phosphorus to the three sites 

upstream from Dayton, Ohio and to the Great Miami River at Hamilton, Ohio, water years 1999 and 2000............ 36

11. Daily nonpoint-source inputs of total nitrogen and total phosphorus and estimated percentage of nonpoint 

inputs deposited onto the basins that enter the stream, water years 1999 and 2000 ................................................... 37

A1. Summary of the quality-control data for nitrogen and phosphorus in the Great Miami River Basin, 

October 1998–September 2000................................................................................................................................... 43

 CONVERSION FACTORS AND ABBREVIATED WATER-QUALITY UNITS

Abbreviated water-quality units used in this report: Chemical concentration is given in milligrams per liter (mg/L), a unit expressing 

the concentration of chemical constituents in solution as weight (milligrams) of solute per unit volume (liter) of water. For concentrations 

less than 7,000 mg/L, the numerical value is approximately the same as for concentrations in parts per million. Nutrient loads are given in 

kilograms (kg), whereas nutrient yields are given in kilograms per square kilometer (kg/km2

).

Multiply By To obtain

 kilometer (km) 0.6214 mile

mile (mi) 1.609 kilometer

acre 0.4047 square hectometer

square kilometer (km2) 0.3861 square mile

square mile (mi2) 2.590 square kilometer

cubic foot per second (ft3

/s) 0.02832 cubic meter per second

kilogram (kg) 2.205 pound

kilogram per square kilometer (kg/km2) 5.711 pound per square mile

million gallons per day (Mgal/d) 0.04381 cubic meter per second
VIII Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000
Abstract 1

Nitrogen and Phosphorus in Streams of the Great Miami River 

Basin, Ohio, 1998–2000

By David C. Reutter

Abstract

Sources and loads of nitrogen and phosphorus in 

streams of the Great Miami River Basin were evaluated as part of the National Water-Quality Assessment 

program. Water samples were collected by the U.S. 

Geological Survey from October 1998 through September 2000 (water years 1999 and 2000) at five locations in Ohio on a routine schedule and additionally 

during selected high streamflows. Stillwater River 

near Union, Great Miami River near Vandalia, and 

Mad River near Eagle City were selected to represent 

predominantly agricultural areas upstream from the 

Dayton metropolitan area. Holes Creek near Kettering 

is in the Dayton metropolitan area and was selected to 

represent an urban area in the Great Miami River 

Basin. Great Miami River at Hamilton is downstream 

from the Dayton and Hamilton-Middletown metropolitan areas and was selected to represent mixed agricultural and urban land uses of the Great Miami River 

Basin. 

Inputs of nitrogen and phosphorus to streams 

from point and nonpoint sources were estimated for 

the three agricultural basins and for the Great Miami 

River Basin as a whole. Nutrient inputs from point 

sources were computed from the facilities that discharge one-half million gallons or more per day into 

streams of the Great Miami River Basin. Nonpointsource inputs estimated in this report are atmospheric 

deposition and commercial-fertilizer and manure 

applications.

Loads of ammonia, nitrate, total nitrogen, orthophosphate, and total phosphorus from the five sites 

were computed with the ESTIMATOR program. The 

computations show nitrate to be the primary component of instream nitrogen loads, and particulate phosphorus to be the primary component of instream 

phosphorus loads. 

The Mad River contributed the smallest loads of 

total nitrogen and total phosphorus to the study area 

upstream from Dayton, whereas the Upper Great 

Miami River (upstream from Vandalia) contributed 

the largest loads of total nitrogen and total phosphorus 

to the Great Miami River Basin upstream from Dayton. An evaluation of monthly mean loads shows that 

nutrient loads were highest during winter 1999 and 

lowest during the drought of summer and autumn 

1999. During the 1999 drought, point sources were the 

primary contributors of nitrogen and phosphorus loads 

to most of the study area. Nonpoint sources, however, 

were the primary contributors of nitrogen and phosphorus loads during months of high streamflow. Nonpoint sources were also the primary contributors of 

nitrogen loads to the Mad River during the 1999 

drought, owing to unusually large amounts of groundwater discharge to the stream.

The Stillwater River Basin had the highest nutrient yields in the study area during months of high 

streamflow; however, the Mad River Basin had the 

highest yields of all nutrients except ammonia during 

the months of the 1999 drought. The high wet-weather 

yields in the Stillwater River Basin were caused by 

agricultural runoff, whereas high yields in the Mad 
2 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

River Basin during drought resulted from the large, 

sustained contribution of ground water to streamflow 

throughout the year.

In the basins upstream from Dayton, an estimated 19 to 25 percent of the nonpoint source of nitrogen and 4 to 5 percent of the nonpoint source of 

phosphorus that was deposited or applied to the land 

was transported into streams. 

Introduction

Living organisms require chemical nutrients to sustain their 

growth and development. If one of these nutrients is in short 

supply, it controls the population density of certain organisms and is said to be the “limiting” nutrient. In most 

aquatic ecosystems, the limiting nutrient is thought to be 

either nitrogen or phosphorus. When the amount of nutrients entering a stream or lake is not controlled and concentrations of nitrogen and phosphorus become sufficiently 

large, then water quality can be adversely affected, as 

reflected by algal blooms, toxicity to aquatic life, and (or) 

toxicity to warmblooded animals that drink the water (Litke, 

1999; Thomann and Mueller, 1987; Hem, 1989). Moreover, 

algal blooms can cause large diurnal variations in dissolvedoxygen concentrations, which consequently can eliminate 

susceptible fish species in streams and lakes. 

Nutrient concentrations in the Nation’s streams and 

lakes increased substantially during the past century. This 

increase was mainly due to increases in municipal and 

industrial discharges, fertilizer use, and atmospheric inputs 

(Puckett, 1995). In the 1970s, however, this trend began to 

change. The Federal Government enacted the Federal Water 

Pollution Control Act of 1972, in part to begin lowering 

concentrations of nutrients in many streams and lakes of the 

Nation. This act (also known as the Clean Water Act) 

helped fund the upgrading of wastewater-treatment facilities 

to remove nutrients and other contaminants from effluent. 

By the 1990s, wastewater-treatment facilities had become 

more efficient in removing nutrients from effluent (Litke, 

1999). For example, the Ohio Environmental Protection 

Agency (Ohio EPA) did studies of the biological integrity 

of the Great Miami River in 1980, 1989, and 1995 and 

observed a trend of improvement. The agency concluded 

that part of the improvement was caused by a decrease in 

ammonia being introduced into streams from wastewatertreatment facilities, a direct result of the Clean Water Act 

(Rankin and others, 1997). Some state and local governments have also banned household use of phosphate detergents in order to limit phosphorus inputs to the environment. Currently (2002) the only counties in the Great Miami 

River Basin (fig. 1) with a ban on phosphate detergents are 

Auglaize and Shelby, and only because parts of these counties drain into Lake Erie. 

Despite the noted improvements, algal blooms were 

observed in the Great Miami River between Dayton and 

Hamilton during the latest biological and water-quality 

assessment of the Lower Great Miami River by the Ohio 

EPA in 1995 (Ohio Environmental Protection Agency, 

1997). The amount of nutrients found in waters of the Great 

Miami River Basin is not only a local concern but also a 

concern for aquatic life in the Gulf of Mexico. A study by 

Goolsby and others (1999) on the flux and sources of nutrients in the Mississippi-Atchafalaya River Basin found that 

the Great Miami River Basin has some of the highest yields 

of nitrogen and phosphorus in the Mississippi River Basin. 

Only a few basins in Iowa and Illinois are thought to produce higher yields. High loads of nutrients in spring runoff 

to the Gulf of Mexico from the Mississippi River Basin 

were found to be responsible for increased algal growth in 

the Gulf of Mexico, which has led to seasonal oxygen 

depletion (hypoxia) (Goolsby and others, 1999).

Purpose and Scope

This report describes and quantifies major sources of 

nutrients (nitrogen and phosphorus) in the Great Miami 

River Basin, describes spatial and temporal variations in 

nutrient concentrations at selected monitoring sites, lists 

estimated loads and yields of nutrients from five stream 

sites monitored, and relates observed loads and yields to 

selected environmental factors and land use. Nutrient 

sources are evaluated by quantifying, where possible, contributions of point and nonpoint sources. Instream concentrations of nutrients are based on analyses of water samples 

collected from three tributaries of the Great Miami River 

and from two main-stem sites. Nutrient loads were computed from analyses of samples collected during October 

1998 through September 2000 (water years 1999–2000). 

These loads are compared with load estimates derived from 

nutrient data collected by the U.S. Environmental Protection Agency (USEPA) and the USGS National Stream 

Quality Accounting Network (NASQAN). Daily mean 

streamflows were determined from gaging-station records 

maintained by the USGS and Miami Conservancy District 

(MCD). 

Acknowledgments

The author acknowledges the significant contributions of the U.S. Environmental Protection Agency; the 

Water Quality Unit of Ohio EPA, Southwest District 

Office; the Miami Conservancy District; and the Ohio 

Department of Agriculture in providing information and 

data vital to this report. The author thanks the numerous 

publicly owned wastewater-treatment facilities that provided monthly operating reports detailing quantity and quality of waters being discharged into streams.
3

Figure 1. Location of U.S. Geological Survey (USGS) and U.S. Environmental Protection Agency (USEPA) water-sampling sites and 

the atmospheric-depostition sampling site for the Great Miami River Basin.

Introduction
4 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Description of Study Area

The Great Miami River drainage area is 5,330 mi2 where 

the Great Miami joins the Ohio River at the Ohio-Indiana 

State line. The Great Miami River originates within the 

drainage basin of Indian Lake in Hardin, Auglaize, and 

Logan Counties. The Stillwater and Mad Rivers merge with 

the Great Miami River within a 2-mi reach near downtown 

Dayton to make up the lower reach of the Great Miami 

River (fig. 1). Long-term (1971–2000) mean daily streamflow for Mad River near Eagle City (03267900) is 310 ft3

/s; 

however, the long-term mean daily streamflow for Mad 

River near Dayton (03270000), 6 mi upstream from the confluence with the Great Miami River, increases to 683 ft3

/s. 

Long-term mean daily streamflows for Great Miami River 

at Taylorsville (03263000) and Stillwater River at Englewood (03266000) are 1,020 ft3

/s and 589 ft3/s, respectively. 

At Great Miami River at Hamilton (03274000), 45 mi 

downstream from the merger of these two rivers, long-term 

mean streamflow is 3,340 ft3/s. In comparison, long-term 

mean streamflow for the mouth of the Ohio River (Grand 

Chain, Ill. (03612500)) is 296,000 ft3/s. Great Miami River 

streamflow, therefore, constitutes slightly more than 1 percent of the entire Ohio River streamflow on average. 

Physiography and geology

The study area is entirely within the Till Plains section of the Central Lowland Physiographic Province (Fenneman, 1938). All of the study area was affected by 

Pleistocene glaciation in which advance and retreat of ice 

sheets produced a flat to gently rolling land surface. 

The geology of the study area is dominated by Quaternary glacial deposits that overlie a sequence of Ordovician, Silurian, and Devonian sedimentary rocks. Glacial 

deposits found in the study area consist of till, outwash, and 

lacustrine deposits. The till is an unsorted mixture of clay, 

silt, sand, and gravel that was deposited by advancing glaciers or by melting stagnant ice. The outwash consists of 

well-sorted sand and gravel that was deposited when ice 

sheets melted and large volumes of meltwater flowed 

through stream valleys; the Mad River Interlobate Area, in 

particular, is characterized by extensive outwash deposits 

that are high-yielding aquifers (Brockman, 1998).The lacustrine sediments consist of layered silt and clay that formed 

in basins or valleys dammed by glacial ice (Debrewer and 

others, 2000). 

Climate

The study area has a temperate continental climate 

characterized by four distinct seasons and moderate 

extremes in annual temperature variations. Mean annual 

precipitation for Dayton is 38 in. (National Oceanic and 

Atmospheric Administration, 2001; Miami Conservancy 

District, 2001). Spring and summer tend to receive greatest 

monthly precipitation amounts, which are usually associated with thunderstorms. The precipitation pattern that 

developed during part of the study period, however, was not 

normal. During most of spring, summer, and autumn 1999, 

monthly precipitation was below the mean monthly precipitation for 1971 through 2000 (fig. 2).

Land Use

Approximately 81 percent of the study area is used 

for agriculture (fig. 3), and most of this agricultural land is 

in corn, soybean, and wheat production. Approximately 30 

percent of the land in the three basins upstream from Dayton is planted in soybeans and 25 percent in corn. Generally 

less than 10 percent of the land is in wheat (Ohio Agricultural Statistics, 1999a, 1999b, and 1999c). Corn and soybeans are planted in spring and early summer and harvested 

in autumn whereas winter wheat is planted in autumn and 

harvested in summer (Debrewer and others, 2000). 

Livestock production is also common in the study 

area, particularly in the Stillwater River Basin. On the basis 

of 1997 data, an estimated 145,000 cattle, 350,000 hogs and 

pigs, and 8,300,000 fowl were raised in the study area. Of 

this, approximately 8,000,000 fowl and 150,000 hogs were 

raised in the Stillwater River Basin. In comparison, approximately 3,000 fowl and 50,000 hogs were raised in the Mad 

River Basin and approximately 140,000 fowl and 90,000 

hogs in the Upper Great Miami River Basin. (U.S. Department of Agriculture, 1999).

Figure 2. Difference in monthly precipitation recorded for the 

study area for water years 1998 through 2001 as compared to 

the mean monthly precipitation for 1971 through 2000. (Shaded 

timespan represents the sampling period for report. Data from 

National Oceanic and Atmospheric Administration, 2002.)
Description of Study Area 5

Figure 3. Land use in the Great and Little Miami River Basins.
6 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Most of the Dayton-Springfield Metropolitan area 

(Clark, Miami, Greene, and Montgomery Counties) is in the 

Great Miami River Basin, although some communities east 

of Dayton lie outside the study area (fig. 3).This metropolitan area has a population of 950,000. South of Dayton is the 

Hamilton-Middletown metropolitan area (Butler County), 

with a population of 330,000 (U.S. Census Bureau, 2001a). 

Total population of the study area has increased little in 

recent decades, from an estimated 1.3 million in 1970 to an 

estimated 1.4 million in 2000 (U.S. Census Bureau, 1995; 

U.S. Census Bureau, 2001a).

For purposes of this study, the farthest downstream 

site selected for nutrient load computations is Great Miami 

River at Hamilton, Ohio. Selection of this site permits the 

study to focus on the part of the Great Miami River Basin 

that includes the Dayton-Springfield and Hamilton-Middletown metropolitan areas but excludes western reaches of the 

Cincinnati metropolitan area and contributions from the 

Whitewater River Basin in southeastern Indiana. For the 

remainder of this report, “Great Miami River Basin” refers 

to only the drainage area of the Great Miami River upstream 

from Hamilton. 

Sampling Sites

Water samples were collected for nutrient analysis at 

five USGS sampling sites (table 1). Three of the sites are 

upstream from Dayton and have drainage areas that are not 

affected by the Dayton metropolitan area (fig. 1). These 

sites are Stillwater River near Union, Great Miami River 

near Vandalia, and Mad River near Eagle City. The basins 

for these sites consist of agricultural lands mixed with lowdensity residential areas. The Mad River site is just 

upstream from the city of Springfield. The Holes Creek site 

is in the Dayton metropolitan area and is in a predominantly 

urban setting that consists of residential and commercial 

land uses. The Holes Creek basin has no industrial or 

municipal point sources and has a drainage area of only 

20 mi2; this site is especially important to the study because 

urban fertilizer application and atmospheric deposition 

would be the main sources of the nutrient loads and yields 

for this basin. The Great Miami River at Hamilton site is 

downstream from the Dayton-Springfield Metropolitan 

area, and the cities of Hamilton, Middletown, Miamisburg 

are also within its drainage area. An unexpected problem 

arose when the bridge at the Hamilton site underwent reconstruction during spring and summer of 2000; samples could 

not be collected at the site during most of that time.

Although the three basins upstream from Dayton are 

in predominantly agricultural lands, urban areas are present 

in each. The Mad River Basin includes Urbana (population 

11,613). The Upper Great Miami River Basin includes Bellfontaine (population 13,069), Piqua (population 20,738), 

Sidney (population 20,211), and Troy (population 21,999). 

The Stillwater River Basin includes Greenville (population 

13,294), Union (population 5,574) and Covington (population 2,559) (U.S. Census Bureau, 2001b). These municipalities have publicly owned wastewater-treatment facilities 

that individually discharge 0.5 Mgal/d or more of effluent 

into streams of the Great Miami River Basin.

Sampling and Analytical Methods

From October 1998 through September 2000 (water years 

1999 and 2000), USGS personnel collected water samples 

to be analyzed for nutrients at the five sites. Samples were 

collected on a routine schedule and additionally during 

selected high streamflows. Sample collection continued 

during water year 2001 at the Mad River, Holes Creek, and 

Great Miami River at Hamilton sites; however, because 

samples were not collected at all sites for water year 2001, 

the samples collected in 2001 were used only for calibrating 

the model used to estimate instream nutrient loads. 

Sampling Frequency

The sampling schedule differed from site to site and 

from season to season (fig. 4). Mad River near Eagle City, 

Holes Creek near Kettering, and the Great Miami River at 

Hamilton were sampled more frequently than Stillwater 

River near Union and Great Miami River near Vandalia. 

Samples were collected at Stillwater River near 

Union and Great Miami River near Vandalia during 31 visits and 30 visits, respectively. Routine samples were collected monthly at both sites throughout the monitoring 

period. During the first 18 months of the monitoring period, 

daily mean streamflows were usually below the 30-year 

daily median streamflows (that is, the median of the daily 

mean streamflows for each calendar day; fig. 4). At both 

sites, the lowest recorded streamflow for the monitoring 

period was during autumn 1999. The 30-year daily median 

streamflow during October through December is 140 ft3/s 

for Stillwater River near Union and 330 ft3/s for Great 

Miami River near Vandalia. From October through December of 1999, however, mean streamflow was 65 ft3

/s for 

Stillwater River near Union and 120 ft3

/s for Great Miami 

River near Vandalia. Not until March 2000 did daily mean 

streamflows reach levels similar to the 30-year daily median 

streamflows. 

Nutrient samples were collected during 51 visits to 

Mad River near Eagle City for water years 1999 and 2000. 

Routine samples were collected at this site monthly during 

autumn and winter and weekly or twice a month during 

spring and summer. Streamflow at this site was below the 

30-year daily median streamflow during most of the sampling period; however, streamflow of the Mad River was 

not as affected by droughts as the other sites in the study 

area because of the large amount of ground water that dis
Sampling and Analytical Methods 7

1Streamflow measured at station 03266000, Stillwater River at Englewood, Ohio, latitude 39o52’10”, longitude 84o16’57”; 2.8 river miles downstream from samp2Streamflow measured at station 03263000, Great Miami River at Taylorsville, Ohio, latitude 39o52’27”, longitude 84o09’45”; 3.2 river miles downstream from sa3Water-quality samples collected by the U.S. Environmental Protection Agency, December 1999–December 2000. 4Water-quality samples collected by the U.S. Geological Survey as part of the National Stream Quality Accounting Network (NASQAN), 1975–93.Table 1. Description of the water-quality, streamflow, and atmospheric stations used in the study[Population density data from 1990 U.S. Census; land-use data from Earth Resource Observations Systems Data Center, 1992 (U.S. Geological Survey, 2002); mi2

Reference 

Number

 Station number Station name

Station

purpose Latitude Longitude

 Drainage 

area

(mi2)

 Population 

density

of drainage 

basin

(people per 

mi2)

Percent

 Agricu

1 395355084173600 Stillwater River near 

Union, Ohio1

Water quality 39o53’55” 84o17’36” 646 124 92 

2 395457084095100 Great Miami River near 

Vandalia, Ohio2

Water quality 39o54’57” 84o09’51” 1,142 150 87 

3 03267900 Mad River at St. Paris 

Pike near Eagle City, Ohio

Water quality and streamflow

39o57’51” 83o49’54” 310 133 82 

4 393944084120700 Holes Creek at Huffman Park near Kettering, Ohio Water quality and streamflow 39o39’44” 84o12’07” 20 1,297 28 

5 03274000 Great Miami River at 

Hamilton, Ohio

Water quality and streamflow

39o23’28” 84o34’20” 3,630 319 80 

6 03274060 Great Miami River at 

Fairfield, Ohio3

Water quality 39o19’03” 84o36’23” 3,670 343 80 

7 03274600 Great Miami River at 

New Baltimore, Ohio4

Water quality 39o15’50” 84o40’00” 3,814 342 80 

8 OH09 Oxford, Ohio Atmospheric 39o31’53” 84o43’27” NA NA NA 
8 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Figure 4. Daily mean streamflow, 30-year median daily streamflow, and sample collections for Stillwater River near Union, Great Miami 

River near Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 

and 2000.
Sampling and Analytical Methods 9

discharges to the stream (Koltun, 1995). This difference can 

be seen in daily-streamflow hydrographs for the 1999 

drought (fig. 4). 

Samples were collected at Holes Creek near Kettering during 53 visits from January 1999 through September 

2000. Samples were collected twice a month during winter 

1999, four times a month during spring and summer 1999, 

then twice a month from October 1999 through September 

2000. Streamflow record for the Holes Creek site were 

unavailable until January 1999 because of problems with 

data storage at the site. Samples collected in October, 

November, and December 1998 could not be included in 

load computations because of missing streamflow data for 

those months.

Samples were collected during 35 visits to Great 

Miami River at Hamilton during water years 1999 and 

2000. As observed at the other sites in the study area, the 

1999 drought had an effect on streamflow at Hamilton: the 

30-year mean streamflow during October through December is 1,500 ft3/s, but mean streamflow was 500 ft3/s from 

October through December 1999. 

Sample Collection and Laboratory Methods

USGS personnel used National Water-Quality 

Assessment (NAWQA) sampling protocols (Shelton, 1994) 

to collect and process samples. These protocols require 

samples to be collected by means of the equal-width increment (EWI) method, in which depth-integrated samples are 

collected at equal distances across the entire stream width 

and composited. 

Samples were analyzed at the USGS National Water 

Quality Laboratory (NWQL) in Lakewood, Colorado, using 

methods described by Fishman (1993). The NWQL determined the long-term method detection level (LT-MDL) for 

each nutrient species. At LT-MDL concentration, 99 percent of reported detections are true detections of the chemical of interest; however, at LT-MDL concentration, there is 

a 50 percent chance of the target chemical’s not being 

detected—a false-negative detection (Childress and others, 

1999). To avoid a high number of false-negative detections, 

the NWQL has established the laboratory reporting level 

(LRL) for a chemical at twice the LT-MDL. Concentrations 

measured between the LRL and the LT-MDL are reported 

as estimated concentrations (Childress and others, 1999). 

Nutrients that were measured at the NWQL, along with the 

LRL established by the NWQL, for the individual nutrient 

species are listed in table 2.

 Quality-Control Sampling

Quality-control samples were collected to estimate 

bias and variability of the environmental data. For this 

study, quality-control samples consisted of field blanks and 

replicates collected periodically throughout the sampling 

period. Field blanks consisted of deionized water, certified 

to be free of inorganic compounds, that was passed through 

all equipment used in the field for sample collection and 

processing. Replicate samples were splits of the environmental-water sample that were processed through the same 

sampling equipment. Field blanks were used to test for bias 

from contamination at any stage of sample collection and 

analysis. Replicates were used to estimate variability from 

sampling and analysis processes (Mark Sandstrom, USGS, 

written commun., 1996). These quality-control samples 

were collected periodically during the sampling period and 

accounted for about 12 percent of the samples collected for 

this study. Results of the quality-control sampling effort are 

given in Appendix A. Field blanks indicated no consistent 

contamination problems with any of the nutrient species. 

. 

Table 2. Nutrients determined by the National Water Quality 

Laboratory

[mg/L, milligrams per liter; N, nitrogen; P, phosphorus]

Constituent Laboratory reporting 

level

Ammonia nitrogen, dissolved 0.02 mg/L as N

Nitrite nitrogen, dissolved 0.01 mg/L as N

Organic nitrogen and ammonia, dissolved 0.1 mg/L as N

Organic nitrogen plus ammonia, total 0.1 mg/L as N

Nitrite plus nitrate, dissolved 0.1 mg/L as N

Phosphorus, total 0.008 mg/L as P

Phosphorus, dissolved 0.006 mg/L as P

Orthophosphate, dissolved 0.01 mg/L as P
10 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Computation of Instream Loads 

Loads and yields of dissolved ammonia, dissolved 

nitrate, dissolved ammonia plus organic nitrogen, total 

nitrogen, dissolved orthophosphate, and total phosphorus 

were estimated for the five sites selected in the study area. 

Nutrient loads during October 1998 through September 

2000 (water years 1999 and 2000) were computed by use of 

the ESTIMATOR program. 

The ESTIMATOR program developed in 1988 by 

the USGS was initially used to estimate nutrient loads entering Chesapeake Bay through its major tributaries 

(T.A.Cohn, U.S. Geological Survey, written commum., 

1995). This program performs multivariate regression computations that include streamflow, time, and seasonal indicators as explanatory variables. Two methods are used for 

load estimates: For uncensored data (no less-than values in 

the data set), ESTIMATOR implements the Minimum Variance Unbiased Estimator procedure. For censored data 

(some concentrations less than the LT-MDL), ESTIMATOR implements the Adjusted Maximum Likelihood Estimator procedure (Cohn and others, 1992; Cohn and others, 

1989). 

The ESTIMATOR program allows the user to select 

a model best suited for the particular study. Results from 

previous studies (Cohn and others, 1992; Goolsby and others, 1999; Trench, 2000) have found that a seven-parameter 

model commonly is sufficient for accurate load estimates. 

The following equation form was chosen for this study:

ln[C] = Bo + B1ln[Q] + B2ln2

[Q] + B3T + B4T2 + B5sin[2πT] 

+ B6cos[2πT] + e,

where ln denotes the natural logarithm function, 

C is constituent concentration (milligrams per liter), 

Q is daily average discharge (cubic feet per second), 

T is time (decimal years), 

B0 through B6 are coefficients estimated from the data, 

and e is an independent random error. 

The sine and cosine terms in the equation adjust the 

model for seasonal variability. Time (T) and natural log of 

streamflow (ln[Q]) are centered values, which are usually 

very close to the mean value. Coefficients B0 through B6

used in the ESTIMATOR concentration models are listed in 

Appendix B.

There was one exception to the use of the sevenparameter model in the study. Samples collected at Great 

Miami River near Vandalia had many ammonia concentrations below the LT-MDL. Because of the low number of 

detectable concentrations, a three-parameter model had to 

be used for this constituent at this site. The following equation form was chosen:

ln[C] = Bo + B1ln[Q] + B2ln2

[Q].

This model was not able to account for annual or seasonal variability not already reflected in the streamflow 

record.

Loads were computed by ESTIMATOR (in kilograms) for each of the months and water years of interest, 

along with the corresponding 95-percent confidence intervals. In general, the accuracy of estimates derived from 

ESTIMATOR models increases with the amount of data 

available for model calibration. 

Sources of Nitrogen and Phosphorus

Nutrients introduced into the Great Miami River Basin 

come from point and nonpoint sources. Nutrients from point 

sources come from a discrete location, such as a pipe or 

drainage ditch. All nutrients from point sources that this 

report covers are assumed to enter the streams. Nutrients 

from nonpoint sources, on the other hand, are deposited 

onto basins over broad areas, such as by fertilizer application, animal-waste excretion, or atmospheric deposition. 

Only some of the available nonpoint-source nutrients are 

transported to streams. 

Nonpoint Sources

Nonpoint sources of nutrients to the study area 

include commercial-fertilizer and manure application to 

cropland, nitrogen fixation from soybeans, and atmospheric 

deposition of nutrients from sources that can extend beyond 

the study area. 

Because of the small amount of data available on 

nutrients from urban runoff, household use of fertilizers, 

combined sewer overflows, and failing septic systems, these 

potential sources were not included as part of the nonpointsource computations in this report. 

Commercial Fertilizer and Manure. Commercial fertilizer applied to agricultural lands has become a primary 

nonpoint source of nitrogen and phosphorus in the United 

States. Application of nitrogen in commercial fertilizer in 

the Nation increased from 0.5 million to more than 10 million metric tons between 1945 and 1993. Application of 

phosphorus in commercial fertilizer also increased during 

this time, from 0.5 million to 1.8 million metric tons (Puckett, 1995). Application of manure to agricultural lands is 

also a common source of nitrogen and phosphorus in the 

Nation. 

Soybeans, corn, and, to a lesser extent, wheat, make 

up the majority of crops planted in the Great Miami River 

Basin. In 1999, approximately 650,000 acres of the study 

area were planted in soybeans, 540,000 acres in corn, and 

105,000 acres in wheat (Ohio Agricultural Statistics Service, 1999a, 1999b, and 1999c). Most of the commercial 
Sources of Nitrogen and Phosphorus 11

nitrogen fertilizer used in the study area, however, is for 

corn. In Ohio, nitrogen fertilizer is applied to 100 percent of 

the corn acreage, 98 percent of the wheat acreage, and 

21 percent of the soybean acreage. Phosphorus fertilizer is 

applied to 97 percent of the corn acreage, 93 percent of the 

wheat acreage, and 35 percent of the soybean acreage (Ohio 

Agricultural Statistics Service, 2000). Nitrogen and phosphorus fertilizers generally are applied in spring during corn 

planting. Nitrogen fertilizer is then reapplied to corn fields 6 

to 10 weeks after planting. Phosphate fertilizer generally is 

applied to corn and soybean fields at planting. For wheat, 

nitrogen and phosphate fertilizers are applied in late summer through early autumn. 

Manure is applied to the land not only to supply 

nutrients but also to improve the water-holding capacity of 

soil, improve aeration of soil, and promote beneficial microorganisms (Ohio State University Extension, 1992). It is 

generally applied in autumn and winter. An estimated 

17 percent of the corn acreage, 8 percent of the soybean 

acreage, and 5 percent of the wheat acreage in Ohio receive 

applications of manure (Ohio State University Extension, 

1995a). 

Nutrient inputs from commercial fertilizer applied to 

agricultural lands in the study area were estimated on a 

county level from information on commercial-fertilizer 

sales collected by the Census of Agriculture in 1997 (U.S. 

Department of Agriculture, 1999). Nutrient inputs from 

manure were estimated on a county level from a census of 

livestock, also collected by the Census of Agriculture in 

1997 (U.S. Department of Agriculture, 1999). Manure estimates are based on average manure production rates per 

type of animal, developed by Goolsby and others (1999). 

Estimates of manure and commercial-fertilizer applications 

for the basins are based on these county estimates. Where 

needed, application amounts were adjusted to reflect the 

percentage area of the county in the basin (table 3). 

Nitrogen Fixation by Soybeans . Residing in root 

nodules of plants in the legume family (such as the soybean) 

are symbiotic bacteria that are able to convert atmospheric 

nitrogen (N2) into ammonia (NH3), the biologically useful 

form of nitrogen. Almost all of the nitrogen converted to 

ammonia is then used by the plant; only a small proportion 

of the fixed nitrogen is transferred to soil (Lindemann and 

Glover, 1990). Although an important source of nitrogen in 

the Great Miami River Basin—owing to the large acreage 

of soybeans in the study area—fixation of nitrogen from 

crops is not used in computations of nonpoint-source inputs 

of nitrogen to the study area because little of this nitrogen is 

available to enter streams. The amount of nitrogen produced 

by crop fixation in the basins (table 3) is based on the area 

of soybeans planted in the basins and an annual nitrogen 

fixation rate of 75 kilograms per hectare, as estimated by 

Burkart and James (1999) for soybeans in the Midwest. 

Atmospheric Deposition. Atmospheric deposition of 

nitrogen has been measured at a site near Oxford, Ohio 

(approximately 30 mi southwest of Dayton), since 1989. 

Data are collected for two USEPA-funded programs. 

Nitrate (NO3) and ammonia (NH3) nitrogen concentrations 

in wet deposition (rain or snow) were obtained from the 

National Atmospheric Deposition Program (NADP) 

(National Atmospheric Deposition Program, 2001). Nitric 

acid (HNO3) vapor, particulate nitrate (NO3), and particulate ammonia (NH3) nitrogen fluxes in dry deposition were 

obtained from the Clean Air Status and Trends Network 

(CASTNET) (U.S. Environmental Protection Agency, 

2001). Atmospheric deposition of phosphorus is not monitored by either NADP or CASTNET but is believed to be an 

insignificant source (National Atmospheric Deposition Program, 2001; U.S. Environmental Protection Agency, 2001). 

Atmospheric loads of inorganic nitrogen for 1998, 

1999, 2000, as well as the 10-year mean load for 1991–

Table 3. Estimated 1997 amounts of nitrogen and phosphorus from manure and commercial-fertilizer applications 

and nitrogen from nitrogen fixation

 [in million kilograms per year]

Manure Commercial fertilizer

Nitrogen 

fixation Total 

Basin Nitrogen Phosphorus Nitrogen Phosphorus Nitrogen Nitrogen Phosphorus

Mad River 0.7 0.2 4.1 0.8 1.7 6.5 1.0

Upper Great Miami River 3.3 1.0 13.8 2.5 6.0 23.1 3.5

Stillwater River 5.7 2.0 9.7 1.8 3.9 19.3 3.8

Great Miami River (study area) 13.7 4.5 44.0 8.1 17.8 75.5 12.6
12 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

2000, were computed from the NADP/CASTNET data from 

the Oxford station (table 4). The source of nitrate and 

ammonium nitrogen is mainly wet deposition, whereas 

nitrogen from dry deposition is mainly in the form of nitric 

acid vapor. The contribution of nitrogen from dry deposition is relatively constant from year to year, whereas the 

contribution of nitrogen from wet deposition depends on the 

amount of precipitation for that year. Wet-deposition inputs 

for 1999 were lower than the 10-year mean, reflecting the 

below-average precipitation for that year. Wet-deposition 

loads for 1998 and 2000, however, were higher than the 

10-year mean, reflecting the above-average precipitation for 

those years (table 4).

 Atmospheric deposition of inorganic nitrogen for 

individual basins and the study area on the whole is based 

on measurements from CASTNET and the NADP at the 

Oxford, Ohio, site (table 5). The 10-year mean of inorganic 

nitrogen deposited from the atmosphere onto the study area 

is estimated to be 8.6 million kg/yr.

Manure and nitrogen fertilization of croplands are 

believed to be the main sources of ammonia in the atmosphere (Vitousek and others, 1997). A USEPA report 

(1998a) estimated that the agricultural sector contributes 

approximately 85 percent of the ammonia emissions to the 

Nation’s atmosphere. Ammonia emitted to the atmosphere 

is in a highly water-soluble form that is easily removed 

from the atmosphere by precipitation (Goolsby and others, 

1999). Fossil-fuel combustion is a major source of nitrogen 

monoxide (NO) and nitrogen dioxide (NO2) to the atmosphere. Nitric acid vapor and particulate NO3 are then 

formed in the atmosphere by oxidation of NO and NO2. Particulate NO3 can be transported for hundreds of miles from 

its source because of its low deposition velocity. Nitric acid 

vapor typically reacts with other pollutants to form particles 

that also have low deposition velocities (Lawrence and others, 1999). 

Nonpoint-Source Distribution of Nutrients in the 

Study Area. Using the most recent data available, nonpointsource inputs of nutrients were computed for each basin. Of 

the sources evaluated, application of commercial fertilizer 

to agricultural lands was the greatest nonpoint-source contributor of nitrogen and phosphorus in the study area (figs. 5 

and 6). Commercial-fertilizer applications account for 

between 70 and 80 percent of the input of nitrogen and 

phosphorus to the Mad River and Upper Great Miami River 

Basins; however, commercial-fertilizer applications contributed only 57 percent of the nitrogen inputs and 46 percent of the phosphorus inputs to the Stillwater River Basin. 

For the Great Miami River Basin, commercial-fertilizer 

applications contributed 67 percent of the nitrogen inputs 

and 64 percent of the phosphorus inputs. 

Manure is a potentially large nonpoint source of 

nitrogen and phosphorus in the Stillwater River Basin. 

Because of the high concentration of livestock in this basin, 

manure contributed 54 percent of the phosphorus input and 

34 percent of the nitrogen input. Farms in this basin do not 

apply all available manure to cropland within the basin, 

however, and much of the manure is transported for application outside of the basin. For example, approximately 

40 percent of the poultry manure generated in Darke County

 Table 4. Atmospheric deposition of inorganic nitrogen and precipitation measured at Oxford, Ohio 

[Sources: Dry-deposition data, Clean Air Status and Trends Network (2001); Wet-deposition and precipitation data, National 

Atmospheric Deposition Program (2001)]

Year Deposition of nitrogen, in kilograms per square kilometer per 

year

Annual 

precipitation 

Dry Wet Total (inches)

1998 346 777 1,123 44.1

1999 376 410 786 29.4

2000 321 607 928 44.5

1991–2000, mean 352 570 922 39.0

Table 5. Estimated atmospheric deposition of inorganic nitrogen to the basins and study area

[in million kilograms of nitrogen per year]

Basin 1998 1999 2000 1991–2000, mean

Mad River 0.9 0.6 0.7 0.7

Upper Great Miami River 3.3 2.3 2.8 2.7

Stillwater River 1.9 1.3 1.6 1.5

Great Miami River (study area) 10.6 7.4 8.7 8.6
Sources of Nitrogen and Phosphorus 13

 

 

Figure 5. Estimated nonpoint-source inputs of nitrogen to the Stillwater River, Upper Great Miami River, Mad River, and 

Lower Great Miami River Basins.
14 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

 

 

Figure 6. Estimated nonpoint-source inputs of phosphorus to the Stillwater River, Upper Great Miami River, Mad River, 

and Lower Great Miami River Basins.
Nitrogen and Phosphorus in Streams 15

within the Stillwater River Basin is exported to other counties within and outside of the Stillwater River Basin (Nikki 

Reese, Darke County Soil and Water Conservation Service, 

oral commun., 2002). The contribution of manure to this 

basin is, therefore, an overestimation. Contributions of 

manure to the Mad River and Upper Great Miami River 

Basins constituted approximately 15 percent of the nitrogen 

inputs and approximately 25 percent of the phosphorus 

inputs. Manure contributed 20 percent of the nitrogen inputs 

and 36 percent of the phosphorus inputs to the overall study 

area. 

Atmospheric deposition was also an important contributor of nitrogen throughout the study area, contributing 

an estimated 9 to 14 percent of the nonpoint source of nitrogen to the basins (fig. 5). 

Nonpoint-source inputs for the Holes Creek Basin 

could not be estimated for this report because of the lack of 

available data on commercial-fertilizer and manure applications to urban lands; however, most of the nutrients found in 

this stream can be attributed to commercial-fertilizer application and atmospheric deposition. 

Point Sources

Nutrient inputs to the Great Miami River Basin from 

point sources were computed for each month of the study 

period. The nutrient inputs are based on information compiled from monthly operating reports (MORs) that dischargers must provide to the Ohio EPA. In most cases, the MORs 

provide mean daily conduit flows and ammonia concentrations measured from the effluent. Many of the dischargers 

must also submit concentration data for nitrite plus nitrate 

and total phosphorus measured in the effluent. Ammonia 

concentrations are measured daily, whereas nitrite plus 

nitrate and total phosphorus are usually measured less frequently. For this study, only facilities that discharge 

0.5 Mgal/d or more into the basin were available for input 

computations (table 6). This cutoff rate, unfortunately, 

excludes many minor dischargers in the study area, which, 

if totaled, could be a significant source of nutrients into the 

basin. Discharges of industrial cooling water also were 

excluded from this study. For months in which the MOR 

was unavailable from a discharger, median concentration 

and discharge, computed from available months, were used. 

In cases where dischargers were not required to submit total 

phosphorus or nitrate measurements as part of their MOR, 

median concentrations measured from previous Ohio EPA 

studies were used. Locations of the dischargers used to 

compute point sources contributing nutrients to the study 

area are shown in figure 7. 

Nitrogen and Phosphorus in Streams

The species distribution patterns of nitrogen and phosphorus found in streams of the Great Miami River Basin were 

determined from analyses of samples collected during water 

years 1999 and 2000 (Appendix C). Variations in concentrations associated with changes in seasons or changes in 

streamflow conditions were also examined during this 2-

year sampling period.

Forms of Nitrogen and Phosphorus

Estimates of total nitrogen concentrations were computed by adding concentrations of total organic nitrogen 

plus ammonia to concentrations of dissolved nitrite plus 

nitrate. Because nitrite and nitrate are highly soluble in 

water, the particulate fraction of the nitrite plus nitrate concentration is considered negligible. Nitrate concentrations 

were obtained by subtracting nitrite concentrations from 

nitrite plus nitrate concentrations. Dissolved organic nitrogen concentrations were computed by subtracting ammonia 

concentrations from dissolved ammonia plus organic nitrogen concentrations. Concentrations of the particulate forms 

of phosphorus were computed by subtracting dissolved 

phosphorus concentrations from total phosphorus concentrations. Concentrations of dissolved phosphorus not in the 

form of orthophosphate were computed by subtracting 

orthophosphate concentrations from dissolved phosphorus 

concentrations. 

Mean concentrations of dissolved ammonia, organic 

nitrogen, nitrite, nitrate and particulate forms of organic 

nitrogen and ammonia were computed from samples collected at the five sites (fig. 8). Mean concentrations of dissolved orthophosphate phosphorus, other forms of dissolved 

phosphorus, and particulate forms of phosphorus also were 

computed for each of the streams sampled. 

The dominant form of nitrogen in the streams is dissolved nitrate. Mean concentrations of dissolved nitrate 

ranged from 0.93 mg/L (56 percent of the total nitrogen 

concentration) for Holes Creek near Kettering to 4.05 mg/L 

(84 percent of the total nitrogen concentration) for Mad 

River near Eagle City. Mean concentrations of dissolved 

organic nitrogen ranged from 0.24 mg/L (5 percent of the 

total nitrogen concentration) for Mad River near Eagle City 

to 0.46 mg/L (20 percent of the total nitrogen concentration) 

for Great Miami River at Hamilton. Mean concentrations of 

dissolved ammonia and dissolved nitrite add up to 0.1 mg/L 

or less (5 percent or less of the total nitrogen concentration) 

at all sites. In many samples, ammonia concentrations were 

below the LT-MDL. Ammonia was less than the LT-MDL 

in 23 percent of samples from Stillwater River near Union 

to 56 percent of the samples from Great Miami River near 

Vandalia. Mean concentrations of total nitrogen were 

between 4 and 5 mg/L for all sampling sites with the 
16 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000 Table 6. Description of dischargers used in point-source input calculations [Mgal/d, million gallons per day; WWTP, wastewater treatment plant] Reference number (fig. 7) Facility name County Receiving stream Current populatio

receiving collection1 

Publicly owned wastewater-treatment facilities 1 Indian Lake WWTP Logan Great Miami River 10,200 

2 Bellfontaine WWTP Logan Blue Jacket Creek 17,000 3 Sidney WWTP Shelby Great Miami River 18,600 4 Arcanum WWTP Darke Painter Creek 5,600 5 Greenville WWTP Darke Greenville Creek 15,100 6 Piqua WWTP Miami Great Miami River 20,400 7 Troy WWTP Miami Great Miami River 23,800 8 Covington WWTP Miami Stillwater River 2,600 9 Urbana WWTP Champaign Mad River 12,100 

10 Clark Southwestern Regional Clark Mad River 3,200 

11 Springfield WWTP Clark Mad River 72,600 

12 New Carlisle WWTP Clark Honey Creek 7,200 13 Fairborn WWTP Greene Mad River 34,300 14 Brookville WWTP Montgomery Wolf Creek 4,900 15 TriCity North Regional WWTP Montgomery Great Miami River 58,200 16 Dayton WWTP Montgomery Great Miami River 147,900 17 Englewood WWTP Montgomery Stillwater River 9,200 18 Union WWTP Montgomery Stillwater River 5,500 19 New Lebanon WWTP Montgomery Bear Creek 5,600 20 Miamisburg WWTP Montgomery Great Miami River 17,800 21 West Carrolton WWTP Montgomery Great Miami River 12,000 22 Western Regional WWTP Montgomery Great Miami River 61,400 23 Eaton WWTP Preble Seven Mile Creek 6,800 24 Lesourdsville Regional WWTP Butler Great Miami River 8,600 25 Middletown WWTP Butler Great Miami River 47,200 26 Oxford WWTP Butler Four Mile Creek 21,200 27 Springboro WWTP Warren Clear Creek 5,300 28 Franklin WWTP / U. S. Filter Warren Great Miami River 22,000 
Nitrogen and Phosphorus in Streams 17

1 Source, U.S. Environmental Protection Agency, 1996.2 Existing flow averaged from monthly operating reports for study period.3 Crystal Paper Co. began diverting wastewater to the Middletown WWTP in November 1999.

Privately-owned dischargers

29 Appleton Papers Montgomery Great Miami River --- 30 Fraser Paper Montgomery Owl Creek --- 31 AK Steel (outfalls 2, 3, 4, 11, and 15) Butler North Branch Dick’s Creek, Dick’s 

Creek, Great Miami River

--- 

32 Bay West Paper Butler Great Miami River --- 33 Crystal Paper Co.3 Butler Great Miami River --- 

34 Miller Brewing Co. Butler Great Miami River --- 

TOTAL 676,300 

Table 6. Description of dischargers used in point-source input calculations—Continued[Mgal/d, million gallons per day; WWTP, wastewater treatment plant]

Reference number

(fig. 7) Facility name County Receiving stream

Current populati

receiving 

collection1
18 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Figure 7. Location of dischargers used in estimating the point-sources inputs to the study area.
Nitrogen and Phosphorus in Streams 19

Figure 8. Mean concentration distribution of nitrogen and phosphorus species computed from samples 

collected at Stillwater River near Union, Great Miami River near Vandalia, Mad River near Eagle City, 

Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 and 2000.
20 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

exception of Holes Creek near Kettering. The mean concentration of total nitrogen for Holes Creek near Kettering was 

1.7 mg/L (fig. 8). 

Mean concentrations of dissolved orthophosphate 

ranged from 0.02 mg/L (18 percent of the total phosphorus 

concentration) at Holes Creek near Kettering to 0.17 mg/L 

(63 percent of the total phosphorus concentration) at Great 

Miami River near Vandalia. Mean concentrations of particulate phosphorus ranged from 0.08 mg/L (30 percent of the 

total phosphorus concentration) at Great Miami River near 

Vandalia to 0.18 mg/L (50 percent of the total phosphorus 

concentration) at Great Miami River at Hamilton. Mean 

concentration of particulate phosphorus at the Holes Creek 

site was 0.09 mg/L, amounting to 80 percent of the total 

phosphorus concentration. All sites had mean concentrations of total phosphorus greater than 0.1 mg/L, the U.S. 

Environmental Protection Agency’s (1986) recommended 

limit for flowing streams (fig. 8). 

Relation of Nitrogen and Phosphorus Concentrations 

to Season

Concentrations of nutrient species commonly vary 

seasonally. Nitrate concentrations, for instance, tend to be 

highest during late autumn through spring and lowest during summer and early autumn (fig. 9). During October 

through March, plants in the study area are dormant and not 

using much of the available nutrients; therefore, nutrients 

build up in the soil. Rains are then able to flush soluble 

nutrients, such as nitrate, from surrounding soils into 

streams. In late spring and early summer, nitrogen fertilizers 

are applied to corn and wheat fields. These fertilizer applications extend the availability of nutrients through early 

summer. During late summer and early autumn, rains 

become less frequent, terrestrial and aquatic plants use 

much of the available nutrients, and nitrate concentrations 

in streams decline. 

Nitrate and total nitrogen concentrations were 

grouped by season and compared by means of Tukey’s test. 

This test confirmed that mean nitrate concentrations were 

statistically different (p<0.05) between winter and autumn 

and between winter and summer at all sites. Mean total 

nitrogen concentrations were statistically different between 

winter and autumn at all sites and between winter and summer at all sites, with the exception of the Holes Creek site. 

Orthophosphate concentrations typically are high 

during autumn and low during spring (fig.10). Orthophosphate is readily consumed by terrestrial and aquatic plants 

during the spring and summer growing period; however, an 

increase in orthophosphate in summer was observed at 

Great Miami River near Vandalia and Great Miami River at 

Hamilton. These sites have a number of wastewater-treatment facilities in their drainage areas. During summer, 

streamflow was low, and effluent from these facilities was a 

major contributor to streamflow. Seasonal variation in total 

phosphorus concentration was minimal in the study area. 

Because total phosphorus is transported to the streams 

mainly by runoff, high concentrations are more associated 

with runoff events than with seasonal variation. Most of the 

high total phosphorus concentrations in the study area were 

from samples collected during runoff events. 

Tukey’s test shows that mean orthophosphate and 

total phosphorus concentrations were not statistically different between any of the seasons for Stillwater River near 

Union and Holes Creek near Kettering; however, mean 

orthophosphate concentrations were statistically different 

between spring and autumn for Great Miami River near 

Vandalia, Mad River near Eagle City, and Great Miami 

River at Hamilton. Mean total phosphorus concentrations 

were statistically different only between spring and summer 

for Great Miami River near Vandalia.

Relation of Nitrogen and Phosphorus Concentrations 

to Land Use

The sites sampled in the Great Miami River Basin 

represent drainage areas in predominantly agricultural 

areas, predominantly urban areas, or a mixture of both. Forested areas represent only a small part of the study area. In 

general, the urban site—Holes Creek near Kettering—had 

the lowest nitrogen and phosphorus concentrations of the 

sites sampled (fig. 8). The sites representing predominantly 

agricultural basins had nitrogen concentrations similar to 

Great Miami River at Hamilton, the mixed-land-use site. 

Great Miami River at Hamilton had the highest phosphorus 

concentrations for the study area (fig. 8), probably because 

of the many point-source dischargers in the Great Miami 

River Basin between Dayton and Hamilton. 

The role of agriculture—specifically, cropland—on 

nitrogen concentrations was investigated by plotting median 

concentrations of total nitrogen and total phosphorus 

against percentage of drainage area in row crops (fig. 11). 

This comparison included surface-water sites with 10 or 

more nutrient samples in the Great Miami and Little Miami 

River Basins NAWQA study area, along with the two adjacent NAWQA study areas—the White River Basin 

NAWQA in Indiana and the Lake Erie-Lake Saint Clair 

Drainages NAWQA in Michigan, Ohio, Indiana, New 

York, and Pennsylvania. As in the Great Miami River 

Basin, corn and soybeans are the principal crops produced 

in these adjacent study areas. As figure 11 shows, higher 

median nitrogen concentrations typically are associated 

with a higher percentage of drainage area in row crops. 

Median phosphorus concentrations, however, did not necessarily increase with an increase in drainage area dedicated 

to row crops.
Nitrogen and Phosphorus in Streams 21

Figure 9. Seasonal distribution of total nitrogen and dissolved nitrate concentrations for Stillwater River near 

Union, Great Miami River near Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great 

Miami River at Hamilton, Ohio, water years 1999 and 2000.
22 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Figure 10. Seasonal distribution of total phosphorus and dissolved orthophosphate concentrations for Stillwater River near 

Union, Great Miami River near Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great Miami River at 

Hamilton, Ohio, water years 1999 and 2000.
Nitrogen and Phosphorus in Streams 23

Estimated Nitrogen and Phosphorus Loads

Transport of nutrients within and out of the study area 

was determined by instream-load computations. Loads 

determined for this study are computed as constituent concentration multiplied by streamflow and a units-conversion 

factor, which in turn is multiplied by an applicable time 

period. The loads are then summed to determine the total 

load for the period of interest. 

Proportions of the individual nitrogen and phosphorus 

species that contribute to the total nitrogen and phosphorus 

loads are similar to what was observed for total nitrogen and 

phosphorus concentrations (figs. 8, 12, and 13). For instance, 

most of the nitrogen load for Great Miami River at Hamilton 

was in the form of nitrate. Nitrate contributed 74 percent of 

the nitrogen load to Great Miami River at Hamilton, whereas 

ammonia and nitrite together contributed only 2 percent of 

the nitrogen load (table 7).

Of the three streams upstream from Dayton, the Upper 

Great Miami River was the largest contributor of total nitrogen to the study area with a mean daily load of 12,600 kg, 

followed by the Stillwater River with a mean daily load of 

9,100 kg and the Mad River with a mean daily load of 2,900 

kg during water years 1999 and 2000. Great Miami River at 

Hamilton had a mean daily total nitrogen load of 30,800 kg. 

The combined daily load of total nitrogen from the three 

streams upstream from Dayton was 24,600 kg, or 83 percent 

of the nitrogen load computed for Great Miami River at 

Hamilton (fig. 12). Point sources used in the computations 

(discharges of 0.5 Mgal/d or more) contributed 5 percent of 

the nitrogen load computed for the three sites upstream from 

Dayton during the 2-year monitoring period. Nonpoint 

sources of nitrogen (commercial fertilizer, manure, and 

atmospheric deposition) and minor point sources (discharges 

less than 0.5 Mgal/d), therefore, contributed 95 percent of the 

nitrogen load computed for the three sites upstream from 

Dayton. 

Particulate phosphorus represented the largest proportion of the total phosphorus load to the sampling sites 

upstream from Dayton and to Great Miami River at Hamilton 

during the study period (fig. 13 and table 8). Of the three 

streams upstream from Dayton, the Upper Great Miami River 

contributed the largest daily load of total phosphorus with 

560 kg, followed by the Stillwater River with 430 kg and the 

Mad River with 160 kg. The daily load of total phosphorus 

increases to 2,400 kg at Great Miami River at Hamilton. The 

combined daily load of total phosphorus for the three 

streams upstream from Dayton is 1,150 kg or 47 percent of 

the total phosphorus load computed for Great Miami River at 

Hamilton (fig.13). 

Nitrogen and phosphorus loads of Holes Creek, however, differ from those of the other streams. Nitrate represents a much smaller proportion of the total nitrogen load, 

whereas ammonia and organic nitrogen represent larger proportions. In addition, particulate phosphorus represents an 

appreciably greater proportion of the total phosphorus load of 

Holes Creek (table 8). 

Monthly Loads. Monthly loads of nitrate, total nitrogen, orthophosphate, and total phosphorus were computed 

for each site sampled by means of the ESTIMATOR program. The degree of confidence in these load estimates varies by nutrient species, site, and streamflow condition for the 

month (Appendix D). In general, monthly loads of nitrate 

and total nitrogen had the smallest confidence limits, typically ranging from 25 to 80 percent of the estimated loads.

Table 7. Percentage contribution to mean total nitrogen and total phosphorus loads by species, October 

1998–September 2000

Nutrient

Stillwater 

River

 near 

Union

Great 

Miami River

 near

 Vandalia

Mad River 

near 

Eagle City

Holes 

Creek near

 Kettering

Great Miami 

River 

at Hamilton

Nitrogen

Dissolved ammonia 1.2 1.0 1.2 5.6 1.4

Dissolved nitrite 0.4 0.4 0.4 1.0 0.6

Dissolved nitrate 81.6 80.0 80.5 45.6 73.9

Dissolved organic nitrogen 7.1 8.1 5.2 17.5 8.6

Particulate nitrogen 9.6 10.5 12.7 30.3 15.5

Phosphorus

Dissolved orthophosphate 33.4 45.4 18.9 8.6 32.3

Other dissolved phosphorus 9.4 4.6 4.5 2.2 5.3

Particulate phosphorus 57.2 50.0 76.6 89.2 62.4
24 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Figure 11. Relation between the percentage of drainage basin in row crops and the median 

concentrations of total nitrogen and total phosphorus for sites in the Great Miami and Little 

Miami Basins, Lake Erie-Lake Saint Clair Drainages, and White River Basin study units.
Nitrogen and Phosphorus in Streams 25

 

Figure 12. Load distribution of nitrogen species based on ESTIMATOR means for Stillwater River near Union, Great Miami River near 

Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 and 2000.
26 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

 

Figure 13. Load distribution of phosphorous species based on ESTIMATOR means for Stillwater River near Union, Great Miami River 

near Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999

and 2000.
Nitrogen and Phosphorus in Streams 27

Monthly loads of ammonia also were computed; however, 

because confidence limits of the ammonia load estimates 

were consistently 100 to 300 percent of the estimated loads 

at all sites, monthly loads of ammonia are not addressed in 

this report. 

Seasonal patterns in nutrient loads were observed at 

all sampling sites. Monthly loads of nitrate and total phosphorus, as displayed in figures 14 and 15, are typical of the 

pattern in the study area. Seasonal patterns in nutrient loads 

(figs. 14 and 15) are similar to monthly streamflow patterns 

in the study area (fig. 4) and thus demonstrate the importance of streamflow to load computations. Dramatic 

increases in streamflow and nutrient loads during winter 

and early spring were followed by reduced streamflow and 

nutrient loads during late spring and summer. Streamflow 

and nutrient loads were lowest during summer and autumn 

1999. The number and intensity of runoff events were 

below normal in the study area for much of summer and 

autumn 1999 (fig. 2), resulting in low flows at most 

streams. Nitrate loads were highest during winter and spring 

1999 and lowest during summer and autumn 1999. Nitrate 

loads were also relatively high throughout spring 2000 (fig. 

14). 

Differences between estimated maximum monthly 

loads and minimum monthly loads for the study period are 

large at all sites with the exception of Mad River near Eagle 

City (table 8). Minimum monthly loads of nitrate and total 

nitrogen estimated at the Mad River site were about 15 percent and 10 percent, respectively, of corresponding maximum monthly loads; at the other sites, however, minimums 

ranged from about 0.2 percent to 2 percent of the corresponding maximums (table 8). A possible explanation for 

this difference is that the more permeable soils in the Mad 

River Basin allow for infiltration of fertilizer-derived nitrogen to shallow ground water, leaving less nitrogen at land 

surface for transport to streams during runoff events. 

Nitrate-bearing shallow ground water, however, will discharge into streams year round as base flow. Nitrate concentrations of ground-water samples collected from 11 shallow 

wells (well depths between 11 and 53 feet) within the Mad 

River Basin were higher than the mean concentration of 

samples collected from the Mad River (5.5 mg/L as compared to 4.05 mg/L). The continuous ground-water discharge provides a stable input of nitrate to the Mad River 

and its tributary streams. By contrast, the differences 

between the minimum monthly loads and the maximum 

monthly loads of orthophosphate and total phosphorus at 

the Mad River site are more similar to those at some of the 

other sites. 

Monthly inputs from point sources into the basins of 

the sampling sites also were included in figures 14 and 15 to 

illustrate the importance of point sources to instream loads 

during low-flow months. Point sources were the primary 

contributor of nitrate loads in all of the rivers during summer and autumn, with the exception of the Mad River and 

Holes Creek (fig.14), and actually contribute more nitrogen 

than is reflected in the computed instream loads for Stillwater River near Union, Great Miami River near Vandalia, and 

Great Miami River at Hamilton during some months in 

summer and autumn 1999. 

Total phosphorus loads were highest during winter 

and spring 1999 and lowest during summer and autumn 

1999. Phosphorus loads were also elevated during winter 

and spring 2000 (fig. 15). As with the nitrogen loads, the 

highest total phosphorus loads occurred in January 1999. 

Point sources were the major contributors of total phosphorus to the Great Miami River and Mad River during summer 

and autumn 1999, whereas point sources were the major 

contributors of total phosphorus to the Stillwater River only 

from August through October 1999.

The anomaly of point-source inputs being higher 

than computed instream discharges of nitrate and total phosphorus in many months is examined for Great Miami River 

at Hamilton in figure 16. In this example, the percentage of 

instream loads from point-source inputs was nearly 400 percent for total nitrogen and 300 percent for total phosphorus 

during summer 1999. Although errors in the load estimates 

could account for some of the high percentages, nutrients 

are likely being used by algae and other aquatic plants in the 

streams, because much of the growth and development of 

aquatic plants occurs during summer and early autumn. 

Porter (2000) found that concentrations of dissolved nitrate 

plus nitrite nitrogen and orthophosphate decreased significantly with increases in algal productivity in Upper Midwest river systems.

Estimated monthly loads contributed by the three 

streams upstream from Dayton are compared to the estimated monthly load at Great Miami River at Hamilton in 

figure 17. Contributions of total nitrogen and total phosphorus upstream from Dayton varied from stream to stream as a 

function of streamflow. The Mad River contributed 20 percent or less of the total nitrogen load of Great Miami River 

at Hamilton during most of the study period; but during the 

drought, total nitrogen contributions from the Mad River 

rose to more than 25 percent of the load of Great Miami 

River at Hamilton. The higher contribution from the Mad 

River during the drought was most likely due to the high 

ground-water discharge to the river. During spring 2000, 

total contributions of total nitrogen from the three streams 

upstream from Dayton exceeded the estimated load for 

Great Miami River at Hamilton by as much as 23 percent. 

This discrepancy may be caused by errors in the load estimates for Great Miami River at Hamilton. (No samples 

were collected at Great Miami River at Hamilton during 

these months because of bridge construction.) 

Loads Computed from U.S. Environmental Protection 

Agency Data. Monthly loads based on analyses of samples 

collected by the USEPA also were computed by use of 

ESTIMATOR. The water samples were collected from
28 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Figure 14. Instream loads and point-source inputs of nitrate for Stillwater River near Union, Great Miami River near Vandalia, 

Mad River near Eagle City, Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 and 2000.
Nitrogen and Phosphorus in Streams 29

Figure 15. Instream loads and point-source inputs of total phosphorus for Stillwater River near Union, Great Miami River near 

Vandalia, Mad River near Eagle City, Holes Creek near Kettering, and Great Miami River at Hamilton, Ohio, water years 1999 

and 2000.
30 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

December 1999 through December 2000 by the USEPA at a 

Great Miami River sampling station in the Greater Cincinnati Water Works’ Bolton well field near Fairfield, Ohio, 

6.7 mi downstream from Great Miami River at Hamilton 

(fig 1). USEPA samples were collected from a single intake 

point at the left bank of the river. An automatic sampler was 

activated each hour to pump water from the intake point. 

Daily composites of these subsamples were stored in a holding facility that was refrigerated to 4oC. A linear regression 

analysis of data for USEPA and USGS samples collected 

on the same day show that concentrations of nitrate, total 

nitrogen, and total phosphorus were similar, with p-values 

less than 0.0001 for the three comparisons (fig. 18). Any 

discrepancies found between sample sets are probably the 

result of different sample-collection methods and use of different laboratories for the sample analyses. For most 

months, loads of nitrate, total nitrogen, and total phosphorus 

from both data sources produced comparable seasonal patterns (fig. 19). 

Both data sources show the highest monthly loads in 

April 2000 and the lowest monthly loads during August and 

September 2000. However, more than half of the nitrate and 

total nitrogen loads computed from USEPA data were outside the 95-percent confidence interval of the loads computed from USGS data; loads computed from USEPA data 

were higher than loads computed from USGS data for all 

months but September 2000. In contrast, total phosphorus 

loads were more comparable; loads computed from USEPA 

data were inside of the 95-percent confidence intervals of 

loads computed from USGS data for all months. 

Historical Trends of Nitrogen and Phosphorus Loads 

for the Great Miami River. Historical loads of nitrogen and 

phosphorus were computed for the Great Miami River by 

means of the ESTIMATOR program calibrated with nutrient data collected by the NASQAN program at Great Miami 

River near New Baltimore from 1974 through 1993 

(Appendix E). Great Miami River at New Baltimore is 

13 mi downstream from Great Miami River at Hamilton and 

Table 8. Statistical summary of the monthly nutrient loads for sites in the Great Miami River Basin, 

October 1998–September 2000

[All loads in kilograms]

Nutrient

 Maximum 

load 

Mean 

load

Median

load

 Minimum

 load 

Stillwater River near Union, Ohio

Nitrate 1,100,000 220,000 47,000 2,100

Total nitrogen 1,300,000 270,000 62,000 3,400

Orthophosphate 46,000 4,300 1,100 180

Total phosphorus 110,000 13,000 1,900 500

Great Miami River near Vandalia, Ohio

Nitrate 1,400,000 310,000 110,000 6,700

Total nitrogen 1,700,000 380,000 140,000 9,800

Orthophosphate 43,000 7,700 3,800 1,600

Total phosphorus 94,000 17,000 7,800 2,100

Mad River near Eagle City, Ohio

Nitrate 160,000 72,000 53,000 25,000

Total nitrogen 250,000 88,000 65,000 28,000

Orthophosphate 4,900 960 630 410

Total phosphorus 50,000 5,100 1,000 700

Holes Creek near Kettering, Ohio

Nitrate 5,500 1,300 850 110

Total nitrogen 14,000 3,000 1,800 180

Orthophosphate 180 28 15 2.2

Total phosphorus 1,500 320 140 6.2

Great Miami River at Hamilton, Ohio

Nitrate 2,900,000 670,000 270,000 41,000

Total nitrogen 3,800,000 930,000 410,000 79,000

Orthophosphate 140,000 24,000 12,000 3,400

Total phosphorus 420,000 73,000 37,000 11,000
Nitrogen and Phosphorus in Streams 31

Figure 17. Monthly loads of total nitrogen and total phosphorus for the three sites above Dayton, Ohio, and Great Miami River at 

Hamilton, Ohio, water years 1999 and 2000.

Figure 16. Percentage of stream load from point-source contributions for total nitrogen and total phosphorus at Great Miami 

River at Hamilton, Ohio, water years 1999 and 2000.
32 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Figure 19. Monthly loads of nitrate, total nitrogen, and total 

phosphorus computed from U.S. Environmental Protection 

Agency (USEPA) and U.S. Geological Survey (USGS) data, 

December 1999 through September 2000.

Figure 18. Comparison of nitrate, total nitrogen, and total 

phosphorus concentrations from samples collected on the 

same day by the U.S. Environmental Protection Agency (USEPA) 

and the U.S. Geological Survey (USGS).
Nitrogen and Phosphorus in Streams 33

is influenced by two additional major point sources 

that contribute an estimated 26 Mgal/d (40 ft3

/s) of 

effluent to the Great Miami River. Streamflow measured at Great Miami River at Hamilton, however, 

was used in load computations for Great Miami River 

at New Baltimore. 

Annual nutrient loads were computed for water 

years 1974 through 2000 for Great Miami River at 

Hamilton using the NASQAN and NAWQA data sets. 

(Nutrient data were not available for water years 1994 

through 1998.) The highest total nitrogen and total 

phosphorus loads occurred during the 1970s and early 

1980s (fig. 20). The 1999 and 2000 annual loads computed from this study were comparatively low, but 

annual mean streamflows for these years also were 

low (fig. 20). In order to determine whether a downtrend in nutrient loads actually occurred from 1974 

through 2000, linear regression analyses adjusted for 

flow were done on total nitrogen and total phosphorus 

annual loads. These analyses found trends of lower 

total nitrogen and total phosphorus to be statistically 

significant (p<0.001). The decrease in nutrient loads 

for this period of record was probably due to improvements in wastewater-treatment plants. Most of the 

major wastewater-treatment plants in the study area 

have upgraded their treatment process at least once 

since 1974 (Ohio Environmental Protection Agency 

1996, 1997, and 2001).

Nitrogen and Phosphorus Yields 

The size of a drainage area often overshadows 

the effects that land use and physiography have on 

loads because large basins contribute large loads. The 

importance of land use and physiography to drainage 

basins is better observed when yields rather than loads 

of nutrients are compared. Yields are computed by 

dividing load by basin area. Maximum, mean, median, 

and minimum monthly yields were computed for each 

site (table 9). 

Nutrient yields commonly are related to landuse practices in the drainage basin. For example, previous 

NAWQA studies have shown that streams in agricultural 

and urban areas typically had the highest nutrient concentrations, whereas streams in undeveloped, forested areas typically had the lowest nutrient concentrations (U.S. 

Geological Survey, 1999). Nutrient sources in urban basins 

include fertilizers applied to lawns and golf courses, auto

mobile emissions, and effluent from wastewater-treatment 

facilities. Agricultural basins with numerous animal feeding 

operations or a high proportion of land dedicated to row 

crops can be major sources of nutrients (U.S. Geological 

Survey, 1999). 

Physiography of a drainage basin can also influence 

nutrient yields. Unconsolidated glacial sediment was deposited throughout the study area during three episodes of 

Pleistocene glaciation. Most of the study area is dominated 

by glacial till—an unsorted mixture of clay, silt, sand, and 

gravel. The Mad River Basin, however, is dominated by 

glacial outwash—sediment consisting of well-sorted sand 

and gravel, which forms a productive aquifer that discharges high volumes of ground water to the Mad River 

(Debrewer and others, 2000; Koltun, 1995). 

Mean nutrient yields were computed for the drainage 

areas of the five sites sampled by the USGS (fig. 21). Mean 

yield was also computed for Great Miami River at Hamilton 

on the basis of NASQAN samples collected at Great Miami 

River near New Baltimore during 1975–93. A comparison 

of mean yields for water years 1999 and 2000 shows that 

Figure 20. Annual loads of total nitrogen and total phosphorus for the 

Great Miami River at Hamilton, Ohio, water years 1974 through 2000.
34 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

mean nitrogen yields for the Stillwater River were the highest in the study area. The Stillwater River and the Upper 

Great Miami River had the highest mean orthophosphate 

yields (85 g/km2/d); however, the highest mean total phosphorus yields were for Great Miami River at Hamilton 

(257 g/km2/d). For comparisons of yields, the analysis 

period was shortened at all sites to include only the months 

that streamflow data were available for Holes Creek (January 1999 through September 2000). The Holes Creek site 

had the lowest yields in the study area for all nutrient species examined; this site differs substantially from the other 

study sites in that it has a drainage area largely absent of 

point sources and dominated by residential and commercial 

land use. Principal sources of nutrients for Holes Creek are 

limited to atmospheric deposition, septic systems, and residential fertilizer applications. 

Estimated historical daily yields of total nitrogen and 

total phosphorus for Great Miami River at Hamilton were 

higher than those computed from the samples collected in 

water years 1999 and 2000. Total nitrogen and total phosphorus daily yields computed from the historical data were 

5.8 kg/km2 and 0.39 kg/km2, respectively, whereas total 

nitrogen and total phosphorus mean daily yields computed 

for water years 1999 and 2000 at Great Miami River at 

Hamilton were 3.3 kg/km2 and 0.26 kg/km2, respectively. 

Lower than normal streamflows during the study period for 

the Great Miami River Basin are most likely the reason for 

this difference. Mean streamflow for Great Miami River at 

Hamilton was 2,350 ft3/s for water years 1999 and 2000, 

compared to 3,570 ft3/s for water years 1975–93. 

An examination of monthly nutrient yields (Appendix D) reveals other variations between basins. For the 

study period, the Stillwater River had some of the smallest

Table 9. Statistical summary of the monthly nutrient yields for sites in the Great Miami River Basin, 

October 1998– September 2000

[All yields in kilograms per square kilometer]

Nutrient

 Maximum 

yield 

Mean 

yield

Median

yield

 Minimum

 yield 

Stillwater River near Union, Ohio

Nitrate 640 130 28 1.2

Total nitrogen 770 170 38 2.1

Orthophosphate 27 2.6 0.67 0.11

Total Phosphorus 64 7.7 1.2 0.30

Great Miami River near Vandalia, Ohio

Nitrate 480 110 36 2.3

Total nitrogen 580 130 48 3.3

Orthophosphate 15 2.6 1.3 0.53

Total Phosphorus 32 5.7 2.6 0.70

Mad River near Eagle City, Ohio

Nitrate 210 89 67 31

Total nitrogen 310 110 81 34

Orthophosphate 6.1 1.2 0.79 0.47

Total phosphorus 63 6.3 1.3 0.88

Holes Creek near Kettering, Ohio

Nitrate 106 25 16 2.1

Total nitrogen 260 58 34 3.5

Orthophosphate 3.5 0.55 0.28 0.04

Total phosphorus 28 6.2 2.7 0.12

Great Miami River at Hamilton, Ohio

Nitrate 310 72 29 4.4

Total nitrogen 400 99 44 8.4

Orthophosphate 16 2.5 1.3 0.37

Total phosphorus 45 8.0 4.0 1.2
Nitrogen and Phosphorus in Streams 35

Figure 21. Daily mean yields of ammonia, nitrate, total nitrogen, orthophosphate, and total phosphorus for Stillwater 

River near Union, Great Miami River near Vandalia, Mad River near Eagle City, and Holes Creek near Kettering, Ohio, 

water years 1999–2000, and Great Miami River at Hamilton, Ohio, water years 1974–1993 and 1999–2000.
36 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

 yields of total nitrogen and total phosphorus during months 

of low streamflow. During months of high streamflow, 

however, the Stillwater River has some of the highest yields 

of total nitrogen and total phosphorus (Appendix D). This 

pattern may reflect the combined effects of intense rowcrop production and high density of animal feeding operations; the feeding operations produce large amounts of 

manure, some of which is applied locally to fertilize corn 

and winter wheat fields. During months of high streamflow, 

the Mad River Basin usually has some of the lowest nutrient 

yields for the study area. However, during summer and 

autumn 1999, the Mad River had the highest nutrient yields 

for the Great Miami River Basin—particularly nitrate. 

Comparison of Nitrogen and Phosphorus Inputs and 

Instream Loads

Instream loads and point-source inputs computed for 

this report indicate that nonpoint sources contribute most of 

the instream nutrient loads to the Stillwater, Upper Great 

Miami, and Mad Rivers upstream from Dayton (table 10). 

Although point sources in the Dayton Metropolitan area 

contribute a significant proportion of nutrient load as compared to that at Great Miami River at Hamilton, nonpoint 

sources of nutrients from the streams upstream from Dayton 

were still the major contributor of nutrients to the study

area. The percentage contributions of point- and nonpointsource loads of total nitrogen and total phosphorus to the 

sites upstream from Dayton and Great Miami River at 

Hamilton are listed in table 10. Total nitrogen loads computed in this comparison are the sum of the ammonia, 

nitrite, and nitrate loads. This total nitrogen load does not 

include organic nitrogen because most point-source dischargers do not include organic nitrogen data as part of their 

monthly operating reports. 

Total nitrogen loads from nonpoint sources were 

greater than 90 percent of the load measured at the sites 

upstream from Dayton but decreased to 78 percent of the 

load measured at Great Miami River at Hamilton. This 

decrease is mainly due to the many point sources in and 

downstream from the Dayton metropolitan area. A similar 

pattern is observed with total phosphorus. Total phosphorus 

loads from nonpoint sources were from 69 to 95 percent of 

the loads measured at the sites upstream from Dayton but 

decreased to 55 percent of the load measured at Hamilton. 

The estimated annual inputs of nutrients to each 

basin from nonpoint sources were much higher than the 

amount that actually enters into the streams. The intention 

of commercial-fertilizer and manure applications is, to provide nutrients to crops—not to the aquatic system. Removal 

of nitrogen and phosphorus by crop harvesting was estimated for the study area. The estimates were computed 

from nitrogen and phosphorus removal rates used by 

Goolsby and others (1999) for harvested soybeans, wheat, 

corn for grain, and corn for silage and from 1997 county 

estimates of harvested crops (U.S. Department of AgriculTable 10. Estimated daily point- and nonpoint-source inputs of total nitrogen and total phosphorus to the three sites 

upstream from Dayton, Ohio, and to the Great Miami River at Hamilton, Ohio, water years 1999 and 2000

[kg, kilograms]

Total nitrogen Total phosphorus

Stillwater

 River

near 

Union

Great 

Miami 

River 

near 

Vandalia

Mad 

River 

near 

Eagle 

City

Great 

Miami 

River at 

Hamilton

Stillwater

 River

near 

Union

Great 

Miami 

River 

near 

Vandalia

Mad 

River 

near 

Eagle 

City

Great 

Miami 

River at 

Hamilton

Estimated mean daily instream 

load (kg) 9,000 12,600 2,900 30,800 420 560 170 2,400

Estimated mean daily point-source 

input (kg)1 160 880 58 6,800 20 180 22 1,100

Point-source load as percentage of 

instream load2 2 7 2 22 5 31 13 45

Nonpoint-source load as percentage of instream load3 98 93 98 78 95 69 87 55

Computed nonpoint-source load in 

streams (kg)4 8,800 11,700 2,800 24,000 400 380 150 1,300

1

Total nitrogen loads computed for point sources include only ammonia, nitrite, and nitrate. 

2Estimated point-source input/estimated stream load x 100. 

3

100 percent minus the percent point-source load. 

4Estimated stream load minus the mean daily point-source input.
Nitrogen and Phosphorus in Streams 37

ture, 1999). These estimates show that 70 million kilograms 

of nitrogen and 10 million kilograms of phosphorus were 

removed from the study area by crop harvesting. These 

amounts equal to 93 percent of the estimated nonpointsource nitrogen inputs (commercial-fertilizer and manure 

applications, atmospheric deposition, and nitrogen fixation) 

and 79 percent of the estimated nonpoint-source phosphorus 

inputs (commercial-fertilizer and manure applications). 

Computations show that a higher percentage of total 

nitrogen from nonpoint-source inputs has been transported 

to streams than total phosphorus from nonpoint-source 

inputs (table 11). Because nitrate is highly soluble and is not 

readily sorbed to soil or organic matter, much of it is available for transport. In contrast, phosphorus is relatively 

insoluble and tends to bind strongly to soil and organic matter. Most phosphorus, therefore, was transported to streams 

during runoff events that are of sufficient magnitude to 

mobilize and transport sediment from surrounding land to 

streams (Becher and others, 2001; U.S. Geological Survey, 

1999).

The data show that, although point sources above 

Great Miami River at Hamilton were major contributors to 

nutrient loads, agricultural nonpoint sources from the 

streams upstream from Dayton contributed most of the 

instream nitrogen loads and almost half of the instream 

phosphorus loads at Hamilton. Monthly nutrient loads show 

that only during periods of low streamflow were point 

sources likely contributing most of the nutrient loads. During periods of low streamflow, however, nutrient loads were 

much lower than during periods of high streamflow. 

The USEPA states that runoff from agricultural nonpoint sources is now the leading source of pollution to rivers 

and lakes in the United States (U.S. Environmental Protection Agency, 2002). In an assessment of 42 interior basins 

of the Mississippi River Basin, Goolsby and others (1999) 

estimate that the Great Miami River Basin had one of the 

highest total nitrogen and total phosphorus yields. Within 

the Great Miami River Basin, the highest nutrient yields 

were from the Stillwater River Basin. These high yields 

were most likely the result of predominantly agricultural 

land use. The USEPA has encouraged the use of best management practices (BMPs) to manage agricultural runoff 

through economic incentives, technical assistance, and costshare programs. Common BMPs in Ohio include conservation tillage and installation of buffers and filter strips on 

fields that border waterways (Ohio State University Extension, 1995b). Implementation of more BMPs in the study 

area would likely help to reduce nutrient loads and yields. 

For example, if BMPs were able to reduce nonpoint-source 

loads 10 percent below current levels, the monthly load of 

total nitrogen at Great Miami River at Hamilton would 

decrease to 850,000 kg, and the monthly yield would 

decrease to 90 kg/km2. The monthly load of total phosphorus would decrease to 68,000 kg and the monthly yield to 

7.2 kg/km2. Comparatively, these reduced yields are still 

high—estimated monthly total nitrogen and total phosphoTable 11. Daily nonpoint-source inputs of total nitrogen and total phosphorus and estimated percentage of 

nonpoint inputs deposited onto the basins that enter the stream, water years 1999 and 2000

[kg, kilograms]

Total nitrogen Total phosphorus

Stillwater

 River

near 

Union

Great 

Miami 

River 

near 

Vandalia

Mad 

River 

near 

Eagle 

City

Great 

Miami 

River at 

Hamilton

Stillwater

 River

near 

Union

Great 

Miami 

River 

near 

Vandalia

Mad 

River 

near 

Eagle 

City

Great 

Miami 

River at 

Hamilton

Computed nonpoint-source load 

in streams (kg)1 8,900 11,700 2,800 24,000 400 380 150 1,300

Nonpoint-source loads deposited 

onto the basin (kg)2 46,200 54,200 15,200 181,000 10,500 9,500 2,600 34,500

Percentage of the nonpoint-source 

load that enters a stream 19 25 18 13 3.8 4.0 5.8 3.8

1

Computations from table 10.

2

Nitrogen loads computed from 1997 manure and commercial-fertilizer application rates from table 4 and the 1991–2000 averaged 

annual atmospheric deposition rates from table 6; phosphorus loads computed from 1997 manure and commercial-fertilizer 

application rates from table 4.
38 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

rus yields for the Mississippi-Atchafalaya River Basin, in 

contrast, are 41 kg/km2

 and 3.5 kg/km2, respectively 

(Goolsby and others, 1999). Although any decrease in nutrient loads and yields would be beneficial, the Great Miami 

River Basin would still have one of the higher nutrient 

yields within the Mississippi River Basin, even with a 

10-percent decrease in nonpoint-source loads. 

Suggestions for Further Work

A program to continue sampling for nutrients in these 

basins would be beneficial for many reasons. A larger sample set could result in improved load estimates by expanding coverage of the range of streamflow conditions and 

providing more values with which to calibrate load models. 

A continuation of sampling would facilitate analysis of any 

trends that might develop or continue over an extended 

period. For example, an examination of nutrients in the 

Great Miami River since the 1970s has shown a decrease in 

total nitrogen concentrations and, to a lesser extent, total 

phosphorus concentrations. Continuation of the sampling 

program would facilitate monitoring and verification of 

such trends, which may accelerate as more BMPs are introduced to agricultural lands in the Great Miami River Basin. 

Summary and Conclusions

Sources and loads of nitrogen and phosphorus in streams 

are described for five sites in the Great Miami River Basin 

monitored from October 1998 through September 2000 by 

the U.S. Geological Survey: Stillwater River near Union, 

Great Miami River near Vandalia, Mad River near Eagle 

City, Holes Creek near Kettering, and Great Miami River at 

Hamilton. The relation of land use and physiography to estimated nutrients loads and yields also are examined for the 

Great Miami River Basin.

Two distinct land uses have developed within the 

Great Miami River Basin. The northern, upper part of the 

basin consists primarily of agricultural land, where soybeans and corn are the chief products. The southern, downstream part of the basin, however, is dominated by urban 

land in and around the cities of Springfield, Dayton, Middletown, and Hamilton. Both land-use types introduce nutrients into streams of the Great Miami River Basin. 

Commercial-fertilizer and manure application onto corn and 

soybean fields is the principal source of nutrients in agricultural areas. Some of the nutrients from agricultural nonpoint 

sources are eventually transported to streams by surface 

runoff, sediment erosion, or ground-water discharge. 

Sources of nutrients in urban areas, in contrast, are mainly 

discharges from wastewater-treatment facilities and fertilizer applications onto lawns. 

An examination of monthly mean loads during water 

years 1999 and 2000 shows that nonpoint sources were the 

main contributor of nutrients to instream loads during 

months of high streamflow, whereas point sources were the 

main contributor of nutrients to instream loads during 

months of low streamflow. Because larger loads are contributed to streams during high streamflows, nonpoint sources 

are considered to be the main overall contributors of nutrients to the Great Miami River. 

Physiographic regions in the study area also have an 

influence on nutrient loads in the Great Miami River. Most 

of the study area consists of till plains that are absent of 

high-yielding aquifers. The Mad River Basin, however, lies 

within an interlobate area that consists of glacial outwash 

with an associated high-yielding aquifer; this high-yielding 

aquifer supplies an unusually large proportion of groundwater discharge to total Mad River streamflow, which 

results in a relatively large nitrogen load during low-flow 

periods. An examination of the three streams upstream from 

Dayton indicates that nitrate and total nitrogen loads were 

highest at Mad River near Eagle City during the drought 

months of summer and autumn 1999. 

An estimate of annual loads of total nitrogen and 

total phosphorus for Great Miami River at Hamilton since 

the mid-1970s indicates that nutrient loads could be 

decreasing for the study area. Although population in the 

Great Miami River Basin increased slightly (about 8 percent) between 1970 and 2000, with accompanying increases 

in wastewater discharges, improvements in many of the 

wastewater-treatment facilities may have decreased the 

amounts of nitrogen and phosphorus being discharged into 

streams.

Mean nutrient yields computed for each basin also 

demonstrate the importance of land use in relation to nutrient loads in the study area. The three agricultural basins 

upstream from Dayton had the highest nitrate and total 

nitrogen yields, whereas the urban Holes Creek Basin had 

the lowest nitrate and total nitrogen yields. Great Miami 

River at Hamilton, whose drainage area is a mixture of agricultural and urban areas, had nitrate and total nitrogen 

yields slightly lower than those of the agricultural basins. 

Nutrient inputs to the three agricultural basins are primarily 

from application of commercial fertilizers and manure onto 

corn and soybean fields, whereas nutrient inputs to the 

Holes Creek Basin are primarily from application of commercial fertilizer to residential lawns and from automobile 

emissions. Little variation was observed in phosphorus 

yields between agricultural, urban, and mixed-land-use 

basins.

The percentages of nonpoint-source nutrients that are 

transported from the applied land surface to the stream vary 

with nutrient type and basin. Between 13 and 22 percent of 

the nonpoint-source nitrogen is able to reach a stream, 

whereas only 4 to 6 percent of the nonpoint-source phosphorus is able to reach a stream. 
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Glossary 41

Glossary

Ammonia - A compound of nitrogen and hydrogen (NH3) 

that is a common byproduct of animal waste. Ammonia 

readily converts to nitrate in soils and streams

Atmospheric deposition - The transfer of substances from 

the air to the surface of the Earth, either in wet form (rain, 

fog, snow, dew, frost, hail) or in dry form (gases, aerosols, 

particles). 

Best management practice (BMP) - A management practice 

that has been determined to be an effective, practical means 

of preventing or reducing nonpoint-source pollution. 

Concentration - The amount or mass of a substance present 

in a given volume or mass of sample. Commonly expressed 

as milligram per liter in water samples. 

Confluence - The flowing together of two or more streams; 

the place where a tributary joins the main stream. 

Cubic foot per second (ft3/s) - Rate of water discharge 

(streamflow) representing a volume of 1 cubic foot passing 

a given point during 1 second, equivalent to approximately 

7.48 gallons per second or 448.8 gallons per minute or 

0.02832 cubic meter per second. 

Environmental sample - A water sample collected from an 

aquifer or stream for the purpose of chemical, physical, or 

biological characterization of the sampled resource. 

Eutrophication - The process by which water becomes 

enriched with plant nutrients, most commonly phosphorus 

and nitrogen. 

Hypoxia - Seasonal depletion of dissolved oxygen (to less 

than 2.0 milligrams per liter) within a water body, related to 

eutrophication of the water body. Most aquatic species cannot survive at such low oxygen levels.

Load - General term that refers to a material or constituent 

in solution, in suspension, or in transport; usually expressed 

in terms of mass or volume. 

Maximum contaminant level (MCL) - Maximum permissible level of a contaminant in water that is delivered to any 

user of a public water system. MCLs are enforceable standards established by the U.S. Environmental Protection 

Agency. 

Method detection limit - The minimum concentration of a 

substance that can be accurately identified and measured 

with present laboratory technologies. 

Milligrams per liter (mg/L) - A unit expressing the concentration of chemical constituents in solution as weight (milligrams) of solute per unit volume (liter) of water; equivalent 

to one part per million. 

Nitrate - An ion consisting of nitrogen and oxygen (NO3

-

). 

Nitrate is a plant nutrient and is very mobile in soils.

Nonpoint source - A pollution source that cannot be defined 

as originating from discrete points such as pipe discharge. 

Areas of fertilizer and pesticide applications, atmospheric 

deposition, manure, and natural inputs from plants and trees 

are types of nonpoint-source pollution. 

Nutrient - Element or compound essential for animal and 

plant growth. Common nutrients in fertilizer include nitrogen, phosphorus, and potassium. 

Orthophosphate - An ion consisting of phosphorus and oxygen (PO4

-3). This is the only inorganic form of phosphate 

that can be used by plants as a nutrient. 

Phosphorus - A nutrient essential for growth that can play a 

key role in stimulating aquatic growth in lakes and streams. 

Physiography - A description of the surface features of the 

Earth, with an emphasis on the origin of landforms. 

Point source - A pollution source at a discrete location such 

as a discharge pipe, drainage ditch, tunnel, well, or concentrated livestock operation. 

Quality assurance - Evaluation of quality-control data to 

allow quantitative determination of the quality of chemical 

data collected during a study. Techniques used to collect, 

process, and analyze water samples are evaluated. 

Season - one of the four natural divisions of the year 

(spring, summer, fall, and winter) indicated by the passage 

of the sun through an equinox or solstice.

Water year - The continuous 12-month period, October 1 

through September 30, in U.S. Geological Survey reports 

dealing with the surface-water supply. The water year is 

designated by the calendar year in which it ends and which 

includes 9 of the 12 months. Thus, the year ending September 30, 1999, is referred to as “water year 1999.” 

Yield - The mass of material or constituent transported by a 

river in a specified period of time divided by the drainage 

area of the river basin. 
42 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendixes
Appendix A. 43

Appendix A. Quality-Control Data

Data from the quality-control sampling effort are listed in 

table A1. Field blanks indicate no consistent contamination 

problem with any of the nutrient species. Median concentrations of all nutrient species in the field blanks were less than 

the respective laboratory reporting limits. Ammonia and 

orthophosphate, however, were detected in at least one field 

blank at a concentration above the laboratory reporting 

limit. The relative percent difference (RPD) is a nonparametric method used to compare replicate samples to environmental samples. The RPD was computed by means of 

the following equation:

RPD = |Sample1 - Sample2| / (Sample1 + Sample2 / 2) 

x 100.

The median relative percent difference for all nutrient species was less than 10 percent, although total ammonia plus organic nitrogen approached this level with a 

median of 9.7 percent (for eight sample sets, the RPD was 

higher than 10 percent). For ammonia, five sample sets had 

an RPD higher than 10 percent, although the median RPD 

was zero. This disparity is probably explained by the large 

number of less-than values associated with this nutrient. In 

most of the sample sets, there were nondetections for both 

replicate samples, resulting in an RPD of zero. 

Table A1. Summary of quality-control data for nitrogen and phosphorus in the Great Miami River Basin, October 1998–September 2000

[LRL, laboratory reporting level; mg/L, milligrams per liter; RPD, relative percent difference; N, nitrogen; P, phosphorus; <, less than; E, estimate]

Constituent LRL

Number

of blank

samples

Maximum

concentration

(mg/L)

Median

concentration

(mg/L)

Number of blank

samples with

concentrations

greater than LRL

Number

of

replicate

samples

Median

RPD

Number of

replicate

samples with

RPD greater

than 10 percent

Ammonia (as N), dissolved 0.02 10 0.04 <0.02 1 161 0 5

Ammonia plus organic nitrogen (as N), total 0.1 10 E 0.06 <0.1 0 16 9.7 8

Ammonia plus organic nitrogen (as N), dissolved 0.1 10 <0.1 <0.1 0 16 3.3 3

Nitrite (as N), dissolved 0.01 10 <0.01 <0.01 0 16 0 0

Nitrite plus nitrate (as N), dissolved 0.05 10 <0.1 <0.05 0 16 0.6 1

Phosphorus (as P), total 0.01 10 <0.01 <0.01 0 16 2 2

Orthophosphate (as P), dissolved 0.01 10 0.02 <0.01 1 16 6.5 3

Phosphorus (as P), dissolved 0.01 10 E 0.003 <0.01 0 16 2 1

1

Two of the ammonia replicate sets produced a detectable concentration with a nondetectable concentration. In these cases, the minimum reporting limit was used in the computations as the

nondetectable concentration.

Appendix A.
44 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix B. Coefficients B0 through B6 used in the ESTIMATOR concentration models

Appendix B. Coefficients B0 through B6 used in the ESTIMATOR concentration models

 Nutrient B0 B1 B2 B3 B4 B5 B6

Stillwater River near Union

Dissolved ammonia -3.4927 -0.2291 0.1513 0.3175 0.4448 0.5041 1.2469

Dissolved nitrate 1.0263 0.1742 0.0351 -0.0773 0.0120 0.7172 -0.0493

Total nitrogen 1.3101 0.1579 0.0487 -0.0191 -0.0190 0.5834 -0.1147

Dissolved orthophosphate -3.2419 0.0501 0.1484 0.3203 0.7486 -0.4012 0.7608

Total phosphorus -1.8692 0.2956 0.1264 0.1009 -0.1038 -0.5084 0.0061

Great Miami River near Vandalia

Dissolved ammonia -4.4116 0.3017 0.3148 -- -- -- --

Dissolved nitrate 0.7665 0.1107 0.0905 0.2857 0.4293 0.5917 0.0536

Total nitrogen 1.2542 0.1886 0.0574 0.1948 0.1066 0.3489 -0.0223

Dissolved orthophosphate -2.5413 -0.1902 0.1875 0.2453 0.6444 -0.3740 0.1291

Total phosphorus -1.4666 0.1064 0.0948 0.1305 0.0274 -0.4837 0.0277

Mad River near Eagle City

Dissolved ammonia -3.5252 0.9407 -0.0472 -0.4395 0.1319 -0.1239 0.2166

Dissolved nitrate 1.4848 0.1013 -0.0831 -0.0125 0.0081 0.0012 0.0542

Total nitrogen 1.7474 0.3012 -0.0600 -0.0289 -0.0376 -0.0682 0.0411

Dissolved orthophosphate -3.1686 0.3881 0.1266 -0.1798 0.0880 -0.6210 0.2028

Total phosphorus -1.7278 1.2774 0.0588 -0.1947 -0.1548 0.0943 -0.8334

Holes Creek near Kettering

Dissolved ammonia -4.2263 0.6336 -0.0142 -1.1910 -0.0055 -0.5768 -0.4142

Dissolved nitrate -0.3850 -0.1258 0.0528 -0.0739 0.0411 0.2727 0.1654

Total nitrogen 0.2548 0.1069 0.0393 -0.1784 0.0423 0.0843 -0.0851

Dissolved orthophosphate -4.6059 0.2884 -0.0317 -0.6419 0.0459 -0.4340 -0.1162

Total phosphorus -3.0243 0.6291 0.0219 -0.2657 0.0800 -0.4968 -0.4880

Great Miami River at Hamilton

Dissolved ammonia -3.0719 0.8079 0.0036 -1.4136 -1.2482 -1.1848 0.3361

Dissolved nitrate 1.0607 0.0732 -0.0118 0.1075 0.0773 0.2716 0.4463

Total nitrogen 1.5022 0.1186 0.0166 0.0404 -0.0329 0.1179 0.2038

Dissolved orthophosphate -2.4990 -0.0578 0.0362 -0.0548 0.1705 -0.3384 0.8695

Total phosphorus -1.1827 0.2750 0.1199 -0.0680 -0.0875 -0.4031 0.0296

Great Miami River at New Baltimore

Total nitrogen 1.6964 0.0908 0.0221 -0.0138 -0.0020 0.0465 0.0089

Total phosphorus -1.0289 -0.1980 0.1754 -0.0400 -0.0015 -0.0801 -0.0445

Great Miami River near Fairfield

Dissolved nitrate 0.8238 0.1958 -0.0490 -1.1641 8.0460 0.7075 -0.5173

Total nitrogen 1.7068 0.1816 -0.0082 -0.7589 -0.6336 0.1050 -0.0714

Total phosphorus -1.6550 0.3073 0.1296 -0.2366 4.2113 0.0667 0.2567
Appendix C. 45

Appendix C. Statistical summary of nitrogen and phosphorus concentrations in the Great Miami River Basin, October 1998–Septem[MCL, maximun contamination limit; RAL, recommended action level; N, nitrogen; P, phosphorus; na, not applicable; <, less than]

Constituent

Number 

of 

samples

Number of detections

Number of detections 

greater 

than MCL 

or RAL

Concentration

in milligrams per 

Minimum

25th

percentile Median Me

Stillwater River near Union, Ohio

Ammonia (as N), dissolved 31 24 na <0.02 0.03 0.06 0.Ammonia plus organic nitrogen (as N), total 31 31 na 0.36 0.61 0.80 0.Ammonia plus organic nitrogen (as N), dissolved 31 31 na 0.31 0.38 0.41 0.Nitrite (as N), dissolved 31 27 na <0.01 0.02 0.02 0.Nitrite plus nitrate (as N), dissolved 30 30 na 1.2 1.6 3.4 4.Nitrate (as N), dissolved1 30 30 1 0.96 1.5 3.3 4.

Phosphorus (as P), dissolved 31 31 na 0.01 0.05 0.12 0.Orthophosphate (as P), dissolved 31 30 na <0.01 0.04 0.10 0.Phosphorus (as P), total 31 31 23 0.06 0.11 0.16 0.

Great Miami River near Vandalia, Ohio

Ammonia (as N), dissolved 30 13 na <0.02 <0.02 <0.02 0.Ammonia plus organic nitrogen (as N), total 30 30 na 0.22 0.55 0.76 0.Ammonia plus organic nitrogen (as N), dissolved 30 30 na 0.11 0.34 0.41 0.Nitrite (as N), dissolved 30 29 na <0.01 0.02 0.03 0.Nitrite plus nitrate (as N), dissolved 30 30 na 0.69 1.9 3.0 3.Nitrate (as N), dissolved1 30 30 0 0.66 1.8 3.0 3.Phosphorus (as P), dissolved 30 30 na 0.05 0.09 0.17 0.Orthophosphate (as P), dissolved 30 30 na 0.03 0.07 0.14 0.Phosphorus (as P), total 30 30 30 0.10 0.14 0.29 0.

Mad River near Eagle City, Ohio

Ammonia (as N), dissolved 51 26 na <0.02 <0.02 <0.02 0.Ammonia plus organic nitrogen (as N), total 51 51 na 0.13 0.21 0.29 0.Ammonia plus organic nitrogen (as N), dissolved 51 50 na <0.1 0.16 0.22 0.

Appendix C.
46 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000 Appendix C. Statistical summary of nitrogen and phosphorus concentrations in the Great Miami River Basin, October 1998–Septem

[MCL, maximun contamination limit; RAL, recommended action level; N, nitrogen; P, phosphorus; na, not applicable; <, less than] Constituent Number of samples Number of detections Number of detections greater than MCL or RAL Concentration

in milligrams per 

Minimum 25th percentile Median Me

Mad River near Eagle City, Ohio - continued Nitrite (as N), dissolved 51 48 na <0.01 0.01 0.02 0.

Nitrite plus nitrate (as N), dissolved 51 51 na 1.4 3.7 3.9 4.Nitrate (as N), dissolved1 51 51 0 1.3 3.6 3.9 4.

Phosphorus (as P), dissolved 51 51 na 0.01 0.03 0.04 0.Orthophosphate (as P), dissolved 51 49 na <0.01 0.02 0.04 0.Phosphorus (as P), total 51 50 13 <0.01 0.04 0.07 0.

Holes Creek at Huffman Park near Kettering, Ohio Ammonia (as N), dissolved 54 28 na <0.02 <0.02 0.02 0.

Ammonia plus organic nitrogen (as N), total 54 54 na 0.15 0.31 0.46 0.Ammonia plus organic nitrogen (as N), dissolved 54 54 na 0.05 0.24 0.33 0.Nitrite (as N), dissolved 54 30 na <0.01 <0.01 0.01 0.Nitrite plus nitrate (as N), dissolved 54 53 na <0.05 0.70 0.91 0.Nitrate (as N), dissolved1 54 53 0 <0.04 0.68 0.90 0.Phosphorus (as P), dissolved 54 52 na <0.004 0.009 0.01 0.Orthophosphate (as P), dissolved 54 29 na <0.01 <0.01 0.01 0.Phosphorus (as P), total 54 51 14 <0.008 0.02 0.04 0.

Great Miami River at Hamilton, Ohio Ammonia (as N), dissolved 35 34 na <0.02 0.02 0.03 0.

Ammonia plus organic nitrogen (as N), total 35 35 na 0.51 0.91 1.2 1.Ammonia plus organic nitrogen (as N), dissolved 35 35 na 0.31 0.41 0.50 0.Nitrite (as N), dissolved 35 34 na <0.01 0.02 0.03 0.Nitrite plus nitrate (as N), dissolved 35 34 na <0.05 2.1 3.1 3.Nitrate (as N), dissolved1 35 34 0 <0.04 2.0 3.1 3.Phosphorus (as P), dissolved 35 35 na 0.02 0.11 0.16 0.Orthophosphate (as P), dissolved 35 34 na <0.01 0.08 0.13 0.Phosphorus (as P), total 35 35 35 0.1 0.27 0.33 0.

1Dissolved nitrite plus nitrate minus dissolved nitrite.
Appendix D. 47

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus

[kg, kilograms; kg/km2, kilograms per square kilometer]

1

Calculated by taking the difference between the upper and lower confidence limit and dividing by monthly load.

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load1

Stillwater River near Union, Ohio—Nitrate

October 1998 6,900 4.1 5,000 9,300 62

November 1998 9,800 5.9 7,400 12,700 54

December 1998 16,000 9.4 12,200 20,000 49

January 1999 1,100,000 640 706,000 1,570,000 78

February 1999 590,000 360 440,000 789,000 59

March 1999 700,000 420 535,000 903,000 53

April 1999 440,000 270 338,000 574,000 55

May 1999 97,000 58 76,000 122,000 47

June 1999 64,000 38 48,000 84,000 56

July 1999 27,000 16 19,400 36,400 63

August 1999 5,500 3.3 4,100 7,300 56

September 1999 2,200 1.3 1,600 2,900 59

October 1999 2,100 1.2 1,600 2,700 57

November 1999 8,000 4.8 5,900 10,600 60

December 1999 13,000 8.1 10,100 17,700 58

January 2000 30,000 18 21,800 39,500 60

February 2000 310,000 190 234,000 410,000 58

March 2000 170,000 100 136,000 216,000 47

April 2000 890,000 530 622,000 1,240,000 70

May 2000 350,000 210 268,000 450,000 51

June 2000 430,000 260 299,000 609,000 72

July 2000 77,000 46 54,300 105,000 66

August 2000 12,000 6.9 8,800 14,700 49

September 2000 9,900 5.9 7,200 13,200 61

Mean 220,000 130 161,000 303,000 65

Median 47,000 28 34,800 61,900 57

Appendix D.
48 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Stillwater River near Union, Ohio—Total Nitrogen 

October 1998 9,800 5.9 7,700 12,300 48

November 1998 13,000 8.0 10,500 15,900 42

December 1998 19,000 12 15,800 23,200 38

January 1999 1,300,000 770 935,000 1,750,000 62

February 1999 670,000 440 530,000 838,000 46

March 1999 780,000 470 634,000 953,000 41

April 1999 520,000 320 418,000 630,000 40

May 1999 120,000 70 97,700 140,000 35

June 1999 85,000 52 68,300 104,000 42

July 1999 38,000 23 30,400 48,100 47

August 1999 8,900 5.3 7,200 10,700 39

September 1999 3,700 2.3 3,000 4,500 41

October 1999 3,400 2.1 2,800 4,200 41

November 1999 12,000 7.1 9,200 14,400 43

December 1999 18,000 11 14,500 22,200 43

January 2000 37,000 22 29,200 46,200 46

February 2000 370,000 240 295,000 455,000 43

March 2000 200,000 120 167,000 239,000 36

April 2000 1,100,000 700 849,000 1,460,000 54

May 2000 460,000 270 374,000 559,000 41

June 2000 630,000 391 475,000 830,000 57

July 2000 110,000 68 87,200 145,000 53

August 2000 18,000 11 15,000 22,200 40

September 2000 16,000 9.8 12,400 19,800 46

Mean 270,000 170 212,000 348,000 50

Median 62,000 38 49,300 76,100 44
Appendix D. 49

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Stillwater River near Union, Ohio—Orthophosphate

October 1998 770 0.46 380 1,390 130

November 1998 1,000 0.60 550 1,720 120

December 1998 1,100 0.64 610 1,740 100

January 1999 46,000 27 17,300 99,100 178

February 1999 11,000 6.8 5,300 21,600 145

March 1999 7,400 4.4 3,600 13,600 133

April 1999 2,200 1.3 1,100 3,800 118

May 1999 390 0.23 230 620 100

June 1999 340 0.20 180 580 115

July 1999 250 0.15 130 440 124

August 1999 180 0.11 100 300 105

September 1999 210 0.12 110 360 114

October 1999 320 0.19 170 540 115

November 1999 720 0.43 370 1,260 123

December 1999 910 0.55 490 1,560 120

January 2000 1,200 0.70 600 2,100 125

February 2000 5,500 3.3 2,800 10,000 130

March 2000 1,600 0.96 940 2,600 100

April 2000 9,500 5.7 3,800 19,900 168

May 2000 2,800 1.7 1,500 5,000 125

June 2000 6,600 4.0 2,700 13,900 167

July 2000 1,400 0.86 680 2,700 143

August 2000 680 0.40 380 1,100 109

September 2000 1,300 0.78 650 2,400 131

Mean 4,300 2.6 1,900 8,700 158

Median 1,100 0.67 600 1,900 118
50 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Stillwater River near Union, Ohio—Total Phosphorus

October 1998 980 0.59 630 1,500 85

November 1998 1,100 0.63 720 1,500 72

December 1998 1,100 0.60 700 1,400 62

January 1999 110,000 64 57,300 183,000 118

February 1999 27,000 16 16,600 42,300 96

March 1999 22,000 13 14,200 33,500 86

April 1999 11,000 6.8 7,400 16,700 85

May 1999 2,000 1.2 1,400 2,700 65

June 1999 2,400 1.4 1,600 3,500 79

July 1999 1,700 1.0 1,100 2,500 82

August 1999 720 0.43 500 1,000 69

September 1999 500 0.30 340 700 74

October 1999 500 0.30 340 710 74

November 1999 1,100 0.68 740 1,600 82

December 1999 1,200 0.70 780 1,700 75

January 2000 1,700 1.0 1,000 2,600 88

February 2000 13,000 7.6 8,100 19,100 85

March 2000 3,800 2.3 2,700 5,200 66

April 2000 41,000 24 22,700 68,300 112

May 2000 14,000 8.6 9,400 21,200 86

June 2000 44,000 26 23,900 73,700 114

July 2000 7,000 4.2 4,100 11,100 100

August 2000 1,500 0.90 1,000 2,100 67

September 2000 1,900 1.1 1,200 2,800 84

Mean 13,000 7.7 7,400 20,800 100

Median 1,900 1.2 1,300 2,800 79
Appendix D. 51

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River near Vandalia, Ohio—Nitrate

October 1998 15,000 5.1 9,400 23,000 93

November 1998 18,000 6.2 12,200 26,800 78

December 1998 30,000 10 20,200 42,300 73

January 1999 1,400,000 480 636,000 2,810,000 151

February 1999 680,000 230 420,000 1,040,000 91

March 1999 960,000 320 626,000 1,400,000 80

April 1999 540,000 180 380,000 753,000 68

May 1999 120,000 40 87,100 161,000 62

June 1999 43,000 14 30,800 58,100 63

July 1999 30,000 10 20,800 41,400 70

August 1999 15,000 5.2 10,700 21,700 73

September 1999 6,700 2.3 4,200 10,200 90

October 1999 10,000 3.5 7,100 14,400 74

November 1999 13,000 4.4 8,900 18,300 72

December 1999 28,000 9.6 18,800 41,300 79

January 2000 95,000 32 58,600 145,000 92

February 2000 650,000 220 419,000 953,000 82

March 2000 270,000 92 192,000 378,000 70

April 2000 1,400,000 460 654,000 2,480,000 135

May 2000 370,000 130 258,000 518,000 70

June 2000 530,000 180 320,000 838,000 98

July 2000 86,000 29 57,600 124,000 78

August 2000 130,000 44 79,200 200,000 92

September 2000 120,000 40 61,900 204,000 117

Mean 310,000 110 183,000 512,000 106

Median 110,000 36 60,300 153,000 73
52 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River near Vandalia, Ohio—Total Nitrogen

October 1998 20,000 6.8 14,600 27,200 65

November 1998 24,000 8.0 17,800 30,800 54

December 1998 36,000 12 27,500 46,400 52

January 1999 1,700,000 580 994,000 2,810,000 104

February 1999 810,000 270 587,000 1,090,000 62

March 1999 1,100,000 380 853,000 1,480,000 56

April 1999 700,000 240 551,000 885,000 47

May 1999 160,000 54 129,000 197,000 42

June 1999 62,000 21 49,100 76,300 44

July 1999 49,000 16 38,000 61,400 47

August 1999 26,000 8.7 20,000 32,900 50

September 1999 9,800 3.3 7,100 13,200 62

October 1999 16,000 5.3 12,200 20,000 50

November 1999 18,000 6.1 14,000 23,000 50

December 1999 37,000 13 28,200 48,900 57

January 2000 130,000 42 88,900 171,000 64

February 2000 770,000 260 572,000 1,010,000 57

March 2000 300,000 100 238,000 380,000 47

April 2000 1,500,000 510 923,000 2,330,000 93

May 2000 440,000 150 343,000 559,000 50

June 2000 700,000 240 495,000 974,000 68

July 2000 110,000 38 85,600 147,000 55

August 2000 190,000 63 133,000 253,000 63

September 2000 160,000 55 104,000 243,000 87

Mean 380,000 130 264,000 538,000 71

Median 140,000 48 96,600 184,000 54
Appendix D. 53

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River near Vandalia, Ohio—Orthophosphate

October 1998 3,400 1.1 2,000 5,500 103

November 1998 3,100 1.0 1,900 4,700 90

December 1998 2,800 0.95 1,800 4,100 82

January 1999 43,000 15 16,600 92,700 176

February 1999 13,000 4.4 7,600 21,000 103

March 1999 14,000 4.7 8,500 21,900 96

April 1999 7,000 2.4 4,700 10,100 79

May 1999 2,200 0.76 1,600 3,100 68

June 1999 1,600 0.53 1,100 2,200 68

July 1999 1,900 0.63 1,300 2,700 74

August 1999 1,900 0.65 1,300 2,800 79

September 1999 1,900 0.65 1,100 3,200 105

October 1999 2,300 0.77 1,500 3,300 82

November 1999 2,200 0.75 1,400 3,300 82

December 1999 2,400 0.81 1,500 3,600 88

January 2000 3,500 1.2 2,100 5,600 97

February 2000 11,000 3.6 6,500 16,300 93

March 2000 4,000 1.3 2,700 5,700 75

April 2000 18,000 5.9 7,600 35,000 157

May 2000 6,200 2..1 4,100 9,000 79

June 2000 14,000 4.6 7,600 22,700 107

July 2000 4,500 1.5 2,900 6,700 84

August 2000 9,200 3.1 5,400 14,700 101

September 2000 13,000 4.3 6,400 22,800 126

Mean 7,700 2.6 4,100 13,400 120

Median 3,800 1.3 2,400 5,600 92
54 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River near Vandalia, Ohio—Total Phosphorus

October 1998 3,700 1.2 2,300 5,600 89

November 1998 3,600 1.2 2,300 5,100 78

December 1998 3,500 1.2 2,400 5,000 74

January 1999 94,000 32 41,700 184,000 151

February 1999 32,000 11 20,100 49,000 91

March 1999 37,000 13 24,100 54,500 82

April 1999 21,000 7.2 14,800 29,400 69

May 1999 5,800 1.9 4,200 7,700 60

June 1999 3,500 1.2 2,500 4,700 63

July 1999 4,200 1.4 3,000 5,900 69

August 1999 3,500 1.2 2,500 4,900 71

September 1999 2,100 0.70 1,300 3,200 90

October 1999 3,100 1.1 2,100 4,400 71

November 1999 2,900 1.0 2,000 4,100 72

December 1999 3,700 1.3 2,500 5,400 80

January 2000 7,800 2.6 4,700 12,200 95

February 2000 27,000 9.3 17,800 40,400 84

March 2000 8,800 3.0 6,200 12,200 67

April 2000 42,000 14 20,600 77,500 135

May 2000 15,000 4.9 10,100 20,400 69

June 2000 34,000 11.6 20,400 54,000 99

July 2000 7,800 2.6 5,300 11,200 76

August 2000 18,000 6.1 11,200 27,600 92

September 2000 21,000 7.2 11,300 37,100 122

Mean 17,000 5.7 9,800 27,800 105

Median 7,800 2.6 5,000 11,700 76
Appendix D. 55

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Mad River near Eagle City, Ohio—Nitrate

October 1998 35,000 44 29,600 41,300 34

November 1998 36,000 44 30,600 41,500 30

December 1998 38,000 48 33,200 44,300 29

January 1999 160,000 200 134,000 196,000 38

February 1999 140,000 170 120,000 157,000 26

March 1999 160,000 200 140,000 177,000 23

April 1999 150,000 180 130,000 164,000 23

May 1999 74,000 92 66,400 81,600 21

June 1999 51,000 64 45,900 56,600 21

July 1999 54,000 68 48,500 60,700 23

August 1999 34,000 43 30,400 38,300 23

September 1999 25,000 31 22,100 28,600 26

October 1999 29,000 36 25,600 33,200 26

November 1999 31,000 39 27,300 35,600 27

December 1999 36,000 45 31,500 41,500 27

January 2000 57,000 71 49,400 65,900 29

February 2000 93,000 120 81,100 106,000 26

March 2000 66,000 83 58,400 74,900 25

April 2000 170,000 210 144,000 192,000 29

May 2000 100,000 130 90,400 113,000 22

June 2000 59,000 74 53,100 65,600 21

July 2000 39,000 49 35,300 44,000 22

August 2000 38,000 47 33,800 42,400 23

September 2000 53,000 66 44,600 61,500 32

Mean 72,000 89 62,800 81,700 26

Median 53,000 67 47,200 61,100 23
56 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Mad River near Eagle City, Ohio—Total Nitogen

October 1998 37,000 46 31,800 42,400 29

November 1998 37,000 46 32,300 42,100 26

December 1998 39,000 49 34,500 44,300 25

January 1999 250,000 310 205,000 301,000 38

February 1999 180,000 220 154,000 197,000 25

March 1999 190,000 240 175,000 215,000 21

April 1999 180,000 230 167,000 206,000 21

May 1999 81,000 100 74,300 88,800 18

June 1999 56,000 70 51,000 61,200 18

July 1999 63,000 78 56,900 69,300 20

August 1999 38,000 47 34,400 42,000 20

September 1999 28,000 34 24,600 30,800 22

October 1999 32,000 40 28,700 35,900 22

November 1999 34,000 42 30,200 38,000 23

December 1999 39,000 48 34,200 43,300 23

January 2000 67,000 83 58,500 76,600 27

February 2000 110,000 140 99,600 126,000 24

March 2000 71,000 89 64,100 79,500 22

April 2000 240,000 300 205,000 282,000 32

May 2000 120,000 150 111,000 136,000 20

June 2000 67,000 83 60,800 73,000 18

July 2000 43,400 54 39,400 47,700 19

August 2000 43,000 53 38,500 46,800 19

September 2000 69,000 85 58,400 80,200 32

Mean 88,000 110 77,900 100,000 25

Median 65,000 81 57,600 71,100 21
Appendix D. 57

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Mad River near Eagle City, Ohio—Orthophosphate 

October 1998 990 1.2 580 1,600 99

November 1998 890 1.1 550 1,400 90

December 1998 730 0.9 470 1,100 86

January 1999 4,900 6.1 1,900 10,500 174

February 1999 1,700 2.2 1,100 2,700 95

March 1999 1,500 1.8 980 2,100 75

April 1999 1,200 1.5 810 1,800 81

May 1999 500 0.63 370 680 64

June 1999 430 0.54 310 580 65

July 1999 630 0.78 430 880 70

August 1999 540 0.68 380 760 70

September 1999 520 0.65 350 750 77

October 1999 630 0.78 420 900 76

November 1999 600 0.74 390 870 80

December 1999 520 0.65 340 780 86

January 2000 680 0.85 400 1,100 104

February 2000 740 0.92 470 1,100 88

March 2000 370 0.47 250 550 81

April 2000 1,900 2.3 740 3,900 163

May 2000 630 0.79 430 900 75

June 2000 410 0.51 300 550 61

July 2000 380 0.47 270 510 63

August 2000 500 0.62 360 680 66

September 2000 1,100 1.3 560 1,800 115

Mean 960 1.2 550 1,600 109

Median 630 0.79 430 900 76
58 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Mad River near Eagle City, Ohio—Total Phosphorus

October 1998 1,000 1.3 560 1,700 118

November 1998 910 1.1 520 1,500 104

December 1998 760 0.94 440 1,200 103

January 1999 50,000 63 12,000 140,000 258

February 1999 8,200 10 3,700 15,800 148

March 1999 5,800 7.2 3,200 9,700 112

April 1999 6,000 7.5 3,100 10,600 126

May 1999 1,100 1.4 740 1,600 75

June 1999 840 1.0 570 1,200 74

July 1999 1,600 2.0 960 2,400 91

August 1999 910 1.1 600 1,300 79

September 1999 710 0.88 450 1,100 87

October 1999 890 1.1 560 1,300 88

November 1999 820 1.0 510 1,300 91

December 1999 700 0.88 430 1,100 94

January 2000 2,500 3.2 870 5,800 199

February 2000 2,800 3.6 1,500 5,000 124

March 2000 780 1.0 480 1,200 94

April 2000 24,000 29 5,200 69,200 267

May 2000 2,800 3.5 1,400 5,000 129

June 2000 1,000 1.2 680 1,400 74

July 2000 710 0.89 480 1,000 75

August 2000 950 1.2 640 1,400 78

September 2000 6,500 8.0 1,900 16,400 225

Mean 5,100 6.3 1,700 12,500 212

Median 1,000 1.3 660 1,500 86
Appendix D. 59

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Holes Creek near Kettering, Ohio—Nitrate

January 1999 5,500 106 3,200 8,900 104

February 1999 3,100 59 1,700 5,100 107

March 1999 2,200 43 1,400 3,300 87

April 1999 1,600 30 1,100 2,300 76

May 1999 490 9.4 360 660 61

June 1999 450 8.6 280 690 91

July 1999 320 6.0 210 450 75

August 1999 280 5.4 170 460 104

September 1999 110 2.1 76 160 74

October 1999 140 2.6 98 180 61

November 1999 250 4.8 170 350 72

December 1999 600 12 400 880 80

January 2000 1,400 26 670 2,500 131

February 2000 2,500 47 1,400 4,000 101

March 2000 1,400 26 920 1,900 73

April 2000 3,600 69 1,900 6,300 121

May 2000 850 16 580 1,200 73

June 2000 1,100 22 600 2,000 124

July 2000 940 18 520 1,600 114

August 2000 250 4.7 160 370 84

September 2000 230 4.5 150 350 83

Mean 1,300 25 730 2,000 100

Median 850 16 460 1,100 80
60 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Holes Creek near Kettering, Ohio—Total Nitrogen

January 1999 14,000 260 9,700 18,700 64

February 1999 7,000 130 4,800 9,900 73

March 1999 4,600 88 3,400 6,100 59

April 1999 3,600 68 2,700 4,600 53

May 1999 930 18 760 1,100 41

June 1999 1,200 22 810 1,600 68

July 1999 810 16 620 1,000 52

August 1999 820 16 560 1,200 74

September 1999 180 3.5 140 240 54

October 1999 190 3.6 150 220 38

November 1999 370 7.1 290 460 46

December 1999 990 19 750 1,300 53

January 2000 2,900 56 1,800 4,600 98

February 2000 5,000 95 3,500 6,900 70

March 2000 2,400 46 1,800 3,000 49

April 2000 9,400 180 6,100 13,800 82

May 2000 1,800 34 1,400 2,300 48

June 2000 3,700 71 2,400 5,500 84

July 2000 3,200 61 2,100 4,600 77

August 2000 590 11 430 800 63

September 2000 500 9.6 370 660 58

Mean 3,000 58 2,100 4,200 70

Median 1,800 34 1,400 2,300 48
Appendix D. 61

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Holes Creek near Kettering, Ohio—Orthophosphate

January 1999 180 3.5 67 400 183

February 1999 72 1.4 25 170 194

March 1999 45 0.87 19 92 162

April 1999 34 0.66 15 67 153

May 1999 9.1 0.17 4.5 16 131

June 1999 14 0.27 4.2 34 214

July 1999 12 0.24 4.7 27 183

August 1999 15 0.29 4.0 41 247

September 1999 2.7 0.05 0.9 6.5 207

October 1999 2.2 0.04 1.1 3.8 123

November 1999 5.0 0.10 2.2 9.9 156

December 1999 12 0.23 4.7 26 175

January 2000 24 0.46 5.3 70 266

February 2000 31 0.60 11 72 196

March 2000 15 0.28 6.3 29 153

April 2000 44 0.84 14 105 205

May 2000 12 0.23 5.4 23 150

June 2000 26 0.50 7.3 68 234

July 2000 27 0.52 8.3 67 214

August 2000 6.9 0.13 2.2 16 202

September 2000 6.3 0.12 2.2 14 190

Mean 28 0.55 9.4 62 186

Median 15 0.28 5.0 38 220
62 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Holes Creek near Kettering, Ohio—Total Phosphorus

January 1999 1,500 28 470 3,500 202

February 1999 620 12 140 1,800 261

March 1999 310 5.8 82 811 235

April 1999 270 5.1 78 680 222

May 1999 46 0.88 18 98 174

June 1999 140 2.7 28 440 293

July 1999 96 1.8 33 220 195

August 1999 160 3.0 34 480 275

September 1999 12 0.23 3.2 32 233

October 1999 6.2 0.12 3.1 11 126

November 1999 16 0.31 6.8 34 169

December 1999 59 1.1 19 140 203

January 2000 330 6.2 49 1,100 333

February 2000 380 7.4 98 1,000 250

March 2000 120 2.2 44 260 175

April 2000 1,000 19 210 3,000 277

May 2000 130 2.4 48 270 169

June 2000 770 15 160 2,300 280

July 2000 720 14 160 2,100 266

August 2000 83 1.6 21 230 253

September 2000 56 1.1 17 140 214

Mean 320 6.2 79 870 253

Median 140 2.7 46 460 278
Appendix D. 63

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River at Hamilton, Ohio—Nitrate

October 1998 130,000 14 93,700 171,000 60

November 1998 160,000 17 120,000 206,000 54

December 1998 290,000 31 219,000 383,000 56

January 1999 2,900,000 310 2,040,000 4,060,000 69

February 1999 2,000,000 210 1,540,000 2,520,000 49

March 1999 2,100,000 220 1,620,000 2,570,000 46

April 1999 1,000,000 110 813,000 1,280,000 46

May 1999 330,000 35 256,000 413,000 48

June 1999 180,000 20 144,000 231,000 48

July 1999 120,000 13 96,200 154,000 47

August 1999 59,000 6.3 47,400 73,100 43

September 1999 41,000 4.4 31,900 52,700 51

October 1999 72,000 7.7 58,000 88,600 42

November 1999 84,000 9.0 66,800 105,000 46

December 1999 190,000 20 146,000 235,000 48

January 2000 520,000 55 374,000 706,000 63

February 2000 1,500,000 160 1,150,000 1,970,000 54

March 2000 910,000 97 706,000 1,150,000 49

April 2000 1,800,000 190 1,340,000 2,370,000 57

May 2000 570,000 61 440,000 728,000 50

June 2000 590,000 63 434,000 782,000 59

July 2000 240,000 26 180,000 327,000 60

August 2000 170,000 18 123,000 229,000 62

September 2000 190,000 21 130,000 279,000 77

Mean 670,000 72 507,000 879,000 55

Median 270,000 29 199,000 355,000 57
64 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River at Hamilton, Ohio—Total Nitrogen

October 1998 180,000 19 153,000 215,000 34

November 1998 200,000 21 169,000 229,000 30

December 1998 330,000 35 280,000 383,000 31

January 1999 3,800,000 400 3,080,000 4,590,000 40

February 1999 2,300,000 250 2,030,000 2,690,000 28

March 1999 2,600,000 270 2,250,000 2,910,000 26

April 1999 1,500,000 160 1,280,000 1,660,000 26

May 1999 500,000 53 432,000 564,000 27

June 1999 320,000 34 282,000 367,000 26

July 1999 240,000 25 206,000 267,000 26

August 1999 120,000 12 104,000 132,000 24

September 1999 79,000 8.4 68,300 90,500 28

October 1999 120,000 13 106,000 135,000 24

November 1999 120,000 13 107,000 138,000 25

December 1999 230,000 25 203,000 265,000 26

January 2000 640,000 68 530,000 765,000 37

February 2000 1,900,000 200 1,640,000 2,230,00 30

March 2000 1,100,000 120 1,000,000 1,320,000 27

April 2000 2,900,000 300 2,400,000 3,370,000 34

May 2000 920,000 98 800,000 1,060,000 28

June 2000 1,100,000 120 960,000 1,340,000 33

July 2000 480,000 51 401,000 562,000 34

August 2000 320,000 35 272,000 385,000 35

September 2000 340,000 36 274,000 421,000 43

Mean 930,000 99 793,000 1,090,000 31

Median 410,000 44 341,000 491,000 34
Appendix D. 65

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer ]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River at Hamilton, Ohio—Orthophosphate 

October 1998 16,000 1.7 8,300 27,600 121

November 1998 20,000 2.1 11,100 33,200 110

December 1998 27,000 2.9 15,200 44,700 109

January 1999 140,000 16 69,300 270,000 138

February 1999 75,000 7.9 43,300 120,000 102

March 1999 56,000 5.9 33,200 87,500 97

April 1999 20,000 2.2 12,500 31,300 94

May 1999 6,800 0.72 4,100 10,600 96

June 1999 4,500 0.48 2,700 7,000 94

July 1999 4,200 0.45 2,600 6,400 91

August 1999 3,400 0.37 2,200 5,200 90

September 1999 3,800 0.40 2,200 6,100 103

October 1999 7,400 0.79 4,700 11,200 88

November 1999 9,000 0.95 5,500 13,900 93

December 1999 14,000 1.5 8,600 22,600 99

January 2000 25,000 2.7 12,800 44,600 127

February 2000 40,000 4.3 22,600 67,100 111

March 2000 18,000 1.9 10,700 28,900 100

April 2000 28,000 3.0 14,800 47,600 117

May 2000 8,700 0.93 5,200 13,900 100

June 2000 10,000 1.1 5,500 17,500 119

July 2000 5,900 0.63 3,200 9,900 113

August 2000 6,400 0.68 3,400 11,100 119

September 2000 11,000 1.1 4,700 20,200 147

Mean 24,000 2.5 12,900 39,900 112

Median 12,000 1.3 6,900 21,400 118
66 Nitrogen and Phosphorus in Streams of the Great Miami River Basin, Ohio, 1998–2000

Appendix D. Monthly loads, yields, and confidence intervals for nitrate, total nitrogen, orthophosphate, and total 

phosphorus—Continued.

[kg, kilograms; kg/km2, kilograms per square kilometer]

Month

Monthly Load 

(kg)

Monthly Yield 

(kg/km2)

95-percent confidence range of monthly loads

Lower 

(kg)

 Upper 

(kg)

Percent of

monthly load

Great Miami River at Hamilton, Ohio—Total phosphorus

October 1998 20,000 2.2 14,900 27,000 60

November 1998 18,000 1.9 13,600 23,100 53

December 1998 23,000 2.5 17,400 30,900 59

January 1999 420,000 45 275,000 615,000 81

February 1999 160,000 17 120,000 210,000 56

March 1999 160,000 17 124,000 204,000 50

April 1999 87,000 9.3 68,300 110,000 48

May 1999 27,000 2.9 21,400 33,900 46

June 1999 23,000 2.5 18,400 28,800 45

July 1999 22,000 2.3 17,500 27,100 44

August 1999 14,000 1.5 11,400 17,300 42

September 1999 11,000 1.2 8,400 13,800 49

October 1999 14,000 1.5 11,600 17,600 43

November 1999 12,000 1.3 9,500 14,800 44

December 1999 16,000 1.7 12,600 20,000 47

January 2000 43,000 4.6 29,100 61,800 76

February 2000 120,000 13 88,000 156,000 57

March 2000 53,000 5.6 40,800 67,000 50

April 2000 240,000 25 157,000 339,000 77

May 2000 53,000 5.7 41,400 67,300 49

June 2000 100,000 11 76,900 140,000 63

July 2000 44,000 4.7 32,400 58,900 60

August 2000 34,000 3.6 24,700 44,800 60

September 2000 39,000 4.2 26,400 56,600 77

Mean 73,000 8.0 52,600 99,400 64

Median 37,000 4.0 25,500 50,700 62
Appendix E. 67

Appendix E. Annual loads and confidence intervals for total nitrogen and total phosphorus

Water year

 Annual load 

(million 

kilograms)

95-percent confidence interval of loads

 Lower (million 

kilograms)

 Upper (million 

kilograms)

 Percent of 

annual load

Great Miami River at New Baltimore, Ohio—Total nitrogen

1974 22.4 18.4 26.9 37.9

1975 26.4 21.9 31.4 36.0

1976 15.2 13.2 17.4 27.3

1977 7.8 6.8 8.8 25.0

1978 25.1 21.5 29.3 31.1

1979 29.0 24.9 33.5 29.7

1980 31.9 27.8 36.4 26.9

1981 18.0 16.0 20.1 23.1

1982 28.4 24.0 33.4 33.1

1983 15.5 13.3 17.9 29.7

1984 22.8 19.9 26.0 26.9

1985 19.0 16.5 21.9 28.4

1986 23.7 20.5 27.4 29.1

1987 17.6 15.5 20.0 25.9

1988 7.4 6.5 8.4 25.4

1989 23.0 19.7 26.7 30.5

1990 22.4 19.1 26.1 31.3

1991 24.0 19.8 28.8 37.6

1992 9.5 7.8 11.3 36.0

1993 19.3 15.7 23.5 40.1

Great Miami River at New Baltimore, Ohio—Total phosphorus

1974 1.9 1.6 2.2 31.6

1975 2.2 1.9 2.6 32.5

1976 1.2 1.1 1.4 21.8

1977 0.73 0.66 0.80 18.9

1978 1.9 1.7 2.2 26.8

1979 2.1 1.9 2.4 25.7

1980 2.2 2.0 2.5 23.3

1981 1.2 1.1 1.3 18.0

1982 1.9 1.6 2.2 29.0

1983 1.1 0.95 1.2 25.7

1984 1.4 1.2 1.5 21.4

1985 1.2 1.0 1.3 23.0

1986 1.4 1.2 1.6 24.7

1987 1.1 0.97 1.2 22.2

1988 0.50 0.46 0.55 19.6

1989 1.3 1.1 1.5 26.8

1990 1.2 1.1 1.4 26.8

1991 1.4 1.1 1.6 34.4

1992 0.58 0.50 0.67 28.9

1993 0.98 0.82 1.2 33.6

Great Miami River at Hamilton, Ohio—Total nitrogen

1999 12.1 10.8 13.2 19.8

2000 10.2 9.2 11.3 20.6

Great Miami River at Hamilton, Ohio—Total phosphorus

1999 0.99 0.77 1.2 43.4

2000 0.77 0.63 0.93 39.0

Appendix E.