Prepared in cooperation with Monroe County Department of Health

Water Resources of Monroe County, New York, 

Water Years 2003–08: Streamflow, Constituent 

Loads, and Trends in Water Quality

Scientific Investigations Report 2010–5216

U.S. Department of the Interior

U.S. Geological Survey
Cover.  Photograph of flow-control structure on Genesee River downstream from Interstate 490 suspension bridge, Rochester, N.Y.
Water Resources of Monroe County, 

New York, Water Years 2003–08: 

Streamflow, Constituent Loads, and 

Trends in Water Quality

By Brett A. Hayhurst, William F. Coon, and David A.V. Eckhardt

Prepared in cooperation with Monroe County Department of Health

Scientific Investigations Report 2010–5216

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Hayhurst, B.A., Coon, W.F., and Eckhardt, D.A., 2010, Water resources of Monroe County, New York, water years 

2003–08: Streamflow, constituent loads, and trends in water quality: U.S. Geological Survey Scientific Investigations 

Report 2010–5216, 34 p., also available at http://pubs.usgs.gov/sir/2010/5216.
iii

Acknowledgments

Special thanks are extended to the personnel of Monroe County Environmental Laboratory 

for assistance in the collection, analysis, and verification of the data presented herein, and in 

particular to Mr. Charles Knauf, Environmental Health Project Analyst of the Monroe County 

Department of Health. 
This page has been left blank intentionally.
v

Contents

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

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

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

Related Studies .....................................................................................................................................2

Study Area ......................................................................................................................................................2

Population .............................................................................................................................................2

Land Use and Land Cover....................................................................................................................2

Climate ...................................................................................................................................................6

Selected Waterways............................................................................................................................6

Water-Resources Data Collection and Processing .................................................................................7

Stage and Streamflow .........................................................................................................................7

Water Temperature ..............................................................................................................................9

Chemical Constituents .........................................................................................................................9

Mean Streamflow Associated with Water-Quality Samples.........................................................9

Water-Resources Data Analyses..............................................................................................................10

Streamflow ..........................................................................................................................................10

Water Quality.......................................................................................................................................11

Water Temperature ...................................................................................................................11

Chemical Constituents ..............................................................................................................12

Nutrients and Total Suspended Solids ..........................................................................12

Chloride and Sulfate.........................................................................................................18

Constituent Loads ...............................................................................................................................18

Temporal Trends..................................................................................................................................26

Summary........................................................................................................................................................31

References Cited..........................................................................................................................................32

Figures

1. Map showing locations of streamflow and water-quality monitoring sites in

Monroe County, N.Y. ....................................................................................................................3

2. Map showing locations of drainage basins of streamflow and water-quality

monitoring sites in Monroe County, N.Y....................................................................................5

3. Graph showing population of Monroe County, N.Y., 1900–2008............................................6

4. Diagram showing precipitation at Rochester, N.Y.: A, monthly measured (2003–08)

and normal (1971–2000) precipitation; and B, monthly mean, maximum, and

minimum (2003–08) and normal (1971–2000) precipitation.....................................................8

5. Graph showing mean annual streamflow yields at nine monitoring sites in

Monroe County, N.Y., water years 2003–08 ............................................................................10

6. Graph showing mean monthly water temperatures at four monitoring sites in

Monroe County, N.Y., water years 2003–08 ............................................................................12
vi

Tables

1. Streamflow and water-quality monitoring sites in Monroe County, N.Y., water years

2003–08 ...........................................................................................................................................4

2. Land uses and land covers in Monroe County, N.Y.................................................................7

3. Median constituent concentrations by water year and summary statistics for

concentrations of selected constituents in water samples from nine monitoring

sites in Monroe County, N.Y., water years 2003–08 ..............................................................13

4. Estimated annual constituent loads at nine monitoring sites in Monroe County, N.Y.,

water years 2003–08, and statistically significant model variables ...................................19

5. Annual yields of selected constituents at nine monitoring sites in Monroe County,

N.Y., water years 2003–08..........................................................................................................22

6. Trends in concentrations of selected constituents at nine monitoring sites in

Monroe County, N.Y., water years 2003–08 ............................................................................27

7. Graph showing annual yields of selected constituents at nine monitoring sites in

Monroe County, N.Y., water years 2003–08: A, chloride; B, sulfate; C, nitrate plus

nitrite nitrogen; D, ammonia plus organic nitrogen; and E, phosphorus ...........................24

8. Diagram showing seasonal variation in constituent concentration at selected 

sites in Monroe County, N.Y., water years 2003–08: A, chloride, Allen Creek 

near Rochester; B, nitrate plus nitrite nitrogen, Oatka Creek at Garbutt; and 

C, phosphorus, Genesee River at Charlotte Pump Station near Rochester......................29

9. Diagram showing seasonal variation in monthly constituent loads at selected 

sites in Monroe County, N.Y., water years 2003–08: A, chloride, Allen Creek 

near Rochester; B, nitrate plus nitrite nitrogen, Oatka Creek at Garbutt; and 

C, phosphorus, Genesee River at Charlotte Pump Station near Rochester......................30
vii

Conversion Factors and Abbreviations

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

square mile (mi2

) 2.590 square kilometer (km2)

Volume

cubic foot (ft3

) 0.02832 cubic meter (m3) 

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

cubic foot per second per square 

mile [(ft3

/s)/mi2]

 0.01093 cubic meter per second per square 

kilometer [(m3/s)/km2]

gallon per minute (gal/min) 0.06309 liter per second (L/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

ton, short (2,000 lb) 0.9072 megagram (Mg) 

ton per day per square mile

 [(ton/d)/mi2

]

0.3503 megagram per day per square 

kilometer [(Mg/d)/km2]

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F-32)/1.8

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

List of Acronyms

MCEL Monroe County Environmental Laboratory 

NLCD National Land Cover Data 

NURP Nationwide Urban Runoff Program 

NYS New York State 

USGS U.S. Geological Survey
This page has been left blank intentionally.
Water Resources of Monroe County, New York, Water 

Years, 2003–08: Streamflow, Constituent Loads, and 

Trends in Water Quality

By Brett A. Hayhurst, William F. Coon, and David A.V. Eckhardt

Abstract

This report, the sixth in a series published since 1994, 

presents analyses of hydrologic data in Monroe County for the 

period October 2002 through September 2008. Streamflows 

and water quality were monitored at nine sites by the Monroe 

County Department of Health and the U.S. Geological 

Survey. Streamflow yields (flow per unit area) were highest in 

Northrup Creek, which had sustained flows from year-round 

inflow from the village of Spencerport wastewater-treatment 

plant and seasonal releases from the New York State Erie 

(Barge) Canal. Genesee River streamflow yields also were 

high, at least in part, as a result of higher rainfall and lower 

evapotranspiration rates in the upper part of the Genesee River 

Basin than in the other study basins. The lowest streamflow 

yields were measured in Honeoye Creek, which reflected a 

decrease in flows due to the withdrawals from Hemlock and 

Canadice Lakes for the city of Rochester water supply.

Water samples collected at nine monitoring sites were 

analyzed for nutrients, chloride, sulfate, and total suspended 

solids. The loads of constituents, which were computed 

from the concentration data and the daily flows recorded at 

each of the monitoring sites, are estimates of the mass of the 

constituents that was transported in the streamflow. Annual 

yields (loads per unit area) also were computed to assess 

differences in constituent transport among the study basins. 

All urban sites—Allen Creek and the two downstream sites 

on Irondequoit Creek—had seasonally high concentrations 

and annual yields of chloride. Chloride loads are attributed to 

the application of road-deicing salts to the county’s roadways 

and are related to population and road densities. The lessurbanized sites in the study—Genesee River, Honeoye Creek, 

and Oatka Creek—had relatively low concentrations and 

yields of chloride. The highest concentrations and yields of 

sulfate were measured in Black Creek, Oatka Creek, and 

Irondequoit Creek at Railroad Mills and are attributable to 

dissolution of sulfate from gypsum (calcium sulfate) deposits 

in Silurian shale bedrock that crops out upstream from these 

monitoring sites. 

Northrup Creek had the highest concentrations of 

phosphorus, orthophosphate, and nitrogen, and high yields 

of nitrate plus nitrite nitrogen and ammonia plus organic 

nitrogen. These results are attributed to discharges from 

the Spencerport wastewater-treatment plant (which ceased 

operation in June 2008), diversions from the New York 

State Erie (Barge) Canal, and manure and fertilizers applied 

to agricultural fields. Concentrations and yields of nitrate 

plus nitrite nitrogen also were high in Oatka Creek and 

Black Creek; basins with substantial agricultural land uses. 

Allen Creek had the second highest yield of ammonia plus 

organic nitrogen. Honeoye Creek, which drains a relatively 

undeveloped basin, had the lowest yields of nitrogen 

constituents. The second highest median concentrations 

and highest sample concentrations of phosphorus and 

orthophosphate, as well as the highest phosphorus yields, were 

measured in the Genesee River.

 A comparison of the yields computed for the two 

downstream sites on Irondequoit Creek—above Blossom 

Road and at Empire Boulevard—permitted an assessment 

of the mitigative effects of the Ellison Park wetland on 

constituent loads, which would otherwise be transported 

to Irondequoit Bay. These effects also include those 

provided by a flow-control structure (installed mid-way 

through the wetland during February 1997), which was 

designed to increase the dispersal and short-term detention 

of stormflows in the wetland. The wetland decreased 

yields of particulate constituents—phosphorus and 

ammonia plus organic nitrogen—but had little effect on 

the yields of dissolved constituents—chloride, sulfate, and 

nitrate plus nitrite nitrogen.

Trends in flow-adjusted concentrations were identified 

at all sites for most of the nutrient constituents that were 

evaluated. All of the linear time trends that were detected in 

the data indicated that nutrient concentrations monotonically 

decreased during the 6-year study period, except for 

phosphorus concentrations in the Genesee River, which 

increased. Seasonal trends also were identified at all sites for 

nearly every constituent that was evaluated. 
2 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

Introduction

Monroe County and the U.S. Geological Survey (USGS) 

have monitored and evaluated the water resources of Monroe 

County since 1904 when a streamflow monitoring station was 

established on the Genesee River at Rochester, N.Y. Since 

that time additional streamflow monitoring sites have been 

established on various streams in the county, and waterquality monitoring also has been conducted. In addition to 

the Genesee River, sites at which flow and water-quality data 

are still collected include Honeoye, Oatka, Black, Allen, 

Irondequoit, and Northrup Creeks (fig. 1). The periods of 

streamflow records at these sites range from 19 years for 

Northrup Creek to 104 years for the Genesee River (table 1). 

The periods of water-quality records at these sites range from 

10 years for Honeoye Creek to 27 years for Allen Creek. 

The hydrologic and water-quality information is used by 

water-resources managers to make decisions regarding flood 

hazards, drought conditions, control of streambank erosion, 

and mitigation of nonpoint-source pollution. 

In 1993, the USGS, in cooperation with the Monroe 

County Department of Health, began a long-term program 

to evaluate and interpret hydrologic data collected at sites 

in Monroe County for calculation of constituent loads 

in streamflow and appraisal of temporal trends in the 

concentrations of selected constituents in streamflow and 

groundwater. Results of the monitoring program have been 

compiled in a series of reports that cover the water years 

(October 1 to September 30, numbered for the year in which 

it ends) 1984 through 2002 (Johnston and Sherwood, 1996; 

Sherwood, 1999; 2001; 2003; and 2005). This report is a 

continuation of this series and covers the 2003–08 water years.

 Purpose and Scope 

This report describes the hydrologic and water-quality 

conditions at nine surface-water monitoring sites in Monroe 

County during water years 2003–08. The report presents 

(1) the methods of data collection, processing, and analysis 

and the statistical methods used for trend analyses and 

estimation of constituent loads; (2) summaries of streamflow 

records, water-quality data, and trends of selected constituents 

in the monitored streams; and (3) an estimation of loads 

and a comparison of yields of selected constituents at the 

monitoring sites.

Related Studies

The hydrologic characteristics of the Irondequoit Creek 

Basin were studied extensively during 1979–81 as part 

of the Nationwide Urban Runoff Program (NURP) (U.S. 

Environmental Protection Agency, 1983; O’Brien and Gere, 

1983; Zarriello and others, 1985; Kappel and others, 1986). 

The NURP study identified the heavily developed areas of 

the Irondequoit Creek Basin as the major sources of chemical 

loads and noted that snowmelt and spring runoff carried a 

disproportionate amount of the annual loads. The effects 

of stormwater-detention basins on the chemical quality of 

runoff from a small residential development were studied by 

Zarriello and Sherwood (1993), and the effects of detention 

basins on peak flows and water quality of major streams 

were studied by Zarriello and Surface (1989) and Zarriello 

(1996). The hydrology, sedimentology, biology, and waterquality processes of the Ellison Park wetland at the mouth of 

Irondequoit Creek were documented by Coon (1997; 2004) 

and Coon and others (2000).

Study Area 

Monroe County encompasses 673 mi2 in northwestern 

New York (fig. 1). Rochester, the county seat and largest 

city, is in the northern part of the county. Two creeks in the 

monitoring network, Northrup and Irondequoit Creeks, have 

drainage basins that are almost entirely within the boundaries 

of Monroe County and drain directly into Lake Ontario 

(fig. 2). In contrast, about 90 percent of the Genesee River 

drainage basin is outside Monroe County. Three streams, 

Oatka, Honeoye, and Black Creeks, are tributaries of the 

Genesee River; their confluences lie within Monroe County, 

but most of their respective drainage areas are south and west 

of the county. Although one monitoring siteIrondequoit 

Creek at Railroad Mills, near Fishersis actually located 

in Ontario County, all nine sites are referred to as “Monroe 

County” sites because funds for the operation and maintenance 

of the stations are provided by Monroe County.

Population 

The estimated population of Monroe County during 

2006–08 was 732,175, a 0.4-percent decrease from the last 

official U.S. census during 2000 when the population was 

about 735,000 (U.S. Census Bureau, 2009a). The population 

of Monroe County increased from 1900 until 1970 (fig. 3; 

U.S. Census Bureau, 2009b), and although the population has 

remained fairly constant since 1970, shifts in the population 

have occurred as people moved from the city of Rochester to 

the developing towns that border the city, including Henrietta, 

Pittsford, Perinton, Penfield, and Greece. Some rural towns, 

such as Mendon and Clarkson also have experienced 

population growth since 1990 (Sherwood, 2005). 

Land Use and Land Cover

The primary land uses or land covers in Monroe County 

are residential, agricultural, and forested. Previous reports 

in this series of analyses of Monroe County hydrologic data 

discussed land types on the basis of land use only; that is, 
Study Area 3

Lake

Ontario

Erie

Erie

Canal

Canal

Creek

Black

Creek

Oatka

Creek

Honeoye

Creek

Genesee

River

Irondequoit

Creek

Allen Creek

(Barge)

(Barge)

Northrup

Irondequoit

Bay

Long Pond

Rochester

Hilton

Webster

Brockport

Fairport

Honeoye Falls

Spencerport

Churchville

Scottsville

East Rochester

Pittsford

Greece

04230500

04229500

04231000

0422026250 431510077363501

0423205025

0423205010

04232050

04232034

04232000

MONROE COUNTY

GENESEE COUNTY

ONTARIO COUNTY

LIVINGSTON COUNTY

WAYNE COUNTY

ORLEANS COUNTY

MONROE COUNTY

LIVINGSTON COUNTY ONTARIO COUNTY

MONROE COUNTY

MONROE COUNTY

Ellison Park Wetland

Byron-Bergen Swamp

78° 77°50' 77°40' 77°30'

43°25'

43°15'

43°05'

42°05'

NEW YORK

Location Map

Monroe

County

0 2.5 5 MILES

0 2.5 5 KILOMETERS

Base from U. S. Geological Survey

digital line graph, 1:100,000,

Universal Transverse Mercator projection, Zone 18

EXPLANATION

City or village

Greater Rochester International Airport

Water-quality monitoring site and site number

Streamflow and water-quality monitoring site 

 and site number 0422026250

0423205025

Figure 1. Locations of streamflow and water-quality monitoring sites in Monroe County, N.Y. (Site names are given in 

table 1.)
4 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality Table 1. Streamflow and water-quality monitoring sites in Monroe County, N.Y., water years 2003–08. [Site locations are shown in figure 1. mi2, square miles; ft3/s, cubic feet per second; --, not applicable or no data] Site number Site name Drainage area (mi2

)

Mean 

annual flow

(ft3/s)

Period of record Water 

temperature

site

Streamflow Water quality

0422026250 Northrup Creek at North Greece 10.1 16.5 1989–2008 1989–2008 Yes04229500 Honeoye Creek at Honeoye Falls 196 168 1945–70; 1972–2008 1998–2008 No04230500 Oatka Creek at Garbutt 200 248 1945–2008 1997–2008 1 No04231000 Black Creek at Churchville 130 147 1945–2008 1965–76; 1998–2008 1 No04232000 Genesee River at Rochester2 2,482 3,400 1904–2008 -- No431510077363501 Genesee River at Charlotte Pump Station, near Rochester3 2,494 -- -- 1990–2008 No04232034 Irondequoit Creek at Railroad Mills near Fishers 39.2 43.0 1991–2008 1992–2008 Yes04232050 Allen Creek near Rochester 30.1 35.5 1959–2008 1979–81; 1983–2008 1 Yes0423205010 Irondequoit Creek above Blossom Road, Rochester 142 154 1980–2008 1980–81; 1983–2008 Yes0423205025 Irondequoit Creek at Empire Boulevard, Rochester4 151 -- 1990–2002 1989–2008 No

1Additional samples were collected intermittently prior to this period.2Site was moved from Driving Park Avenue (site 04232000) 3.1 miles upstream to Ford Street (site 04231600), October 1, 2005.3Flows at this site were estimated from recorded flows at site 04232000 (at Driving Park Avenue) 6 miles upstream, or 04231600 (at Ford Street), 9 miles upstream.4Flows at this site were estimated from recorded flows at site 0423205010, 4.4 miles upstream.
Study Area 5

Silver Lake

Conesus Lake

Hemlock Lake

Canadice Lake

Honeoye Lake

Canandaigua Lake

Lake Ontario

Irondequoit Bay

Rushford

 Lake

MONROE

ORLEANS

GENESEE

WYOMING

ALLEGANY

STEUBEN

ONTARIO

LIVINGSTON

WAYNE

YATES

CATTARAUGUS

NEW YORK

PENNSYLVANIA

Wellsville

Portageville

Mount 

Morris Dam

Rochester

Macedon

78°30' 78° 77°30'

43°

42°30'

42°

04232050

04232034 04230500

04229500

04231000

0423205025

0423205010

0422026250 431510077363501

Genesee

River

Erie

(Barge)

Canal

NEW YORK

PENNSYLVANIA

Location Map

Genesee River 

Basin

0 5 10 MILES

0 10 KILOMETERS 5

EXPLANATION

Northrup Creek Basin

Black Creek Basin

Oatka Creek Basin

Honeoye Creek Basin

Genesee River Basin

Irondequoit Creek Basin

0422026250 Streamflow and water-quality

monitoring site and site number

Base from U. S. Geological Survey

digital line graph, 1:100,000,

Universal Transverse Mercator projection, Zone 18

Monroe County boundary

Figure 2. Locations of drainage basins of streamflow and water-quality monitoring sites in Monroe County, N.Y.
6 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

1890 1910 1930 1950 1970 1990 2010

POPULATION

YEAR

Figure 3. Population of Monroe County, N.Y., 1900–2008.

property types as classified by New York State Office of Real 

Property Services (2009) for tax purposes. If a land-cover 

based classification system, such as the National Land Cover 

Data (NLCD; Homer and others, 2004), is used, the relative 

magnitudes of land-type categories can vary substantially, 

however. For instance, on the basis of property-tax data, 

48 and 23 percent of the county is used for developed 

(residential, commercial, and industrial) and agricultural 

purposes, respectively (table 2) (Tongyan Li, Monroe County 

Department of Planning and Development, written commun., 

2009). Only 4 percent of the county is classified as forested, 

which includes conservation lands and public parks. On the 

basis of NLCD, 30 percent of the county was developed land 

in 2001, and 40 percent was agricultural land (cultivated crops, 

hay, and pasture). Land covered by forests in 2001 accounted 

for 21 percent of the county. Despite the large differences 

in land-type percentages, the data from both classification 

systems indicate a continued pattern of land conversion from 

agricultural uses to residential uses, as shown by Sherwood 

(2005) in the previous water-resources report for Monroe 

County. On the basis of property-tax data, since 2002 (table 2), 

residential land use has increased from 35.4 to 38.6 percent 

of the county, whereas agricultural uses have decreased from 

26.1 to 22.7 percent (New York State Office of Real Property 

Services, 2009).

Climate 

Weather data in Monroe County are collected by 

the National Weather Service at the Greater Rochester 

International Airport, which is located near the center of the 

county, just southwest of the city of Rochester (fig. 1). Average 

annual precipitation (1971–2000) in the Rochester area is 

33.98 in., including an average snowfall of 95.8 in. (National 

Climatic Data Center, 2009a). 

The weather in the county is greatly affected by Lake 

Ontario, which has a moderating effect on air temperatures 

and inhibits the extreme temperature fluctuations that are 

recorded further inland (National Climatic Data Center, 

2009b). Monthly 30-year mean temperatures range from 

23.9°F in January to 70.7°F in July (National Climatic Data 

Center, 2009a). Lake Ontario, which rarely freezes completely 

during the winter, plays a major role in snowfall distribution. 

Lake-effect storms can produce snowfalls of 1 to 2 ft or 

more in a 24hr period near the lake and by season’s end can 

account for about half the total snowfall in the area (National 

Climatic Data Center, 2009b). Seasonal snowfall quantities 

can vary widely and usually decrease with distance from the 

lake. Precipitation is fairly evenly distributed throughout the 

year; monthly 30-year mean quantities range from 2.04 in. 

during February to 3.54 in. during August (National Climatic 

Data Center, 2009a). Heavy rain events occur infrequently 

and generally are caused by slowly moving thunderstorms, 

slowly moving or stalled major low-pressure systems, or by 

hurricanes and tropical storms that move inland (National 

Climatic Data Center, 2009b). 

Average annual precipitation during the 6-year study 

period (2003–08) was 35.27 in., more than an inch greater 

than the 30-year mean precipitation (1971–2000; National 

Climatic Data Center, 2009a). This departure from the annual 

normal precipitation resulted from 2 very wet years during 

the study period; 37.81 in. and 41.06 in. of precipitation fell 

during 2004 and 2006, respectively (fig. 4A). During water 

years 2003–08 (National Climatic Data Center, 2009c), the 

largest monthly departure from the normal values occurred 

during July with an average of 4.37 in. of precipitation. The 

30-year monthly normal precipitation for July is 2.93 in. 

(fig. 4B). Precipitation totals during July 2004 (6.35 in.) and 

July 2006 (8.02 in.) are responsible for the large departures 

from that month’s normal value.

Selected Waterways

The Genesee River, which flows northward from its 

origin in northwestern Pennsylvania to Lake Ontario at 

Rochester (fig. 2), is the largest river in Monroe County and 

has a drainage area of 2,494 mi2 at its mouth. Since 1951, 

the flow rates in the Genesee River have been affected by 

operation of the dam at Mount Morris (fig. 2), about 39 mi 

upstream from Rochester. The magnitude and frequency 

of damaging floods have been lowered, and the regulated 

outflow from Mount Morris Lake has maintained base flows 

at slightly higher rates than those that occurred prior to 

the dam’s construction (Coon, 2008). The Genesee River 

is a large source of sediment to Lake Ontario (New York 

State Department of Environmental Conservation, 2003). 

Much of the load is derived from highly erodible soils on 

the alluvial plain through which the river flows for most of 

its length. Extensive agricultural activity and continuing 

land development throughout the basin also contribute to 

sediment loads. 
Water-Resources Data Collection and Processing 7

Table 2. Land uses and land covers in Monroe County, N.Y.

[Values are in percent.]

Property type1 2002 2008 Land use - land cover2 2001

Forested, conservation lands, and public parks

Agricultural

Vacant land

Total developed

Residential

Commercial

Industrial

Recreation and entertainment

Community services

Public services

3.72

26.14

18.70

45.11

35.41

4.41

2.25

3.04

4.33

2.00

4.06

22.66

18.62

48.36

38.64

4.76

2.13

2.83

4.43

1.87

Forest

Total Agricultural

Cultivated crops

Hay and pasture

Total developed

Open space and low intensity

Medium intensity

High intensity

Wetlands

21.2

39.6

17.0

22.6

30.1

24.6

4.0

1.5

7.0

1

Data from New York State Office of Real Property Services (2009).

2

Data from National Land Cover Database (Homer and others, 2004).

Honeoye Creek, Oatka Creek, and Black Creek are 

tributaries of the Genesee River in southwestern Monroe 

County (fig. 1), and the drainage areas range from 201 mi2

to 267 mi2. All three basins have large forested areas, but 

agricultural activities dominate the land uses of most of 

these basins. A considerable part of the Black Creek Basin 

is covered by wetlands, including an over 2,000-acre 

wetland complex, the Byron-Bergen Swamp (fig. 1; Genesee 

County, 2009).

East of the Genesee River, Irondequoit Creek, which 

drains 169 mi2, flows northward into Irondequoit Bay and then 

into Lake Ontario. The land uses in the basin transition from 

forested and agricultural uses in the southern part to intensive 

urbanized uses in the north.

Northrup Creek drains 23.5 mi2 in western Monroe 

County and flows into Long Pond (fig. 1), a small embayment 

on the southern shore of Lake Ontario. The drainage area has 

a mixture of land types, including forest, agriculture, and lowintensity development. 

The New York State (NYS) Erie (Barge) Canal (fig. 1 

and 2) flows generally eastward through the middle of the 

county and receives a small amount of inflow from two 

tributaries in the Town of Pittsford, as well as storm runoff 

from areas immediately adjacent to the canal in the villages of 

Pittsford and Fairport; a total area of 8.45 mi2 drains directly 

to the canal in these areas. Overflow spillways and siphons 

divert canal water to local streams, including Allen Creek 

and Northrup Creek, to augment summertime low flows in 

these small streams. These diversions to Allen Creek were 

periodically measured during 2000–03 and averaged about 

3.5 ft3/s from one spillway and about 2 ft3/s from each of two 

siphons (U.S. Geological Survey, 2009a). These diversions 

cease during the non-navigation season (November to April) 

when the canal is drained. The canal intersects the Genesee 

River 11.8 mi upstream from the river’s mouth. Water, 

which is diverted by the canal from the Niagara River and 

Tonawanda Creek to the west, discharges into and joins 

the Genesee River as it flows northward to Lake Ontario. 

A relatively small amount of water from the Genesee River 

enters the eastern continuation of the canal and flows eastward 

from this point. During the navigation season (from late 

April to mid-November), daily flows in the canal east of the 

Genesee River typically range from 200 to 300 ft3/s (data from 

the USGS monitoring site at Lock 30 at Macedon (fig. 2); site 

number 04219000 (U.S. Geological Survey, 2009a)). 

Water-Resources Data Collection 

and Processing

Water levels at the nine monitoring sites and water 

temperatures at four of the sites were recorded continuously 

during the study period. Water-quality samples were collected 

periodically and analyzed for nutrients, selected ions, and total 

suspended solids.

Stage and Streamflow

The water level or stage of the stream at each of the 

nine monitoring sites was measured every 15 min using 

standard USGS procedures (Buchanan and Somers, 1968) 
8 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

0

1

2

3

4

5

6

7

8

9

PRECIPITATION, IN INCHES

MONTH-YEAR

A

01-2003 01-2004 01-2005 01-2006 01-2007 01-2008

Monthly measured precipitation (2003–08)

Monthly normal precipitation (1971–2000)

01-2009

YEAR

2.75

2.10

2.27

2.82

2.29

2.73

4.37

3.24

3.59

3.04 3.13 2.95

0

1

2

3

4

5

6

7

8

9

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT OCT. NOV. DEC.

B

PRECIPITATION, IN INCHES

Monthly normal (1971–2000)

Monthly minimum (2003–08)

Monthly maximum (2003–08)

Monthly mean (2003–08)

(1971–2000) precipitation; and B, monthly mean, maximum, and minimum (2003–08) and normal 

(1971–2000) precipitation. (Data from the National Weather Service station at the Greater 

Rochester International Airport.)

Figure 4. Precipitation at Rochester, N.Y.: A, monthly measured (2003–08) and normal 
Water-Resources Data Collection and Processing 9

and recorded by an electronic data logger. Streamflow was 

measured regularly by personnel from the Monroe County 

Environmental Laboratory (MCEL) and periodically by 

personnel from the USGS, according to procedures described 

in Carter and Davidian (1968), Buchanan and Somers 

(1969), and Rantz and others (1982). Stage and streamflow 

data were compiled and streamflows were computed from 

stage-to-discharge relations that were developed through 

standard USGS procedures (Kennedy, 1983). Streamflows 

were computed by the USGS, and daily mean flows were 

published in the USGS annual water data reports (U.S. 

Geological Survey, 2009b).

Water Temperature

Water temperatures were recorded every 15 min by 

thermistors placed in well mixed locations near the bed of 

the channels at four monitoring sites (table 1). As quality 

checks on the recorded temperatures, seasonal equal-width 

cross-sectional measurements of temperature were made 

with a digital thermistor by USGS personnel. In general, 

corrections were made to the recorded temperatures on the 

basis of cross-sectional temperatures only when discrepancies 

of 1.0°C (1.8°F) or more were noted. Erroneous temperatures 

that were recorded during periods of thermistor malfunction 

were deleted from the record. Daily mean temperatures were 

computed and rounded to the nearest 0.5°C (0.9°F). 

Chemical Constituents

Water samples were collected by automatic samplers at 

each of the nine monitoring sites. Samplers were activated 

during a base-flow period or in anticipation of a storm event, 

and water samples were extracted hourly from the channel 

(near the centroid of flow). Samples collected over a period 

of up to 7 hours were composited in a single sample bottle, 

which is presumed to represent water chemistry that existed 

in a stream during that time period. Subsequently, water 

samples were composited into a single sample that represented 

base flow or storm runoff over a period ranging from 1 to 

7 days. A sample for analysis was extracted from this multiday composite sample. This method of compositing samples, 

which fails to flow-weight the sub-sample volumes, will likely 

underestimate the “true” concentrations of some constituents 

in stormwater samples; however, this protocol has been used 

since the beginning of the Monroe County stream-monitoring 

program and is inherent in the results presented in previous 

reports in this water-resources series (Johnston and Sherwood, 

1996; Sherwood, 1999, 2001, 2003, and 2005). Samples were 

collected from the field and processed by personnel from 

MCEL. The frequency of sampling varied year-to-year with 

more than 60 samples collected at Genesee River at Charlotte 

Pump Station during 2003 and as few as three samples 

collected at some sites during 2006. 

Samples were analyzed for phosphorus, orthophosphate, 

ammonia, nitrate plus nitrite nitrogen, ammonia plus organic 

nitrogen, chloride, sulfate, and total suspended solids in the 

MCEL. Analytical procedures used by MCEL are described 

by American Public Health Association and others (2010). 

Results of the water-quality analyses are stored in the USGS 

National Water Information System (U.S. Geological Survey, 

2009a). The MCEL participated in the semiannual USGS 

quality-assurance Standard Reference Sample program (U.S. 

Geological Survey, 2009c) that is coordinated by the USGS 

Office of Water Quality for cooperating analytical laboratories. 

The results from this program indicated that the MCEL 

performed well in the analyses of constituents measured as 

part of the Monroe County water-quality monitoring program. 

No problem in analytical techniques was identified.

Mean Streamflow Associated with 

Water-Quality Samples

The mean streamflow that was associated with the time 

period covered by the water-quality samples was computed 

from the continuous streamflow recorded at each monitoring 

site, except at Genesee River at Charlotte Pump Station and 

Irondequoit Creek at Empire Boulevard. Streamflow was not 

measured at the Genesee River at Charlotte Pump Station; 

rather streamflow values associated with these samples were 

obtained from records for the Genesee River at Rochester, 

which was measured upstream from Driving Park Avenue 

(site 04232000) until September 30, 2005, and at Ford Street 

(site 04231600 ) after that date. Although the Ford Street 

site is about 3.1 mi upstream from the Driving Park Avenue 

site, the streamflow records at both sites are considered 

equivalent owing to the small difference in drainage area 

(8 mi2 or 0.3 percent) between the sites and to the fact that 

the stormwater drainage system for most of Rochester routes 

water to an underground storage area for eventual treatment at 

a regional wastewater-treatment facility and discharge to Lake 

Ontario (C. Knauf, Monroe County Department of Health, 

written commun., 2010). Similarly, and for the same reasons, 

measured streamflows were used without adjustment as flow 

estimates for the water-quality site at Charlotte Pump Station, 

which is at least 6 mi downstream from the streamflowmonitoring sites (a difference in drainage area of 12–20 mi2 or 

0.5–0.8 percent). 

Streamflows in Irondequoit Creek at Empire Boulevard 

have not been measured since December 2002. Therefore 

streamflows at this site were estimated from the measured 

flows at Irondequoit Creek at Blossom Road, 4.4 mi upstream. 

This estimation was performed by a regression equation that 

was developed from daily streamflows that were concurrently 

measured at Blossom Road and Empire Boulevard during the 

1997–2001 water years. 
10 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

Water-Resources Data Analyses

Mean annual flows at the nine monitoring sites were 

computed and then normalized by their respective drainagebasin areas to account for differences in drainage-area size, 

which permitted direct comparison of streamflow yields (flow 

per square mile) among the nine sites. Differences in yields 

among the sites could result from streamflow diversions, 

such as are found in Northrup Creek, Allen Creek, and 

Honeoye Creek, or from variability in precipitation and 

evapotranspiration across a large basin. The Genesee River, 

for example, drains an area near the New York-Pennsylvania 

border where the mean annual precipitation is 32 in., and the 

mean annual runoff is 14 in. (Randall, 1996). Basins further 

north, which are closer to or within Monroe County, drain an 

area where the mean annual precipitation is 30 in., and the 

mean annual runoff is 12 in.

Water temperatures and constituent-concentration 

data were summarized for the study period. The loads and 

yields of constituents were computed from streamflow and 

concentration records, and trends in constituent concentrations 

were identified, where possible. 

Streamflow 

Northrup Creek at North Greece, which drains the 

smallest basin in the Monroe County network (10.1 mi2

), had 

sustained flows and the highest streamflow yield (fig. 5) of 

all the monitoring sites. The site’s hydrology is affected by 

year-round discharges from the village of Spencerport (fig. 1) 

wastewater-treatment plant (discontinued after June 2008) 

and seasonal releases from the NYS Erie (Barge) Canal; both 

water sources are about 5.4 mi upstream from the monitoring 

site. The wastewater-treatment plant discharged, on average 

(1991–2003), 0.9 Mgal/d (1.39 ft3/s) (Craig Jackson, New 

York State Department of Environmental Conservation, 

written commun., 2010), and the releases from the canal were, 

on average (2001–03), about 5 ft3/s (U.S. Geological Survey, 

2009a). The mean annual flow in Northrup Creek at North 

Greece for the 2003–08 water years was 16.5 ft3/s, and the 

mean annual streamflow yield was 1.63 (ft3/s)/mi2. 

Honeoye Creek at Honeoye Falls drains an area of 

196 mi2

, which includes Honeoye, Hemlock, and Canadice 

Lakes (fig. 2). Honeoye Lake is unregulated, but flow from 

Canadice Lake is diverted to Hemlock Lake, which supplies 

an average of 37 Mgal/d (57 ft3/s) to the city of Rochester. 

Spillage over the dam at the north end of Hemlock Lake 

occurs infrequently (mainly during spring high-runoff 

periods); otherwise, the lake does not contribute flows to 

Honeoye Creek (Donald Root, City of Rochester Water 

Supply, written commun., 2009). Honeoye Creek had a mean 

annual flow of 169 ft3

/s and a mean annual streamflow yield 

of 0.86 (ft3

/s)/mi2 for the 2003–08 water years. This yield was 

the lowest mean annual yield (fig. 5) of all the monitoring sites 

due to the withdrawals from Hemlock Lake; otherwise the 

yield, adjusted for the water-supply diversion to Rochester, 

would have been 1.15 (ft3/s)/mi2. 

0.5

1.0

1.5

2.0

2.5

2003 2004 2005 2006 2007 2008

Northrup Creek Irondequoit Creek at Railroad Mills

Honeoye Creek Allen Creek

Oatka Creek Irondequoit Creek above Blossom Road

Black Creek Irondequoit Creek at Empire Boulevard

Genesee River

MEAN ANNUAL STREAMFLOW YIELD,

IN CUBIC FEET PER SECOND PER SQUARE MILE

Figure 5. Mean annual streamflow yields at nine monitoring sites in Monroe County, N.Y., water years 2003–08.
Water-Resources Data Analyses 11

Oatka Creek at Garbutt, with a drainage area of 200 mi2, 

had a mean annual flow for the 2003–08 water years of 

248 ft3/s and a mean annual yield of 1.24 (ft3/s)/mi2. Black 

Creek at Churchville, which has a drainage area of 130 mi2, 

had a mean annual flow of 147 ft3/s and a mean annual yield of 

1.13 (ft3/s)/mi2.

The mean annual flow in Genesee River at Rochester 

for the 2003–08 water years was 3,400 ft3/s, a mean annual 

yield of 1.37 (ft3/s)/mi2. The combined streamflows from 

the three tributaries—Honeoye, Oatka, and Black Creeks—

accounted for about 17 percent (564 ft3/s) of the total mean 

annual flow in the Genesee River at Rochester. The streamflow 

yield of the Genesee River was the second highest yield of 

all the monitoring sites (fig. 5) and is attributed, in part, to 

the relatively high yields from the upper part of the Genesee 

River Basin, which has higher elevations, more precipitation, 

and less evapotranspiration than most of the area drained by 

the other study basins (Gilbert and Kammerer, 1971; Randall, 

1996). This conclusion is supported by the high mean annual 

streamflow yields of 1.63 and 1.67 (ft3/s)/mi2 that were 

computed for the 2003–08 water years for two monitoring 

sites located in the upper part of the Genesee River Basinthe 

Genesee River at Wellsville and at Portageville, respectively 

(fig. 2). 

Four of the nine monitoring sites in Monroe County 

are in the Irondequoit Creek Basin; three of these sitesone 

on Allen Creek and two on Irondequoit Creek (fig. 1) 

measure streamflows. The site on Irondequoit Creek at 

Railroad Mills monitors flows from 39.2 mi2 of mixed land 

uses that include forests, pasture, cultivated crops, and some 

residential and commercial areas. The mean annual flow for 

the 2003–08 water years was 43 ft3/s with a mean annual 

yield of 1.10 (ft3/s)/mi2. Suburban development increases 

northward across the Irondequoit Creek Basin. Allen Creek 

drains 30.1 mi2 of land that is dominated by moderate- to 

high-intensity residential and commercial uses. The hydrology 

of this basin is not representative of most of the Irondequoit 

Creek Basin because peak flows in Allen Creek generally are 

characterized by quick runoff from impervious surfaces in 

the basin. Diversions from the NYS Erie (Barge) Canal occur 

during the navigation season (late April to mid-November) to 

augment summer low flows in Allen Creek. Summer diurnal 

fluctuations in streamflow are common as water is withdrawn 

from the creek and its tributary, East Branch Allen Creek, to 

irrigate golf courses. The mean annual flow for the 2003–08 

water years was 36 ft3/s with a mean annual yield of 1.18 

(ft3/s)/mi2. The northern part of the Irondequoit Creek Basin is 

highly developed. The collective effects of this urbanization 

are monitored at the Blossom Road site, near Rochester. The 

drainage area of Irondequoit Creek above Blossom Road is 

142 mi2, and mean annual flow for the 2003–08 water years 

was 155 ft3/s with a mean annual yield of 1.09 (ft3/s)/mi2. 

Water Quality

Measurements of physical characteristics, such as water 

temperature, and chemical constituents, such as nutrients 

and common ions, can be used to assess water quality. 

Concentrations and estimated loads of constituents in streams 

can highlight differences in water quality from basin to basin 

and, through trend analysis, can indicate whether water-quality 

conditions are improving or deteriorating in a given stream 

over time.

Water Temperature

Water temperature affects many aspects of water quality, 

such as the solubility of constituents (including dissolved 

oxygen concentrations), the rate of chemical reactions, the 

level of activity of organisms in the aquatic environment, 

and the growth and death rates of microorganisms. Water 

temperatures, in turn, are affected by several factors, including 

groundwater contributions, precipitation and storm runoff, 

the amount of solar radiation reaching the stream, and the 

temperature of tributary inflows.

Temperature records have been kept for Northrup 

Creek at North Greece and three of the four monitoring 

sites in the Irondequoit Creek Basin since 1994. Mean 

monthly water temperatures during water years 2003–08 

(fig. 6) ranged from 33°F in February to 72°F in July; both 

extremes were recorded at Northrup Creek. Of the three sites 

on Irondequoit Creek, the upstream-most site at Railroad 

Mills had the coolest year-round temperatures. Water 

temperatures were generally warmer in Allen Creek than at 

Railroad Mills, and temperatures measured downstream at 

Blossom Road were 5 to 7°F warmer than at Railroad Mills. 

The relatively high temperatures at the downstream sites 

likely reflect urbanization effects, including heated runoff 

from roofs and asphalt roads and the urban heat island effect 

(Somerfield, 2010).

The New York State Department of Environmental 

Conservation (NYSDEC; 1991) restricts high temperatures 

in water discharged to trout streams. The regulations stipulate 

that no discharge will exceed 70oF, and no discharge from 

June through September will increase a stream’s temperature 

by more than 2oF. Although no direct discharges were 

monitored as part of this study, the maximum recorded daily 

water temperatures during 2003–08 exceeded 72°F on many 

consecutive days during the summer and early autumn months 

at all monitoring sites except Railroad Mills. Infrequently, 

the water temperature at some of these sites exceeded 72oF 

for an entire day. Cold-water fish are stressed by these 

high temperatures (Elliott, 1981), but no fish die offs have 

been reported. 
12 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

30

35

40

45

50

55

60

65

70

75

OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT.

Northrup Creek

Irondequoit Creek at Railroad Mills

Allen Creek

Irondequoit Creek above Blossom Road

MEAN MONTHLY WATER TEMPERATURE,  IN DEGREES FAHRENHEIT

Figure 6. Mean monthly water temperatures at four monitoring sites in Monroe County, N.Y., water 

years 2003–08.

Chemical Constituents

A summary of all constituent concentrations at the nine 

monitoring sites for water years 2003–08 is shown in table 3. 

Median values were presented in the table as a measure of 

central tendency rather than the mean because the median is 

insensitive to extreme values in the data.

Nutrients and Total Suspended Solids

Northrup Creek had the highest median annual 

concentrations of phosphorus, orthophosphate, and ammonia 

plus organic nitrogen of the nine monitored streams (table 3). 

The 2003–08 median concentrations of phosphorus and 

orthophosphate, 0.162 mg/L and 0.050 mg/L, respectively, 

were almost twice as great as those at most of the other 

monitoring sites. The 2003–08 median concentration of 

ammonia plus organic nitrogen was 0.97 mg/L. These results 

were primarily attributed to the village of Spencerport 

wastewater-treatment plant; discharges from the plant 

increased the concentrations of all measured constituents in 

Northrup Creek, except sulfate (based on a comparison of data 

concurrently collected from Northrup Creek and the outflows 

from the wastewater-treatment plant and the canal during 

2001–03; U.S. Geological Survey, 2009a). Diversions from 

the NYS Erie (Barge) Canal actually had a diluting effect on 

ambient concentrations for all constituents, except sulfate. 

Other possible contributors to the high nutrient concentrations 

in Northrup Creek include manure and fertilizers applied to 

agricultural fields. 

In the Genesee River, median annual concentrations of 

phosphorus (0.122 mg/L) and orthophosphate (0.018 mg/L) 

were also high, and the maximum sample concentrations of 

the study were 0.977 mg/L for phosphorus and 0.401 mg/L 

for orthophosphate. The high phosphorus concentrations in 

the Genesee River presumably reflect solid-phase transport 

associated with the large suspended-sediment loads that 

are derived from agricultural areas in the basin and from 

streambank erosion (New York State Department of 

Environmental Conservation, 2003). Although not always 

correlated with suspended-sediment concentrations (Gray and 

others, 2000), total suspended solids concentrations are often 

used as a substitute for suspended-sediment concentrations. 

Compared to the other study sites, the Genesee River had a 

relatively high median annual concentration (44 mg/L) and 

the highest measured concentration of total suspended solids 

(1,890 mg/L).

Median annual concentrations of nitrate plus nitrite 

nitrogen were highest in Oatka Creek, Northrup Creek, 

and Black Creek, basins with substantial agricultural areas. 

The maximum sample concentrations of nitrate plus nitrite 

nitrogen, which occurred during winter periods, were 

4.53 mg/L for Black Creek and 3.70 mg/L for Oatka Creek. 

In the Black Creek Basin, two factors could have had an 

effect on nutrient concentrations. The Byron-Bergen Swamp 

(Genesee County, 2009), which extends from 3 to 8 mi west of 

Churchville, and a dam in Churchville about 1,700 ft upstream 

from the monitoring site, which creates an impoundment 

that extends over 2.5 mi upstream, presumably would have 

mitigative effects on particulate and sediment loads, but these 

effects have not been assessed.
Water-Resources Data Analyses 13

Table 3. Median constituent concentrations by water year and summary statistics for concentrations of selected constituents in water samples from nine monitoring sites in Monroe County, N.Y., water years 2003–08.—Continued[Site locations are shown in figure 1. Concentrations are in milligrams per liter. Water year concentrations are the median concentration of all samples collected during a given year. Median annual concentrations are the medians of the tabulated annual medians. Maximum and minimum sample concentrations are based on data for the entire period, 2003–08. U.S. Geological Survey National Water Information System parameter code numbers in parentheses. N, nitrogen; P, phosphorus; <, less than; --, no data]

Water year1

and 

statistic

Number 

of

samples

Total 

suspended 

solids, 

unfiltered 

(00530)

Ammonia 

as N, 

filtered 

(00608)

Ammonia 

plus organic 

nitrogen 

as N, 

unfiltered 

(00625)

Nitrate plus 

nitrite 

as N, 

unfiltered 

(00630)

Phosphorus 

as P, 

unfiltered 

(00665)

Orthophosphate 

as P, 

filtered 

(00671)

Chloride, 

filtered 

(00940)

Sulfate, 

filtered 

(00945)

0422026250 Northrup Creek at North Greece 

2003 27 53 0.302 1.20 2.10 0.162 0.078 179 612004 16 15 .063 1.25 2.02 .161 .071 93 622005 11 48 .030 .93 1.42 .202 .049 83 512006 8 31 .063 .96 1.79 .152 .051 124 ˉˉ2007 9 38 .024 .94 1.51 .172 .038 79 ˉˉ2008 10 30 .104 .99 1.34 .136 .043 114 ˉˉ

Total number of samples 81 61 81 81 81 81 81 79 45Median annual concentration ˉˉ 35 .063 .97 1.65 .162 .050 103 61Maximum sample concentration ˉˉ 782 1.80 5.20 3.46 .609 .198 367 96Minimum sample concentration ˉˉ < 5 < .010 .53 .48 .030 < .003 30 32

04229500 Honeoye Creek at Honeoye Falls

2003 41 92 .010 .50 0.54 .051 .013 54 312004 17 51 .025 .69 .35 .169 .021 43 212005 7 59 .018 .61 .28 .135 .009 40 222006 9 22 .010 .67 .26 .103 .012 39 ˉˉ2007 11 46 .013 .50 .23 .099 .013 34 ˉˉ2008 11 39 .018 .56 .27 .093 .009 50 ˉˉ

Total number of samples 96 62 96 96 96 96 96 94 59Median annual concentration ˉˉ 49 .016 .59 .27 .101 .013 41 22Maximum sample concentration ˉˉ 414 1.29 3.10 3.17 .644 .135 129 100Minimum sample concentration ˉˉ 8 < .010 .29 .02 .018 < .001 20 11
14 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality Table 3. Median constituent concentrations by water year and summary statistics for concentrations of selected constituents in water samples from nine monitoring sites in Monroe County, N.Y., water years 2003–08.—Continued [Site locations are shown in figure 1. Concentrations are in milligrams per liter. Water year concentrations are the median concentration of all samples collected during a given year. Median annual concentrations are the medians of the tabulated annual medians. Maximum and minimum sample concentrations are based on data for the entire period, 2003–08. U.S. Geological Survey National Water Information System parameter code numbers in parentheses. N, nitrogen; P, phosphorus; <, less than; --, no data] Ammonia Total Nitrate plus Ortho- Ammonia plus organic Phosphorus Water year1 Number suspended nitrite phosphate Chloride, Sulfate, as N, nitrogen as P, and of solids, as N, as P, filtered filtered filtered as N, unfiltered statistic samples unfiltered unfiltered filtered (00940) (00945) (00608) unfiltered (00665) (00530) (00630) (00671) (00625) 04230500 Oatka Creek at Garbutt 2003 45 8 .018 .44 2.04 .038 .012 71 253 2004 17 20 .024 .65 1.86 .087 .025 61 131 2005 9 19 .016 .67 2.00 .079 .011 54 116 2006 3 58 .030 .97 1.57 .096 .019 53 ˉˉ 2007 12 32 .015 .70 1.61 .091 .014 43 ˉˉ 2008 11 22 .013 .55 2.16 .059 .009 58 ˉˉ Total number of samples 97 94 97 97 97 97 97 94 62 Median annual concentration ˉˉ 21 .017 .66 1.93 .083 .013 56 131 Maximum sample concentration ˉˉ 171 1.21 3.90 3.70 .548 .095 115 504 Minimum sample concentration ˉˉ < 3 < .010 .24 .89 .019 < .001 33 46 04231000 Black Creek at Churchville 2003 36 57 .038 .67 1.19 .057 .019 81 482 2004 12 21 .027 .88 1.63 .089 .032 68 146 2005 9 17 .027 .80 1.62 .079 .018 53 149 2006 3 14 .028 .84 1.24 .060 .014 51 ˉˉ 2007 8 20 .023 .71 1.30 .074 .015 43 ˉˉ 2008 11 20 .030 .86 1.64 .078 .011 60 ˉˉ Total number of samples 79 45 79 79 79 79 79 78 48 Median annual concentration ˉˉ 20 .028 .82 1.46 .076 .017 56 149 Maximum sample concentration ˉˉ 106 .768 2.20 4.53 .368 .074 112 618 Minimum sample concentration ˉˉ < 5 < .010 .37 .05 .022 < .001 30 74
Water-Resources Data Analyses

15

Table 3. Median constituent concentrations by water year and summary statistics for concentrations of selected constituents in water samples from nine monitoring sites in Monroe County, N.Y., water years 2003–08.—Continued[Site locations are shown in figure 1. Concentrations are in milligrams per liter. Water year concentrations are the median concentration of all samples collected during a given year. Median annual concentrations are the medians of the tabulated annual medians. Maximum and minimum sample concentrations are based on data for the entire period, 2003–08. U.S. Geological Survey National Water Information System parameter code numbers in parentheses. N, nitrogen; P, phosphorus; <, less than; --, no data]

Ammonia Total Nitrate plus Ortho- Ammonia plus organic Phosphorus Water year1 Number suspended nitrite phosphate Chloride, Sulfate, as N, nitrogen as P, and of solids, as N, as P, filtered filtered filtered as N, unfiltered statistic samples unfiltered unfiltered filtered (00940) (00945) (00608) unfiltered (00665) (00530) (00630) (00671) (00625)

04232034 Irondequoit Creek at Railroad Mills near Fishers

2003 13 135 .010 .72 1.18 .100 .010 108 128

2004 20 19 .017 .48 .90 .041 .010 104 1442005 14 37 .016 .65 .76 .078 .007 92 149

2006 8 40 .018 .78 1.01 .098 .007 98 ˉˉ

2007 13 63 .010 .67 .85 .121 .011 96 ˉˉ

2008 12 38 .013 .55 .92 .072 .008 109 ˉˉ

Total number of samples 80 70 80 80 80 80 80 77 36

Median annual concentration ˉˉ 39 .014 .66 .91 .088 .009 101 144

Maximum sample concentration ˉˉ 217 .267 1.90 1.49 .659 .104 200 316

Minimum sample concentration ˉˉ 3 < .010 .18 .09 .009 < .001 55 76

04232050 Allen Creek near Rochester

2003 27 16 .017 .64 1.21 .089 .015 281 67

2004 15 35 .025 1.00 .97 .081 .018 159 52

2005 11 21 .031 .88 .92 .105 .006 187 50

2006 10 38 .013 .85 .80 .106 .011 286 ˉˉ

2007 13 70 .032 1.00 .95 .167 .016 174 ˉˉ

2008 13 43 .016 .65 .91 .074 .009 245 ˉˉ

Total number of samples 89 69 89 89 89 89 89 86 41

Median annual concentration ˉˉ 37 .021 .87 .94 .097 .013 216 52

Maximum sample concentration ˉˉ 365 .150 4.60 2.70 .733 .065 1,170 102

Minimum sample concentration ˉˉ 4 < .010 .38 .26 .025 < .001 66 40
16 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality Table 3. Median constituent concentrations by water year and summary statistics for concentrations of selected constituents in water samples from nine monitoring sites in Monroe County, N.Y., water years 2003–08.—Continued [Site locations are shown in figure 1. Concentrations are in milligrams per liter. Water year concentrations are the median concentration of all samples collected during a given year. Median annual concentrations are the medians of the tabulated annual medians. Maximum and minimum sample concentrations are based on data for the entire period, 2003–08. U.S. Geological Survey National Water Information System parameter code numbers in parentheses. N, nitrogen; P, phosphorus; <, less than; --, no data] Ammonia Total Nitrate plus Ortho- Ammonia plus organic Phosphorus Water year1 Number suspended nitrite phosphate Chloride, Sulfate, as N, nitrogen as P, and of solids, as N, as P, filtered filtered filtered as N, unfiltered statistic samples unfiltered unfiltered filtered (00940) (00945) (00608) unfiltered (00665) (00530) (00630) (00671) (00625) 0423205010 Irondequoit Creek above Blossom Road, Rochester 2003 57 64 .010 .48 1.48 .060 .013 223 146 2004 22 23 .025 .67 .98 .075 .021 120 92 2005 17 54 .017 .77 .96 .109 .014 120 83 2006 16 32 .010 .66 .84 .084 .012 158 ˉˉ 2007 19 48 .018 .66 .82 .098 .015 141 ˉˉ 2008 16 55 .013 .71 .88 .110 .012 146 ˉˉ Total number of samples 147 101 147 147 147 147 147 142 84 Median annual concentration ˉˉ 51 .015 .66 .92 .091 .014 144 92 Maximum sample concentration ˉˉ 401 .111 2.10 1.93 .617 .084 518 310 Minimum sample concentration ˉˉ < 5 < .010 .29 .36 .022 < .001 61 43 0423205025 Irondequoit Creek at Empire Boulevard, Rochester 2003 58 117 .010 .61 1.38 .100 .016 248 150 2004 22 57 .025 .93 .93 .160 .025 121 98 2005 17 54 .027 .82 .88 .142 .019 117 83 2006 15 30 .010 .53 .78 .080 .009 162 ˉˉ 2007 19 53 .016 .65 .75 .119 .024 128 ˉˉ 2008 16 38 .013 .56 .89 .071 .013 152 ˉˉ Total number of samples 147 99 147 147 147 147 147 142 85 Median annual concentration ˉˉ 54 .014 .63 .89 .110 .017 140 98 Maximum sample concentration ˉˉ 338 .434 2.00 1.98 .580 .128 575 327 Minimum sample concentration ˉˉ 4 < .010 .15 .05 .032 < .001 75 49
Water-Resources Data Analyses

17

Table 3. Median constituent concentrations by water year and summary statistics for concentrations of selected constituents in water samples from nine monitoring sites in Monroe County, N.Y., water years 2003–08.—Continued[Site locations are shown in figure 1. Concentrations are in milligrams per liter. Water year concentrations are the median concentration of all samples collected during a given year. Median annual concentrations are the medians of the tabulated annual medians. Maximum and minimum sample concentrations are based on data for the entire period, 2003–08. U.S. Geological Survey National Water Information System parameter code numbers in parentheses. N, nitrogen; P, phosphorus; <, less than; --, no data]

Ammonia Total Nitrate plus Ortho- Ammonia plus organic Phosphorus Water year1 Number suspended nitrite phosphate Chloride, Sulfate, as N, nitrogen as P, and of solids, as N, as P, filtered filtered filtered as N, unfiltered statistic samples unfiltered unfiltered filtered (00940) (00945) (00608) unfiltered (00665) (00530) (00630) (00671) (00625)

431510077363501 Genesee River at Charlotte Pump Station near Rochester

2003 67 30 .101 .56 .94 .067 .020 59 ˉˉ

2004 47 50 .061 .68 1.17 .136 .022 46 ˉˉ

2005 48 38 .056 .65 1.15 .112 .017 53 ˉˉ

2006 46 47 .045 .67 .97 .125 .017 47 ˉˉ

2007 45 48 .043 .63 .99 .148 .018 48 ˉˉ

2008 50 41 .029 .52 .89 .118 .017 53 ˉˉ

Total number of samples 303 256 302 303 301 303 303 300 ˉˉ

Median annual concentration ˉˉ 44 .051 .64 .98 .122 .018 51 ˉˉ

Maximum sample concentration ˉˉ 1,890 1.60 3.00 2.53 .977 .401 363 ˉˉ

Minimum sample concentration ˉˉ < 2 < .010 .19 .21 .019 < .001 18 ˉˉ

1Water year is the period from October 1 of one year through September 30 of the following year, numbered for the year in which it ends.
18 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

Chloride and Sulfate

The primary source of chloride in Monroe County 

is road-deicing salt (sodium chloride) used during the 

winter; over 120,000 tons of salt were applied to Monroe 

County roads during the winters of 2000–02 (Sherwood, 

2005; table 16). The deleterious effects of road salt on the 

water quality of Monroe County streams (Monroe County 

Water Quality Planning Bureau, 2001) and Irondequoit 

Bay (Bubeck and Burton, 1989) are well documented. 

Chloride concentrations were highest in the urban basins 

where population, road densities, and salt-application rates 

(Sherwood, 2005) were greater than those in rural basins. 

Of all the monitoring sites, Allen Creek had the highest 

median annual concentration of chloride (216 mg/L) and the 

highest measured concentration (1,170 mg/L). The lowest 

concentrations of chloride were found in Honeoye Creek 

and the Genesee River, which had median annual chloride 

concentrations of 41and 51 mg/L, respectively (table 3). Both 

Oatka Creek and Black Creek had median annual chloride 

concentrations of 56 mg/L.

Concentrations of sulfate were measured in samples 

collected only during 2003–05 for all sites, except 

Genesee River at Charlotte Pump Station, for which 

sulfate concentrations were not analyzed. Median annual 

concentrations of sulfate ranged from 22 mg/L in Honeoye 

Creek to 149 mg/L in Black Creek. The highest concentrations 

of sulfate, 618 and 504 mg/L, were measured in Black 

Creek and Oatka Creek, respectively. Relatively high sulfate 

concentrations also were measured in Irondequoit Creek at 

Railroad Mills. These high concentrations are attributed to 

dissolution of sulfate from thick gypsum (calcium sulfate) 

layers in Silurian shale bedrock (Broughton and others, 

1962) that crops out upstream from these monitoring sites 

(Young, 1993). The Honeoye Creek monitoring site lies south 

(upstream) of the gypsum-bearing outcrops and springs; 

hence, sulfate concentrations at this site did not reflect this 

source. Sulfate in the urbanized lower parts of the Irondequoit 

Creek Basin, which generally lie north of the gypsum-bearing 

outcrops, was attributed to the Silurian shale outcrops but also 

to atmospheric deposition from industrial and transportation 

sources. The median annual concentrations of sulfate in 

Irondequoit Creek decreased from 144 mg/L at Railroad Mills 

to 92 mg/L downstream at Blossom Road.

Constituent Loads

Load calculations provide an estimate of the amount 

(mass per unit of time) of a given constituent that moves in 

streamflow past a given point (water-quality monitoring site) 

or into a receiving body of water. Knowledge of the magnitude 

and trends in loads of chemical constituents is important in 

evaluating transport processes and assessing the effectiveness 

of management practices that may control constituent sources 

within the basin. 

In this study, the USGS LOADEST program (Runkel and 

others, 2004; Cohn and others, 1992) was used to estimate 

daily mean constituent concentrations and loads through a 

log-linear regression model that uses streamflow, time, and 

seasonal indicators (cyclic sine and cosine functions of time) 

as explanatory variables. The program handles censored 

concentrations (those values found to be below an analytical 

detection limit) through an adjusted maximum likelihood 

estimation routine. Regression coefficients and associated 

t-statistics for each explanatory variable are calculated, and 

daily loads are computed from the estimated daily mean 

constituent concentrations and measured daily mean flows. 

The daily load estimates are summed to derive monthly and 

annual totals. In this report, the model variables were retained 

only when t values for the estimated regression coefficients 

exceeded 95-percent confidence levels (a probability [p] less 

than 0.05 indicates that the coefficient was not statistically 

different from zero). 

The LOADEST regression coefficients can be directly 

related to basin characteristics or to physical and biological 

processes. For example, the linear dependence of logtransformed concentration on log-transformed streamflow 

may be indicative of the source of the constituent; negative 

coefficient values indicate a dilution effect on point sources, 

and positive values generally indicate nonpoint (spatially 

diffuse) sources and reflect increased transport during periods 

of storm runoff and high streamflow. The magnitude and the 

positive (increasing) or negative (decreasing) component of 

the linear time variable indicates the presence and direction 

of a monotonic trend in constituent load for the 6-year 

study period. The presence of a seasonal (annually cyclic) 

trend is determined through the regression coefficients for 

a combined sine-plus-cosine Fourier function. The overall 

dependence of concentration and load on the variables—flow 

(Q and Q2), monotonic time trend (T), and seasonal trend 

(based on a sinusoidal function, SS)—is measured by the 

coefficient of determination (R2), which describes the amount 

of variance in constituent loads explained by the model. The 

statistically significant model variables, the R2 coefficients, 

and the estimated annual loads are summarized in table 4 for 

five constituents at the nine sites. Insufficient data precluded 

load and trend analyses for ammonia, total suspended solids, 

and orthophosphate.

Loads of chloride, sulfate, ammonia plus organic 

nitrogen, nitrate plus nitrite nitrogen, and phosphorus at 

most study sites were estimated using a regression model. 

Statistically significant positive flow-related coefficients were 

determined for all constituents at five study sites. For three 

sites, insufficient data precluded estimation of loads using the 

regression model. Loads were estimated as the product of the 

median constituent concentrations (2003–08) and annual mean 

flow for phosphorus at Northrup Creek and Oatka Creek, and 

for nitrate plus nitrite nitrogen at Honeoye Creek. For one site, 

Genesee River near Rochester, sulfate concentrations were 

not measured; therefore, sulfate loads were not estimated. 

All other constituent loads at the nine sites were positively 
Water-Resources Data Analyses 19

Table 4. Estimated annual constituent loads at nine monitoring sites in Monroe County, N.Y., water years 2003–08, and statistically significant model variables.—Continued[Site locations are shown in figure 1. Q, flow; T, linear time trend; SS, sinusoidal functions to account for the effects of seasonality; N, nitrogen; R2, regression coefficient of determination, in percent; ln, natuaral logarithm; --, no data]

Constituent Model variables1 R2 Number of samples Annual load, in tons per year 2003 2004 2005 2006 2007 2008 Mean

0422026250 Northrup Creek at North Greece 

Chloride ln(Q), SS 87.0 79 1,860 1,960 2,550 1,570 2,470 1,850 2,050

Sulfate ln(Q), SS 93.9 45 720 880 1,010 680 1,090 750 855Ammonia plus organic N ln(Q), T 84.0 81 17 25 24 12 23 13 19Nitrate plus nitrite N ln(Q), T, SS 94.2 81 29 30 34 19 28 18 26Phosphorus Estimated 2 -- 81 2.1 3.0 3.1 1.9 3.5 2.2 2.6

04229500 Honeoye Creek at Honeoye Falls 

Chloride ln(Q, Q2), SS 98.2 94 5,950 10,300 8,840 6,100 10,000 6,690 7,980Sulfate ln(Q, Q2), SS 97.3 59 3,350 6,170 5,350 3,570 6,260 3,900 4,770Ammonia plus organic N ln(Q), SS 98.0 96 82 175 123 74 162 83 117Nitrate plus nitrite N Estimated 2 -- 96 32 62 49 30 61 34 45Phosphorus ln(Q, Q2), SS 95.3 96 24 61 36 14 43 14 32

04230500 Oatka Creek at Garbutt

Chloride ln(Q, Q2), SS 98.0 94 12,900 17,100 16,000 14,000 16,000 13,500 14,900Sulfate ln(Q) 90.6 62 30,100 36,700 34,000 32,200 34,000 30,100 32,800Ammonia plus organic N ln(Q), SS 96.3 97 141 233 191 140 209 144 176Nitrate plus nitrite N ln(Q, Q2), T, SS 98.1 97 498 647 586 449 531 419 522Phosphorus Estimated 2 -- 97 17 25 22 18 22 18 20

04231000 Black Creek at Churchville 

Chloride ln(Q, Q2), SS 99.0 77 7,130 9,680 9,630 8,020 10,400 8,370 8,870Sulfate ln(Q, Q2), SS 94.3 48 18,600 26,400 24,900 23,000 26,700 20,800 23,400Ammonia plus organic N ln(Q), SS 97.5 78 92 163 131 95 157 110 125Nitrate plus nitrite N ln(Q, Q2), T, SS 95.6 78 298 345 355 251 310 233 299Phosphorus ln(Q, Q2), SS 95.9 78 8.5 21 13 8.8 18 11 13

04232034 Irondequoit Creek at Railroad Mills, near Fishers 

Chloride ln(Q), SS 93.0 77 4,000 4,960 5,140 4,110 4,960 4,670 4,640Sulfate ln(Q, Q2), SS 72.5 36 4,870 6,290 6,090 5,420 5,840 5,650 5,700Ammonia plus organic N ln(Q), T, SS 88.6 80 25 40 36 21 32 24 30Nitrate plus nitrite N ln(Q), SS 66.0 80 39 45 47 39 45 44 43Phosphorus ln(Q), SS 81.6 80 3.0 7.2 6.7 3.3 6.8 4.7 5.3
20 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality Table 4. Estimated annual constituent loads at nine monitoring sites in Monroe County, N.Y., water years 2003–08, and statistically significant model variables.—Continued [Site locations are shown in figure 1. Q, flow; T, linear time trend; SS, sinusoidal functions to account for the effects of seasonality; N, nitrogen; R2, regression coefficient of determination, in percent; ln, natuaral logarithm; --, no data] Model Number Annual load, in tons per year Constituent R2 variables1 of samples 2003 2004 2005 2006 2007 2008 Mean 04232050 Allen Creek near Rochester Chloride ln(Q), SS 89.0 86 8,630 10,600 10,300 7,440 10,000 8,260 9,210 Sulfate ln(Q) 91.1 41 1,860 2,750 2,240 1,980 2,200 1,830 2,140 Ammonia plus organic N ln(Q), SS 90.8 89 26 60 38 35 40 23 37 Nitrate plus nitrite N ln(Q), T, SS 93.0 89 36 46 39 27 34 24 34 Phosphorus ln(Q), SS 86.8 89 3.4 13 6.1 6.8 6.9 3.0 6.6 0423205010 Irondequoit Creek above Blossom Road, Rochester Chloride ln(Q, Q2), SS 88.3 141 22,200 27,200 26,600 22,300 27,600 26,300 25,400 Sulfate ln(Q), SS 83.9 84 13,800 16,600 15,700 14,500 16,200 15,500 15,400 Ammonia plus organic N ln(Q, Q2), T, SS 94.6 146 98 173 122 93 123 89 116 Nitrate plus nitrite N ln(Q, Q2), T, SS 94.7 146 142 172 159 117 149 128 145 Phosphorus ln(Q), T, SS 89.2 146 17 54 28 22 27 14 27 0423205025 Irondequoit Creek at Empire Boulevard, Rochester Chloride ln(Q), SS 88.6 142 24,500 30,600 30,500 24,300 32,400 29,800 28,700 Sulfate ln(Q), SS 88.1 85 15,100 18,900 17,700 16,100 18,400 17,300 17,300 Ammonia plus organic N ln(Q, Q2), T, SS 93.6 147 100 172 120 86 114 78 112 Nitrate plus nitrite N ln(Q), T. SS 90.3 147 152 182 168 110 148 117 146 Phosphorus ln(Q), T, SS 89.5 147 18 46 26 18 24 13 24 431510077363501 Genesee River at Charlotte Pump Station near Rochester Chloride ln(Q), SS 87 300 152,000 193,000 161,000 146,000 186,000 153,000 165,000 Sulfate3 -- -- -- -- -- -- -- -- -- -- Ammonia plus organic N ln(Q, Q2), T, SS 90 303 2,520 3,410 2,290 1,920 2,980 1,990 2,520 Nitrate plus nitrite N ln(Q, Q2), T, SS 94 301 3,810 4,870 3,950 3,340 4,380 3,400 3,960 Phosphorus ln(Q, Q2), T, SS 88 303 686 1,110 680 584 1,270 755 848

1Loads estimated using regression model described by Cohn and others (1992) and Runkel and others (2004), except where noted.2Insufficient data for estimation using regression model. Load estimated from the product of median constituent concentration (2003–08) and annual mean flow for given year.3Sulfate concentrations were not analyzed at this site.
Water-Resources Data Analyses 21

correlated with streamflow, indicating that loads in these 

streams were dominated by runoff and nonpoint sources. 

For example, the loads of chloride were derived from the 

application of road salt to paved areas throughout the study 

area during winter months and were transported to streams 

in runoff during rainfall and snowmelt. A discussion of the 

seasonal and monotonic time trends is presented in the next 

section of the report. 

Because constituent loads were directly related to 

streamflow, the large basins generated large constituent 

loads simply by virtue of their size (table 4). Basin-tobasin comparisons of constituent transport were enabled by 

normalizing the load data by basin area to derive constituent 

yield (load per unit area). Annual yields of the five constituents 

are summarized for the nine study sites in table 5 and figure 7. 

Annual yields of chloride (fig. 7A) were greatest in the 

urbanized basin of Allen Creek (250 to 350 ton/mi2), where 

roads received large applications of road-deicing salt in 

winter months. The lower Irondequoit Creek Basin also had 

relatively large yields of chloride (160 to 220 ton/mi2) due to 

road-salt applications. The basins with low population and 

road densities―Honeoye Creek, Black Creek, Oatka Creek, 

and Genesee River―had relatively low yields of chloride 

(30 to 86 ton/mi2). An apparent anomaly among the results 

was the chloride data from Northrup Creek. Compared to 

loads at the other monitoring sites, the total loads of chloride 

in Northrup Creek were small; however, the yields of chloride 

ranked second (160 to 250 ton/mi2) after those computed for 

Allen Creek. The results indicated that road-salt application in 

Spencerport and chloride in discharges from the Spencerport 

wastewater-treatment plant probably contributed to the high 

chloride yields in this stream; however, an as-yet-unidentified 

natural source could have been a contributing factor. 

Although sulfate concentrations were not measured in 

water samples collected during the 2006–08 water years, 

loads and yields were computed for these years from the 

regression equations developed with the 2003–05 data. No 

sulfate loads or yields were computed for the Genesee River 

because sulfate-concentration data were not available. Sulfate 

yields (fig. 7B) were greatest in Black Creek, Oatka Creek, 

and Irondequoit Creek in the upper basin (120 to 210 ton/mi2

), 

which drain areas where Silurian bedrock contains thick beds 

of gypsum (Broughton and others, 1962). The gypsum beds 

crop out downstream from the Honeoye Creek monitoring site 

and likely contributed to the lowest measured sulfate yields 

(17 to 32 ton/mi2). 

Nitrogen yields in Northrup Creek were generally greater 

than at other sites, presumably as a result of the discharge of 

water (fig. 5) and nutrients to the creek from the Spencerport 

wastewater-treatment plant. The Erie (Barge) Canal was a 

second source of nutrients to the creek. On the basis of limited 

data that were collected during 2001–03 (U.S. Geological 

Survey, 2009a), constituent concentrations in canal water 

generally were lower than concentrations in concurrently 

collected creek water; however, the constituent loads from 

the canal were large owing to the near-constant flow from this 

source. The combined contributions from the wastewatertreatment plant and the canal were estimated from the 2001–03 

data (U.S. Geological Survey, 2009a); these estimates indicate 

that 30 to 40 percent of the computed loads of ammonia plus 

organic nitrogen, nitrate plus nitrite nitrogen, and phosphorus 

in Northrup Creek at Greece could be attributed to the loads 

input from these two sources. 

The high yields of nitrate plus nitrite nitrogen 

(1.8 to 3.4 ton/mi2

; fig. 7C) and ammonia plus organic 

nitrogen (1.2 to 2.5 ton/mi2; fig. 7D) in Northrup Creek also 

could have been derived from fertilizers and manure that 

were applied to agricultural land within the Northrup Creek 

Basin. The basins of Oatka Creek and Black Creek also had 

substantial agricultural sources of nitrogen that are reflected 

in relatively high yields of nitrate plus nitrite nitrogen (1.8 to 

3.2 ton/mi2; fig. 7C) for these streams. In contrast, Honeoye 

Creek Basin is relatively undeveloped, has less intensive 

agricultural use than the Oatka Creek and Black Creek 

Basins, and has low streamflow yield (fig. 5); all factors that 

contribute to relatively low nitrogen yields. Allen Creek had 

the second highest yields of ammonia plus organic nitrogen 

(0.76 to 2.0 ton/mi2; fig. 7D).

The Ellison Park wetland, a 423-acre predominantly 

cattail marsh, covers the Irondequoit Creek valley bottom 

between the Blossom Road and Empire Boulevard 

monitoring sites. The natural mitigative effects of the 

wetland on constituent loads, especially those of particulate 

constituents, which would otherwise be transported to 

Irondequoit Bay, have been documented by Coon (2000). 

During February 1997, a flow-control structure designed 

to increase the dispersal and short-term detention of storm 

runoff in the wetland was installed mid-way through the 

wetland at a point locally referred to as the Narrows. This 

structure increased the wetland’s removal efficiency for 

phosphorus from 28 to 45 percent and that of total suspended 

solids from 47 to 52 percent (Coon, 2004). The continued 

mitigative effects of the wetland and the flow-control 

structure on phosphorus and ammonia plus organic nitrogen 

loads were evident in this study (2003–08 water years). 

Yields of phosphorus were 16 percent lower, and yields of 

ammonia plus organic nitrogen were 9 percent lower, at 

Empire Boulevard than at Blossom Road (fig. 7D and 7E; 

table 5). Yields of dissolved constituents (chloride, sulfate, 

and nitrate plus nitrite nitrogen) were similar at both sites, 

a result that Coon (2004) found for these constituents from 

data collected during 1990–2001. The flow-control structure 

was removed during March and July 2009 by order of the 

Regulatory Branch of the U.S. Army Corps of Engineers 

after evaluation of the potential future benefits to Irondequoit 

Bay and the expected adverse effects of the control structure 

on the wetland ecology (P.D. Frapwell, U.S. Army Corps of 

Engineers, written commun., 2007).

Estimated yields for the Genesee River (table 5) reflect 

constituent loads (table 4) that were delivered to Lake 

Ontario 0.5 mi downstream from the monitoring site. The 

relatively high yields of phosphorus for the Genesee River 
22 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality Table 5. Annual yields of selected constituents at nine monitoring sites in Monroe County, N.Y., water years 2003–08.—Continued [Site locations are shown in figure 1. Site numbers in parentheses. Yields are in tons per square mile. E, estimated from median concentration (2003–08) and annual mean discharge; --, no data] Water year1 Northrup Creek at North Greece (0422026250 ) Honeoye Creek at Honeoye Falls (04229500) Oatka Creek at Garbutt (04230500) Black Creek at Churchville (04231000) Irondequoit Creekat Railroad Mills, near Fishers (04232034) Allen Creek near Rochester (04232050) Irondequoit Creek above Blossom Road, Rochester (0423205010) Irondequoit Creek at Empire Boulevard, Rochester (0423205025) Genesee River at Charlotte Pump Station near Rochester (431510077363501) Ammonia plus organic nitrogen 2003 1.7 0.42 0.71 0.71 0.64 0.86 0.69 0.66 1.0 2004 2.5 .89 1.2 1.3 1.0 2.0 1.2 1.1 1.4 2005 2.4 .63 .96 1.0 .92 1.3 .86 .79 .93 2006 1.2 .38 .70 .73 .54 1.2 .65 .57 .78 2007 2.3 .83 1.0 1.2 .82 1.3 .87 .75 1.2 2008 1.3 .42 .72 .85 .61 .76 .63 .52 .81 Nitrate plus nitrite nitrogen 2003 2.9 E .16 2.5 2.3 .99 1.2 1.0 1.0 1.5 2004 3.0 E .32 3.2 2.7 1.1 1.5 1.2 1.2 2.0 2005 3.4 E .25 2.9 2.7 1.2 1.3 1.1 1.1 1.6 2006 1.9 E .15 2.2 1.9 .99 .90 .82 .73 1.4 2007 2.8 E .31 2.7 2.4 1.1 1.1 1.0 .98 1.8 2008 1.8 E .17 2.1 1.8 1.1 .80 .90 .77 1.4 Phosphorus 2003 E .21 .12 E .09 .07 .08 .11 .12 .12 .28 2004 E .29 .31 E .12 .16 .18 .43 .38 .30 .45 2005 E .31 .18 E .11 .10 .17 .20 .20 .17 .28 2006 E .19 .07 E .09 .07 .08 .23 .15 .12 .24 2007 E .34 .22 E .11 .14 .17 .23 .19 .16 .51 2008 E .22 .07 E .09 .08 .12 .10 .10 .09 .31 Chloride 2003 180 30 65 55 100 290 160 160 62 2004 190 53 86 74 130 350 190 200 78 2005 250 45 80 74 130 340 190 200 65 2006 160 31 70 62 110 250 160 160 59

2007 250 51 80 80 130 330 190 220 752008 180 34 68 64 120 270 190 200 62
Water-Resources Data Analyses

23

Table 5. Annual yields of selected constituents at nine monitoring sites in Monroe County, N.Y., water years 2003–08.—Continued[Site locations are shown in figure 1. Site numbers in parentheses. Yields are in tons per square mile. E, estimated from median concentration (2003–08) and annual mean discharge; --, no data]

Irondequoit Irondequoit Genesee Irondequoit Northrup Honeoye Oatka Black Creekat Allen Creek at River at Creek above Creek at Creek at Creek at Creek at Railroad Mills, Creek near Empire Charlotte Water year1 Blossom Road, North Greece Honeoye Falls Garbutt Churchville near Rochester Boulevard, Pump Station Rochester (0422026250 ) (04229500) (04230500) (04231000) Fishers (04232050) Rochester near Rochester (0423205010) (04232034) (0423205025) (431510077363501)

Sulfate

2003 71 17 150 140 120 62 97 100 ˉˉ

2004 87 31 180 200 160 91 120 130 ˉˉ2005 100 27 170 190 160 74 110 120 ˉˉ2006 67 18 160 180 140 66 100 110 ˉˉ

2007 110 32 170 210 150 73 110 120 ˉˉ2008 74 20 150 160 140 61 110 110 ˉˉ

1Water year is the period from October 1 of one year through September 30 of the following year, numbered for the year in which it ends.
24 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

0

100

200

300

400

2003 2004 2005 2006 2007 2008

ANNUAL YIELD OF CHLORIDE,

IN TONS PER SQUARE MILE 

A CHLORIDE

0

50

100

150

200

250

2003 2004 2005 2006 2007 2008

ANNUAL YIELD OF SULFATE,

IN TONS PER SQUARE MILE 

B SULFATE

0.0

1.0

2.0

3.0

4.0

2003 2004 2005 2006 2007 2008

ANNUAL YIELD OF NITRATE PLUS NITRITE NITROGEN,

IN TONS PER SQUARE MILE 

C NITRATE PLUS NITRITE NITROGEN

Figure 7. Annual yields of selected constituents at nine monitoring sites in Monroe 

County, N.Y., water years 2003–08: A, chloride; B, sulfate; C, nitrate plus nitrite 

nitrogen; D, ammonia plus organic nitrogen; and E, phosphorus.
Water-Resources Data Analyses 25

0.0

0.5

1.0

1.5

2.0

2.5

3.0

2003 2004 2005 2006 2007 2008

D AMMONIA PLUS ORGANIC NITROGEN 

ANNUAL YIELD OF AMMONIA PLUS ORGANIC

NITROGEN, IN TONS PER SQUARE MILE 

0.0

0.1

0.2

0.3

0.4

0.5

0.6

2003 2004 2005 2006 2007 2008

ANNUAL YIELD OF PHOSPHORUS,

IN TONS PER SQUARE MILE 

E PHOSPHORUS

Northrup Creek

Irondequoit Creek at Railroad Mills

Honeoye Creek

Allen Creek

Oatka Creek

Irondequoit Creek above Blossom Road

Black Creek

Irondequoit Creek at Empire Boulevard

Genesee River at Charlotte pump station

EXPLANATION

DATE

Figure 7. Annual yields of selected constituents at nine monitoring sites in Monroe County, 

N.Y., water years 2003–08: A, chloride; B, sulfate; C, nitrate plus nitrite nitrogen; D, ammonia 

plus organic nitrogen; and E, phosphorus. —Continued
26 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

(0.24 to 0.51 ton/mi2; fig. 7E) were associated with suspendedsediment generated from agricultural areas and streambank 

erosion (New York State Department of Environmental 

Conservation, 2003).

Temporal Trends

A shift in population from Rochester to the surrounding 

townships over the past few decades has resulted in the 

conversion of agricultural and forested land to residential and 

commercial uses; this process has slowed in some towns in 

recent years, however. Monotonic time-trend and seasonaltrend analyses can be used to assess the effect of development 

on surface-water quality within the study basins.

A monotonic time trend, as used in this report, is a linear 

change (increase or decrease) in the concentration of a given 

constituent at a specific sampling site over the 6-year study 

period. Seasonal trends are annually cyclic patterns that are 

seen each year. The USGS software program ESTREND 

(EStimate TREND; Shertz and others, 1991) was used to 

discern both types of trend through a linear model that uses an 

adjusted maximum-likelihood estimation approach. The trends 

are considered to be statistically significant when the t-statistic 

for each trend coefficient has a p value less than 0.05, which 

indicates a 95-percent confidence level that the estimated 

trend in concentration is valid. Generally, the monotonic trend 

tests require at least 5 years of data for reliable results (Hirsch 

and others, 1982). In the analysis, variability in constituent 

concentrations resulting from variations in streamflow 

was minimized through regression of log-transformed 

concentrations as a function of log-transformed flows. This 

regression produced a residual (flow-adjusted) concentration 

that was then used in the trend tests. The effects of seasonal 

(annually cyclic) trends, if present, were removed through 

a set of sine-plus-cosine Fourier functions. The flow and 

seasonally adjusted concentrations were then used to evaluate 

the slope of the monotonic trend rate (Sen, 1968), its positive 

or negative sign (increasing or decreasing concentration over 

time), and significance (p value less than 0.05).

Monotonic time trends were identified at all sites for most 

of the nutrient constituents that were evaluated (table 6). All of 

the monotonic time trends detected in the nutrient data indicate 

that concentrations decreased (negative rates in table 6) during 

the 6-year study period, with one exception―phosphorus. 

Phosphorus concentrations increased by 5.7 percent at the 

Genesee River monitoring site. At four other sites (table 

6), phosphorus concentrations decreased during the study 

period. Nitrate plus nitrite nitrogen concentrations decreased 

at all sites except Irondequoit Creek at Railroad Mills where 

a trend was not detected. The general decrease in nutrient 

concentrations was most notable for Irondequoit Creek at 

Empire Boulevard, where the mitigative effects of the Ellison 

Park wetland and the flow-control structure at the Narrows 

were evident. Monotonic trends in chloride concentrations 

were not detected at any site. 

Constituent concentrations typically reflect seasonal 

variations in biochemical or hydrologic processes or 

human activities (fig. 8). In this study, seasonal trends in 

concentration were identified at all sites for nearly every 

constituent that was evaluated (table 6). The seasonal 

variability in constituent concentrations and flow is reflected 

in the transport of constituent loads (fig. 9). For example, the 

seasonal nature of the chloride concentrations and loads for the 

suburban, developed basin of Allen Creek are shown in figure 

8A and figure 9A. The effect of road-salt applications to paved 

areas throughout the basin during winter months is shown by 

chloride loads that were four to eight times higher in runoff 

during winter and early spring than during summer months. 

Chloride concentrations in streams are typically highest 

in January and February, whereas high loads of chloride 

persist from January through April as runoff is augmented by 

snowmelt in early spring. The same general pattern of seasonal 

chloride transport is seen in the other study basins.

The concentrations and loads of the nitrogen constituents 

were generally highest during late fall through spring, when 

fertilizers and manure applied to residential lawns or fallow 

farm fields are transported to streams by snowmelt and spring 

rains and when denitrification (bacterial transformation of 

nitrate) is minimal. During summer months, nitrate transport 

is minimal because of low flows, limited nitrogen applications 

on growing crops, and biologically active denitrification 

processes. As an example, the seasonal nature of the nitrate 

plus nitrite nitrogen concentrations and loads for the largely 

agricultural basin of Oatka Creek are shown in figure 8B and 

figure 9B. The same general pattern was seen in the other 

study basins, including the suburban developed basin of 

Allen Creek.

The loads of phosphorus and other constituents (table 

4; fig. 7) at the Genesee River site, for the most part, are 

delivered directly to Lake Ontario. The seasonal nature of 

the phosphorus concentrations and loads for the largely 

agricultural basin of the Genesee River are shown in figure 

8C and figure 9C. As with the nitrogen species, phosphorus in 

soils, fertilizers, and manure is eroded and transported during 

storm runoff, and the transport process is most significant 

during late fall, winter, and early spring months when fields 

are fallow and runoff is often high. The monthly pattern of 

concentrations and loads of phosphorus differs slightly from 

that of nitrate plus nitrite nitrogen, in part, because phosphorus 

is affected more by runoff processes that control solid-phase 

particulate transport, whereas nitrate is transported largely in a 

dissolved phase.
Water-Resources Data Analyses 27

Table 6. Trends in concentrations of selected constituents at nine monitoring sites in Monroe County, N.Y., 

water years 2003–08.—Continued

[Site locations are shown in figure 1. mg/L, milligrams per liter; nd, trend not detected; --, insufficient data for trend analysis; 

p, probability that trend is not statistically significant]

Constituent Number of 

samples Seasonal trend1 Monotonic trend in concentration2

(mg/L per year) (percent per year)

0422026250 Northrup Creek at North Greece

Chloride 79 Yes nd nd

Sulfate 45 Yes -- --

Ammonia plus organic nitrogen 81 nd -0.05 -5.0

Nitrate plus nitrite nitrogen 81 Yes -.18 -9.9

Phosphorus 81 Yes -.013 -6.9

04229500 Honeoye Creek at Honeoye Falls

Chloride 94 Yes nd nd

Sulfate 59 Yes -- --

Ammonia plus organic nitrogen 96 Yes nd nd

Nitrate plus nitrite nitrogen 96 Yes -.03 -10

Phosphorus 96 Yes nd nd

04230500 Oatka Creek at Garbutt

Chloride 94 Yes nd nd

Sulfate 62 nd -- --

Ammonia plus organic nitrogen 97 Yes nd nd

Nitrate plus nitrite nitrogen 97 Yes -.06 -3.0

Phosphorus 97 Yes -.010 -9.8

04231000 Black Creek at Churchville

Chloride 77 Yes nd nd

Sulfate 48 Yes -- --

Ammonia plus organic nitrogen 78 Yes nd nd

Nitrate plus nitrite nitrogen 78 Yes -.13 -9.1

Phosphorus 78 Yes nd nd

04232034 Irondequoit Creek at Railroad Mills, near Fishers 

Chloride 77 Yes nd nd

Sulfate 36 Yes -- --

Ammonia plus organic nitrogen 80 Yes -.05 -7.0

Nitrate plus nitrite nitrogen 80 Yes nd nd

Phosphorus 80 Yes nd nd

04232050 Allen Creek near Rochester 

Chloride 86 Yes nd nd

Sulfate 41 nd -- --

Ammonia plus organic nitrogen 89 Yes nd nd

Nitrate plus nitrite nitrogen 89 Yes -.07 -7.7

Phosphorus 89 Yes nd nd
28 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

Table 6. Trends in concentrations of selected constituents at nine monitoring sites in Monroe County, N.Y., 

water years 2003–08.—Continued

[Site locations are shown in figure 1. mg/L, milligrams per liter; nd, trend not detected; --, insufficient data for trend analysis; 

p, probability that trend is not statistically significant]

Constituent Number of 

samples Seasonal trend1 Monotonic trend in concentration2

(mg/L per year) (percent per year)

 0423205010 Irondequoit Creek above Blossom Road, Rochester 

Chloride

Sulfate

Ammonia plus organic nitrogen

Nitrate plus nitrite nitrogen

Phosphorus

141

84

146

146

146

Yes

Yes

Yes

Yes

Yes

nd

--

-.04

-.06

-.008

nd

--

-5.3

-5.9

-6.1

0423205025 Irondequoit Creek at Empire Boulevard, Rochester 

Chloride

Sulfate

Ammonia plus organic nitrogen

Nitrate plus nitrite nitrogen

Phosphorus

142

85

147

147

147

Yes

Yes

Yes

Yes

Yes

nd

--

-.09

-.09

-.020

nd

--

-11

-9.8

-14

431510077363501 Genesee River at Charlotte Pump Station near Rochester 

Chloride

Sulfate

Ammonia plus organic nitrogen

Nitrate plus nitrite nitrogen

Phosphorus

300

0

303

301

303

Yes

--

Yes

Yes

Yes

nd

--

-.02

-.05

+.011

nd

--

-3.2

-4.8

+5.7

1

Seasonal trends determined through annual Fourier function described by Schertz and others (1991); p less than or equal to 0.05.

2

Monotonic trends estimated from concentrations adjusted for flow and seasonal effects through the adjusted maximum likelihood estimation method described by Schertz and others (1991) and trend rate methods of Sen (1968); positive sign indicates 

increasing concentration; negative sign indicates decreasing concentration; p less than or equal to 0.05. 
Water-Resources Data Analyses 29

0

200

400

600

800

1,000

1,200

CONCENTRATION,

IN MILLIGRAMS PER LITER

A CHLORIDE, ALLEN CREEK NEAR ROCHESTER

0.5

1.5

2.5

3.5

CONCENTRATION, IN MILLIGRAMS PER LITER

B NITRATE PLUS NITRITE NITROGEN, OATKA CREEK

 AT GARBUTT

0.0

0.2

0.4

0.6

0.8

1.0

CONCENTRATION, IN MILLIGRAMS PER LITER

C PHOSPHORUS, GENESEE RIVER AT CHARLOTTE PUMP

 STATION NEAR ROCHESTER

EXPLANATION

Upper whisker extends to largest value within 

1.5 times IQR above the 75th percentile 

75th percentile

Median

25th percentile

Upper outlier 

Lower whisker extends to smallest value within 

1.5 times IQR below the 25th percentile

Lower outlier 

IQR

(Inter-quartile range)

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEP. OCT. NOV. DEC.

MONTH

1.0

2.0

3.0

4.0

Figure 8. Seasonal variation in constituent concentration at selected sites in Monroe County, N.Y., water years 2003–08: 

A, chloride, Allen Creek near Rochester; B, nitrate plus nitrite nitrogen, Oatka Creek at Garbutt; and C, phosphorus, 

Genesee River at Charlotte Pump Station near Rochester.
30 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

0

1,000

2,000

3,000

LOAD, IN TONS PER MONTH

A CHLORIDE, ALLEN CREEK NEAR ROCHESTER

0

50

100

150

200

B NITRATE PLUS NITRITE NITROGEN, OATKA CREEK

 AT GARBUTT

LOAD, IN TONS PER MONTH

0

100

200

300

C PHOSPHORUS, GENESEE RIVER AT CHARLOTTE PUMP

 STATION NEAR ROCHESTER

LOAD, IN TONS PER MONTH

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEP. OCT. NOV. DEC.

MONTH

EXPLANATION

Upper whisker extends to largest value within 

1.5 times IQR above the 75th percentile 

75th percentile

Median

25th percentile

Upper outlier 

Lower whisker extends to smallest value within 

1.5 times IQR below the 25th percentile

Lower outlier 

IQR

(Inter-quartile range)

Figure 9. Seasonal variation in monthly constituent loads at selected sites in Monroe County, N.Y., water years 2003–08: 

A, chloride, Allen Creek near Rochester; B, nitrate plus nitrite nitrogen, Oatka Creek at Garbutt; and C, phosphorus, Genesee 

River at Charlotte Pump Station near Rochester.
Summary 31

Summary

This report, the sixth in a series of analyses of the 

hydrologic data collected in Monroe County since 1984, 

presents interpretations of flow and water-quality data at nine 

monitoring sites for the period from October 2002 through 

September 2008. Monroe County encompasses 673 mi2 of 

mixed land uses (agricultural and residential) and land covers 

(forests and wetlands) in northwestern New York. Although 

the population within Monroe County has remained fairly 

constant during the past 39 years (1970–2008), realignment 

of the population has occurred as people have moved from 

the city of Rochester to the developing towns that border the 

city. In response to this shift in population, the percentages of 

forested and agricultural lands have decreased, whereas those 

of developed land uses have increased.

Streamflow and water quality were monitored at nine 

sites jointly operated by the Monroe County Department of 

Health and the U.S. Geological Survey. The smallest basin 

in the monitoring network, Northrup Creek, had the highest 

streamflow yields (flow per unit area) due to sustained yearround discharges from the Spencerport wastewater-treatment 

plant and seasonal releases from the NYS Erie (Barge) Canal. 

Genesee River streamflow yields also were high due, in part, 

to the relatively high yields from the upper part of the Genesee 

River Basin. The lowest streamflow yields were measured 

in Honeoye Creek, which reflects a decrease in flows due to 

withdrawals from Hemlock Lake and Canadice Lake for the 

city of Rochester water supply.

Water samples from the nine monitoring sites were 

analyzed for nutrients, chloride, sulfate, and total suspended 

solids. The loads of constituents were computed from the 

concentration data and the daily flows recorded at each of 

the monitoring sites (where concentration data permitted). 

Evaluation of the loads indicated that all constituents at all 

sites were positively correlated with streamflow, except 

phosphorus at Northrup Creek and Oatka Creek, and nitrate 

plus nitrite nitrogen at Honeoye Creek. At these three 

sites, insufficient data precluded estimation of loads with 

regression models. 

Annual constituent yields (loads per unit area) were 

computed to assess the relative contributions, and permit direct 

comparison, of loads among the study basins. All urban sites—

Allen Creek and the two downstream sites on Irondequoit 

Creek—had seasonally high chloride concentrations and 

high annual yields of chloride (160 to 350 ton/mi2). Chloride 

concentrations and yields, which increased with an increase in 

population and road density, were attributed to the application 

of road-deicing salts. The less-urbanized sites in the study—

Genesee River, Honeoye Creek, Oatka Creek, and Black 

Creek—had relatively low concentrations and yields of 

chloride (30 to 86 ton/mi2). The highest concentrations and 

yields of sulfate were measured in Black Creek, Oatka Creek, 

and Irondequoit Creek at Railroad Mills (120 to 210 ton/

mi2). These high concentrations and yields were attributed to 

dissolution of sulfate from gypsum (calcium sulfate) deposits 

in Silurian shale bedrock that crops out upstream from these 

monitoring sites. The Honeoye Creek monitoring site lies 

south (upstream) of the gypsum-bearing outcrops; hence, 

sulfate concentrations and yields at this site (17 to 32 ton/ mi2) 

did not reflect this source. Sulfate in the urban streams, which 

generally lie north of the gypsum-bearing outcrops, was 

attributed to this bedrock source, as well as to atmospheric 

deposition from industrial and transportation sources. 

Samples from Northrup Creek had the highest 

concentrations of phosphorus, orthophosphate, and nitrogen, 

and high yields of nitrate plus nitrite nitrogen (1.8 to 

3.4 ton/mi2) and ammonia plus organic nitrogen (1.2 to 

2.5 ton/mi2). These results were attributed to a combination of 

sources, including discharges from the village of Spencerport 

wastewater-treatment plant (which ceased operation in 

June 2008), diversions from the NYS Erie (Barge) Canal, 

and manure and fertilizers applied to agricultural fields. 

Concentrations and yields of nitrate plus nitrite nitrogen were 

also high in Oatka Creek and Black Creek (1.8 to 3.2 ton/mi2), 

which drain substantial areas in agricultural use. Allen Creek 

had the second highest yields of ammonia plus organic 

nitrogen (0.76 to 2.0 ton/mi2). Honeoye Creek, which drains 

the relatively undeveloped source areas of drinking water for 

the city of Rochester—Hemlock and Canadice Lakes—had the 

lowest yields of nitrate plus nitrite nitrogen and ammonia plus 

organic nitrogen. The second highest median concentrations 

and highest sample concentrations of phosphorus and 

orthophosphate were measured in samples from the Genesee 

River. This stream also had the highest phosphorus yields 

(0.24 to 0.51 ton/mi2), which presumably were associated with 

nutrient and sediment transport from agricultural areas in the 

basin and from streambank erosion. 

A comparison of the yields computed for the two 

downstream sites on Irondequoit Creek—at Blossom Road and 

Empire Boulevard—permitted an assessment of the mitigative 

effects of the Ellison Park wetland on constituent loads, 

which otherwise would have been transported to Irondequoit 

Bay. These effects were enhanced by a flow-control structure 

(installed mid-way through the wetland during February 

1997), which was designed to increase the dispersal and shortterm detention of stormflows in the wetland. The wetland 

significantly decreased yields of particulate constituents—

phosphorus and ammonia plus organic nitrogen—but had 

little effect on the yields of dissolved constituents—chloride, 

sulfate, and nitrate plus nitrite nitrogen.

Trends in flow-adjusted concentrations were identified 

at all sites for five of the nutrient constituents that were 

evaluated—chloride, sulfate, ammonia plus organic nitrogen, 

nitrate plus nitrite nitrogen, and phosphorus. All of the 

monotonic time trends indicated that nutrient concentrations 

decreased during the 6-year study, except for phosphorus 

concentrations at the Genesee River monitoring site, which 

increased. Seasonal trends in concentrations also were 

identified at all sites for nearly every constituent that was 

evaluated. The effect of applications of road salt to paved 
32 Water Resources of Monroe County, New York, Water Years, 2003–08: Streamflow, Constituent Loads, and Trends in Water Quality

areas throughout the study area during winter months was 

increased chloride concentrations from December through 

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through the early spring months, when fertilizers and manure 

that had been applied to residential lawns or fallow farm fields 

were transported to streams by snowmelt and spring rains and 

when denitrification by bacterial action was minimal. During 

summer months, nitrate plus nitrite nitrogen loads were 

minimal because of low flows, limited nitrogen applications 

on growing crops, and active denitrification processes. The 

monthly pattern of concentrations and loads of phosphorus 

differed slightly from that of nitrate plus nitrite nitrogen, in 

part because phosphorus is affected more by runoff processes 

that control solid-phase particulate transport, whereas nitrate is 

transported largely in a dissolved phase.

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W.M., 1985, Quantity and quality of storm runoff in the 

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Prepared by the Pembroke Publishing Service Center

For additional information write to:

New York Water Science Center

U.S. Geological Survey

30 Brown Rd.

Ithaca, NY 14850

Information requests:

(518) 285-5602

or visit our Web site at:

http://ny.water.usgs.gov
Hayhurst and others—Water Resources of Monroe County, NY, Water Years 2003–08: Streamflow, Constituent Loads, and Trends—Scientific Investigations Report 2010–5216

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