Irondequoit Wetlands

Genesee Falls at Driving 

Park Ave., Rochester

Irondequoit Creek at Blossom Road

Maggie Brooks

County Executive

More than 20 years of hydrologic-data collection in 

Monroe County provides a basis for evaluation of the effects of 

urban growth and land-use changes on the chemical quality of 

streams and assessing the effectiveness of current water-resourcemanagement practices. Since 1980, the Monroe County Department 

of Health has maintained a cooperative agreement with the U.S. 

Geological Survey (USGS) to collect and analyze hydrologic 

data from several sites and use the results to identify sources of 

contamination, quantify the annual loads and yields of selected 

chemical constituents, and 

identify temporal trends in 

these loads. 

Monroe County encompasses 

673 square miles in the Lake 

Ontario Plain region of New 

York (fig. 1) (Heffner and 

Goodman, 1973). Precipitation 

in this region is evenly 

distributed throughout the year, 

averaging about 2.7 inches per 

month and about 32 inches per 

year (National Oceanic and Atmospheric Administration, 

1983-99) measured at the Rochester-Monroe County Airport 

(fig. 1). The even distribution of precipitation during the year 

is a result of the proximity to Lake Ontario and Lake Erie 

which affect local rain and snowfall patterns. The annual 

maximum precipitation during 1984-2001 (45.9 inches) 

occurred during 1998; the minimum (24.8 inches) occurred 

during 1985 (fig. 2). 

Loads and Yields of Selected Constituents 

in Streams and Rivers of Monroe County, 

New York, 1984-2001

By Donald A. Sherwood

U.S. Department of the Interior Water-Resources Investigations Report 03-4197 

U.S. Geological Survey June 2004

In cooperation with Monroe County Department of Health
2

��������

�����

������������

����

�����

����

�����

����� �����

��������� ���������

����� �����

������ �����

�������

�����

�������

�����

����

�����������

���

�����

�����

����

�����

������

�����

�������� �����

�����

�����������

����

����

�����������

STREAMFLOW-GAGING STATION AND MONITORING SITE

WATER-QUALITY ONLY SITE

0422026250 Northrup Creek at North Greece 04232034 Irondequoit Creek at Railroad Mills

04232040 Irondequoit Creek at Pittsford 04232046 Thomas Creek at Fariport

04232047 Irondequoit Creek at Linden Ave. 0423204920 East Branch Allen Creek at Pittsford

04232050 Allen Creek near Rochester 0423205010 Irondequoit Creek at Blossom Road 

431510077363501 04232000 Genesee River at Rochester

Pump Station, Rochester

MONROE

COUNTY

Lake Ontario

Plain

NEW YORK

MILES

KILOMETERS

�����

LOCATION MAP

78o00’ 77o50’ 77o40’ 77o30’

25’

43o

20’

43o

10’

15’

43o

10’

05’

0 5

0 5

Base from U.S. Geological Survey

Digital line graph, 1:100,000

DRAINAGE BASIN

Genesee River at Charlotte 

������������

CITY OR VILLAGE

COUNTY LINE

COUNTY ORLEANS

BROCKPORT

HILTON

GENESEE

COUNTY

CHURCHVILLE

SCOTTSVILLE

LIVINGSTON COUNTY

ONTARIO COUNTY

SPENCERPORT

��������

HONEOYE

FALLS

WEBSTER

PITTSFORD FAIRPORT

COUNTY

ONTARIO

����������������������

RochesterMonroe County Airport

Northrup

Creek Basin

WAYNE COUNTY

ROCHESTER

����������

��������

����������

��������

����������

���������������

��������

��������

��������

Figure 1. Principal geographic features of Monroe County, N.Y., and locations of selected monitoring sites in study area. 

(From Sherwood, 2003; fig. 1.)
3

Figure 2. Annual total 

precipitation and long-term 

mean at Rochester-Monroe 

County Airport, N.Y., water 

years 1984-2001. (Location 

1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 is shown in fig. 1.) 20

50

25

30

35

40

45

Mean annual

precipitation (1961-90)

ANNUAL PRECIPITATION, IN INCHES

Chemical Loads and Yields

Streamflow samples have been collected at monitoring 

sites in Monroe County since 1984 and analyzed for 

nutrients (nitrogen and phosphorus), common ions 

(chloride and sulfate), and total suspended solids (Johnston 

and Sherwood, 1996; Sherwood, 1999a, 1999b, 2001, 

2003). Concentration data from these samples are 

combined with streamflow (discharge) data to estimate 

the loads and yields of these constituents. Load represents 

the mass (usually in pounds or tons) of a given constituent 

moving past a given point per unit time and is calculated 

through a multivariate linear regression that provides 

a quantitative relation between measured constituent 

concentrations and daily stream discharge (Cohn and 

others, 1992). Yield is the load divided by the drainage 

area. Yields are helpful in comparisons between basins of 

differing size and streamflow characteristics; for example, 

a given stream may have a greater total load than another 

simply because it has a larger basin, yet it may have a 

smaller yield. Thus, the differences in yields of given 

streams can be more indicative of land-use differences 

among basins, or of changes in land use within a basin, 

than differences in loads.

Trend Analysis

A trend is an overall change in volume of streamflow 

or constituent load at a given site over a specified period 

of time (usually several years). Loads of constituents 

transported by a given stream are dependent on the volume 

of flow in that stream; thus, trends in streamflow 

are an important consideration when evaluating trends 

in constituent loading. Upward or downward trends in 

constituent loads may be due entirely or in part to an 

upward or downward trend in streamflow, rather than to an 

actual increase or decrease in concentration.

The total flow of streams generally varies from year 

to year, depending on the amount, intensity, and time of 

year of precipitation. Changes in land use also can affect 

streamflow volume; for example, converting agricultural 

or forested land to suburban development increases the 

amount of impervious or paved surface area, which in 

turn decreases the amount of stormwater infiltration and 

increases the volume of storm runoff that enters nearby 

streams. These factors can affect the short- and long-term 

trends in streamflow.

The effects of land-use changes and water-quality 

management practices on surface-water quality can best 

be examined through an analysis of water-quality trends—

the overall changes in a chemical constituent loads at a 

specific site over a specified period of time. Annual loads 

of nine constituents at nine streamflow sites in Monroe 

County were tested for trends with a statistical routine 

called the Kendall slope estimator (Hirsch and others, 

1982) to determine the direction and statistical significance 

of the trend. Annual loads were first normalized (annual 

load divided by annual mean discharge) to remove the 

effects of flow prior to trend analysis. These normalized 

loads (essentially annual mean concentrations) were then 

tested for trends. Annual mean loads of most constituents 

at Irondequoit basin sites show a long-term decrease over 

the period of record at all sites, although most are not 

statistically significant (α = 0.05).
4

Figure 3. Locations of selected streamflow-gaging stations within the 

Irondequoit Creek basin, Monroe County, N.Y.

VICTOR

77o 37' 30" 30'

43o

15'

10'

05'

43o

42o55'

22' 30"

Base from U.S. Geological Survey

State base map, 1974, 1:500,000

�

WEBSTER

�����������

���

EAST

ROCHESTER

MONROE

COUNTY

COUNTY

ONTARIO

MONROE COUNTY

WAYNE COUNTY

�����

�����

���� ��� �����

�����

������ �����

�����

Mendon Ponds

County Park

PITTSFORD

FAIRPORT

Genesee River Basin

������������

ROCHESTER

����

�������

�����

�����������

0

0

1 2 3 MILES

1 2 3 KILOMETERS

�����������

Drainage-basin

boundary 

������� �����

����������

��������

����������

��������

Active site

��������

��������

��������

Inactive site

LIVINGSTON COUNTY

��������������

04232040

������������

04232040

0423205010

04232050 Allen Creek near

Rochester

04232034 Irondequoit Creek at

Railroad Mills

0423205010 Irondequoit Creek at

Blossom Road

0423204920 East Branch Allen 

Creek at Pittsford

04232047 Irondequoit Creek at Linden Ave.

04232046 Thomas Creek at Fairport

Irondequoit Creek at Pittsford

IRONDEQUOIT CREEK BASIN

 The Irondequoit Creek basin lies in the 

eastern part of Monroe county and drains 

northward into Irondequoit Bay (fig. 3). 

Irondequoit Creek receives drainage from 

the east side of the City of Rochester as 

well as from adjacent Ontario and Wayne 

counties. The Erie (Barge) Canal crosses 

the middle of the basin from east to west. 

During the navigation season, water from 

the canal is diverted into Irondequoit Creek 

and some of its tributaries to augment flow 

in those streams during low-flow conditions. 

The headwaters (southern parts) of the basin 

are generally rural and agricultural, whereas 

the central and northern parts are urbanized.

The Irondequoit Creek basin was the 

original focal point of long-term waterresources study because Irondequoit Bay 

has been eutrophic for several decades due 

to the adverse effects on water quality of 

the sewage, sediments, and nutrients that 

are transported to the Bay by Irondequoit 

Creek. The discharge of treated sewage to 

Irondequoit Creek was eliminated in 1979, 

when the County Wastewater Treatment 

Facility along the shore of Lake Ontario 

began operation.

Streamflow and water-quality data have 

been collected at seven sites in the basin 

since 1984 (fig. 3). Four of the sites are 

currently active—Irondequoit Creek at 

Blossom Road (since 1984), Irondequoit 

Creek at Railroad Mills (streamflow since 

1991 and water quality since 1992), Allen 

Creek near Rochester (streamflow since 

1959 and water quality since 1984), and 

East Branch Allen Creek at Pittsford (since 

1991); the three discontinued (inactive) sites 

are Irondequoit Creek at Pittsford (1984-

90), Irondequoit Creek at Linden Ave. 

(1984-88), and Thomas Creek at Fairport 

(1984-88). 

Mean Annual Constituent Loads

Mean annual constituent loads calculated 

for the four active and three inactive sites 

in the Irondequoit Creek basin are given 

in table 1. The greatest mean annual loads 

for all constituents among the active sites, were at Irondequoit Creek 

at Blossom Road (fig. 4), although the mean annual load of ammonia 

at Irondequoit Creek at Linden Avenue (an inactive site) was higher 

during its period of record than at Blossom Road. Generally, the 

East Branch Allen Creek site (which has the smallest drainage area 

and the lowest mean annual flow) had the lowest mean annual loads 

of all constituents for all sites, but this site had the highest yields of 

orthophosphate and nitrite + nitrate. 
5

1 2 3 4 5 6 7 8 9 100

1,000,000

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

1 2 3 4 5 6 7 8 9 0.1

1,000

0.2

0.5

1

2

5

10

20

50

100

200

500

1 2 3 4 5 6 7 8 9 1

1,000

2

5

10

20

50

100

200

500

1 2 3 4 5 6 7 8 9 0.1

100

0.2

0.5

1

2

5

10

20

50

1 2 3 4 5 6 7 8 9 1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

1 2 3 4 5 6 7 8 9 10

10,000

20

50

100

200

500

1,000

2,000

5,000

1 2 3 4 5 6 7 8 9 1,000

1,000,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

1 2 3 4 5 6 7 8 9 100

1,000,000

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

TOTAL SUSPENDED SOLIDS AMMONIA TOTAL

PHOSPHORUS

ORTHOPHOSPHATE AMMONIA + ORGANIC

NITROGEN

NITRITE + NITRATE

DISSOLVED

CHLORIDE

DISSOLVED SULFATE

Inactive Irondequoit Creek Basin sites

Active Irondequoit Creek Basin sites

Sites outside Irondequoit Creek Basin

���������������������������������������

6. Irondequoit Creek at Railroad Mills (1992-2001)

7. Irondequoit Creek at Blossom Road (1984-2001)

8. Northrup Creek near North Greece (1990-2001)

9. Genesee River at Charlotte Pump Station

at Rochester (1990-2001)

1. Irondequoit Creek at Pittsford (1984-90)

2. Thomas Creek at Fairport (1984-88)

3. Irondequoit Creek at Linden Ave. (1984-88)

4. East Branch Allen Creek at Pittsford (1991-2001)

5. Allen Creek near Rochester (1984-2001)

�����������

SITE SITE

SITE

LOAD, IN TONS

Figure 4. Mean annual loads of selected constituents at nine sites in Monroe County, N.Y., for period of record. 

(Locations are shown in fig. 1.)
6

Constituent Yields

�������� Statistical summary of annual loads, and results of trend tests on loads of selected flow-adjusted

constituents, at three inactive and four active sites in the Irondequoit Creek basin, Monroe County, N.Y.,

 for period of record.

[����������������������������������������������������������������� ��������� ����������������������������������������������������

������]

Mean

annual

Maximum Minimum Units per 

year

percent

Discharge and constituent Value Year Value Year per year �

��������������

����������������������������������������

��������������������������������� ���� ���� ���� ���� ���� ����� ���� ����

Total suspended solids 6,190 9,400 1990 3,590 1989 ���� ���� ���

������� ���� ���� ���� ���� ���� ����� ���� ���

�������������������������� ���� ���� ���� ���� ���� ���� �� ���

����������������� ���� ���� ���� ���� ���� ���� ���� ���

���������������� ���� ���� ���� ���� ���� ���� ���� ���

�������������� ���� ���� ���� ���� ���� �� �� ��

������������������ ����� ����� ���� ����� ���� ���� ��� ���

����������������� ����� ����� ���� ����� ���� ���� ��� �

����������������������������������

��������������������������������� ���� ���� ���� ���� ���� ����� ����� ���

���������������������� ��� ��� ���� ��� ���� ���� ��� ���

Ammonia 0.92 1.55 1984 0.37 1988 ����� ����� ���

�������������������������� ���� ���� ���� ���� ���� ����� ���� ���

����������������� ���� ���� ���� ���� ���� ���� ����� ���

���������������� ���� ���� ���� ���� ���� ���� ��� ���

�������������� ���� ���� ���� ���� ���� ���� ��� ���

������������������ ����� ����� ���� ����� ���� ���� ��� ���

����������������� ����� ����� ���� ����� ���� ���� ��� ���

������������������������������������������

��������������������������������� ���� ��� ���� ���� ���� ����� ���� ���

���������������������� ����� ������ ���� ����� ���� ���� ��� ���

������� ���� ���� ���� ���� ���� ����� ����� ���

�������������������������� ���� ��� ���� ���� ���� ���� ���� ���

����������������� ��� ��� ���� ���� ���� ���� ���� ���

���������������� ���� ���� ���� ���� ���� ��� ���� ���

�������������� ���� ���� ���� ���� ���� ����� ��� �

������������������ ����� ����� ���� ����� ���� ���� ��� ���

����������������� ������ ������ ���� ������ ���� ���� ��� ���

 Annual Load Flow-adjusted trend

Among the active sites, the highest yields of ammonia 

(0.03 tons per square mile), ammonia + organic nitrogen 

(0.93 tons per square mile), and chloride (175 tons per 

square mile) were at the Allen Creek site, and the highest 

yields of orthophosphate (0.024 tons per square mile) and 

nitrite + nitrate (1.44 tons per square mile) were at the East 

Branch Allen Creek site (fig 5). The highest yields of total 

phosphorus were at Irondequoit Creek at Blossom Road. 

The lowest yields of all constituents except suspended 

solids and dissolved sulfate were at the most upstream 

Irondequoit Creek site, Railroad Mills. Among the inactive 

sites, the highest yields of ammonia, ammonia + organic 

nitrogen, nitrite + nitrate, and chloride were at Irondequoit 

Creek at Linden Ave. The lowest yields of all constituents 

except ammonia, orthophosphate, and dissolved chloride 

were at Thomas Creek. The high yields of dissolved 

sulfate at Railroad Mills were reflected at the Pittsford site 

(inactive), about 2 miles downstream.
7

�������� Statistical summary of annual loads, and results of trend tests on loads of selected flow-adjusted 

constituents, at three inactive and four active sites in the Irondequoit Creek basin, for period of record (continued).

 Annual Load

Mean 

annual

Maximum Minimum Units per 

year

percent 

Discharge and constituent Value Year Value Year per year �

������������

������������������������������������������������

��������������������������������� ���� ���� ���� ���� ���� ���� ��� ���

Total suspended solids 1,100 1,580 1998 475 2001 ���� ���� ���

������� ���� ����� ������������ ����� ���� ����� ���� ���

Ammonia + organic nitrogen 7.18 9.95 1993 3.32 1999 ���� ���� ����

����������������� ���� ���� ���� ����� ���� ���� ���� ���

���������������� ���� ����� ���� ����� ���� ���� ���� ���

�������������� ���� ����� ���� ����� ���� ������ ���� ���

Dissolved chloride 1,120 1,720 2000 692 1995 ��� ��� ����

����������������� ��� ��� ���� ��� ���� ��� ��� ���

��������������������������������������

��������������������������������� ���� ���� ���� ���� ���� ���� ���� ���

���������������������� ����� ������ ���� ������ ���� ���� ��� ���

Ammonia 0.94 2.28 1984 0.21 1995 ����� ���� ���

Ammonia + organic nitrogen 28.1 50.6 1984 10.5 1998 ���� ���� ����

����������������� ���� ����� ���� ����� ���� ���� ���� ���

���������������� ���� ����� ���� ����� ���� ������ ���� ���

�������������� ���� ����� ���� ����� ��������� ����� ��� ���

Dissolved chloride 5,260 7,040 1996 3,520 1988 ��� ��� ����

Dissolved sulfate 1,810 2,980 1994 1,170 1995 ����� ���� ���

���������������������������������������������

��������������������������������� ��� ��� ���� ���� ���� ���� ��� ���

���������������������� ������ ������� ���� ������ ���� ����� ���� ���

Ammonia 3.44 9.02 1984 0.98 2001 ����� ���� ����

Ammonia + organic nitrogen 133 209 1986 52.6 1999 ���� ���� ����

����������������� ��� ��� ���� ����� ���� ����� ���� ���

���������������� ���� ����� ���� ���� ���� ������ ���� ���

�������������� ���� ����� ���� ����� ���� ������ ���� ���

Dissolved chloride 16,400 21,000 1993 11,600 1988 ���� ��� ����

����������������� ������ ������� ���� ������� ���� ���� ���� ���

������������������������������������������������ ��

��������������������������������� ���� ���� ���� ���� ���� ����� ��� � ����

���������������������� ����� ������� ���� ����� ���� �� �� ��

������� ���� ���� ���� ���� ���� ����� ���� ���

Ammonia + organic nitrogen 22.9 47.3 1993 11.9 1999 ����� ���� ���

����������������� ���� ���� ���� ���� ���� ���� ��� ���

���������������� ���� ���� ���� ���� ���� ����� ���� ���

�������������� ���� ���� ���� ���� ���� ����� ��� ���

Dissolved chloride 2,750 3,420 1998 1,840 1995 ��� ��� ����

����������������� ����� ����� ���� ����� ���� ��� ��� ���

Flow-adjusted trend
8

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

-0.2

2.5

0

0.5

1.0

1.5

2.0

CONCENTRATION, IN MILLIGRAMS PER LITER

PHOSPHORUS, TOTAL

LOWESS TREND LINE

Improved phosphorus treatment at

Spencerport waterwater-treatment plant

Figure 5. Concentrations of total phosphorus in samples from Northrup Creek with LOWESS trend line before and 

after implementation of improved phosphorus treatment at the Spencerport wastewater-treatment plant, Monroe 

County, N.Y., during August 1995. (Locations are shown in fig. 1.)

Trends

All active sites in the Irondequoit Creek basin showed 

significant downward trends in flow-adjusted loads 

of ammonia + organic nitrogen (table 1), probably 

as a result of the gradual loss of agricultural lands to 

suburban development. Annual loads of ammonia 

showed a significant downward trend at the Allen Creek 

and Blossom Road sites, as did suspended solids at the 

East Branch Allen Creek site. The downward trend in 

suspended solids at this site is a result of a stormwaterdetention basin that was constructed upstream during the 

summer of 1995 to allow settling (removal) of suspended 

material. Annual loads of chloride showed an upward trend 

at all sites.

Two of the three inactive sites had the minimum 

recommended period of record (5 years) for trend 

analysis. Only two statistically significant trends were 

noted at these sites—Thomas Creek, which showed a 

downward trend in ammonia, and Irondequoit Creek at 

Pittsford, which showed an upward trend in suspended 

solids.

NORTHRUP CREEK

Long Pond, a shallow embayment along the southern 

edge of Lake Ontario (fig. 1) has become hypereutrophic 

(overly enriched with nutrients) in recent years as a result 

of nitrogen and phosphorus transported to those waters by 

Northrup Creek. An overabundance of these nutrients has 

resulted in the development of algal mats and decaying 

algal clumps that cause odors, discolor the water, and 

interfere with the esthetic quality of the pond and its 

recreational uses.

In 1989, the Monroe County Department of Health 

and the Town of Greece, in cooperation with the USGS, 

began a monitoring program on Northrup Creek at a 

site about 5 mi north of the Spencerport wastewatertreatment plant to assess nutrient loads being delivered 

to Long Pond by Northrup Creek (Sherwood, 1999a). 

The program entailed the collection and analysis of water 

samples and streamflow data for calculation of chemical 

loads. Northrup Creek begins just south of the village of 

Spencerport and flows about 10.5 miles northward into 

Long Pond. Northrup Creek’s 23.5-square-mile basin 

contains agricultural land, housing developments, and 

a small amount of urban land. The major contributor of 

nutrients (particularly phosphorus) to Northrup Creek 

is the Spencerport wastewater-treatment plant. In 1995, 

the plant began a program to improve the removal of 

phosphorus from the effluent.

Total phosphorus loads in Northrup Creek during 

1990-2001 averaged 3.80 tons per year, whereas 

orthophosphate loads averaged 1.54 tons per year (table 

2). Yields of nutrients in the Northrup Creek basin were 

considerably higher than any of those in Irondequoit 

Creek or the Genesee River (fig. 6). Trend testing of 

flow-adjusted loads indicated one constituent (total 

phosphorus) with a significant downward trend (fig. 5), 

which is attributed to the improved wastewater treatment 

(Sherwood, 2003), and two constituents (dissolved chloride 

and dissolved sulfate) with significant upward trends.
9

�������� Statistical summary of annual loads and results of trend tests on loads of selected flow-adjusted

constituents at Northrup Creek at North Greece, Monroe County, N.Y., 1990 through 2001.

[����� ��� �� ����� �������� ���� ��������� ����� �� ���������� �� � � ����� � ����� �� ����������������� �������� �� �����������������

 Annual Load

Mean

Maximum Minimum Units per 

year

percent

Discharge and constituent Value Year Value Year per year �

��������� ������ ���� ��� ������� ���� ���� ���� ���� ���� ���� ���� ����

���������������������� ����� ����� ���� ��� ���� ���� ���� ���

������� ���� ���� ���� ���� ���� ���� ��� ���

�������������������������� ���� ���� ���� ��� ���� ���� ���� ���

����������������� ���� ���� ���� ���� ���� ��� ��� ���

Total phosphorus 3.80 4.79 1993 ���� 2001 ���� ���� ���

�������������� ���� ���� ���� ���� ���� ���� ���� ���

Dissolved chloride 1,260 1,750 2001 ��� 1995 ���� ��� ���

Dissolved sulfate 657 920 1998 ��� 1995 ���� ��� ���

� �

Flow-adjusted trend

�������� Statistical summary of annual loads and results of trend tests on loads of selected flow-adjusted 

constituents at Genesee River at Charlotte Pump Station, Rochester, N.Y., 1990 through 2001.

[����������������������������������������������������������������� � ������� �������� �� ����������������� �������� �� �����������������

Discharge and constituent Mean 

Maximum Minimum Units per 

year

percent 

Value Year Value Year per year �

��������������������������������� ����� ����� ���� ����� ���� ����� ���� ����

���������������������� ������� ������� ���� ������� ���� ����� ���� ���

������� ��� ��� ���� ��� ���� ����� ���� ���

Ammonia + organic nitrogen 1,780 2,420 1993 830 1999 ����� ���� ����

����������������� ����� ����� ���� ����� ���� ����� ���� ���

���������������� ��� ��� ���� ��� ���� ����� ���� ���

Orthophosphate 51 77 1998 31 1989 ���� ��� ����

Dissolved chloride 134,000 186,000 1991 71,400 1999 ����� ���� ���

����������������� ������� ������� ���� ������ ���� ���� ���� ���

 Annual Load Flow-adjusted trend

GENESEE RIVER

The Genesee River flows northward from the New 

York-Pennsylvania border through Monroe County and 

Rochester into Lake Ontario. Its basin contains 2,480 

square miles and is primarily agricultural except in the 

City of Rochester, where it is urban. Flow of the Genesee 

River at Rochester has been monitored since 1919, and 

water-quality monitoring began in 1971 at Charlotte Docks 

under the USGS National Stream Quality Accounting 

Network (NASQAN) program. In 1989, Monroe County 

began collection and analysis of water-quality data from 

the Genesee River at the Charlotte Pump Station, about 1 

mile north (downstream) from the NASQAN site (fig. 1). 

The annual constituent loads (table 3) are based on data 

collected by Monroe County at the Charlotte Pump Station.

The Genesee River annually transports 362,000 tons of 

suspended solids, 134,000 tons of dissolved chloride, and 

147,000 tons of dissolved sulfate to Lake Ontario (fig. 4). 

Nutrients are transported at the rate of 1,780 tons per year 

for ammonia + organic nitrogen, 3,060 tons per year for 

nitrite + nitrate, and 347 tons per year for total phosphorus. 

Yields of all constituents in the Genesee River basin were 

within the range of those found in the Irondequoit Creek 

basin (fig. 6). Ammonia + organic nitrogen and dissolved 

chloride showed significant downward trends, whereas 

orthophosphate showed a significant upward trend.

Water-quality monitoring has been started on three 

tributaries to the Genesee River—Black Creek, Honeoye 

Creek, and Oatka Creek (fig. 1). The period of record is 

too short at present for statistical analysis, however. 
10

Figure 6. Mean annual yield of selected constituents at nine sites in Monroe County, N.Y., for period of record. 

(Locations are shown in fig. 1.)

0

300

100

200

0

0.25

0.05

0.10

0.15

0.20

0

0.4

0.1

0.2

0.3

0

0.20

0.05

0.10

0.15

0.4

1.6

0.6

0.8

1.0

1.2

1.4

1.6

0.8

2.0

1.0

1.2

1.4

1.6

1.8

1 2 3 4 5 6 7 8 9 0

200

50

100

150

1 2 3 4 5 6 7 8 9 40

160

60

80

100

120

140

TOTAL SUSPENDED SOLIDS AMMONIA TOTAL PHOSPHORUS

ORTHOPHOSPHATE AMMONIA + ORGANIC

NITROGEN

NITRITE + NITRATE

DISSOLVED DISSOLVED

SULFATE CHLORIDE

Inactive Irondequoit Creek Basin sites

Active Irondequoit Creek Basin sites

Sites outside Irondequoit Creek Basin

�����������

SITE SITE

1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9

SITE

1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9

1 2 3 4 5 6 7 8 9

���������������������������������������

1. Irondequoit Creek at Pittsford (1984-90) 6. Irondequoit Creek at Railroad Mills (1992-2001)

2. Thomas Creek at Fairport (1984-88) 7. Irondequoit Creek at Blossom Road (1984-2001)

3. Irondequoit Creek at Linden Ave. (1984-88) 8. Northrup Creek near North Greece (1990-2001)

4. East Branch Allen Creek at Pittsford (1991-2001) 9. Genesee River at Charlotte Pump Station

5. Allen Creek near Rochester (1984-2001) at Rochester (1990-2001)

YIELD, IN TONS PER SQUARE MILE
11

SUMMARY

Hydrologic data collected in Monroe County since 

the 1980’s and earlier, including long-term records 

of streamflow and chemical loads, provide a basis 

for assessment of water-management practices. All 

monitored streams except Northrup Creek showed a slight 

(nonsignificant) overall decrease in annual streamflow 

over their period of record; Northrup Creek showed a 

slight increase. 

The highest yields of all constituents except chloride 

and sulfate were at Northrup Creek; these values exceeded 

those of the seven Irondequoit Creek basin sites and 

the Genesee River site. The highest yields of dissolved 

chloride were at the most highly urbanized site (Allen 

Creek), whereas the highest yields of dissolved sulfate 

were at the most upstream Irondequoit Creek sites—

Railroad Mills (active) and Pittsford (inactive). Yields of 

all constituents in the Genesee River at the Charlotte Pump 

Station were within the range of those at the Irondequoit 

Creek basin sites.

The four active Irondequoit Creek basin sites showed 

significant downward trends in flow-adjusted loads 

of ammonia + organic nitrogen, possibly from the 

conversion of agricultural land to suburban land. Two 

active sites (Allen Creek and Blossom Road) and one 

inactive site (Thomas Creek) showed downward trends 

in loads of ammonia. All active sites showed significant 

upward trends in dissolved chloride loads. Northrup 

Creek showed a significant downward trend in total 

phosphorus load since the improvement in phosphorus 

removal at the Spencerport wastewater-treatment plant, 

and upward trends in dissolved chloride and sulfate 

loads. The Genesee River at the Charlotte Pump Station 

showed significant downward trends in loads of ammonia 

+ organic nitrogen and chloride, and an upward trend in 

loads of orthophosphate.

The improved treatment or diversion of sewagetreatment-plant-effluent has produced decreased yields of 

some constituents throughout the county, particularly in 

the Irondequoit Creek basin, where the loads of nutrients 

delivered to Irondequoit Bay have been decreased.

REFERENCES CITED

Cohn, T.A., Caulder, D.L., Gilroy, E.J., Zynjuk, L.D., 

and Summers, R.M., 1992, The validity of a simple 

statistical model for estimating fluvial constituent 

loads—an empirical study involving nutrient loads 

entering Chesapeake Bay: Water Resources Research, 

v. 28, no. 9, p. 2353-2363.

Heffner, R.L., and Goodman, S.D., 1973, Soil survey 

of Monroe County, New York: U.S. Department of 

Agriculture, 172 p.

Hirsch, R.M., Slack, J.R., and Smith, R.A., 1982, 

Techniques of trend analysis for monthly water quality 

data: Water Resources Research, v. 18, no. 1, p. 107-121.

Johnston, W.H., and Sherwood, D.A., 1996, Water 

Resources of Monroe County New York, Water 

Years 1984-88, with emphasis on water quality in the 

Irondequoit Creek basin, part 2: U.S. Geological Survey 

Water-Resources Investigations Report 96-4054, 84 p.

National Oceanic and Atmospheric Administration, 

1983-99, Climatological data annual summary, New 

York: Asheville, N.C., National Climatic Data Center, 

no. 13, v. 106-108 [issued annually].

Sherwood, D.A., 1999a, Phosphorus loads entering 

Long Pond, a small embayment of Lake Ontario near 

Rochester, New York: U.S. Geological Survey Fact 

Sheet FS-128-99, 4 p.

Sherwood, D.A., 1999b, Water Resources of Monroe 

County New York, Water Years 1989-93, with 

emphasis on water quality in the Irondequoit Creek 

basin, part 2: U.S. Geological Survey Water-Resources 

Investigations Report 99-4084, 50 p.

Sherwood, D.A., 2001, Water Resources of Monroe 

County New York, Water Years 1994-96, with 

emphasis on water quality in the Irondequoit Creek 

basin: U.S. Geological Survey Water-Resources 

Investigations Report 00-4201, 39 p.

Sherwood, D.A., 2003, Water Resources of Monroe 

County New York, Water Years 1997-99, with 

emphasis on water quality in the Irondequoit Creek 

basin: U.S. Geological Survey Water-Resources 

Investigations Report 02-4221, 55 p.
Irondequoit Bay

FOR MORE INFORMATION: 

Subdistrict Chief

U.S. Geological Survey

30 Brown Rd.

Ithaca, N.Y. 14850

Copies of this report can be 

purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver, CO 80225-0286

This report and additional earth science information can be found on the World Wide Web at http://ny.usgs.gov