4. Human Use of the Watershed 2: Water Issues
4.1. Water Use of the Salmon River Watershed
Water is an essential commodity to mankind, and the largest available source of
fresh water lies underground. Increased demands for water have stimulated development
of underground water supplies. Inevitably, when progress magnifies and adds new
problems, efforts are increased to solve these problems. This is especially true for ground
water. Methods for investigating the occurrence and movement of groundwater have
been improved, better means for extracting ground water have been developed, principles
of conservation have been established, and research of several types has contributed to a
better understanding of the subject. As a result, knowledge of groundwater hydrology,
once veiled in mystery, has expanded rapidly. Anticipating the ever-increasing use of
ground water, it is reasonable to presume that such knowledge will grow at an even
greater rate in the future (Todd 1959, Black 1991, Hornberger et al. 1998).
Groundwater begins with rain and snowmelt that seeps into the ground. The
amount of water that seeps into the ground varies widely from place to place according to
the type of land surface that is present. In forested watersheds, most of the rain and
snowmelt may seep into the ground. In less porous surface material, where seepage is
much slower, perhaps only 5% will seep into the ground. The remainder of the rain and
snowmelt runs off the land surface into streams, rivers, or other water bodies or returns to
the clouds by evaporation and evapotranspiration. Ground seepage is also strongly
influenced by the season of the year. Evaporation is greater during the warm months, and
during cold months, the ground surface is frozen and hinders water seepage. (Raymond
1988). In the Salmon River watershed, much of that seepage occurs during the spring
thaw, as this region receives well over 180 inches (0.457 m rainfall equivalent) of
snowfall per year during the winter months.
4.1.1. Water Withdrawals
The large Tug Hill Aquifer travels beneath the Salmon River watershed. This
finger-like aquifer stretches from northern-central Jefferson County through the easterncentral portion of Oswego County, and on into northwest Oneida County. In the Salmon
River Watershed, the aquifer encompasses towns of the eastern basin including Altmar,
Pineville, Richmond, and Orwell. Groundwater is the major source of water for residents
living on, or in some places, adjacent to the Tug Hill Aquifer. Before 1960, groundwater
use was low because development was sparse. Most groundwater withdrawals were from
springs, dug wells, and some drilled wells that supplied homes, farms, and small
communities. After 1960, people began to realize that some parts of the aquifer could
yield large quantities of water. Since 1960, a paper company (Schoeller Technical Papers
Inc.) and a fish hatchery (the Altmar Fish Hatchery) have developed well fields that yield
as much as 1.5 and 2.3 million gallons (5,454 and 8,364 m3) per day respectively (Krebs
et al. 1986). The Altmar Fish Hatchery, the only facility with permits to draw surface
water from the area, also receives water from the lower Salmon River reservoir in
addition to the aquifer (Stephen Murphy, Reliant Energy, personal communication 4/02).
Table 4-1 summarizes the two industries, two private water systems, and the two
municipal community water systems there are in this watershed. All other establishments
Salmon River Watershed Chapter 4
43
in the watershed have wells that are outside of the aquifer area, which tap into the general
water table of that particular area.
Source
Population Served
(approximate)
Average Pumpage
(Mgal/d)
250
2500
.02
.25
350
400
.03
.04
-----
2.3
1.5
Municipal
Community Water
Systems
Hamlet of Orwell
Village of Pulaski
Private
Water Systems
Village of Altmar
Hamlet of
Richmond
Industry
Fish Hatchery
Paper Company
Table 4-1: Types of system, approximately how many people the water system serves,
and how much is pumped out on a daily basis from the Tug Hill Aquifer. These numbers
do not reflect the many wells around the Salmon River watershed that do not tap into the
main aquifer but do withdrawal groundwater. Data taken from Krebs et al. 1986.
4.1.2. Point-source discharges
Based upon United States Environmental Protection Agency data
(http://oaspub.epa.gov/enviro2002), there currently are two, or possibly three, water
discharge facilities in the Salmon River Watershed (as of April 2002). All three have
registered with the EPA and have obtained permits to discharge foreign bodies into
tributaries of the Salmon River, or into the Salmon River itself.
a. Schoeller Technical Papers Inc. direct discharge to the Salmon River by permit
Barium compounds (80 lbs/yr) Smaller amounts of:
Ethylene glycol (3670 lbs/yr)
Lead
N-butyl alcohol (4207 lbs/yr)
Copper
Zinc
Chromium
Aluminum
Chloroform
Phenols
1, 1 – dichloroethelene
1, 1, 1 – trichloroethane
1, 2 – dichloropropane
Formaldehyde
Salmon River Watershed Chapter 4
44
b. Altmar Fish Hatchery Direct Discharge to Beaver Creek
Hydrogen peroxide
Chloramine
Ammonia
Potassium permanganate
Phosphorus
Chlorine
Chloride (1 and 3% solutions
Coliform
Terramycin
Suspended and settleable solids
Formalin
c. Brennan Beach discharge to Lake Ontario
Chlorine
Coliform particulate matter
Phosphorus
Suspended and settleable solids
The third facility that has a permit to discharge substances into the Salmon River
Watershed are the Brennan Beach Campgrounds. Although this facility is located about
2 miles north of the Salmon River, it is possible that their sand filter discharge of sewage
travels south into the watershed. Well tests south of the facility would be able to
determine if this was the case.
Historically, there has been a wastewater treatment plant in the city of Pulaski.
Very recently, due to poor practice this facility has lost its permit to discharge water. The
following compounds were discharged directly into the Salmon River via pipe, and
although not currently operating, may still have an impact on the watershed:
d. Pulaski Wastewater Treatment Plant discharge to the Salmon River
Chlorine
Coliform particulate matter
Suspended and settleable solids
4.2. Hydroelectric power generation in the watershed
Hydroelectric power is currently the world’s largest renewable energy source,
accounting for between 15 and 24% of the world’s electricity (Baird 1993). It is
estimated that hydroelectric power supplies over one billion individuals with electricity
worldwide (National Renewable Energy Laboratory 1998). In 1998, hydroelectric power
facilities produced over 2.3 trillion kilowatt-hours of electricity, which is equivalent to
approximately 3.6 billion barrels of oil (National Renewable Energy Laboratory 1998).
Hydroelectric power is generated from the energy present in flowing water. Falling water
is channeled through a turbine that converts the water’s energy into mechanical power.
Salmon River Watershed Chapter 4
45
The power that is generated is then transported to a generator, which produces electricity
(Baird 1993). The amount of power or energy that is generated depends on both the
volume of water flow measured as volume per unit time and the amount of “head”
created by the dam (Baird 1993). The head is the vertical distance from the turbines in
the power plant to the surface of the water body.
A typical hydroelectric power facility includes a dam, reservoir, pipes or
penstocks, a powerhouse, and an electrical power substation. Dams hold back a
tremendous amount of water, which is stored in a reservoir. Near the bottom of the dam
wall there is the water intake, at which gravity causes the water from the reservoir to fall
through the penstock inside the dam. At the end of the penstock there is a turbine
propeller, which is turned by the moving water (USGS 2001). The turbine is connected to
a generator, which uses the rotating propeller to generate power. The generator is
connected to power lines that transfer the energy produced by the hydroelectric facility to
residential homes and businesses. After the water is passed through the propeller of the
generator, it then passes through a tailrace on the other side of the dam and continues to
flow downstream (USGS 2001)
4.2.1. Layout of dams and hydroelectric plants on the Salmon River
There are two hydroelectric power facilities/dam structures located on the Salmon
River. They are the Bennetts Bridge operation and the Lighthouse Hill facility. The total
drainage basin area for Bennetts Bridge and Lighthouse Hill are 191 mi2 (495 km2) and
198 mi2 (513 km2), respectively (Niagara Mohawk 1993). The Salmon River Reservoir
is located between the hamlets of Redfield and Orwell and is the major regulating water
body in the drainage basin. It is located downstream from the confluence of the
following tributaries: the north branch of the Salmon River, Mad River, Mill Stream,
Fall Brook, as well as the east and west forks of the Salmon River.
Figure 4-1. Partial map of Oswego County, showing location of reservoirs. (Source: Oswego County)
The Salmon River Reservoir is also known as the Bennetts Bridge, Stillwater, or
Redfield Reservoir. It is 3,550 acres (1,437 ha) in size and is surrounded by little
development (Niagara Mohawk 1993). The Salmon River Reservoir is used to store
excess runoff during spring peak flow periods and this water is later released during
Salmon River Watershed Chapter 4
46
summer low flow periods. The Bennetts Bridge facility discharges into the Lighthouse
Hill Reservoir, which is the only other water body with any flood-control function on the
Salmon River. It is much smaller that the Salmon River Reservoir, covering an area of
170 acres (Niagara Mohawk 1993). The land surrounding the Lighthouse Hill Reservoir
is almost completely undeveloped. The current summer base flows in the Salmon River
are approximately 2.5 times greater than natural summer low flow periods (USGS water
records, comparing Salmon River to Sandy Creek, and adjacent, unregulated drainage).
The energy generated by the Salmon River Reservoir is integrated into the Reliant
Energy power grid, which provides upstate New York customers with 5.1 MW of power
(Orion Power 2001).
4.2.2. Bennetts Bridge Facility
The Bennetts Bridge hydroelectric facility is located approximately 18 miles (29
km) from the point where the Salmon River and Lake Ontario converge (Niagara
Mohawk 1993). Construction of the dam began in 1913 and was concluded in 1914. The
Bennetts Bridge hydroelectric facility consists of a concrete gravity dam, as well as three
earthen dikes, which together form the six-mile long Salmon River Reservoir (Niagara
Mohawk 1993). Water is transported by a 3,000-meter long pipe to a powerhouse which
contains four turbine generator units. Water is then released from the powerhouse into the
Lighthouse Hill Reservoir (Niagara Mohawk 1993).
The Bennetts Bridge powerhouse functions primarily as a store and release
facility that operates in peaking mode. Originally, the peaking operation of the facility
resulted in the flows out of the reservoir unequal to the inflows. Steps have been taken to
ensure that the water levels on the portion of the Salmon River downstream of the dam
are never extremely low. The powerhouse is 63 meters long by 21.3 meters wide and is a
concrete structure with a brick and steel superstructure (Niagara Mohawk 1993). The
tailrace channel of the Bennetts Bridge facility joins up with the Light House Hill
Reservoir approximately 290 meters downstream of the powerhouse.
Annual operation of the Bennetts Bridge facility is based on the regulation of the
Salmon River Reservoir. The typical reservoir inflow during the springtime runoff
average is 1,500 cubic feet per second (cfs) (Niagara Mohawk 1993). In addition, the
average maximum seasonal draw down level of the Salmon River Reservoir is
approximately 7 meters below the normal level of 285 meters (Niagara Mohawk 1993).
The maximum hydraulic capacity of the facility is 1,800 cfs (Niagara Mohawk 1993).
Table 4-2. Bennetts Bridge Facility specifications (adapted from Niagara Mohawk 1993).
Bennetts Bridge
Nameplate Rating
31,500 KW
Normal Max Surface Elevation
937 Feet
Normal Max Surface Area
3,550 Acres
Gross Storage Capacity
66,000 Acre-Feet
Usable Storage Capacity
56,000 Acre-Feet
Salmon River Watershed Chapter 4
47
The dam utilized by the Bennetts Bridge hydroelectric power facility is a 185
meter long concrete gravity structure which is 13.7 meters high at the tallest point. The
dam consists of the following sections (Niagara Mohawk 1993):
a) 32.6 m long non-overflow section with a permanent crest elevation of 284 m
b) 74.4 m long ungated spillway section with a 285 m permanent crest elevation
c) 78 m long gated spillway section which contains eleven, 3.5 m high by 6 m
wide tainter gates with a permanent crest elevation of 282 m.
4.2.3. Lighthouse Hill Facility
The Lighthouse Hill hydroelectric facility, which is located east of the village of
Altmar, is positioned approximately one mile downstream of Bennetts Bridge
powerhouse. The Lighthouse Hill powerhouse and the Bennetts Bridge facility operate
together with the same store and release patterns. The Salmon River Falls, which is over
100 feet high (30 m) at its tallest point, is located between the two hydroelectric facilities
and discharges directly into the Lighthouse Hill Reservoir (Niagara Mohawk 1993). The
New York State Department of Conservation (NYSDEC) operates a fish hatchery
approximately 2.5 km downstream of the facility.
The Lighthouse Hill powerhouse, like the Bennett Bridge facility, operates in
peaking mode. The Lighthouse Hill facility is a 1,311 m impoundment formed by a
116.4 m long concrete gravity dam, a 99 m long by 12.2 m wide earthen dike, a
powerhouse, and 4.6 m long sluice gate (Niagara Mohawk 1993). The 38.4 m long by
19.2 m wide Lighthouse Hill powerhouse has a concrete structure and a brick and steel
superstructure (Niagara Mohawk 1993). Pipes emerging from the powerhouse discharge
water into a 12.2 m wide tailrace channel which joins the Salmon River 853 m
downstream of the facility (Niagara Mohawk 1993). The maximum hydraulic capacity of
the Lighthouse Hill powerhouse is 2,000 cfs.
Construction of the Lighthouse Hill dam was began in 1929 and was completed in
1930. The Lighthouse Hill dam consists of the following components (Niagara Mohawk
1993):
a) 47.2 m long non-overflow section with a permanent crest elevation of 200 m
b) 13.1 m long ungated spillway with a permanent crest elevation of 198 m
c) 56 m long gated spillway section housing eight, 6.1 m wide by 2.1 m high
tainter gates with a permanent crest elevation of 196 m.
4.2.4. Environmental Iimpacts of Hydroelectric Power
Hydroelectric power generation, like all other energy sources, has impacts on the
environment. Hydroelectric power is often viewed as a clean and environmentally safe
method of producing electricity. This belief is rooted in the fact that hydroelectric power
facilities do not emit any of the atmospheric pollutants such as carbon dioxide or sulfur
dioxide which are given off by fossil fuel powered facilities. This lack of harmful
pollutants is definitely a positive aspect of hydropower operation, but there are also
Salmon River Watershed Chapter 4
48
negative effects that these facilities have on the aquatic ecosystems in which they are
located.
Dams and reservoirs can also have impacts on a watershed. Damming a river can
prevent migrating fish, such as salmon, from traveling upstream to spawn. These impacts
can be minimized with the construction of fish ladders that allow fish to move upstream
past the dam. In addition, silty materials that are normally transported by the river
downstream are held by the dam and deposited in the reservoir. This silt can build up
over time and reduce the storage capacity of the reservoir. The downstream portion of
the river is also deprived of silt, which fertilizes the river’s flood plain during high flow
periods (Baird 1993).
The operation of hydroelectric power facilities can also decrease the amount of
recreation occurring in the Salmon River in areas close to the operation. The water
flowing from the dam can be dangerous to anyone who ventures too close, due to the
magnitude and force of the flowing water.
The reservoirs located with the Salmon River watershed can negatively affect the
water temperatures of the Salmon River. The Salmon River and Lighthouse Reservoirs
both increase the annual water temperatures of the Salmon River, resulting in warmer
water later into the autumn season (see Section 4.4 below). Warmer water temperatures
in the Salmon River can be undesirable to coldwater adapted fish and other aquatic
organisms inhabiting the water body. Fish are unable to regulate their own body
temperatures and as a result, when water temperatures rise, their metabolic rates also
increase and they require more food to survive (Geis 1982). Furthermore, fish undergo
physiological stress at temperatures above their thermal optima, and may die at elevated
temperatures. Some aquatic macroinvertebrates, which are the major food source for the
fish species in the Salmon River, are also unable to tolerate higher water temperatures
and therefore may not be available to the fish to supplement the increased consumptive
demands of fish. On the other hand, other macroinvertebrate taxa appear to be increasing
with warmer temperature (Chapter 2).
In addition to prolonging the warmer water temperatures in the Salmon River
during the fall season, the reservoirs are also not deep enough the provide cold water to
the lower reaches of the river. During the summer months of July and August, the
average lower reservoir water temperature is approximately 72 – 74 °F (22 – 23 °C) (L.R.
Wedge, NY DEC, personal communication). These high water temperatures prohibit the
area from being used as nursery areas for the steelhead and coho salmon of the Salmon
River, which normally are present for at least one full year (L.R. Wedge, NY DEC,
personal communication).
The Salmon River Reservoir is used primarily for water storage; the significant
annual draw-down reduces the reservoir’s productivity dramatically during these low
flow periods. The low flow can minimize the amount of living space or habitat that is
available for the fish and other aquatic organisms of the Salmon River. This reduction in
habitat can result in lower reproductive rates of the fish and can also place the fish under
a large amount of stress. This stress forces the fish to compete for both food and space
within the reservoir, and this can result in reduction in fish population numbers.
Salmon River Watershed Chapter 4
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4.2.5. Status of Hydroelectric Properties in the Salmon River Watershed
The ownership of the hydroelectric properties has been in flux in the last few
years. Up until 1999, Niagara Mohawk owned and operated the hydroelectric plant on
the Salmon River. The operation of the plant made water flow unpredictable and had a
negative economic impact on the area. Anglers, whitewater rafters, and wildlife were all
negatively affected by the changing water levels. In the 1980s, government agencies,
conservation groups, and recreationists initiated a legal suit to force Niagara Mohawk
into obtaining a license. The outcome was positive and Niagara Mohawk was required to
follow regulations when operating its hydroelectric plant. This increased awareness and
interest in promoting the river. A flow management team was created that included an
array of interest groups (Carpenter 2000).
In August of 1999, Niagara Mohawk sold all of its hydroelectric plants to ORION
Power Holdings. Because Niagara Mohawk’s hydroelectric power stations were already
under government regulation, no major changes in operation policy occurred. In
December 14, 2001, Orion Power merged with Reliant Resources and again, this should
not have an effect on the operating policies.
4.3. Water Quality: Non-Point Source Influences
In almost every watershed, non-point source pollution plays a role in determining
the water quality of the hydrologic system. This hydrologic system includes
groundwater, surface water, and any other source of water that drains into the lowest part
of the watershed, in this case the Salmon River. In order to assess the quality of water in
this system, an evaluation of land use and land cover of all of its tributaries is required in
order to correlate water quality with potential contamination. Three counties - Jefferson,
Oswego, and Lewis - within the Salmon River watershed are involved in this evaluation.
These counties share the responsibility to oversee possible non-point source pollution
concerns.
Non-point source pollution is considered by the New York State Department of
Environmental Conservation to be “caused by diffuse sources that contaminate water
bodies through atmospheric deposition, runoff from the land, and/or percolation through
the soil” (NYSDEC 1989). Examples of these types of non-point source pollution
sources in the Salmon River watershed could include agricultural land, silviculture
practices, land disposal sites, construction, and mining. Depending on the proximity of
the pollution source to the water body, and the frequency and intensity of inputs to the
system, the degree of contamination will fluctuate. Indications of non-point source
pollution may include elevated levels of organic chemicals, such as solvents and
pesticides; inorganic chemicals, such as nitrates, chlorides, and trace metals; and
biological substances, such as bacteria and viruses (NYSDEC 1989). Any element or
substance in excess could lead to impaired water quality, inhibited biological activity in
the river, discoloration, odor, etc.
According to our GIS inventory, the Salmon River watershed is 90% forested
(deciduous, evergreen mixed, and forested wetland) and 6.5% agricultural (cropland and
pasture). Most of the agriculture is concentrated in the western, lower elevation portions
of the watershed (Figure 3-2) whereas forests predominate in the central and eastern
basin (Figure 3-1). It is predicted, according to this land use, that agriculture and
Salmon River Watershed Chapter 4
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silviculture practices would contribute the largest sources of non-point source pollution to
the watershed as a whole. Most agricultural effects would be anticipated downstream,
and silvicultural impacts would be concentrated in those areas with intense logging.
4.3.1. Agriculture
Although a small portion of the Salmon River watershed consists of agricultural
land, its location will determine the impact to the water quality. Currently, the majority
of agricultural land is located in the area surrounding and west of the town of Pulaski.
This land includes cropland, which is often irrigated, and grazed land, which is often used
for livestock. Agricultural land is often perceived as a source of non-point source
pollution because of the use of pesticides, the increased sources of nitrogen and
phosphorous from animal waste runoff, and increased sedimentation from irrigated field
runoff. The most common agricultural practices within the Salmon River Watershed are
cattle farming and corn production. There is potential for erosion and possibly
sedimentation into the Salmon River. In addition to agricultural land, golf course
development is a source of high nutrients and pesticides.
The U.S. Environmental Protection Agency classifies the Salmon-Sandy
watershed as having a moderate level of potential impact from agricultural impact based
on data collected between 1990-1995 (USEPA 2002). Even though this is the given
classification, as of October 2001, the New York State Department of Agriculture and
Markets has listed three Agricultural Non-point Source Abatement and Control Programs
for Jefferson County; one of which is for the Sandy Creek/South Sandy Creek Nutrient
Management Project (NYSAM 2001). Lewis County and Oswego County do not have
any such programs.
4.3.2. Silviculture
In 1991, the NYS DEC published the Priority Water Problem List based on
silvicultural practices within New York State. According to the distribution of these nonpoint source pollution concerns, the Salmon River watershed was neither classified to
have silviculture as the primary nor secondary source of water pollution (NYSDEC
1993). However, there is still reason for concern. Any harvesting practice taking place
near a body of water may cause sedimentation. The short and long-term impacts of
severe sediment loading include: destruction of spawning areas, elimination of food
sources, gill abrasions to fish, reduced flow capacity, decreased recreational values, and
increased cost for water treatment (NYSDEC 1993). In addition to sedimentation, there
is potential pollution by petroleum products, organic matter, and pesticides. A rise in
stream temperature would be expected in many areas where silviculture removes shade
cover along the river. Because 90% of the Salmon River Watershed is forested, there is a
potential for commercial harvesting impact to the water quality, physically and
chemically. Future economic development may trigger forest harvesting.
Salmon River Watershed Chapter 4
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4.4. Water Quality: Nutrients and Temperature
According to the Environmental Protection Agency Watershed Health
Information, the Salmon-Sandy Watershed scored a 3, designating less serious problems
and low vulnerability to the aquatic resources (USEPA 2002) in relation to water quality.
Water temperatures and major nutrients were among variables that were included
in several synoptic surveys of the Salmon River and its tributaries from October 1999
through early August 2000 (J. Hallock, thesis work in progress). Water temperatures
were more or less consistently elevated below the two reservoirs, and can be seen in the
means of samples taken on five dates (23 October, 4 December, 23 January, 5 March, and
10 August, Figure 4-2). Collectively, pooled upstream samples were 1.3 degrees C lower
than pooled downstream samples over the same period.
Mean water temperatures on 5 dates, Oct 99 - Aug 00
9.0
8.5
R
E
S
E
R
V
O
I
R
S
Temperature, C
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
0
10
20
30
40
50
60
KM from mouth
Figure 4-2. Mean water temperatures surveyed at six sites along the Salmon River. Triangle
symbols represent the East Branch Salmon River, a major upstream tributary. Data: J. Hallock,
SUNY-ESF.
Mean values of dissolved organic carbon (DOC), which is related to the degree of
material processing during ecosystem production and decomposition, also showed an
increase below the reservoirs (Figure 4-3).
Salmon River Watershed Chapter 4
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Dissolved organic carbon, Oct 99 - Aug 00
5
R
E
S
E
R
V
O
I
R
S
DOC, mg/L
4
3
2
1
0
0
10
20
30
40
50
60
KM from mouth
Figure 4-3. Mean dissolved organic carbon (± standard error) surveyed at six sites along the
Salmon River. Sites as in Figure 4-2. Data: J. Hallock, SUNY-ESF.
The elevated DOC downstream may be due to higher temperatures, but also to
higher loads of phosphorus, an essential nutrient for plant production. Total phosphorus
levels increased over two-fold below the reservoir (Figure 4-4). This is likely due to
loads into the reservoir, as well as loadings from agricultural lands and from discharges
into Beaverdam Brook from the Salmon River Hatchery. The hatchery contributes
approximately 500 kg P per year to Beaverdam Brook.
Total P, micrograms/L
Total phosphorus, Oct 99 - Aug 00
18
16
14
12
10
8
6
4
2
0
R
E
S
E
R
V
O
I
R
S
0
10
20
30
40
50
60
KM from mouth
Figure 4-4. Mean total phosphorus (± standard error) surveyed at six sites along the
Salmon River. Sites as in Figure 4-2, plus two tributaries: Beaverdam Brook (square with
cross) and Orwell Brook (solid square). Data: J. Hallock, SUNY-ESF.
Salmon River Watershed Chapter 4
53
Total nitrogen does not show the same upstream-downstream patterns of
enrichment, although levels are slightly elevated downstream of the reservoirs (Figure 45). Beaverdam Brook is not a major contributor of total N, but Orwell Brook has
elevated levels of total N. The elevations of both total P and total N concentrations in
Orwell Brook suggest that Orwell is a sub-catchment with agricultural runoff. Nitrate-N
(NO3-N) declined slightly below the reservoirs (0.304 mg/L above vs 0.272 mg/L below
the lower reservoir), but highest concentrations were once again detected in Orwell
Brook (0.6 (± 0.1 s.d.) mg/L NO3-N). As a comparison, an agriculturally dominated
stream (Sprout Creek) in Dutchess County, NY had summertime nitrate concentrations of
0.66 mg/L, and the Fishkill Creek, a major, highly developed tributary to the Hudson
River, had nitrate levels of 2.25 mg/L (Limburg, unpublished data).
Total nitrogen, Oct 99 - Aug 00
1.20
R
E
S
E
R
V
O
I
R
S
Total N, mg/L
1.00
0.80
0.60
0.40
0.20
0.00
0
10
20
30
40
50
60
KM from mouth
Figure 4-5. Mean total nitrogen (± standard error) surveyed at six sites along the
Salmon River. Sites as in Figure 4-2, plus two tributaries: Beaverdam Brook (square
with cross) and Orwell Brook (solid square). Data: J. Hallock, SUNY-ESF.
To summarize, the reservoirs have a marked effect on water temperatures and
downstream productivity. Phosphorus levels increase below the reservoirs, but some of
this is due to loadings from sources in the lower tributaries. Nitrogen does not increase
significantly, but concentrations of total N and nitrate are elevated in Orwell Brook,
indicating agricultural non-point source pollution there. Future studies should probably
investigate more of the sources downstream in the more developed portions of the
watershed.
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