Latest water quality information
NEW! Onondaga Lake Progress Report 2006 (4 pages, issued June 2007)
Comments on this report are encouraged and may be directed to Joseph J. Mastriano, Operations Manager. Click here to email, or phone 315-435-2260.
The 2005 results are consistent with the trend of
improving conditions. Phosphorus and ammonia
concentrations have decreased to the lowest
concentrations ever measured in the lake over the 36
years of Onondaga County monitoring.
Concentrations of
dissolved oxygen have increased, and
algal blooms are diminishing. Improved water clarity
has allowed the beds of aquatic plants to
expand; this has provided improved nesting and nursery
habitat for the warm-water fish
community.
Improvements to the county's wastewater collection and
treatment system are primarily
responsible for the improved water quality conditions
in the lake. Significant public investment in
wastewater treatment technology has achieved far lower
discharges of wastewater-related
pollutants, particularly ammonia and phosphorus.
Dissolved oxygen has increased, algal blooms are diminishing. Improved water clarity has allowed the beds of aquatic plants to expand, providing improved nesting and nursery habitat for warm-water fish.
Onondaga Lake has exhibited elevated ammonia
concentrations for decades. Monitoring results
from 1970 to 2002 documented that ammonia levels in
the lake waters were above New York
State's ambient water quality standards designed to
protect aquatic life. Metro effluent was the
largest source of ammonia to the lake, averaging about
90% of the total annual input. Recent
improvements to Metro were designed to reduce ammonia
levels in the treated effluent and bring
the lake's water quality into compliance with state
standards.
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The final stage of the Metro improvements for ammonia
treatment came on line in early 2004.
The Biological Aerated Filter (BAF) system has
resulted in year-round nitrification (conversion
of ammonia to nitrate) in wastewater. Metro had
reduced its annual discharge of ammonia from
an average of 1210 metric tons (MT) from 1990-1997, to
an average of 521 MT from 1998 to
2003. In 2004, the annual Metro ammonia discharge was
reduced to 152 MT as the BAF system
came on line. In 2005 the Metro contribution fell to
21 MT. As of 2005, Metro is no longer the
largest source of ammonia N to Onondaga Lake.
Lake
ammonia concentrations in 2005 were the
lowest ever measured, and remained at safe levels for
even the most sensitive aquatic organisms.
Enhanced phosphorus removal from wastewater is another
objective of the Metro improvements
currently underway. A High Rate Flocculated Settling
(HRFS) physical-chemical treatment
system (known as ACTIFLO) was brought on-line in 2005
to reduce effluent total P
concentration. This stage of phosphorus treatment is
designed to bring effluent TP levels to meet
a 12-month rolling average limit of 0.12 mg/L.
Compliance with this limit will be assessed
beginning in April 2006. The TP concentration in
Metro's main outfall (Outfall 001) in 2005 was
reported at 0.195 mg/L. As a basis of comparison, the
average Metro TP concentration from 2000-2004 was 0.351 mg/L.
In 2005, Metro contributed about 43% of the total
external phosphorus load to Onondaga Lake
through the main outfall (38%) and the bypass (4.9%).
The balance of the external loading comes
from nonpoint sources throughout the large watershed.
The magnitude of the nonpoint sources
varies each year depending on the weather. The total
loading from point and nonpoint sources
determines the in-lake concentrations. The 2005 lake
phosphorus concentrations were the lowest
measured since Onondaga County began monitoring in
1969.
Lake ammonia concentrations in 2005 were the lowest ever measured and remained at safe levels for even the most sensitive aquatic organisms.
Bacteria concentrations were monitored at a network of
near-shore stations as well as at South
Deep, the primary water quality monitoring site. These
data are used to track progress towards
water quality conditions that support recreational
use. In 2005, bacteria concentrations at the
northern near-shore stations met standards for water
contact recreation for the entire summer
recreational period. However, concentrations at the
southern near-shore stations, near the major
tributaries and Metro discharge, were elevated
following storms. This result highlights the need
for continued progress with CSOs, as well as the need
for improved storm water management to
reduce nonpoint source pollution from urban areas.
Dissolved oxygen (DO) levels also showed improvement
in 2005. The volume-days of anoxia*
have declined, and DO concentrations in surface water
during the fall mixing period, a critical
period in Onondaga Lake, were in compliance with
regulatory standards [>5 mg/L during turnover
October 1 to December 1 (daily average); >4 mg/L
(minimum)].
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* One measure of the lake's dissolved oxygen status is "volume-days of anoxia." This measurement has been used in Long Island Sound and other aquatic systems where low concentrations of dissolved oxygen (anoxia) are a
significant water quality management issue. Both the volume of water affected by +anoxia and the duration (days) of anoxia are calculated in a single measurement that can be tracked from year to year.
Phosphorus concentrations in the lake are declining.
In 2005, the summer average total
phosphorus concentration was 34 µg/L in the lake's
upper waters. Algal abundance has been
variable over this same time period. Chlorophyll-a
concentration in the lake's upper waters
averaged 11.8 µg/L during the summer of 2005. In 2005
the maximum chlorophyll-a
concentration (24 µg/L) occurred in May. Spring algal
blooms are typical in Onondaga Lake.
However, the 2005 spring chlorophyll-a concentration
remained below the level that EPA
suggests as an appropriate threshold for a nuisance
bloom in their nutrient criteria guidance
document (this threshold is 30 µg/L). Moderate and
variable algal levels were measured through
much of the summer recreational period, occasionally
exceeding 15 µg/L; the level at which users
reported to EPA diminished suitability (impairment)
for recreational use. Overall, 63% of
summertime measurements were below this perceived
impairment threshold. The average
summer chlorophyll-a concentration was lower in 2005
compared to 2004.
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Water clarity of the lake is variable both within and
between years. A spring clear-water phase
was evident from the mid-1990s through 2000. Water
clarity from 2000 to 2005 was not as high
as the 1990s but exceeded the measurements from the
mid-1980s.
Blue-green algae (cyanobacteria) are of concern to
lake managers because blooms of these
organisms are associated with degraded water quality
and aesthetics. Onondaga Lake water
quality has improved significantly with respect to the
percentage of the algal community
comprised of blue-greens. The percent contribution of
cyanobacteria to the total phytoplankton
community has been greatly reduced since the
mid-1990s when they represented more than half
of the total biomass of algae in the lake. In 2005
this figure fell to less than 2%. Blue-green algal
blooms have been steadily diminishing, presumably in
response to reductions in nutrient loads.
Zooplankton grazing is a significant factor affecting
water clarity. The spring clearing event,
observed through water clarity measurements, was
attributed to a seasonal peak in the abundance
of larger zooplankton. However, larger zooplankton
are now essentially absent from the lake,
and the spring clearing events have disappeared as
well. Larger zooplankton, which are efficient
grazers of phytoplankton, are the preferred food
source of the alewife. The reduction in
population of these larger zooplankton taxa was
evident in late summer 2002 when young-of-the-year
alewives first became abundant. The extirpation
of larger zooplankton by alewives caused a
decline in total zooplankton biomass from 2003 to
2005. Alewives have become prolific in the
lake in recent years, and the effects of this species
are seen throughout the food web.
Fish are one of the most visible components of the
lake ecosystem. Results of the 2005 AMP fish
program indicate that the lake's fish community
continues to be dominated by warm-water species
tolerant of pollution. Largemouth and smallmouth bass
are present, and are more common in the
lake's northern basin. This abundance pattern is
consistent with other indices (including
macrophytes, macroinvertebrates, and substrate
quality) showing that the southern basin provides
poorer habitat quality. Other game fish, such as
walleye and northern pike, are present but are far
less common than bass. Panfish, such as yellow perch,
pumpkinseed, and bluegill, are abundant
in near-shore areas. Catch rates of pumpkinseed and
bluegill have declined in the past few years;
it is not clear whether this reflects natural
variability. The alewife and gizzard shad were highly
dominant in 2005, comprising more than 90% of the
electrofishing catch. Alewife accounted for
65% of electrofishing catch, down from 90% in 2004.
Alewife also dominated catches in fine-mesh
open water gill net. A hydroacoustical survey was
conducted in the spring of 2005; using
this technique, biomass of alewives was estimated at
70 kg/ha.
Macrophytes (rooted aquatic plants and algae) have
changed profoundly in recent years. The
number of species present (termed
species richness)
has increased from 5 in 1991 to 17 in 2005,
although the community is still dominated by a few
species. Percent cover of macrophytes has
increased about two-fold throughout the lake since
2000. The range of percent cover in the lake is
now within an ideal range for largemouth bass
reproduction.
Littoral macroinvertebrates were monitored in 2005.
The combined influences of
eutrophication and habitat degradation appear to be
major structuring elements of the benthic
community in Onondaga Lake. The macroinvertebrate
community in Onondaga Lake's littoral
zone ranged from moderately to severely impacted in
2005. Sites in the north end of the lake
appeared to be less affected than south end sites.
Only small changes to the macroinvertebrate
community have occurred since the 2000 survey.
Onondaga County completed a focused water quality
monitoring effort at selected stations along
the Seneca-Oneida-Oswego River system in 2005. The
river program is designed to assess water
quality conditions with respect to ambient water
quality standards and support the Three Rivers
Water Quality Model. The dry summer of 2005 led to low
stream flow in the Seneca River.
Oxygen depletion was evident during the warm weather
low flow conditions; DO concentrations
were below 2 mg/L at some sites along the river.
Ammonia concentrations in the river met the
NYSDEC ambient water quality standard. The river's
water quality conditions continue to be
strongly influenced by zebra mussels.
The 2005 AMP report includes a special topic chapter
on mercury concentration in fish. New
York State routinely collects fish from Onondaga Lake
and other regional water bodies and
analyzes the fish for contaminant burden. NYSDEC
maintains a database of fish and wildlife
contaminants. The database incorporates results of 36
years (1970-2005) of contaminant testing
of fish caught in over 100 water bodies throughout New
York. The analysis presented in Chapter
4 indicates that fish collected in Onondaga Lake and
the lake's tributaries have higher mercury
concentrations than fish from other water bodies in the
state, and this has been the case since the
1970s. There is considerable variability in the
data, and mercury concentrations measured in
some fish collected from other NY water bodies approach
or exceed the concentrations measured
in Onondaga Lake fish.
Onondaga County Department of Water Environment
Protection (OCDWEP) conducts an annual
program to evaluate the water quality conditions of
Onondaga Lake, the lake tributaries, and a
portion of the Seneca River. An Amended Consent
Judgment signed in 1998 requires Onondaga
County to complete three major tasks: first, to
upgrade the level of treatment at the Metropolitan
Syracuse Wastewater Treatment Plant (Metro); second,
to mitigate the Combined Sewer
Overflows (CSOs); and third, to implement an Ambient
Monitoring Program (AMP) that will
track the effectiveness of these improvements to the
wastewater collection and treatment
infrastructure. The AMP builds on Onondaga County's
historical monitoring program, which
provides a basis for evaluating trends over time. Each
year the County prepares an annual report
of its findings.
The AMP is designed to identify sources of materials
(nutrients, sediment, microorganisms, and
chemicals) to the lake, evaluate in-lake water quality
conditions, and examine the interactions
between Onondaga Lake and the Seneca River. In
addition to the water quality-related program,
the AMP examines many levels of the biological
community of the lake and its watershed. The
AMP includes an assessment of zebra mussels, benthic
macroinvertebrates, aquatic plants,
phytoplankton, zooplankton, and fish.
A rigorous quality assurance/quality control program
is in place. Results of internal and
external audits, blanks, and duplicates are presented
in the annual AMP report. Samples are
collected by trained technicians and analyzed in a
state-certified laboratory. The annual AMP
work plan is subject to New York State Department of
Environmental Conservation (NYSDEC)
review and approval. Technical experts (the Onondaga
Lake Technical Advisory Committee)
review the program findings and interpretive reports
each year.
Technological advances enable the County to monitor
water quality on a near-real-time basis. A
water quality buoy with an array of probes that
measure physical and chemical characteristics of
the lake water is deployed on the lake at its deepest
point (referred to as the South Deep station).
Data from the buoy provide a window into how the lake
quality changes in response to winds and
waves. Acoustic Doppler devices, installed at the
lake's outlet by the U.S. Geological Survey,
provide data needed to assess water exchange between
the lake and the Seneca River.
As part of the annual AMP, OCDWEP tests over 20,000
water samples and examines several
thousand biological samples. The 2005 data have been
appended to the custom long-term
database developed by Dr. William W. Walker Jr. The
database, which merges the County's
tributary and lake data from 1968 to the current year,
has greatly improved data management and
reporting tasks.
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Onondaga County Dept of Water Environment Protection