Description of Onondaga Lake

Onondaga Lake has a surface area of 12 km² (4.5 mi²), a volume of 131 x 106 m³ (35 billion gallons), and a maximum depth of 19.5 m  (64 ft) The watershed (642 km², 244 mi²) supports a population of approximately 450,000, that resides mostly in Syracuse and adjoining suburbs. The lower reaches of Onondaga Creek drain a significant portion of the City of Syracuse, and receive inputs of dilute untreated domestic waste during runoff events (storms and snow melts) via approximately 40 combined sewer overflow structures (CSOs) within the City. Effluent discharged to the southern end of the lake from the Metropolitan Syracuse Wastewater Treatment Plant (METRO) contributes almost 20% of the annual inflow, and often is the single largest input in late summer. No other lake in the United Statesreceives as much of its inflow as treated wastewater. The lake flushes approximately 4 times a year; that is, its water volume is replaced four times each year.

Combined Sewer Overflows releasing into Onondaga Creek

This is much faster than Skaneateles Lake which flushes once every 12 years or Lake Superior, which flushes only once every 191  years! With its rapid flushing rate, Onondaga Lake should respond quickly to changes in material loading (material that flows into the lake).

Onondaga Lake and adjoining portions of the Seneca River are tightly linked with respect to water quality, ecological concerns and management issues. Fish populations and other wildlife (primarily birds) actively  migrate between these systems (i.e., fish that have been trapped and tagged in Onondaga Lake have been caught by fishermen in the Seneca River and Oneida Lake).

A Brief History

The Syracuse area was settled (late 1700s), in large part, because of Onondaga Lake and the unusual hydrogeology of the region. The region's expansion in the 1800s was coupled to the growth of commercial salt (NaCl) production from brine  wells that adjoined the lake and construction of the Erie Canal.

Onondaga Lake maximum depth 19.5 m mean depth 10.9 m surface area 12 km2 volume 131x106 m3 watershed area 642 km2 length 7.6 km width 2.0 km average elevation 111 m average flushing rate 4 times/year monitoring site 43º 04’ 43” N 76º 11’ 50” W

Before European settlement, Onondaga Lake was oligo-mesotrophic (low levels of  aquatic plant growth) characterized by high clarity and low nutrient inputs. The lake initially supported a commercially viable cold-water fishery which was sustained by the harvesting of Onondaga Lake Whitefish and  Atlantic Salmon. A number of resorts were built along its shoreline in the late 1800s. As the industrial revolution took hold, and the city's population expanded, the lake was used increasingly for the disposal of domestic and industrial waste. Conspicuous signs of deterioration of the lake ecosystem began to emerge by the end of the 19th century. The cold-water fishery was lost by 1890. Ice-harvesting was banned in 1901, swimming  in 1940, and fishing (due to mercury contamination) in 1970.

Since passage of the Clean Water Act in 1973, several actions have been taken to abate domestic waste inputs to the lake, and in 1986 the major industrial polluter closed its operations. In 1994, a number of sites proximate to the lake were added to the federal "Superfund" National Priority List. Despite the reductions in pollutant loadings, Onondaga Lake is arguably the most polluted lake in the United States.

Several initiatives have been undertaken to clean up Onondaga Lake. A 15 year  multi-stage program is underway to improve sewage treatment and eliminate related violations of water quality standards in the lake. The initial stage of the program is  estimated to cost $380 million dollars, which is equivalent to an expenditure of almost $1,000 per capita within the watershed. At the conclusion of the initial stages, the program will be evaluated as to its success or failure. If further remediation is deemed necessary, a third stage (and additional dollars) will be added to the  program in an attempt to meet water quality standards.

Municipal Waste

METRO is the dominant source of phosphorus (60%) and nitrogen (90%) to the lake. The prevailing areal annual loads (a measure of loading per area of lake surface) of total phosphorus and total nitrogen are among the highest reported for any lake. Aquatic plants (i.e. algae) require phosphorus and nitrogen for growth. Excessive amounts of these nutrients can cause a lake to become overgrown with aquatic plants. High concentrations of nitrogen species (i.e., free ammonia) are harmful to other aquatic life (i.e., fish).

Onondaga Lake is now hypereutrophic (having excessive growth of aquatic plants) because of the

METRO effluent flowing into Onondaga Lake

phosphorus load received from METRO. Water quality manifestations of hypereutrophy include severe phytoplankton (algae) blooms, poor clarity, rapid loss of dissolved oxygen from the hypolimnion (lower waters of lake). With the loss of dissolved oxygen in the lower waters, reduced species (by-products of anaerobic bacteria) begin to accumulate. Oxidation of these reduced (chemicals) species  results in the depletion of dissolved oxygen in the upper water  during fall turnover (the period when the entire water column mixes top to bottom). Oxygen concentrations in the upper layers often decrease to < 4 mg/L during this interval. This represents a particularly severe manifestation of cultural eutrophication and a violation of New York State water quality standards. The State's guidance value for total phosphorus concentration (20 µg/L) is exceeded by a wide margin, and violations of the clarity  standard for swimming safety (Secchi disc > 1.2 m) occur each summer.

Onondaga Lake is also severely polluted with various forms of nitrogen as a result of  loads received from METRO. Concentrations of total ammonia and nitrate in the upper productive layers (near the lake's surface) remain well above levels considered limiting to plant growth (phosphorus is the limiting nutrient). Concentrations of total ammonia and nitrite exceed standards, often by a wide  margin, intended to protect aquatic life against the toxic effects of these forms of nitrogen.

Industrial Waste

The primary source of industrial waste to the lake has been a soda ash (Solvay

Waste  beds on west shore of Onondaga Lake

Process)/chlor-alkali facility located on the lake's western shore. This facility discharged large quantities of ionic (mostly chloride,  sodium,and calcium) waste to the lake, until its closure in 1986. It was the single largest source of chloride to Lake Ontario. The residual load of ionic waste from approximately 1,000 acres of "waste beds" adjoining the lake continues to be substantial (approximately 12% of pre-closure load). Large sediment loads that enter the  lake from Onondaga Creek have been attributed to solution mining activities by the manufacturer. This facility also discharged approximately 75,000 kg of mercury to  the lake over the 1946-1970 interval.

Onondaga Lake as a Community Resource

Although Onondaga Lake is severely impacted by pollution, it remains a potentially valuable

Onondaga L. shoreline recreational trail

resource to the community. The lake's setting draws many visitors. More than one million people visit Onondaga Lake each year, making it one the most visited lakes in Central New York. However, the recreational activities are largely limited to the surrounding park land owned by Onondaga County. Imagine the potential of this resource if the waters of the lake could be fully utilized.

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Last Modified: Tuesday, July 01, 2008