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Otisco Lake is the easternmost of the Finger Lakes, and is located totally within Onondaga County, New York. It’s position with respect to the other ten Finger lakes is shown below
A summary of morphometric features of the lake is presented in the Table to right.
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Otisco Lake
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maximum depth
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21 m
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mean depth
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10.2 m
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surface area
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7.6 km2
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volume
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79x106 m3
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watershed area
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93.8 km2
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length
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8.7 km
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maximum width
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1.2 km
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average elevation
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240 m
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monitoring site
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42º 52’ 07” N
76º 17’ 40” W
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Otisco Lake has the forth smallest surface area, the third smallest volume, the second smallest mean depth, and the third smallest maximum depth of the Finger Lakes. A bathymetric map of the lake appear on the left side of this page A notable feature of the lake is the presence of a causeway, which separates the smaller and shallower southern end of the lake from the northern portion of the lake. A distinct contrast in turbidity and color often prevail between the two basins, with the southern basin commonly having a more brown turbid appearance. This has been attributed to sediment resuspension in this shallow basin.
 The net flow of water in the lake is from south to north; the single outlet forms Ninemile Creek. The largest tributaries are Spafford Creek, Amber Brook, Rice Brook, and Willow Brook. The area of the drainage basin is composed of cropland and woodland. The lake flushes, on average, approximately once every two years; the third fastest of the Finger Lakes.
Otisco Lake has multiple resource uses, including recreation, and as a water supply. The shoreline is largely developed with cottages and year-round homes. Boating and swimming are popular activities, and it is considered a good fishing (warm water species) lake. New York State and Onondaga County both have active fish stocking programs. The lake serves as a water supply for much of Metropolitan Syracuse (supplier is the Onondaga County Water Authority (OCWA)); it is classified AA by the New York State Department of Health. Previously water taken in by OCWA often exceeded the EPA turbidity limit of 1 NTU (Nephelometric Turbidity Units), and infrequently exceeded the temporary variance limit of 5 NTU established by the State of New York. However, since the construction of the water treatment plant, the water supplied from the lake by OCWA regularly meets turbidity limits. The lake is treated with copper sulfate on a “needs” basis to control algae associated with taste and odor problems.
Otisco Lake is mesotrophic, supporting an intermediate level of biological production, as indicated by the intermediate concentrations of chlorophyll a. “Whiting”, the precipitation of calcium carbonate, is a recurring phenomenon in the lake, that can easily be mistaken for a phytoplankton bloom. Annual, dissolved oxygen (DO) is depleted rapidly from the lower layers of the lake. Following the complete loss of DO (anoxia) from the bottom layers, phosphorus is released from the sediments. Features of the loss of DO from the lower layers of the lake have not substantively changed since the early 1900’s.
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