Otsego Lake lies in the glacially overdeepened headwaters of the Susquehanna River in Otsego County, New York (42E40'N-70E00'W ) within the northern portions of the Appalachian Plateau. It is oriented, with its main axis north to south, in a glacially overdeepened valley at an elevation of between 364.2 and 364.5 m. The lake is enclosed on the east and west by truncated slopes rising to the divide at a height of about 610 m. The lake is bounded on the northern end by the Richfield Springs drumlin field and on the south by an end moraine and outwash plain that dammed the valley and impounded the waters trapped therein. Detail ed studies concerning the glacial history of the Otsego Lake region are available (Sales et al.,1978; Fleisher, 1978; Fleisher and Mullins, 1990).
The parent rocks in the watershed (Figure 3) were deposited as marine sands, silts, clays, and carbonates in the Appalachian geosynclinal sea during the Lower and Middle Devonian Period. Most of the Susquehanna watershed lies on acid sandstones and shales low in calcium and other compounds important in organic metabolism. In this region th ey are the Hamilton-Panther Mountain and Marcellus formations which are roughly 100 meters in thickness. However, the north end of Otsego Lake and the greatest portion of its watershed lie on the southern exposure of the Onondaga limestone formation (ca. 30 m thick) and drain areas of the older (Lower Devonian) Helderberg limestones to the north. This results in naturally hard, productive waters, appearing incongruous when viewed between unproductive hills of arenaceous shales and siltstones.
Glacial outwash, till, and alluvial sediments have partially filled the lake basin and valleys to the south to depths as great as 75 m compared to roughly 15 m in areas north of the lake (Fleisher and Mullins, 1990).