 The Susquehanna Basin occupies about one-third of the south border of the state.The river takes its rise in Otsego Lake, and, flowing southwest to the Pennsylvania line, receives Charlotte River from the south and the Unadilla River from the north.After a course of a few miles in Pennsylvania, it again enters New York and flows in a general westerly direction to near the western border of Tioga County, whence it turns south and again enters Pennsylvania.