Variability of Annual Runoff in the Lake Ontario Basin

A study of variability of runoff in the Lake Ontario basin is undertaken to provide background information for the International Field Year on the Great Lakes to be held in 1972 on Lake Ontario, since it is realized that a period of 1 year is a small sample in the life history of a lake basin and that there are large annual fluctuations in the variables in the water balance. Because of a lack of long-term records of measured runoff, the Thornthwaite-Mather water balance model for estimating point runoff from climatic data is used for the 81 stations in and near the basin with records of 15–136 years. Statistical tests show that annual station runoff has a normal distribution, and standard deviations are computed to express variability. Maps of average runoff, as well as plus and minus two standard deviations of runoff, are drawn and thus permit the estimation of the volumes of annual runoff that can be expected in the Lake Ontario basin. A coefficient of variability of runoff map indicates that the southwestern areas of the basin have the most variable runoff.