The report describes the time and space distribution of measured chemical, physical, and biological factors for a one-year cycle in the western and central basins of Lake Erie. The nearshore descriptions are based upon data gathered in a biweekly sampling program at 17 Ohio domestic water supply intakes from March 1968 through March 1969. The midlake descriptions are based upon data gathered at 20 midlake stations sampled four times between May 1967 and January 1968. Although the sampling times for nearshore and midlake were one year apart, for the purposes of this report the data are assumed to be comparable.