Continuing an effort begun in 1983, the water quality of Lakes Erie, Huron, and Michigan was surveyed in 1984.^Sampling, which was restricted to the open waters of the three lakes, was conducted from the R/V Roger Simons in three surveys (spring, summer, and fall) and from helicopter in a winter survey that took place during January and February of 1985.^The samples were analyzed for traditional limnological parameters and for nutrients.^The data were compared with the results of the 1983 survey as well as with other historical data and the results of numerical simulations made using dynamic eutrophication models.^Sampling in 1984 shows that the three lakes were significantly cooler than they were in 1983.^Although statistically significant differences were found in comparisons of the 1983 and 1984 estimates of the concentration of many of the measured substances, these differences are of questionable environmental significance.^The variability of the concentration estimates made using data collected during the spring isothermal period was generally comparable in the two years and similar to the estimated analytical uncertainty.^Because phosphorus loading estimates are unavailable for the period 1983 to 1984, model simulations of total phosphorus concentration were driven with hypothetical loads based on the most recent (1982) estimates.^The models do not appear to simulate the annual patterns suggested by the data, but the data, not being intended for model validation, may be too sparse to provide a fair basis for comparison.

Report in partial fulfillment of Interagency Agreement with U.S. Environmental Protection Agency, Great Lakes National Program Office. "April 1987." "ANL/ER-87-1." Two microfiches in pocket. Includes bibliographical references (p. 137-141).