Dr. Richard Vollenweider and the Great Lakes

Abstract

It was in 1968 when Swiss-born Richard Vollenweider, with support from the Organization for Economic Cooperation and Development (OECD), published his landmark study on eutrophication of lakes (Vollenweider, 1968). He had investigated nutrient loadings and basic physical characteristics of a number of lakes, particularly in Europe and North America. The fundamental relationship he then developed was the comparison of trophic state with total phosphorus loading in gm m−2 yr−1, where m2 is the lake surface area, plotted against the lake mean depth. He was then able to show in a graph, a band of values that separated oligotrophic lakes, with less loading, from eutrophic lakes with greater phosphorus loading. The lower oligotrophic side of the band was labelled “admissible limits” and the upper side “dangerous limits.” Vollenweider had also developed a similar graph for nitrogen loadings.At the same time, under the aegis of the International Joint Commission (IJC), a major bilateral study was underway of pollution of the lower Great Lakes, Ontario and Erie. Erie, especially the western and central basins, was already eutrophic, and Ontario was beginning to show disturbing trends in that direction. Scientists working out of the newly formed Canada Centre for Inland Waters (CCIW) from several federal government departments were making the major contributions to these IJC studies. They soon ran into the problem of quantifying the nutrient loading that would restore or protect the lakes. This led to recognition of the potential power of Vollenweider's insights and his now famous graph, as a means of guiding pollution control measures to restore these lakes to reasonable health.Through the efforts of Dr. Wally Johnson (Freshwater Institute, Winnipeg) and the author of this piece, Vollenweider was persuaded to leave the beautiful shores of Lago Maggiore (Limnological Institute) to join the scientists at CCIW. With his assistance, phosphorus loading targets were then established for the two lakes. On Vollenweider's graph, Lake Ontario was seen to be on the “dangerous limit” line in 1967 and would move strongly into eutrophic conditions by 1986, unless vigorous phosphorus controls were put in place. Lake Erie was well in the eutrophic zone in 1967, but could be moved to the dangerous limit line (mesotropic) with recommended phosphorus controls. The 1969 reports to the IJC from the lower Great Lakes Study Boards thus featured versions of Vollenweider's graphs, tailored to the recently acquired knowledge of existing phosphorus loadings (IJC, 1969). A set of proposed control measures to reduce phosphorus in detergents, in sewage treatment plant effluents, and from agricultural and other diffuse sources, was developed to achieve reduced target loadings. Of course, the pollution study also addressed other forms of pollution: toxic chemicals, bacteriological, oil spills, etc.After a series of public hearings, in which Jack Vallentyne played an important role, the governments agreed that a Great Lakes Water Quality Agreement should be signed between Canada and U.S.A. Recommendations from the IJC Study Boards became the foundation for the Great Lakes Water Quality Agreement which was signed by President Richard Nixon and Prime Minister Pierre Trudeau in Ottawa in 1972. The pollution control efforts went into full swing under the Canada Water Act of 1970, which permitted federal regulation of detergent phosphates, and under the U.S. Clean Water Act of 1972. An estimated $5 billion in pollution control activities was undertaken in the following decade. Ontario Water Resources Commission was a strong partner. As a result the trophic state of the lakes had greatly improved by the early 1980s. The “dead” and “dying” lakes had been saved from gross eutrophication. Vollenweider-based targets had carried the day.As an unfortunate post script, the coastal areas of all the Great Lakes, except Superior, were showing significant signs of backsliding by the end of the first decade of the 21st century. This has been attributed to diffuse sources of phosphorus and other contaminants from agricultural and urban areas. Changing agricultural practices, especially intensive animal feed lots, and frequent overflow of storm sewers into urban sanitary systems have been identified as key sources. Their effects have been amplified by increased frequency of high intensity rains, especially in springtime, less winter ice and warming waters in the changing climate. Another round of costly interventions will be needed to restore phosphorus loadings to “acceptable” levels, which continue to be assessed through Richard Vollenweider's seminal work.Lake Winnipeg faces similar eutrophication problems today to those experienced in Lake Erie in the 1960s. In addition to evidence of renewed eutrophication, the Great Lakes now face many aquatic ecosystem problems. These include depredation by invasive species from ship ballast waters, extensive deposition of mercury emitted from coal-fired power plants, pharmaceuticals, and other gender modifying chemicals. Would that Dr. Vollenweider was still with us to provide sound advice to address these new and renewed problems.