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Eutrophication, or the enrichment of lakes and reservoirs with plant nutrients such as nitrogen and phosphorus, is an ongoing concern facing human societies around the world. Once thought to have been resolved using engineering approaches such as municipal wastewater treatment and storm water management, the problem of nutrient enrichment not only persists, but even continues to increase, being manifested in harmful algal blooms, limitations on access to safe drinking water supplies, and related concerns associated with fresh water in lakes and reservoirs. The continuing concern surrounding eutrophication fulfils the many attributes of a 'wicked' or complex problem facing society. This report reviews seriatim the ten attributes of a wicked problem, and the implications of these attributes for lake and reservoir management are discussed. Recognition of eutrophication as a wicked problem requires site-specific approaches, based on specific knowledge of individual water bodies, as well as an ongoing commitment to lake and reservoir management to respond to new manifestations of the problems of nutrient enrichment as they continue to be revealed over time.Key words eutrophication, eutrophication management, integrated lake basin management, lake and reservoir management, payments for improving ecosystem services at the watershed-scale.

It is generally believed that excessive P release from lake sediments. i . e . internill P loed. is only a problem in deep lakes with stagnant anaerobic bottom waters . However. substantial amounts of P can also be released from sediments in shallow. well-mixed lakes . The dynamics and magnitude of P ralease from sediments in these typss of lakes are affected primarily by physical factors.such as ssasonal variations in water temperature and year-to-year differences in water renewal .Thesz factors. in turn. indue3 chemical and microbiological processes which regulate the exchange of substances betwaen sediments and water . The fractional distribution of sedimentary P and the chelating capacity of the water are also important factors that can provide insights t o the processes involved and their quantitative impact on the P status in shallow. eutrophic lakes .

The transport of PCBs (Aroclor 1242) in a river system in southern Sweden was governed by outflow from sediment in a 26-ha contaminated lake. Experiments in the lake revealed that 14 g PCBs/d escaped from the sediment, while sedimentation was 3 g PCB/d. Volatilization of PCBs from the lake surface was 0.02 g/d, which was considerably higher than the atmospheric fallout [Formula: see text]. The majority of the sediment-desorbed compounds (80%) remained at the river mouth, 60 km downstream, and entered the Baltic Sea. Desorption increased the ratio of tetrachlorobiphenyls to pentachlorobiphenyls in the water. Transport across the water/air interface was higher for trichlorobiphenyls, while atmospheric deposition was dominated by penta- and hexachlorobiphenyls. Therefore, the sediment of the lake acted as a source of PCBs entering the river system as well as the atmosphere.