Relative influence of lake age and watershed land use on trophic state and water quality of artificial lakes in Kansas

Eutrophication is an extensively documented concern for lake and reservoir management throughout the world. Eutrophication is also recognized as a naturally occurring process in both natural and artificial lakes, although it can be greatly augmented by human activities and is then referred to as "cultural eutrophication." Unfortunately, natural process eutrophication is still sometimes used as a rationalization for not working toward the prevention or abatement of nutrient related pollution. Here, trophic state and other water quality data from a long-term ( 1975 to present) lake monitoring program were examined to determine the relative influences of watershed land use conditions and age in determining the trophic state conditions of artificial lakes in Kansas. The results indicate that age alone exerts very limited influence on eutrophication whereas watershed land use exerts an extreme, and often rapid, impact. Regardless of age, lakes within relatively unimpacted watersheds displayed trophic state conditions near regional reference conditions. Conversely, lakes within watersheds rich in human activities, regardless of water body age, tended toward greatly elevated trophic status. Eutrophication as a natural process is shown to be an invalid argument for ignoring excessive nutrient export from watersheds.