Catchment, morphometric, and water quality characteristics differ between reservoirs and naturally formed lakes on a latitudinal gradient in the conterminous United States

Abstract

Constructed lakes and impoundments (reservoirs) likely exhibit substantial differences in their physics, chemistry, and biology from naturally formed lakes; however, because reservoirs and natural lakes generally have different latitudinal distributions, less is known about quantitative, generalized differences between the 2 waterbody types. We compared a suite of limnological variables among 1033 reservoirs and natural lakes across multiple size classes on a latitudinal gradient in the conterminous United States. In general, reservoirs had significantly greater perimeters, catchment areas, and catchment area:surface area ratios than natural lakes. Interestingly, several lakeshore land use, morphometric, and water quality response variables exhibited significant interactions between waterbody type and latitude. Southern reservoirs were deeper and had higher proportions of forested land and less agriculture and developed land use in their lakeshore than southern natural lakes, whereas northern reservoirs were shallower and had less forest and more agriculture and developed land in their lakeshore than northern natural lakes. Following the waterbody depth and land use data, natural lakes also had greater total phosphorus (TP) concentrations and shallower Secchi disk depths at lower latitudes, whereas reservoirs had greater TP concentrations and shallower Secchi disk depths at higher latitudes. Overall, natural lakes were more eutrophic than reservoirs, having greater total nitrogen and chlorophyll a concentrations, regardless of latitude. Our findings indicate that many physical, chemical, and lakeshore land use characteristics of reservoirs and natural lakes vary on a latitudinal gradient, which has implications for the water quality, ecology, and management of these waterbodies.