Missouri reservoirs in the Glacial Plains: evaluating small impoundments

Missouri reservoirs are located in a mid-contment ecotonal zone at the intersection of historic prairies and broad-leafed forests. Reservoir nutrients span the trophic state range and increase along a south-to-north axis across several distinct physiographic regions (JoNES et al. 2008a). Empirical analyses show this pattem is largely accounted for by cropland cover in the catchments (a surrogate for nutrient los s from agriculture) as modified by morphology and hydrology (JoNES et al. 2004, 2008b, 2009). These findings are consistent with limnological theory about the role ofhydrology and morphology moditying extemal nutrient loads to lakes. Most Missouri reservoirs were constructed within the past 50 years, but many are half that age. With few exceptions, land cover at the time of impoundment closely matched current conditions (JoNES et al. 2004, 2009). As such, nutrient loads were in place prior to creating these artificiallakes on the landscape. Reservoir age does not influence cross-system pattems for nutrients, suggesting that trophic state is largely