The age of water and carbon in lake-catchments: A simple dynamical model

The rate at which water and carbon move through lake-catchments influences carbon metabolism, storage, and transport to down-stream ecosystems. This article focuses on conceptual-mathematical modeling of the age of water and carbon in lake-catchment systems, where age is defined as the time since the water parcel and environmental tracer entered the system. We test a framework for implementing models and data for the Lake Mendota lake-catchment system. We show that the lake-catchment system provides the basis for predicting time varying age of carbon along flow paths, and the residence times of dissolved organic carbon (DOC) leaving each compartment, which further helps to provide a deeper understanding of fundamental biogeochemical dynamic processes of carbon and water cycling within the lake-catchment system. Three scenarios illustrate how the age of DOC might evolve from climate or land cover change that alters the hydrologic water balance through increases or decreases in lake-catchment precipitation and evapotranspiration.