Application of Hierarchy Theory to Cross-Scale Hydrologic Modeling of Nutrient Loads

We describe a framework called <Emphasis Type="Bold">Regional <Emphasis Type="Bold">Hydrologic <Emphasis Type="Bold">Modeling for <Emphasis Type="Bold">Environmental <Emphasis Type="Bold">Evaluation (RHyME<Superscript>2</Superscript>) for hydrologic modeling across scales. Rooted from hierarchy theory, RHyME<Superscript>2</Superscript> acknowledges the rate-based hierarchical structure of hydrological systems. Operationally, hierarchical constraints are accounted for and explicitly described in models put together into RHyME<Superscript>2</Superscript>. We illustrate RHyME<Superscript>2</Superscript>with a two-module model to quantify annual nutrient loads in stream networks and watersheds at regional and subregional levels. High values of R<Superscript>2</Superscript> (>0.95) and the Nash–Sutcliffe model efficiency coefficient (>0.85) and a systematic connection between the two modules show that the hierarchy theory-based RHyME<Superscript>2</Superscript> framework can be used effectively for developing and connecting hydrologic models to analyze the dynamics of hydrologic systems. Copyright Springer Science+Business Media Dordrecht 2013