Challenges/Advances in Distributed Watershed Modeling: A Review and Application of the AgroEcoSystem-Watershed (AgES-W) Model

Progress in the understanding of physical, chemical, and biological processes influencing water quality, coupled with advances in the collection and analysis of hydrologic data, provide opportunities for significant innovations in the manner and level with which watershed-scale processes may be quantified and modeled. This paper first provides a brief review of current challenges and advances in distributed watershed modeling including quantifying and coping with the uncertainty, data availability, influence of data resolution and scaling issues, and the use of environmental modeling frameworks that help maintain model modularity, reusability, and interoperability (or compatibility). Important findings and observed trends from this work include: 1) limitations in scaling of hydrological/water quality processes for watershed modeling; 2) the impacts of data provisioning (availability and resolution) on watershed modeling capabilities, and 3) recommendations concerning the employment of a more holistic component-based modeling approach that is capable of examining individual processes and systems and the interconnection between them. In addition, an application of the AgroEcoSystem-Watershed (AgES-W) modular, Java-based spatially distributed model to the Upper Gera, Germany and Upper Cedar Creek, Indiana, USA watersheds is presented to demonstrate many of the advances described above that are currently available for watershed management at multiple scales. Model evaluations will include statistical comparisons of AgES-W simulated flows and N/sediment loads using monitoring data from the Upper Gera and Upper Cedar Creek outlets.