The AgroEcoSystem-Watershed (AgES-W) Model: Overview and Application to Experimental Watersheds

Abstract.

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 synopsis of current challenges and advances in distributed watershed modeling. Next, we provide an overview of major AgroEcoSystem-Watershed (AgES-W) model processes, simulation components, and input/output file structure. AgES-W is a modular, Java-based spatially distributed model which implements hydrologic/water quality (H/WQ) simulation components under the Object Modeling System (OMS3) environmental modeling framework. AgES-W has been previously evaluated for streamflow and recently has been enhanced with the addition of nitrogen (N) and sediment modeling components refactored from various agroecosystem models including SWAT, WEPP, and RZWQM2. Application of the AgES-W model to the Upper Gera, Germany and Upper Cedar Creek, Indiana, USA watersheds is presented to demonstrate many of the modeling advances that are currently available for watershed management at multiple scales. AgES-W model evaluation includes statistical comparisons of simulated flows and N/sediment loads using monitoring data from the Upper Gera and Upper Cedar Creek watershed outlets. Comparisons of simulated and observed daily and average monthly streamflow/N loading and daily sediment load for different simulation periods resulted in E_NS and PBIAS values that were within the range of those reported in the literature for other H/WQ models at a similar scale and time step. Considering that AgES-W was applied with minimal calibration, study results indicate that the model reasonably reproduced the hydrological, N, and sediment dynamics of the experimental watersheds and should serve as a foundation upon which to better quantify additional water quality indicators (e.g., phosphorus dynamics) at the watershed scale. In addition to the above AgES-W evaluation, we also examine the efficacy of AgES-W for assessing spatially targeted agricultural conservation effects on water quantity and quality on the South Fork Watershed in central Iowa, USA.