Simulating watersheds using loosely integrated model components: Evaluation of computational scaling using OpenMI

Complicated research and management questions regarding watershed systems often require the use of more than one simulation model. Therefore, it is necessary to develop a means to integrate multiple simulation models to predict holistic system response. In this paper we explore the use of a component-based approach for the runtime integration of models, implemented as ''plug-and-play'' software components. The motivation for this work is to quantify performance overhead costs introduced by adopting a component-based paradigm for loosely integrating hydrologic simulation models. We construct a standard rainfall/runoff watershed model using the Open Modeling Interface (OpenMI) Software Development Kit (SDK) where infiltration, surface runoff, and channel routing processes are each implemented as independent model components. We then analyze the performance of this loosely integrated model to quantify computational scaling, using the Hydrologic Engineering Center's Hydrologic Modeling System (HMS) for comparison. Our results suggest that the overhead introduced by runtime communication of data is not significant when applied for semi-distributed watershed modeling. Our analysis was limited to semi-distributed watershed modeling, however, and future research is needed to understand performance and accuracy for more data demanding hydrologic models.