Simulation Decomposition Analysis of the Iowa Food–Water–Energy System

This study applies Simulation Decomposition (SimDec) to a large-scale Iowa food–water–energy (IFEW) system model, focusing on nitrogen export into the Mississippi River. The paper demonstrates how SimDec enables sensitivity analysis not only at the low-level input stage (individual livestock and crop variables), but also at the aggregate level (manure nitrogen, commercial nitrogen, fixation nitrogen, grain nitrogen).

The analysis reveals manure nitrogen (MN) as the dominant driver of nitrogen surplus, while also uncovering heterogeneous interactions between aggregate variables that conventional Sobol’-based approaches cannot visualize clearly. A multi-level sensitivity profile connects low-level inputs to aggregate drivers and ultimately to system-level outcomes, illustrating how SimDec supports holistic interpretation of complex environmental models.

The work showcases SimDec’s ability to handle dependent variables and to integrate sensitivity indices directly with visual decomposition, providing decision-relevant insight for large computational sustainability models.