Toward data-driven generation and evaluation of model structure for integrated representations of human behavior in water resources systems

Abstract:

Simulations of human behavior in integrated systems are challenged by uncertainty in model structure and parameters. The increasing availability of multi-sector observations describing these systems provides the opportunity to infer a set of plausible model structures using data-driven approaches. This study develops a three-phase approach to the inference of model structures and parameterizations from heterogeneous data: problem definition, model generation, and model evaluation. The approach is illustrated on a case study in the Tulare Basin, California, where agricultural land use decisions are informed by past land use, water availability, and economic data. We encode the generalized decision problem as an arbitrary mapping from a high-dimensional data space to the action of interest and use multi-objective genetic programming to search over a family of functions that perform this mapping for both regression and classification tasks. To facilitate the discovery of models that are both realistic and interpretable, the algorithm selects model structures based on multi-objective optimization of (1) their performance on a training set and (2) complexity, measured by the number of variables, constants, and operations composing the model. After training, optimal model structures are further evaluated according to their ability to generalize to held-out test data and clustered based on their performance, complexity, and generalization properties. Finally, we diagnose the causes of good and bad generalization by performing sensitivity analysis across model inputs and within clusters. This study serves as a template to inform and automate the problem-dependent task of constructing robust data-driven model structures to describe human behavior in integrated systems.