hydroMOPSO: A flexible and model-independent multi-objective optimisation R package for environmental and hydrological models

This article introduces hydroMOPSO , a multi-objective, model-independent R package for the calibration of hydrological and environmental models. It supports both R-based and R-external models through wrapper functions, providing flexibility for a wide range of optimisation problems. The package includes fine-tuning options to generate a Pareto-optimal front. The performance of hydroMOPSO was compared to the caRamel R package using benchmark functions and case studies involving two R-based hydrological models in an Andean catchment. hydroMOPSO outperformed caRamel on benchmarks, with faster convergence in the two hydrological models. An R-external case study demonstrated the flexibility and ease of use of hydroMOPSO , through its application to the calibration of the SWAT+ model. The package also enables the generation of informative outputs for modellers, with particular emphasis on hydrographs and parameter sets from the Pareto-optimal front. hydroMOPSO constitutes a valuable tool for researchers and practitioners seeking to implement multi-objective optimisation in environmental and hydrological modelling.