GLOBAL-FATE: A GIS-based model for assessing contaminantsfate in the global river network

Abstract. GLOBAL-FATE is an open-source, multiplatform, and flexible contaminant fate model that links human consumption of pharmaceutical-like compounds with their concentration in the river network at the global scale. GLOBAL-FATE simulates human consumption and excretion of pharmaceuticals, the attenuation of the contaminant load in wastewater treatment plants, and runoff and contaminant routing along the river network under steady-state, including first order decay of the contaminant in rivers reaches, lakes, and reservoirs. We provide a comprehensive description of model equations and the overall structure of the model, with particular attention to input/output datasets. GLOBAL-FATE is written in C and can be compiled in any platform, and uses inputs in standard GIS format. Additionally, the model can be run inside QGIS as a plug-in. The model has no built-in working resolution, which depends on the user inputs. We exemplify the application of GLOBAL-FATE solving the global concentration of diclofenac in the river network. A comparison with a dataset of diclofenac concentration observations in rivers suggest that GLOBAL-FATE can be successfully applied in real case modelling exercises. The model is particularly sensitive to the generation of contaminant loads by human pharmaceutical consumption, and also to the processes governing contaminant attenuation in the river network.