Modeling Total Phosphorus Transport in the European Riverine System: Parameterization and Projections under Climate and Socioeconomic Scenarios

Abstract. Eutrophication is recognized as a critical ecological challenge that detrimentally affects aquatic ecosystems in both riverine and marine environments. Understanding how future human actions may influence nutrient pollution is crucial for mitigating these effects. While studies have focused on phosphorus trends related to fertilizer use in cropland areas only, this study also considers land-use changes and human development as defined by the Shared Socioeconomic Pathways (SSPs). Phosphorus transport trends are estimated using a new parameterization in a hydrological model, taking into account the evolution of agricultural, urban, and natural land use types, in line with the SSP narratives, as well as aquaculture activities, atmospheric deposition, and weathering process. Additionally, the effects of global warming are integrated by incorporating simulated hydrological data following three Representative Concentration Pathways scenarios. Total phosphorus load budgets are estimated for the four semi-enclosed European seas. The findings indicate that phosphorus losses are primarily driven by human development and land-use expansion, outweighing the response from pollution control policies and technological advances and, to some extent, hydrological changes due to climate change. The scenario data generated, and the new parameterization implemented within an Earth system model framework, can serve as a valuable resource for ecosystem modeling efforts.