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Knowledge about the long history of the anthropogenic inputs of Nitrogen (N) and Phosphorus (P) is crucial to capture long-term N and P processes (legacies) and to investigate water quality and ecosystem health. These inputs include N and P point sources, that originate mainly from wastewater, and that are directly discharged into surface waters, thus having an immediate impact on ecosystem functioning. However, N and P point sources are challenging to estimate, due to the scarcity and uncertainty in observational data. Here, we contribute towards improved characterisation of N and P point sources from wastewater, by providing a long-term (1950--2019), high resolution (0.015625°~ 1.4 km on average) dataset for Germany. The dataset includes both the domestic and industrial emissions treated in wastewater treatment plants and untreated domestic emissions that are collected in the sewer system. We adopt a modelling approach that relies on a large range of data collected from different sources. Importantly, we account for the uncertainties arising from different modelling choices (i.e., coefficients and downscaling approach). We provide 200 gridded N and P point sources realisations, which are constrained and evaluated using available (recent) observations of wastewater treatment plants outgoing loads. We discuss the uncertainties in our reconstructed dataset over a large sample of river basins in Germany, and provide guidance for future uses. Overall, by capturing the long-term spatial and temporal variations in N and P point sources and accounting for uncertainties, our dataset can facilitate long-term and large-scale robust water quality studies. The dataset is available at https://doi.org/10.5281/zenodo.10500535 (Sarrazin et al., 2024). [ABSTRACT FROM AUTHOR]

Long‐term nitrogen (N) transport and retention dynamics across catchments are not well understood. Using a process‐based model for 89 German catchments, results across study catchments reveal that most N surplus (during 1950–2014) was removed by denitrification (mean ± standard deviation: 58 ± 15%) while the remaining fraction was mostly stored in the soil (14% ± 11%). The mean groundwater transit times in these catchments varied from 3.2 to 20.3 years. These results indicate that past N inputs could continue to affect surface and groundwater quality in the coming years. We identified four catchment groups with distinct archetypal N transport and retention dynamics, which are linked to the catchments' climate, topographic, and geological conditions. Overall, our results shed light on long‐term N dynamics in German catchments and how they are linked to catchment characteristics, emphasizing the role of long‐term N accumulation and transport for water quality management and evaluation programs. Plain Language Summary: High nitrate concentrations in German water bodies are quite common. It is unclear to what degree current nitrogen levels in water bodies are due to current or past nitrogen (N) application on agricultural fields. What happened to excess N (N was not taken up by plants) in catchments has not been fully understood. In this study, we modeled the fate of excess N in 89 German catchments during the period 1950–2014. Our results suggest that most of the excess N was removed from the catchment in gaseous form (denitrification), and a substantial portion of the remaining excess N was stored in the soil zone. This soil N can leach into the deeper zone (groundwater) where it may travel for 3–20 years to reach the catchment outlet. We also identified four distinct groups of catchments with different behavior in terms of N transport and storage, which further exhibited different climatic, topographic, and subsurface conditions, suggesting that these factors could play a role in catchment N transport and retention. Overall, our results show that there could be a substantial delay between implemented management practices and resulting changes in surface or groundwater quality, which should be considered in water quality management. Key Points: We provided insights into the long‐term (1950–2014) nitrogen (N) transport and retention across various German catchmentsLarge‐sample assessment shows that 57% of N surplus was removed by denitrification and 15% of N surplus was accumulated in the soil zoneFour catchment clusters with distinct nitrogen transport and retention dynamics were linked to climatic, topographic, and geological factors [ABSTRACT FROM AUTHOR]

The Soil and Water Assessment Tool (SWAT) is one of the most widely used and well-tested eco-hydrological models. However, parameter calibration, sensitivity analysis and uncertainty analysis remain among the most challenging tasks. Existing SWAT parameter calibration, sensitivity analysis, and uncertainty analysis tools are either commercial products or free tools with limited options. This study demonstrates an interactive graphical user interface tool in the R environment for SWAT parameter calibration, sensitivity and uncertainty analyses, and visualization, called R-SWAT. Different R functions/packages for parameter calibration, sensitivity analysis, and uncertainty analysis have been incorporated into R-SWAT. Third-party packages can be integrated into R-SWAT with minimum effort. The application of R-SWAT for a test case study demonstrates its functionalities. In general, R-SWAT (1) is a potential platform for developing and testing new sensitivity or optimization packages, and (2) promotes the understanding of hydrological processes with open-source SWAT and R. • An R tool for SWAT parameter calibration, sensitivity analysis, and uncertainty analysis is introduced. • Integration with new sensitivity or optimization packages is streamlined. • The proposed tool enhances hydrological research with SWAT and R. [ABSTRACT FROM AUTHOR]