Articles | Volume 26, issue 23
https://doi.org/10.5194/hess-26-6227-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/hess-26-6227-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
12 Dec 2022
Research article |
| 12 Dec 2022
| 12 Dec 2022
Disentangling scatter in long-term concentration–discharge relationships: the role of event types
Felipe A. Saavedra
CORRESPONDING AUTHOR
Department Catchment Hydrology, Helmholtz Centre for Environmental Research – UFZ, Halle (Saale), 06120, Germany
Andreas Musolff
Department of Hydrogeology, Helmholtz Centre for Environmental Research – UFZ, Leipzig, 04318, Germany
Jana von Freyberg
School of Architecture, Civil and Environmental Engineering, EPFL, 1015 Lausanne, Switzerland
Mountain Hydrology and Mass Movements, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), 8903 Birmensdorf, Switzerland
Ralf Merz
Department Catchment Hydrology, Helmholtz Centre for Environmental Research – UFZ, Halle (Saale), 06120, Germany
Stefano Basso
Department Catchment Hydrology, Helmholtz Centre for Environmental Research – UFZ, Halle (Saale), 06120, Germany
Larisa Tarasova
Department Catchment Hydrology, Helmholtz Centre for Environmental Research – UFZ, Halle (Saale), 06120, Germany
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Christian Czakay, Larisa Tarasova, and Bodo Ahrens
Nat. Hazards Earth Syst. Sci., 26, 5609–5631, https://doi.org/10.5194/nhess-26-5609-2026, https://doi.org/10.5194/nhess-26-5609-2026, 2026
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In this study, we simulated streamflow in German river catchments for climate projections using a deep learning model. Flood-generating processes were identified using explainable artificial intelligence. In the median, the models project mostly less rain-on-snow floods in Germany in the future and an overall lower importance of snowmelt. The average and strongest rain-on-snow floods will have a higher magnitude. The trends found for the individual climate models can vary considerably.
Tam V. Nguyen, Rohini Kumar, José L. J. Ledesma, Pia Ebeling, Jan H. Fleckenstein, and Andreas Musolff
Hydrol. Earth Syst. Sci., 30, 5749–5768, https://doi.org/10.5194/hess-30-5749-2026, https://doi.org/10.5194/hess-30-5749-2026, 2026
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Lumped and landscape-explicit dissolved organic carbon (DOC) models are commonly calibrated using stream DOC concentrations, while internal DOC dynamics in different model compartments are not given enough attention. Our study shows that stream DOC alone is insufficient to constrain internal DOC dynamics. Applying models calibrated in this way under changing boundary conditions may therefore lead to unrealistic results.
José L. J. Ledesma, Paul D. Burkhardt, Susana Bernal, and Andreas Musolff
EGUsphere, https://doi.org/10.5194/egusphere-2026-4221, https://doi.org/10.5194/egusphere-2026-4221, 2026
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We compared more than 200 rainfall events in four small forested river basins, from Mediterranean Spain to Germany and Sweden. Rainfall amount and prior wetness controlled how strongly streams and nearby groundwater responded, but the timing and connection between them differed among climates. These differences help explain when water and dissolved substances are mobilised and how headwater environments may respond to a changing climate.
Alexander Hubig, Pia Ebeling, and Andreas Musolff
EGUsphere, https://doi.org/10.5194/egusphere-2026-3240, https://doi.org/10.5194/egusphere-2026-3240, 2026
This preprint is open for discussion and under review for Hydrology and Earth System Sciences (HESS).
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Reports of riverine algal blooms during recent droughts imply a link between low-flow conditions and eutrophication impacts. Here, we present evidence from observations of total phosphorus, chlorophyll a, and discharge that anomalously low discharge relates to anomalously high chlorophyll a per total phosphorus across multiple sites as well as more frequent algal blooms. The increased risk of algal blooms highlight the challenges for future river management under intensifying drought conditions.
Alexander Hubig, Pia Ebeling, Daniel Graeber, Ulrike Scharfenberger, and Andreas Musolff
EGUsphere, https://doi.org/10.5194/egusphere-2026-830, https://doi.org/10.5194/egusphere-2026-830, 2026
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This study investigates seasonal eutrophication patterns in rivers using chlorophyll a and total phosphorus concentration data from 133 monitoring sites in Germany. We identified five archetypal seasonal patterns explained by distinct seasonal dynamics of nutrients and physical drivers and by properties of the upstream catchment and river network. These patterns highlight critical locations and periods of phytoplankton blooms and implications for eutrophication management.
Pia Ebeling, Alexander Hubig, Alexander Wachholz, Ulrike Scharfenberger, Sarah Haug, Tam Nguyen, Fanny Sarrazin, Masooma Batool, Andreas Musolff, and Rohini Kumar
Earth Syst. Sci. Data, 18, 691–712, https://doi.org/10.5194/essd-18-691-2026, https://doi.org/10.5194/essd-18-691-2026, 2026
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The updated river water quality data set for Germany offers longer records, new variables such as water temperature and oxygen, and time series of pollution sources, and it adds more stations with both water quality and flow data. These improvements provide clearer insights into how stream water quality changes over time and how human activities affect aquatic ecosystems.
Pia Ebeling, Andreas Musolff, Rohini Kumar, Andreas Hartmann, and Jan H. Fleckenstein
Hydrol. Earth Syst. Sci., 29, 2925–2950, https://doi.org/10.5194/hess-29-2925-2025, https://doi.org/10.5194/hess-29-2925-2025, 2025
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Groundwater is a crucial resource at risk due to droughts. To understand drought effects on groundwater levels in Germany, we grouped 6626 wells into six regional and two national patterns. Weather explained half of the level variations with varied response times. Shallow groundwater responds fast and is more vulnerable to short droughts (a few months). Dampened deep heads buffer short droughts but suffer from long droughts and recoveries. Two nationwide trend patterns were linked to human water use.
Izabela Bujak-Ozga, Jana von Freyberg, Margaret Zimmer, Andrea Rinaldo, Paolo Benettin, and Ilja van Meerveld
Hydrol. Earth Syst. Sci., 29, 2339–2359, https://doi.org/10.5194/hess-29-2339-2025, https://doi.org/10.5194/hess-29-2339-2025, 2025
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Stream networks expand and contract, affecting the amount and quality of water in perennial streams. This study presents measurements of changes in water chemistry and the flowing portion of the drainage network during rainfall events in two neighboring catchments. Despite the proximity and similar size, soil, and bedrock, water chemistry and stream network dynamics differed substantially in the two catchments. These differences are attributed to the differences in the slope and channel network.
Hsing-Jui Wang, Ralf Merz, and Stefano Basso
Hydrol. Earth Syst. Sci., 29, 1525–1548, https://doi.org/10.5194/hess-29-1525-2025, https://doi.org/10.5194/hess-29-1525-2025, 2025
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Extreme floods are more common than expected. Knowing where these floods are likely to occur is key for risk management. Traditional methods struggle with limited data, causing uncertainty. We use common streamflow dynamics to indicate extreme flood propensity. Analyzing data from Atlantic Europe, northern Europe, and the US, we validate this novel approach and unravel intrinsic linkages between regional geographic patterns and extreme flood drivers.
Ralf Loritz, Alexander Dolich, Eduardo Acuña Espinoza, Pia Ebeling, Björn Guse, Jonas Götte, Sibylle K. Hassler, Corina Hauffe, Ingo Heidbüchel, Jens Kiesel, Mirko Mälicke, Hannes Müller-Thomy, Michael Stölzle, and Larisa Tarasova
Earth Syst. Sci. Data, 16, 5625–5642, https://doi.org/10.5194/essd-16-5625-2024, https://doi.org/10.5194/essd-16-5625-2024, 2024
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The CAMELS-DE dataset features data from 1582 streamflow gauges across Germany, with records spanning from 1951 to 2020. This comprehensive dataset, which includes time series of up to 70 years (median 46 years), enables advanced research on water flow and environmental trends and supports the development of hydrological models.
Christina Franziska Radtke, Xiaoqiang Yang, Christin Müller, Jarno Rouhiainen, Ralf Merz, Stefanie R. Lutz, Paolo Benettin, Hong Wei, and Kay Knöller
Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2024-109, https://doi.org/10.5194/hess-2024-109, 2024
Revised manuscript not accepted
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Most studies assume no difference between transit times of water and nitrate, because nitrate is transported by water. With an 8-year high-frequency dataset of isotopic signatures of both, water and nitrate, and a transit time model, we show the temporal varying difference of nitrate and water transit times. This finding is highly relevant for applied future research related to nutrient dynamics in landscapes under anthropogenic forcing and for managing impacts of nitrate on aquatic ecosystems.
Alessio Gentile, Jana von Freyberg, Davide Gisolo, Davide Canone, and Stefano Ferraris
Hydrol. Earth Syst. Sci., 28, 1915–1934, https://doi.org/10.5194/hess-28-1915-2024, https://doi.org/10.5194/hess-28-1915-2024, 2024
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Can we leverage high-resolution and low-cost EC measurements and biweekly δ18O data to estimate the young water fraction at higher temporal resolution? Here, we present the EXPECT method that combines two widespread techniques: EC-based hydrograph separation and sine-wave models of the seasonal isotope cycles. The method is not without its limitations, but its application in three small Swiss catchments is promising for future applications in catchments with different characteristics.
Matteo Pesce, Alberto Viglione, Jost von Hardenberg, Larisa Tarasova, Stefano Basso, Ralf Merz, Juraj Parajka, and Rui Tong
Proc. IAHS, 385, 65–69, https://doi.org/10.5194/piahs-385-65-2024, https://doi.org/10.5194/piahs-385-65-2024, 2024
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The manuscript describes an application of PArameter Set Shuffling (PASS) approach in the Alpine region. A machine learning decision-tree algorithm is applied for the regional calibration of a conceptual semi-distributed hydrological model. Regional model efficiencies don't decrease significantly when moving in space from catchments used for the regional calibration (training) to catchments used for the procedure validation (test) and, in time, from the calibration to the verification period.
Hsing-Jui Wang, Ralf Merz, Soohyun Yang, and Stefano Basso
Hydrol. Earth Syst. Sci., 27, 4369–4384, https://doi.org/10.5194/hess-27-4369-2023, https://doi.org/10.5194/hess-27-4369-2023, 2023
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Accurately assessing heavy-tailed flood behavior with limited data records is challenging and can lead to inaccurate hazard estimates. Our research introduces a new index that uses hydrograph recession to identify heavy-tailed flood behavior, compare severity, and produce reliable results with short data records. This index overcomes the limitations of current metrics, which lack physical meaning and require long records. It thus provides valuable insight into the flood hazard of river basins.
Michael Rode, Jörg Tittel, Frido Reinstorf, Michael Schubert, Kay Knöller, Benjamin Gilfedder, Florian Merensky-Pöhlein, and Andreas Musolff
Hydrol. Earth Syst. Sci., 27, 1261–1277, https://doi.org/10.5194/hess-27-1261-2023, https://doi.org/10.5194/hess-27-1261-2023, 2023
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Agricultural catchments show elevated phosphorus (P) concentrations during summer low flow. In an agricultural stream, we found that phosphorus in groundwater was a major source of stream water phosphorus during low flow, and stream sediments derived from farmland are unlikely to have increased stream phosphorus concentrations during low water. We found no evidence that riparian wetlands contributed to soluble reactive (SR) P loads. Agricultural phosphorus was largely buffered in the soil zone.
Carolin Winter, Tam V. Nguyen, Andreas Musolff, Stefanie R. Lutz, Michael Rode, Rohini Kumar, and Jan H. Fleckenstein
Hydrol. Earth Syst. Sci., 27, 303–318, https://doi.org/10.5194/hess-27-303-2023, https://doi.org/10.5194/hess-27-303-2023, 2023
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The increasing frequency of severe and prolonged droughts threatens our freshwater resources. While we understand drought impacts on water quantity, its effects on water quality remain largely unknown. Here, we studied the impact of the unprecedented 2018–2019 drought in Central Europe on nitrate export in a heterogeneous mesoscale catchment in Germany. We show that severe drought can reduce a catchment's capacity to retain nitrogen, intensifying the internal pollution and export of nitrate.
Jie Yang, Qiaoyu Wang, Ingo Heidbüchel, Chunhui Lu, Yueqing Xie, Andreas Musolff, and Jan H. Fleckenstein
Hydrol. Earth Syst. Sci., 26, 5051–5068, https://doi.org/10.5194/hess-26-5051-2022, https://doi.org/10.5194/hess-26-5051-2022, 2022
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We assessed the effect of catchment topographic slopes on the nitrate export dynamics in terms of the nitrogen mass fluxes and concentration level using a coupled surface–subsurface model. We found that flatter landscapes tend to retain more nitrogen mass in the soil and export less nitrogen mass to the stream, explained by the reduced leaching and increased potential of degradation in flat landscapes. We emphasized that stream water quality is potentially less vulnerable in flatter landscapes.
Pia Ebeling, Rohini Kumar, Stefanie R. Lutz, Tam Nguyen, Fanny Sarrazin, Michael Weber, Olaf Büttner, Sabine Attinger, and Andreas Musolff
Earth Syst. Sci. Data, 14, 3715–3741, https://doi.org/10.5194/essd-14-3715-2022, https://doi.org/10.5194/essd-14-3715-2022, 2022
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Environmental data are critical for understanding and managing ecosystems, including the mitigation of water quality degradation. To increase data availability, we present the first large-sample water quality data set (QUADICA) of riverine macronutrient concentrations combined with water quantity, meteorological, and nutrient forcing data as well as catchment attributes. QUADICA covers 1386 German catchments to facilitate large-sample data-driven and modeling water quality assessments.
Joni Dehaspe, Fanny Sarrazin, Rohini Kumar, Jan H. Fleckenstein, and Andreas Musolff
Hydrol. Earth Syst. Sci., 25, 6437–6463, https://doi.org/10.5194/hess-25-6437-2021, https://doi.org/10.5194/hess-25-6437-2021, 2021
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Increased nitrate concentrations in surface waters can compromise river ecosystem health. As riverine nitrate uptake is hard to measure, we explore how low-frequency nitrate concentration and discharge observations (that are widely available) can help to identify (in)efficient uptake in river networks. We find that channel geometry and water velocity rather than the biological uptake capacity dominate the nitrate-discharge pattern at the outlet. The former can be used to predict uptake.
Benedikt J. Werner, Oliver J. Lechtenfeld, Andreas Musolff, Gerrit H. de Rooij, Jie Yang, Ralf Gründling, Ulrike Werban, and Jan H. Fleckenstein
Hydrol. Earth Syst. Sci., 25, 6067–6086, https://doi.org/10.5194/hess-25-6067-2021, https://doi.org/10.5194/hess-25-6067-2021, 2021
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Export of dissolved organic carbon (DOC) from riparian zones (RZs) is an important yet poorly understood component of the catchment carbon budget. This study chemically and spatially classifies DOC source zones within a RZ of a small catchment to assess DOC export patterns. Results highlight that DOC export from only a small fraction of the RZ with distinct DOC composition dominates overall DOC export. The application of a spatial, topographic proxy can be used to improve DOC export models.
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Short summary
Nitrate contamination of rivers from agricultural sources is a challenge for water quality management. During runoff events, different transport paths within the catchment might be activated, generating a variety of responses in nitrate concentration in stream water. Using nitrate samples from 184 German catchments and a runoff event classification, we show that hydrologic connectivity during runoff events is a key control of nitrate transport from catchments to streams in our study domain.
Nitrate contamination of rivers from agricultural sources is a challenge for water quality...
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