Articles | Volume 30, issue 12
https://doi.org/10.5194/hess-30-4001-2026
© Author(s) 2026. 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-30-4001-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
29 Jun 2026
Research article |
| 29 Jun 2026
| 29 Jun 2026
When does nitrate peak in rivers and why? Catchment traits and climate relate to synchrony with discharge
Lu Yang
CORRESPONDING AUTHOR
School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom
Kieran Khamis
School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom
Julia L. A. Knapp
Department of Earth Sciences, Durham University, Durham, DH1 3LE, United Kingdom
Chair of Hydrology, University of Bayreuth, 95440 Bayreuth, Germany
Joshua R. Larsen
School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, United Kingdom
Birmingham Institute for Forest Research (BIFoR), University of Birmingham, B15 2TT, United Kingdom
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Hydrol. Earth Syst. Sci., 30, 2613–2636, https://doi.org/10.5194/hess-30-2613-2026, https://doi.org/10.5194/hess-30-2613-2026, 2026
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Investigating changing snow in response to global warming can be done with a simple model and only temperature and precipitation data, simplifying snow dynamics with assumptions and parameters. We provide a large-scale and long-term evaluation of this approach and its performance across diverse climates. Temperature thresholds are more robust over cold climates but melt parameters are more robust over warmer climates with deep snow. The model performs well across climates despite its simplicity.
Carolin Winter, Julia L. A. Knapp, and James W. Kirchner
EGUsphere, https://doi.org/10.5194/egusphere-2026-2218, https://doi.org/10.5194/egusphere-2026-2218, 2026
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Droughts not only affect stream water quantity but also its quality, potentially aggravating water scarcity. To understand the underlying mechanisms, we studied the impacts of drought on stream concentrations of ten substances in a forested mountain area. We found that drought affected all substances. The different responses could be explained by changes in the transport by water, combined with biological and chemical processes that alter the availability and mobility of certain substances.
Sudhanshu Dixit, Sumit Sen, Tahmina Yasmin, Kieran Khamis, Debashish Sen, Wouter Buytaert, and David M. Hannah
Nat. Hazards Earth Syst. Sci., 26, 1251–1268, https://doi.org/10.5194/nhess-26-1251-2026, https://doi.org/10.5194/nhess-26-1251-2026, 2026
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Flash floods are becoming more frequent in mountainous regions due to heavier rainstorms. To protect people and property, we are working to better understand local hydrology and improve the efficiency of early warning systems for urban flooding in Lesser Himalayas. By combining community knowledge, low-cost technology, we can enhance understanding of flood dynamics and strengthen preparedness in mountains. This work is a step toward building resilience by bridging science and community insight.
Bradly Deeley and Joshua Larsen
EGUsphere, https://doi.org/10.5194/egusphere-2026-185, https://doi.org/10.5194/egusphere-2026-185, 2026
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Rivers form branching networks that shape how water, pollutants, and organisms move through landscapes. We developed a new computational approach allowing river networks to respond dynamically to rain and flow changes over time. We show that small in-channel structures can strongly increase how long water stays locally in rivers, even when overall downstream flow is unchanged. Helping explain why local modifications can have ecological and environmental effects with minimal water balance impact.
Julia L. A. Knapp, Wouter R. Berghuijs, Marius G. Floriancic, and James W. Kirchner
Hydrol. Earth Syst. Sci., 29, 3673–3685, https://doi.org/10.5194/hess-29-3673-2025, https://doi.org/10.5194/hess-29-3673-2025, 2025
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This study explores how streams react to rain and how water travels through the landscape to reach them, two processes rarely studied together. Using detailed data from two temperate areas, we show that streams respond to rain much faster than rainwater travels to them. Wetter conditions lead to stronger runoff by releasing older stored water, while heavy rainfall moves newer rainwater to streams faster. These findings offer new insights into how water moves through the environment.
Moctar Dembélé, Mathieu Vrac, Natalie Ceperley, Sander J. Zwart, Josh Larsen, Simon J. Dadson, Grégoire Mariéthoz, and Bettina Schaefli
Proc. IAHS, 385, 121–127, https://doi.org/10.5194/piahs-385-121-2024, https://doi.org/10.5194/piahs-385-121-2024, 2024
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This study assesses the impact of climate change on the timing, seasonality and magnitude of mean annual minimum (MAM) flows and annual maximum flows (AMF) in the Volta River basin (VRB). Several climate change projection data are use to simulate river flow under multiple greenhouse gas emission scenarios. Future projections show that AMF could increase with various magnitude but negligible shift in time across the VRB, while MAM could decrease with up to 14 days of delay in occurrence.
Danny Croghan, Pertti Ala-Aho, Jeffrey Welker, Kaisa-Riikka Mustonen, Kieran Khamis, David M. Hannah, Jussi Vuorenmaa, Bjørn Kløve, and Hannu Marttila
Hydrol. Earth Syst. Sci., 28, 1055–1070, https://doi.org/10.5194/hess-28-1055-2024, https://doi.org/10.5194/hess-28-1055-2024, 2024
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The transport of dissolved organic carbon (DOC) from land into streams is changing due to climate change. We used a multi-year dataset of DOC and predictors of DOC in a subarctic stream to find out how transport of DOC varied between seasons and between years. We found that the way DOC is transported varied strongly seasonally, but year-to-year differences were less apparent. We conclude that the mechanisms of transport show a higher degree of interannual consistency than previously thought.
Adrià Fontrodona-Bach, Bettina Schaefli, Ross Woods, Adriaan J. Teuling, and Joshua R. Larsen
Earth Syst. Sci. Data, 15, 2577–2599, https://doi.org/10.5194/essd-15-2577-2023, https://doi.org/10.5194/essd-15-2577-2023, 2023
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We provide a dataset of snow water equivalent, the depth of liquid water that results from melting a given depth of snow. The dataset contains 11 071 sites over the Northern Hemisphere, spans the period 1950–2022, and is based on daily observations of snow depth on the ground and a model. The dataset fills a lack of accessible historical ground snow data, and it can be used for a variety of applications such as the impact of climate change on global and regional snow and water resources.
Anthony Michelon, Natalie Ceperley, Harsh Beria, Joshua Larsen, Torsten Vennemann, and Bettina Schaefli
Hydrol. Earth Syst. Sci., 27, 1403–1430, https://doi.org/10.5194/hess-27-1403-2023, https://doi.org/10.5194/hess-27-1403-2023, 2023
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Streamflow generation processes in high-elevation catchments are largely influenced by snow accumulation and melt. For this work, we collected and analyzed more than 2800 water samples (temperature, electric conductivity, and stable isotopes of water) to characterize the hydrological processes in such a high Alpine environment. Our results underline the critical role of subsurface flow during all melt periods and the presence of snowmelt even during the winter periods.
Tahmina Yasmin, Kieran Khamis, Anthony Ross, Subir Sen, Anita Sharma, Debashish Sen, Sumit Sen, Wouter Buytaert, and David M. Hannah
Nat. Hazards Earth Syst. Sci., 23, 667–674, https://doi.org/10.5194/nhess-23-667-2023, https://doi.org/10.5194/nhess-23-667-2023, 2023
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Floods continue to be a wicked problem that require developing early warning systems with plausible assumptions of risk behaviour, with more targeted conversations with the community at risk. Through this paper we advocate the use of a SMART approach to encourage bottom-up initiatives to develop inclusive and purposeful early warning systems that benefit the community at risk by engaging them at every step of the way along with including other stakeholders at multiple scales of operations.
Moctar Dembélé, Mathieu Vrac, Natalie Ceperley, Sander J. Zwart, Josh Larsen, Simon J. Dadson, Grégoire Mariéthoz, and Bettina Schaefli
Hydrol. Earth Syst. Sci., 26, 1481–1506, https://doi.org/10.5194/hess-26-1481-2022, https://doi.org/10.5194/hess-26-1481-2022, 2022
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Climate change impacts on water resources in the Volta River basin are investigated under various global warming scenarios. Results reveal contrasting changes in future hydrological processes and water availability, depending on greenhouse gas emission scenarios, with implications for floods and drought occurrence over the 21st century. These findings provide insights for the elaboration of regional adaptation and mitigation strategies for climate change.
Doris E. Wendt, John P. Bloomfield, Anne F. Van Loon, Margaret Garcia, Benedikt Heudorfer, Joshua Larsen, and David M. Hannah
Nat. Hazards Earth Syst. Sci., 21, 3113–3139, https://doi.org/10.5194/nhess-21-3113-2021, https://doi.org/10.5194/nhess-21-3113-2021, 2021
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Managing water demand and supply during droughts is complex, as highly pressured human–water systems can overuse water sources to maintain water supply. We evaluated the impact of drought policies on water resources using a socio-hydrological model. For a range of hydrogeological conditions, we found that integrated drought policies reduce baseflow and groundwater droughts most if extra surface water is imported, reducing the pressure on water resources during droughts.
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Short summary
Human activities have greatly increased riverine nitrogen pollution, making it crucial to understand when river nitrate peaks align with high or low flows to improve in management. Across 66 English catchments, agricultural ones peaked during high flows (29%) with wetter winters enhancing hydrological connectivity, whereas urban ones peaked under extremely low-flow conditions (26%). Mixed catchments (45%) shifted towards low-flow peaks in wetter years and to high-flow peaks with rapid runoff.
Human activities have greatly increased riverine nitrogen pollution, making it crucial to...
