Articles | Volume 22, issue 23
https://doi.org/10.5194/bg-22-7647-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-22-7647-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
05 Dec 2025
Research article |
| 05 Dec 2025
| 05 Dec 2025
Investigating relationships between nitrogen inputs and in-stream nitrogen concentrations and exports across catchments in Victoria, Australia
Olaleye Babatunde
CORRESPONDING AUTHOR
Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, Australia
Meenakshi Arora
Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, Australia
Siva Naga Venkat Nara
Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, Australia
Danlu Guo
School of Engineering, College of Systems & Society, The Australian National University, Canberra, ACT, Australia
Ian Cartwright
School of Earth, Atmosphere and Environment, Monash University, Clayton, Vic, Australia
Andrew W. Western
Department of Infrastructure Engineering, The University of Melbourne, Parkville, VIC, Australia
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Tobias F. Selkirk, Andrew W. Western, and J. Angus Webb
Hydrol. Earth Syst. Sci., 29, 5737–5754, https://doi.org/10.5194/hess-29-5737-2025, https://doi.org/10.5194/hess-29-5737-2025, 2025
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This study finds three cycles in yearly rainfall worldwide of approximately 13, 20 and 28 years. The cycles rise and fall together across continents and also appear in the El Niño–Southern Oscillation (ENSO), a major climate driver of rain. However the signal in ENSO is too small to explain the strong local influence, the results point to another, still-unknown force that may shape both the climate modes and global rainfall.
Tobias F. Selkirk, Andrew W. Western, and J. Angus Webb
Hydrol. Earth Syst. Sci., 29, 2167–2184, https://doi.org/10.5194/hess-29-2167-2025, https://doi.org/10.5194/hess-29-2167-2025, 2025
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This study investigated rainfall in eastern Australia to search for patterns that may aid in predicting flood and drought. The current popular consensus is that such cycles do not exist. We analysed 130 years of rainfall using a very modern technique for identifying cycles in complex signals. The results showed strong evidence of three clear cycles of 12.9, 20.4 and 29.1 years with a confidence of 99.99 %. When combined, they showed an 80 % alignment with years of extremely high and low rainfall.
Stephen Lee, Dylan J. Irvine, Clément Duvert, Gabriel C. Rau, and Ian Cartwright
Hydrol. Earth Syst. Sci., 28, 1771–1790, https://doi.org/10.5194/hess-28-1771-2024, https://doi.org/10.5194/hess-28-1771-2024, 2024
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Global groundwater recharge studies collate recharge values estimated using different methods that apply to different timescales. We develop a recharge prediction model, based solely on chloride, to produce a recharge map for Australia. We reveal that climate and vegetation have the most significant influence on recharge variability in Australia. Our recharge rates were lower than other models due to the long timescale of chloride in groundwater. Our method can similarly be applied globally.
Theresa Boas, Heye Reemt Bogena, Dongryeol Ryu, Harry Vereecken, Andrew Western, and Harrie-Jan Hendricks Franssen
Hydrol. Earth Syst. Sci., 27, 3143–3167, https://doi.org/10.5194/hess-27-3143-2023, https://doi.org/10.5194/hess-27-3143-2023, 2023
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In our study, we tested the utility and skill of a state-of-the-art forecasting product for the prediction of regional crop productivity using a land surface model. Our results illustrate the potential value and skill of combining seasonal forecasts with modelling applications to generate variables of interest for stakeholders, such as annual crop yield for specific cash crops and regions. In addition, this study provides useful insights for future technical model evaluations and improvements.
Keirnan Fowler, Murray Peel, Margarita Saft, Tim J. Peterson, Andrew Western, Lawrence Band, Cuan Petheram, Sandra Dharmadi, Kim Seong Tan, Lu Zhang, Patrick Lane, Anthony Kiem, Lucy Marshall, Anne Griebel, Belinda E. Medlyn, Dongryeol Ryu, Giancarlo Bonotto, Conrad Wasko, Anna Ukkola, Clare Stephens, Andrew Frost, Hansini Gardiya Weligamage, Patricia Saco, Hongxing Zheng, Francis Chiew, Edoardo Daly, Glen Walker, R. Willem Vervoort, Justin Hughes, Luca Trotter, Brad Neal, Ian Cartwright, and Rory Nathan
Hydrol. Earth Syst. Sci., 26, 6073–6120, https://doi.org/10.5194/hess-26-6073-2022, https://doi.org/10.5194/hess-26-6073-2022, 2022
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Recently, we have seen multi-year droughts tending to cause shifts in the relationship between rainfall and streamflow. In shifted catchments that have not recovered, an average rainfall year produces less streamflow today than it did pre-drought. We take a multi-disciplinary approach to understand why these shifts occur, focusing on Australia's over-10-year Millennium Drought. We evaluate multiple hypotheses against evidence, with particular focus on the key role of groundwater processes.
Zibo Zhou, Ian Cartwright, and Uwe Morgenstern
Hydrol. Earth Syst. Sci., 26, 4497–4513, https://doi.org/10.5194/hess-26-4497-2022, https://doi.org/10.5194/hess-26-4497-2022, 2022
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Streams may receive water from different sources in their catchment. There is limited understanding of which water stores intermittent streams are connected to. Using geochemistry we show that the intermittent streams in southeast Australia are connected to younger smaller near-river water stores rather than regional groundwater. This makes these streams more vulnerable to the impacts of climate change and requires management of the riparian zone for their protection.
Qichun Yang, Quan J. Wang, Andrew W. Western, Wenyan Wu, Yawen Shao, and Kirsti Hakala
Hydrol. Earth Syst. Sci., 26, 941–954, https://doi.org/10.5194/hess-26-941-2022, https://doi.org/10.5194/hess-26-941-2022, 2022
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Forecasts of evaporative water loss in the future are highly valuable for water resource management. These forecasts are often produced using the outputs of climate models. We developed an innovative method to correct errors in these forecasts, particularly the errors caused by deficiencies of climate models in modeling the changing climate. We apply this method to seasonal forecasts of evaporative water loss across Australia and achieve significant improvements in the forecast quality.
Ian Cartwright
Hydrol. Earth Syst. Sci., 26, 183–195, https://doi.org/10.5194/hess-26-183-2022, https://doi.org/10.5194/hess-26-183-2022, 2022
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Using specific conductivity (SC) to estimate groundwater inflow to rivers is complicated by bank return waters, interflow, and flows off floodplains contributing to baseflow in all but the driest years. Using the maximum SC of the river in dry years to estimate the SC of groundwater produces the best baseflow vs. streamflow trends. The variable composition of baseflow hinders calibration of hydrograph-based techniques to estimate groundwater inflows.
Danlu Guo, Camille Minaudo, Anna Lintern, Ulrike Bende-Michl, Shuci Liu, Kefeng Zhang, and Clément Duvert
Hydrol. Earth Syst. Sci., 26, 1–16, https://doi.org/10.5194/hess-26-1-2022, https://doi.org/10.5194/hess-26-1-2022, 2022
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We investigate the impact of baseflow contribution on concentration–flow (C–Q) relationships across the Australian continent. We developed a novel Bayesian hierarchical model for six water quality variables across 157 catchments that span five climate zones. For sediments and nutrients, the C–Q slope is generally steeper for catchments with a higher median and a greater variability of baseflow contribution, highlighting the key role of variable flow pathways in particulate and solute export.
Michael Kilgour Stewart, Uwe Morgenstern, and Ian Cartwright
Hydrol. Earth Syst. Sci., 25, 6333–6338, https://doi.org/10.5194/hess-25-6333-2021, https://doi.org/10.5194/hess-25-6333-2021, 2021
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The combined use of deuterium and tritium to determine travel time distributions in streams is an important development in catchment hydrology (Rodriguez et al., 2021). This comment, however, argues that their results do not generally invalidate the truncation hypothesis of Stewart et al. (2010) (i.e. that stable isotopes underestimate travel times through catchments), as they imply, but asserts instead that the hypothesis still applies to many other catchments.
Dylan J. Irvine, Cameron Wood, Ian Cartwright, and Tanya Oliver
Hydrol. Earth Syst. Sci., 25, 5415–5424, https://doi.org/10.5194/hess-25-5415-2021, https://doi.org/10.5194/hess-25-5415-2021, 2021
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It is widely assumed that 14C is in contact with the atmosphere until recharging water reaches the water table. Unsaturated zone (UZ) studies have shown that 14C decreases with depth below the land surface. We produce a relationship between UZ 14C and depth to the water table to estimate input 14C activities for groundwater age estimation. Application of the new relationship shows that it is important for UZ processes to be considered in groundwater mean residence time estimation.
Shuci Liu, Dongryeol Ryu, J. Angus Webb, Anna Lintern, Danlu Guo, David Waters, and Andrew W. Western
Hydrol. Earth Syst. Sci., 25, 2663–2683, https://doi.org/10.5194/hess-25-2663-2021, https://doi.org/10.5194/hess-25-2663-2021, 2021
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Riverine water quality can change markedly at one particular location. This study developed predictive models to represent the temporal variation in stream water quality across the Great Barrier Reef catchments, Australia. The model structures were informed by a data-driven approach, which is useful for identifying important factors determining temporal changes in water quality and, in turn, providing critical information for developing management strategies.
Theresa Boas, Heye Bogena, Thomas Grünwald, Bernard Heinesch, Dongryeol Ryu, Marius Schmidt, Harry Vereecken, Andrew Western, and Harrie-Jan Hendricks Franssen
Geosci. Model Dev., 14, 573–601, https://doi.org/10.5194/gmd-14-573-2021, https://doi.org/10.5194/gmd-14-573-2021, 2021
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In this study we were able to significantly improve CLM5 model performance for European cropland sites by adding a winter wheat representation, specific plant parameterizations for important cash crops, and a cover-cropping and crop rotation subroutine to its crop module. Our modifications should be applied in future studies of CLM5 to improve regional yield predictions and to better understand large-scale impacts of agricultural management on carbon, water, and energy fluxes.
Shovon Barua, Ian Cartwright, P. Evan Dresel, and Edoardo Daly
Hydrol. Earth Syst. Sci., 25, 89–104, https://doi.org/10.5194/hess-25-89-2021, https://doi.org/10.5194/hess-25-89-2021, 2021
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We evaluate groundwater recharge rates in a semi-arid area that has undergone land-use changes. The widespread presence of old saline groundwater indicates that pre-land-clearing recharge rates were low and present-day recharge rates are still modest. The fluctuations of the water table and tritium activities reflect present-day recharge rates; however, the water table fluctuation estimates are unrealistically high, and this technique may not be suited for estimating recharge in semi-arid areas.
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Short summary
Excess nitrogen from agriculture can pollute streams and degrade water quality. We estimated fertiliser-nitrogen inputs across land uses, incorporated contributions from other sources, and compared these with long-term stream measurements. Only a small share of inputs left via rivers. Land use, rainfall, and flow regimes strongly influenced nitrogen dynamics and export. These findings support strategies to reduce stream pollution and protect water quality in agricultural areas.
Excess nitrogen from agriculture can pollute streams and degrade water quality. We estimated...
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