Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study
<p>Excess export of nitrate to streams affects ecosystem structure and functions and has been an environmental issue attracting worldwide attention. The dynamics of catchment-scale solute export from diffuse nitrogen sources can be explained by the changes of dominant flow paths, as solute att...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-10-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://hess.copernicus.org/articles/26/5051/2022/hess-26-5051-2022.pdf |
| _version_ | 1811241855474466816 |
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| author | J. Yang Q. Wang I. Heidbüchel I. Heidbüchel C. Lu Y. Xie A. Musolff J. H. Fleckenstein J. H. Fleckenstein |
| author_facet | J. Yang Q. Wang I. Heidbüchel I. Heidbüchel C. Lu Y. Xie A. Musolff J. H. Fleckenstein J. H. Fleckenstein |
| author_sort | J. Yang |
| collection | DOAJ |
| description | <p>Excess export of nitrate to streams affects ecosystem
structure and functions and has been an environmental issue attracting
worldwide attention. The dynamics of catchment-scale solute export from
diffuse nitrogen sources can be explained by the changes of dominant flow
paths, as solute attenuation (including the degradation of nitrate) is
linked to the age composition of outflow. Previous data-driven studies
suggested that catchment topographic slope has strong impacts on the age
composition of streamflow and consequently on in-stream solute
concentrations. However, the impacts have not been systematically assessed
in terms of solute mass fluxes and solute concentration levels, particularly
in humid catchments with strong seasonality in meteorological forcing. To
fill this gap, we modeled the groundwater flow and nitrate transport for a
small agricultural catchment in Central Germany. We used the fully coupled
surface and subsurface numerical simulator HydroGeoSphere (HGS) to model
groundwater and overland flow and nitrate transport. We computed the
water ages using numerical tracer experiments. To represent various
topographic slopes, we additionally simulated 10 synthetic catchments
generated by modifying the topographic slope from the real-world scenario.
Results suggest a negative correlation between the young streamflow fraction
and the topographic slope. This correlation is more pronounced in flat
landscapes with slopes <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo><</mo><mn mathvariant="normal">1</mn><mo>:</mo><mn mathvariant="normal">60</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="38pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="ac31ad2535427cbbe56efba3e546dacf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-26-5051-2022-ie00001.svg" width="38pt" height="10pt" src="hess-26-5051-2022-ie00001.png"/></svg:svg></span></span>. Flatter landscapes tend to retain
more N mass in the soil (including mass degraded in soil) and export less N
mass to the stream, due to reduced leaching and increased degradation. The
mean in-stream nitrate concentration shows a decreasing trend in response to
a decreasing topographic slope, suggesting that a large young streamflow
fraction is not sufficient for high in-stream concentrations. Our results
improve the understanding of nitrate export in response to topographic slope
in a temperate humid climate, with important implications for the management
of stream water quality.</p> |
| first_indexed | 2024-04-12T13:43:22Z |
| format | Article |
| id | doaj.art-dca324d0fe1d481b8392573878f7544d |
| institution | Directory Open Access Journal |
| issn | 1027-5606 1607-7938 |
| language | English |
| last_indexed | 2024-04-12T13:43:22Z |
| publishDate | 2022-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Hydrology and Earth System Sciences |
| spelling | doaj.art-dca324d0fe1d481b8392573878f7544d2022-12-22T03:30:47ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382022-10-01265051506810.5194/hess-26-5051-2022Effect of topographic slope on the export of nitrate in humid catchments: a 3D model studyJ. Yang0Q. Wang1I. Heidbüchel2I. Heidbüchel3C. Lu4Y. Xie5A. Musolff6J. H. Fleckenstein7J. H. Fleckenstein8State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, ChinaState Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, ChinaDepartment of Hydrogeology, UFZ – Helmholtz-Centre for Environmental Research GmbH, Leipzig, GermanyHydrologic Modeling Unit, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, GermanyState Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, ChinaSchool of Earth Sciences and Engineering, University of Nanjing, Nanjing, ChinaDepartment of Hydrogeology, UFZ – Helmholtz-Centre for Environmental Research GmbH, Leipzig, GermanyDepartment of Hydrogeology, UFZ – Helmholtz-Centre for Environmental Research GmbH, Leipzig, GermanyHydrologic Modeling Unit, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany<p>Excess export of nitrate to streams affects ecosystem structure and functions and has been an environmental issue attracting worldwide attention. The dynamics of catchment-scale solute export from diffuse nitrogen sources can be explained by the changes of dominant flow paths, as solute attenuation (including the degradation of nitrate) is linked to the age composition of outflow. Previous data-driven studies suggested that catchment topographic slope has strong impacts on the age composition of streamflow and consequently on in-stream solute concentrations. However, the impacts have not been systematically assessed in terms of solute mass fluxes and solute concentration levels, particularly in humid catchments with strong seasonality in meteorological forcing. To fill this gap, we modeled the groundwater flow and nitrate transport for a small agricultural catchment in Central Germany. We used the fully coupled surface and subsurface numerical simulator HydroGeoSphere (HGS) to model groundwater and overland flow and nitrate transport. We computed the water ages using numerical tracer experiments. To represent various topographic slopes, we additionally simulated 10 synthetic catchments generated by modifying the topographic slope from the real-world scenario. Results suggest a negative correlation between the young streamflow fraction and the topographic slope. This correlation is more pronounced in flat landscapes with slopes <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo><</mo><mn mathvariant="normal">1</mn><mo>:</mo><mn mathvariant="normal">60</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="38pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="ac31ad2535427cbbe56efba3e546dacf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-26-5051-2022-ie00001.svg" width="38pt" height="10pt" src="hess-26-5051-2022-ie00001.png"/></svg:svg></span></span>. Flatter landscapes tend to retain more N mass in the soil (including mass degraded in soil) and export less N mass to the stream, due to reduced leaching and increased degradation. The mean in-stream nitrate concentration shows a decreasing trend in response to a decreasing topographic slope, suggesting that a large young streamflow fraction is not sufficient for high in-stream concentrations. Our results improve the understanding of nitrate export in response to topographic slope in a temperate humid climate, with important implications for the management of stream water quality.</p>https://hess.copernicus.org/articles/26/5051/2022/hess-26-5051-2022.pdf |
| spellingShingle | J. Yang Q. Wang I. Heidbüchel I. Heidbüchel C. Lu Y. Xie A. Musolff J. H. Fleckenstein J. H. Fleckenstein Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study Hydrology and Earth System Sciences |
| title | Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study |
| title_full | Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study |
| title_fullStr | Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study |
| title_full_unstemmed | Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study |
| title_short | Effect of topographic slope on the export of nitrate in humid catchments: a 3D model study |
| title_sort | effect of topographic slope on the export of nitrate in humid catchments a 3d model study |
| url | https://hess.copernicus.org/articles/26/5051/2022/hess-26-5051-2022.pdf |
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