Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plain
<p>Glacierized alpine catchments are rapidly evolving due to glacier retreat and consequent geomorphological and ecological changes. As more terrain becomes ice-free, reworking of exposed terrain by the river as well as thawing of the top layer may lead to an increase in surface and subsurface...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-02-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://hess.copernicus.org/articles/28/735/2024/hess-28-735-2024.pdf |
| _version_ | 1797303252844281856 |
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| author | T. Müller T. Müller M. Roncoroni D. Mancini S. N. Lane B. Schaefli B. Schaefli |
| author_facet | T. Müller T. Müller M. Roncoroni D. Mancini S. N. Lane B. Schaefli B. Schaefli |
| author_sort | T. Müller |
| collection | DOAJ |
| description | <p>Glacierized alpine catchments are rapidly evolving due to glacier retreat and consequent geomorphological and ecological changes. As more terrain becomes ice-free, reworking of exposed terrain by the river as well as thawing of the top layer may lead to an increase in surface and subsurface water exchanges, leading to potential changes in water storage and release, which in turn may impact ecological, geomorphological and hydrological processes. In this study, we aim to understand the current and future hydrological functioning of a typical outwash plain in a Swiss Alpine catchment. As with many other fluvial aquifers in alpine environments, this outwash plain is located at the valley bottom, where catchment-wide water and sediment fluxes tend to gather from multiple sources, may store water and provide specific habitats for alpine ecosystems. Their dynamics are however rarely studied in post Little Ice Age proglacial zones. Based on geophysical investigations as well as year-round stream and groundwater observations, we developed a simplified physically based 3D MODFLOW model and performed an optimized automatic calibration using PEST HP. We highlight the strong interactions between the upstream river and the aquifer, with stream infiltration being the dominant process of recharge. Groundwater exfiltration occurs in the lower half of the outwash plain, balancing out the amount of river infiltration at a daily timescale. We show that hillslope contributions from rain and snowmelt have little impact on groundwater levels. We also show that the outwash plain acts as a bedrock-dammed aquifer and can maintain groundwater levels close to the surface during dry periods lasting months, even in the absence of glacier meltwater, but may in turn provide only limited baseflow to the stream. Finally, we explore how new outwash plains may form in the future in this catchment due to glacier recession and discuss from a hydrological perspective which cascading impacts the presence of multiple outwash plains may have. For this case study, we estimate the total dynamic storage of future outwash plains to be about 20 mm, and we demonstrate their limited capacity to provide more stream water than that which they infiltrate upstream, except for very low river flows (<span class="inline-formula"><150</span> to 200 L s<span class="inline-formula"><sup>−1</sup></span>). Below this limit, they can provide limited baseflow on timescales of weeks, thus maintaining moisture conditions that may be beneficial for proglacial ecosystems. Their role in attenuating floods also appears limited, as less than 0.5 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span> of river water can be infiltrated. The studied outwash plain appears therefore to play an important role for alpine ecosystems but has a marginal hydrological effect on downstream river discharge.</p> |
| first_indexed | 2024-03-07T23:50:12Z |
| format | Article |
| id | doaj.art-8480af026bfd4b748915fb427526f238 |
| institution | Directory Open Access Journal |
| issn | 1027-5606 1607-7938 |
| language | English |
| last_indexed | 2024-03-07T23:50:12Z |
| publishDate | 2024-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Hydrology and Earth System Sciences |
| spelling | doaj.art-8480af026bfd4b748915fb427526f2382024-02-19T07:41:17ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382024-02-012873575910.5194/hess-28-735-2024Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plainT. Müller0T. Müller1M. Roncoroni2D. Mancini3S. N. Lane4B. Schaefli5B. Schaefli6Institute of Earth Surface Dynamics, University of Lausanne, 1015 Lausanne, SwitzerlandInstitute of Geography (GIUB), University of Bern, 3012 Bern, SwitzerlandInstitute of Earth Surface Dynamics, University of Lausanne, 1015 Lausanne, SwitzerlandInstitute of Earth Surface Dynamics, University of Lausanne, 1015 Lausanne, SwitzerlandInstitute of Earth Surface Dynamics, University of Lausanne, 1015 Lausanne, SwitzerlandOeschger Centre for Climate Change Research (OCCR), University of Bern, 3012 Bern, SwitzerlandInstitute of Geography (GIUB), University of Bern, 3012 Bern, Switzerland<p>Glacierized alpine catchments are rapidly evolving due to glacier retreat and consequent geomorphological and ecological changes. As more terrain becomes ice-free, reworking of exposed terrain by the river as well as thawing of the top layer may lead to an increase in surface and subsurface water exchanges, leading to potential changes in water storage and release, which in turn may impact ecological, geomorphological and hydrological processes. In this study, we aim to understand the current and future hydrological functioning of a typical outwash plain in a Swiss Alpine catchment. As with many other fluvial aquifers in alpine environments, this outwash plain is located at the valley bottom, where catchment-wide water and sediment fluxes tend to gather from multiple sources, may store water and provide specific habitats for alpine ecosystems. Their dynamics are however rarely studied in post Little Ice Age proglacial zones. Based on geophysical investigations as well as year-round stream and groundwater observations, we developed a simplified physically based 3D MODFLOW model and performed an optimized automatic calibration using PEST HP. We highlight the strong interactions between the upstream river and the aquifer, with stream infiltration being the dominant process of recharge. Groundwater exfiltration occurs in the lower half of the outwash plain, balancing out the amount of river infiltration at a daily timescale. We show that hillslope contributions from rain and snowmelt have little impact on groundwater levels. We also show that the outwash plain acts as a bedrock-dammed aquifer and can maintain groundwater levels close to the surface during dry periods lasting months, even in the absence of glacier meltwater, but may in turn provide only limited baseflow to the stream. Finally, we explore how new outwash plains may form in the future in this catchment due to glacier recession and discuss from a hydrological perspective which cascading impacts the presence of multiple outwash plains may have. For this case study, we estimate the total dynamic storage of future outwash plains to be about 20 mm, and we demonstrate their limited capacity to provide more stream water than that which they infiltrate upstream, except for very low river flows (<span class="inline-formula"><150</span> to 200 L s<span class="inline-formula"><sup>−1</sup></span>). Below this limit, they can provide limited baseflow on timescales of weeks, thus maintaining moisture conditions that may be beneficial for proglacial ecosystems. Their role in attenuating floods also appears limited, as less than 0.5 m<span class="inline-formula"><sup>3</sup></span> s<span class="inline-formula"><sup>−1</sup></span> of river water can be infiltrated. The studied outwash plain appears therefore to play an important role for alpine ecosystems but has a marginal hydrological effect on downstream river discharge.</p>https://hess.copernicus.org/articles/28/735/2024/hess-28-735-2024.pdf |
| spellingShingle | T. Müller T. Müller M. Roncoroni D. Mancini S. N. Lane B. Schaefli B. Schaefli Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plain Hydrology and Earth System Sciences |
| title | Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plain |
| title_full | Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plain |
| title_fullStr | Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plain |
| title_full_unstemmed | Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plain |
| title_short | Current and future roles of meltwater–groundwater dynamics in a proglacial Alpine outwash plain |
| title_sort | current and future roles of meltwater groundwater dynamics in a proglacial alpine outwash plain |
| url | https://hess.copernicus.org/articles/28/735/2024/hess-28-735-2024.pdf |
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