Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope
Abstract Runoff from boreal hillslopes is often affected by distinct soil boundaries, including the frozen boundary and the organic‐mineral boundary (OMB), where highly porous and hydraulically conductive organic material overlies fine‐grained mineral soils. Viewed from the surface, ground cover app...
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crwiley:10.1002/hyp.11205 2024-09-15T18:30:13+00:00 Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope Koch, Joshua C. Toohey, Ryan C. Reeves, Donald M. 2017 http://dx.doi.org/10.1002/hyp.11205 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fhyp.11205 https://onlinelibrary.wiley.com/doi/pdf/10.1002/hyp.11205 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Hydrological Processes volume 31, issue 13, page 2453-2463 ISSN 0885-6087 1099-1085 journal-article 2017 crwiley https://doi.org/10.1002/hyp.11205 2024-06-27T04:20:54Z Abstract Runoff from boreal hillslopes is often affected by distinct soil boundaries, including the frozen boundary and the organic‐mineral boundary (OMB), where highly porous and hydraulically conductive organic material overlies fine‐grained mineral soils. Viewed from the surface, ground cover appears as a patchwork on sub‐meter scales, with thick, moss mats interspersed with lichen‐covered, silty soils with gravel inclusions. We conducted a decameter‐scale subsurface tracer test on a boreal forest hillslope in interior Alaska to quantify locations and mechanisms of transport and storage in these soils, focusing on the OMB. A sodium bromide tracer was added as a slug addition to a pit and sampled at 40 down‐gradient wells, screened primarily at the OMB and within a 7 × 12 m well field. We maintained an elevated head in the injection pit for 8.5 hr to simulate a storm. Tracer breakthrough velocities ranged from <0.12 to 0.93 m hr −1 , with the highest velocities in lichen‐covered soils. After 12 hr and cessation of the elevated head, the tracer coalesced and was only detected in thick mosses at a trough in the OMB. By 24 hr, approximately 17% of the tracer mass could be accounted for. The majority of the mass loss occurred between 4 and 12 hr, while the tracer was in contact with lichen‐covered soils, which is consistent with tracer transport into deeper flow paths via preferential flow through discrete gravelly areas. Slow breakthroughs suggest that storage and exchange also occurred in shallow soils, likely related to saturation and drainage in fine‐grained mineral soils caused by the elevated hydraulic head. These findings highlight the complex nature of storage and transmission of water and solutes from boreal hillslopes to streams and are particularly relevant given rapid changes to boreal environments related to climate change, thawing permafrost and increasing fire severity. Article in Journal/Newspaper permafrost Alaska Wiley Online Library Hydrological Processes 31 13 2453 2463 |
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Open Polar |
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Wiley Online Library |
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language |
English |
description |
Abstract Runoff from boreal hillslopes is often affected by distinct soil boundaries, including the frozen boundary and the organic‐mineral boundary (OMB), where highly porous and hydraulically conductive organic material overlies fine‐grained mineral soils. Viewed from the surface, ground cover appears as a patchwork on sub‐meter scales, with thick, moss mats interspersed with lichen‐covered, silty soils with gravel inclusions. We conducted a decameter‐scale subsurface tracer test on a boreal forest hillslope in interior Alaska to quantify locations and mechanisms of transport and storage in these soils, focusing on the OMB. A sodium bromide tracer was added as a slug addition to a pit and sampled at 40 down‐gradient wells, screened primarily at the OMB and within a 7 × 12 m well field. We maintained an elevated head in the injection pit for 8.5 hr to simulate a storm. Tracer breakthrough velocities ranged from <0.12 to 0.93 m hr −1 , with the highest velocities in lichen‐covered soils. After 12 hr and cessation of the elevated head, the tracer coalesced and was only detected in thick mosses at a trough in the OMB. By 24 hr, approximately 17% of the tracer mass could be accounted for. The majority of the mass loss occurred between 4 and 12 hr, while the tracer was in contact with lichen‐covered soils, which is consistent with tracer transport into deeper flow paths via preferential flow through discrete gravelly areas. Slow breakthroughs suggest that storage and exchange also occurred in shallow soils, likely related to saturation and drainage in fine‐grained mineral soils caused by the elevated hydraulic head. These findings highlight the complex nature of storage and transmission of water and solutes from boreal hillslopes to streams and are particularly relevant given rapid changes to boreal environments related to climate change, thawing permafrost and increasing fire severity. |
format |
Article in Journal/Newspaper |
author |
Koch, Joshua C. Toohey, Ryan C. Reeves, Donald M. |
spellingShingle |
Koch, Joshua C. Toohey, Ryan C. Reeves, Donald M. Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope |
author_facet |
Koch, Joshua C. Toohey, Ryan C. Reeves, Donald M. |
author_sort |
Koch, Joshua C. |
title |
Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope |
title_short |
Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope |
title_full |
Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope |
title_fullStr |
Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope |
title_full_unstemmed |
Tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope |
title_sort |
tracer‐based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope |
publisher |
Wiley |
publishDate |
2017 |
url |
http://dx.doi.org/10.1002/hyp.11205 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fhyp.11205 https://onlinelibrary.wiley.com/doi/pdf/10.1002/hyp.11205 |
genre |
permafrost Alaska |
genre_facet |
permafrost Alaska |
op_source |
Hydrological Processes volume 31, issue 13, page 2453-2463 ISSN 0885-6087 1099-1085 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/hyp.11205 |
container_title |
Hydrological Processes |
container_volume |
31 |
container_issue |
13 |
container_start_page |
2453 |
op_container_end_page |
2463 |
_version_ |
1810471684136763392 |