On the shape of forward transit time distributions in low-order catchments
<p>Transit time distributions (TTDs) integrate information on timing, amount, storage, mixing and flow paths of water and thus characterize hydrologic and hydrochemical catchment response unlike any other descriptor. Here, we simulate the shape of TTDs in an idealized low-order catchment and i...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2020-06-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/24/2895/2020/hess-24-2895-2020.pdf |
| _version_ | 1818548190887018496 |
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| author | I. Heidbüchel J. Yang A. Musolff P. Troch T. Ferré J. H. Fleckenstein |
| author_facet | I. Heidbüchel J. Yang A. Musolff P. Troch T. Ferré J. H. Fleckenstein |
| author_sort | I. Heidbüchel |
| collection | DOAJ |
| description | <p>Transit time distributions (TTDs) integrate information
on timing, amount, storage, mixing and flow paths of water and thus
characterize hydrologic and hydrochemical catchment response unlike any
other descriptor. Here, we simulate the shape of TTDs in an idealized
low-order catchment and investigate whether it changes systematically with
certain catchment and climate properties. To this end, we used a physically
based, spatially explicit 3-D model, injected tracer with a precipitation
event and recorded the resulting forward TTDs at the outlet of a small
(<span class="inline-formula">∼6000</span> m<span class="inline-formula"><sup>2</sup></span>) catchment for different scenarios. We found
that the TTDs can be subdivided into four parts: (1) early part – controlled
by soil hydraulic conductivity and antecedent soil moisture content, (2) middle part – a transition zone with no clear pattern or control, (3) later
part – influenced by soil hydraulic conductivity and subsequent
precipitation amount, and (4) very late tail of the breakthrough curve –
governed by bedrock hydraulic conductivity. The modeled TTD shapes can be
predicted using a dimensionless number: higher initial peaks are observed if
the inflow of water to a catchment is not equal to its capacity to discharge
water via subsurface flow paths, and lower initial peaks are connected to
increasing available storage. In most cases the modeled TTDs were humped
with nonzero initial values and varying weights of the tails. Therefore,
none of the best-fit theoretical probability functions could describe the
entire TTD shape exactly. Still, we found that generally gamma and
log-normal distributions work better for scenarios of low and high soil
hydraulic conductivity, respectively.</p> |
| first_indexed | 2024-12-12T08:16:37Z |
| format | Article |
| id | doaj.art-d8ef7301c82448d6aabf1f11c493e37a |
| institution | Directory Open Access Journal |
| issn | 1027-5606 1607-7938 |
| language | English |
| last_indexed | 2024-12-12T08:16:37Z |
| publishDate | 2020-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Hydrology and Earth System Sciences |
| spelling | doaj.art-d8ef7301c82448d6aabf1f11c493e37a2022-12-22T00:31:34ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382020-06-01242895292010.5194/hess-24-2895-2020On the shape of forward transit time distributions in low-order catchmentsI. Heidbüchel0J. Yang1A. Musolff2P. Troch3T. Ferré4J. H. Fleckenstein5Department of Hydrogeology, Helmholtz Centre for Environmental Research – UFZ, 04318 Leipzig, GermanyDepartment of Hydrogeology, Helmholtz Centre for Environmental Research – UFZ, 04318 Leipzig, GermanyDepartment of Hydrogeology, Helmholtz Centre for Environmental Research – UFZ, 04318 Leipzig, GermanyDepartment of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, 85721, USADepartment of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, 85721, USADepartment of Hydrogeology, Helmholtz Centre for Environmental Research – UFZ, 04318 Leipzig, Germany<p>Transit time distributions (TTDs) integrate information on timing, amount, storage, mixing and flow paths of water and thus characterize hydrologic and hydrochemical catchment response unlike any other descriptor. Here, we simulate the shape of TTDs in an idealized low-order catchment and investigate whether it changes systematically with certain catchment and climate properties. To this end, we used a physically based, spatially explicit 3-D model, injected tracer with a precipitation event and recorded the resulting forward TTDs at the outlet of a small (<span class="inline-formula">∼6000</span> m<span class="inline-formula"><sup>2</sup></span>) catchment for different scenarios. We found that the TTDs can be subdivided into four parts: (1) early part – controlled by soil hydraulic conductivity and antecedent soil moisture content, (2) middle part – a transition zone with no clear pattern or control, (3) later part – influenced by soil hydraulic conductivity and subsequent precipitation amount, and (4) very late tail of the breakthrough curve – governed by bedrock hydraulic conductivity. The modeled TTD shapes can be predicted using a dimensionless number: higher initial peaks are observed if the inflow of water to a catchment is not equal to its capacity to discharge water via subsurface flow paths, and lower initial peaks are connected to increasing available storage. In most cases the modeled TTDs were humped with nonzero initial values and varying weights of the tails. Therefore, none of the best-fit theoretical probability functions could describe the entire TTD shape exactly. Still, we found that generally gamma and log-normal distributions work better for scenarios of low and high soil hydraulic conductivity, respectively.</p>https://www.hydrol-earth-syst-sci.net/24/2895/2020/hess-24-2895-2020.pdf |
| spellingShingle | I. Heidbüchel J. Yang A. Musolff P. Troch T. Ferré J. H. Fleckenstein On the shape of forward transit time distributions in low-order catchments Hydrology and Earth System Sciences |
| title | On the shape of forward transit time distributions in low-order catchments |
| title_full | On the shape of forward transit time distributions in low-order catchments |
| title_fullStr | On the shape of forward transit time distributions in low-order catchments |
| title_full_unstemmed | On the shape of forward transit time distributions in low-order catchments |
| title_short | On the shape of forward transit time distributions in low-order catchments |
| title_sort | on the shape of forward transit time distributions in low order catchments |
| url | https://www.hydrol-earth-syst-sci.net/24/2895/2020/hess-24-2895-2020.pdf |
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