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| Titel |
Water movement through blanket peat is dominated by a complicated pattern of near-surface flows |
| VerfasserIn |
Ed Turner, Andy Baird, Mike Billett, Pippa Chapman, Kerry Dinsmore, Joseph Holden |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112956
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| Publikation (Nr.) |
 EGU/EGU2015-13146.pdf |
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| Zusammenfassung |
| Blanket peatland formation and functioning depend strongly on hydrology. Omitting the
potential for pipe flow, the acrotelm-catotelm model is still widely held to apply to blanket
peatlands. In the model, water flow through the peat profile is dominated by near-surface flow
in the acrotelm, whereas water movement below the level of (near) permanent saturation (the
catotelm) is characterised by very low hydraulic conductivity (K). Whilst some work has
been done on characterising Kat different depths in blanket peatlands, very little is known
about near-surface K, particularly with respect to how it varies between microforms and over
fine spatial scales.
We undertook a detailed investigation of near-surface (0 – 12 cm) and deeper (30 and 50
cm) K at a blanket peatland site in the Flow Country in Scotland (UK). Near-surface Kof
peat samples taken across a range of microforms was measured vertically (Kv) and
horizontally (Kh) in the laboratory using a new ‘split cylinder’ method (n = 48 excluding
repeat tests). K30 (n = 20) andK50 (n = 20) were estimated in situ using the piezometer or
seepage-tube method. To help our interpretation of the near-surface K measurements
we recorded the vegetation cover from where the peat samples were taken and
characterised each peat sample in terms of its plant macrofossil assemblage and dry bulk
density.
We found that Kvand Khwere highly variable between microforms in the near-surface
samples, ranging over two orders of magnitude (0.489 – 0.003 cm s-1). Kernel density
plots show that Kvwas most commonly in the region of ~0.03 cm s-1 at 0 – 6 cm,
and ~0.015 cm s-1 at 6 – 12 cm, whereas Kh was ~0.05 and ~0.001 cm s-1
respectively. These data reveal a high degree of absolute variability and anisotropy in
K over small scales. The deeper K30and K50 values were typically an order of
magnitude or more lower than the near-surface K, and were less variable between test
locations with the exception of poorly humified Sphagnum-dominated peat. These
results are a step forward for improving models of blanket peatland hydrology,
and understanding pore-water residence times and wider catchment behaviour. |
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