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| Titel |
Is the blocking of drainage channels in upland peats an effective means of reducing water colour at catchment scales? |
| VerfasserIn |
Kate Turner, Fred Worrall |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250033575
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| Zusammenfassung |
| Catchments with extensive peat coverage commonly have high fluvial dissolved organic
carbon (DOC) concentrations. Long term water colour (a proxy for DOC) records from the
River Tees, UK, indicate an increasing water colour trend, a trend that has been recognised in
series of UK streams. It is considered that the release of carbon from these areas
can be related to changes in water table depth in the soil profile with DOC being
produced within the aerobic layer of the peat. The drainage of upland peatlands, by the
cutting of open drainage channels was common practice in Northern England. The
practice succeeded in lowering the water table but led to an increase in recorded
DOC concentration leaving the catchment. The blocking of these channels has thus
been proposed as a means of peat restoration. The reduction in drainage capacity
will cause increases in the water table, rewetting the peat and reducing losses in
carbon.
This study aims to assess the effectiveness of drain blocking as a method of reducing
DOC levels at the catchment scale. Also the effects of blocking on the water balance and any
changes in the flow pathways of water through the catchments post blocking will be
determined via fingerprinting studies. A series of nested blocked and unblocked catchments
were studied in Upper Teesdale, Northern England. Drain water samples at nine
localities were taken at least daily. These sites were located such that individual drains
could be monitored in the context of a larger catchment. Water table depth, flow
and weather parameters were recorded along with the collection of run off and
soil water samples. A detailed sampling programme was undertaken in which a
series of drains were studied in the 12 months prior to blocking and the 12 months
after.
Results indicate that the blocking of zero order drainage channels leads to a decrease in
DOC export on an individual drain scale. However, this is due to a reduction in water yield
rather than concentration. Concentrations are seen to rise by a small yet statistically
significant amount in blocked zero order streams. The effect at a larger scale is more
complex. Annual export values in the unblocked control catchment show a rise from zero to
first order streams indicating that water is being added to the system at this scale from
external spatially variable sources. This pattern is also recognised in the blocked catchment.
The DOC concentration record in blocked drains at this larger scale however indicated a
reduction relative to the unblocked catchment. This reduction points to a change in flow
pathways post blocking as highly coloured water re-navigates its way downstream. |
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