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| Titel |
Suspended sediment export in five intensive agricultural river catchments with contrasting land use and soil drainage characteristics |
| VerfasserIn |
Sophie Sherriff, John Rowan, Alice Melland, Phil Jordan, Owen Fenton, Daire Ó hUallacháin |
| 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 |
250113222
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| Publikation (Nr.) |
 EGU/EGU2015-13420.pdf |
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| Zusammenfassung |
| Soil erosion and sediment loss from land can have a negative impact on the chemical and
ecological quality of freshwater resources. In catchments dominated by agriculture,
prediction of soil erosion risk is complex due to the interaction of physical characteristics
such as topography, soil erodibility, hydrological connectivity and climate. Robust
measurement approaches facilitate the assessment of sediment loss magnitudes in relation to
a range of agricultural settings. These approaches improve our understanding of
critical sediment transfer periods and inform development of evidence-based and
cost-effective management strategies. The aim of this study was to i) assess the efficacy of
out-of-channel (ex-situ) suspended sediment measurement approaches, ii) to quantify the
variability of sediment exported from five river catchments with varying hydrology and
agricultural land uses over multiple years and iii) to investigate trends in relation to
physical and land use characteristics when sediment data were compared between
catchments.
Sediment data were collected in five intensive agricultural river catchments in Ireland
(3-11 km2) which featured contrasting land uses (predominantly intensive grassland
or arable) and soil drainage classes (well, moderate and poor). High-resolution
suspended sediment concentration data (SSC - using a calibrated turbidity proxy) were
collected ex-situ and combined with in-stream discharge data measured at each
catchment outlet to estimate suspended sediment yield (SSY – t km-2 yr-1). In two
catchments additional in-stream turbidity monitoring equipment replicated ex-situ
measurements including site specific calibration of individual in-stream and ex-situ turbidity
probes. Depth-integrated samples were collected to assess the accuracy of both
approaches.
Method comparison results showed that true SSC values (from depth-integrated
sampling) were predominantly within the 95% confidence interval of ex-situ predicted SSC
consequently confirming the robust cross-validation of these results. Average annual SSCs
and SSYs were higher in poorly drained catchments (17-27 t km-2 yr-1) than those with
well drained soils (8-10 t km-2 yr-1). Catchments with both poorly-drained soils and land
use dominated by tillage were most susceptible to field-scale soil erosion due to rapid
establishment of overland flow pathways and periods of bare soils during cropping cycles.
However results suggest that relatively high SSY may also occur in grassland catchments,
particularly on poorly drained soils and with higher stocking densities and greater
likelihood of channel bank erosion. Whilst the mean SSY rates are low by international
standards, inter-annual variability was significant highlighting the spatial and temporal
fluctuations in runoff and soil erosion risk. Such issues are of particular concern as
Ireland pursues an agricultural policy of sustainable intensification. Effective soil
erosion and sediment management should address catchment specific characteristics. |
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