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| Titel |
Investigating suspended sediment dynamics in contrasting agricultural catchments using ex situ turbidity-based suspended sediment monitoring |
| VerfasserIn |
S. C. Sherriff, J. S. Rowan, A. R. Melland, P. Jordan, O. Fenton, D. Ó Hullacháin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 19, no. 8 ; Nr. 19, no. 8 (2015-08-03), S.3349-3363 |
| Datensatznummer |
250120776
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| Publikation (Nr.) |
 copernicus.org/hess-19-3349-2015.pdf |
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| Zusammenfassung |
| Soil erosion and suspended sediment (SS) pose risks to chemical and
ecological water quality. Agricultural activities may accelerate erosional
fluxes from bare, poached or compacted soils, and enhance connectivity
through modified channels and artificial drainage networks. Storm-event
fluxes dominate SS transport in agricultural catchments; therefore, high
temporal-resolution monitoring approaches are required, but can be expensive
and technically challenging. Here, the performance of in situ turbidity
sensors, conventionally installed submerged at the river bankside, is
compared with installations where river water is delivered to sensors ex
situ, i.e. within instrument kiosks on the riverbank, at two experimental
catchments (Grassland B and Arable B). The in situ and ex situ installations
gave comparable results when calibrated against storm-period,
depth-integrated SS data, with total loads at Grassland B estimated at
12 800 and 15 400 t, and 22 600 and 24 900 t at Arable B, respectively.
The absence of spurious turbidity readings relating to bankside debris around
the in situ sensor and its greater security make the ex situ sensor more
robust. The ex situ approach was then used to characterise SS dynamics and
fluxes in five intensively managed agricultural catchments in Ireland which
feature a range of landscape characteristics and land use pressures. Average
annual suspended sediment concentration (SSC) was below the Freshwater Fish
Directive (78/659/EEC) guideline of 25 mg L−1, and the continuous
hourly record demonstrated that exceedance occurred less than 12 % of the
observation year. Soil drainage class and proportion of arable land were key
controls determining flux rates, but all catchments reported a high degree of
inter-annual variability associated with variable precipitation patterns
compared to the long-term average. Poorly drained soils had greater
sensitivity to runoff and soil erosion, particularly in catchments with
periods of bare soils. Well drained soils were less sensitive to erosion even
on arable land; however, under extreme rainfall conditions, all bare soils
remain a high sediment loss risk. Analysis of storm-period and seasonal
dynamics (over the long term) using high-resolution monitoring would be
beneficial to further explore the impact of landscape, climate and land use
characteristics on SS export. |
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