Inter-event variability of turbidity-suspended sediment concentration :
implications for sediment load estimation of freshwater ecosystems.
S. Sherriff1,2, Rowan, J.S.2, Melland, A.R.3, Murphy, P.3, Fenton, O.1, Jordan,
P.4 and Ó hUallacháin, D.1
1
Teagasc, Johnstown Castle Research Centre, Wexford, Ireland
School of the Environment, University of Dundee, Dundee, DD1 4HN,
Scotland, UK
3
Agricultural Catchment Programme, Teagasc, Johnstown Castle, Wexford,
Ireland
4School of Environmental Sciences, University of Ulster, Coleraine, Northern
Ireland
2
Email: sophie.sherriff@teagasc.ie
Sediment supply to watercourses provides essential nutrients for chemical
and ecological functioning- key requirements of the Water Framework
Directive. Excessive contributions have been shown to degrade habitat
conditions for river biota including native salmonid and Freshwater Pearl
Mussel populations (protected under the Habitats directive). Elevated
sediment inputs commonly result from rainfall events, particularly in
catchments with intensive land-uses. Accurate estimation of suspended
sediment concentration (SSC) is dependent on the quality of turbidity-SSC
calibration.
This study considers the inter-event variability of this relationship and the
consequential implications on load estimation. High-resolution turbidity data
collected from an intensive agricultural grassland catchment were calibrated
with laboratory-processed SSC samples taken at 30 minute intervals during
multiple hydrosedimentary events. Single event regressions show distinct
variability, and consequently may cause inaccurate sediment load and yield
estimations for short-lived or narrow range calibration programmes. This study
will result in more accurate sediment estimations and will influence
appropriate aquatic mitigation measures.