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Mitigation Measures – What we can learn from Agricultural Catchments
Sara E. Vero Mitigation Measures –Tullamore
2019Agricultural Catchments Program, Teagasc, Wexford, Ireland
Sophie Sherriff, John Rowan, Owen Fenton, Phil Jordan, Alice Melland & Daire Ó hUallacháin
How we measure sediment in ACP Catchments
In-situ: Sediment Samplers Ex-situ: Turbidity Probe
Physical Sediment Mobilisation
Impacts of Sediment• An irritant to fish gills• Blocks pores in river bed gravel
• Impairs macroinvertebrates• Harmful to fish eggs and
freshwater pearl mussel
Impacts of SedimentAs a vector for other contaminants – Phosphorus and PesticidesSource: Soil surface, roadways and banksMobilisation 1: Physical removal by overland flowMobilisation 2: Chemical mobilisation in stream
Sediment Particle
P
P
P
P
Physical Mobilization: Storm Emma/The Beast from the East
Vero et al., (In Review)
In-Stream P Mobilisation – Castledockrell Catchment
Vero et al., (In Prep)
Sediment yield: four-year annual averages
Sherriff et al., (2015) Hydrology and Earth System Sciences, 19, 3349-3363
Annual Variation
9
Drainage: Good Poor Moderate Good Mod/poor
Sherriff et al., (2015) Hydrology and Earth System Sciences, 19, 3349-3363
Sediment fingerprinting
Fingerprinting results – poorly drained grass
Fingerprinting results – well-drained arable
Fingerprinting results – moderately drained arable
Potential Mitigation Measures
Many measures will be pathway focussedBut it is still possible to reduce sourcesSite-specific Time-specific
Outlet
Main Stream
Sources – Fields
• Proximity to watercourse• Saturation• Connectivity• Cover
Sources – High-flow ditches• Connectivity • Slope/design• Bank stability
Shore et al., (2014) Agriculture, Ecosystems and Environment. 199: 207-215
• Streams - primarily transfer sediment & PP • Banks should be stabilised (hedges)
• Sloping Ditches– primarily mobilise sediment & PP• Mobilisation potential should be minimised (vegetation)
• Flat Ditches – primarily retain sediment & PP• Retention capacity should be maintained (dredging).
Sources - Roadways
Sediment• Sherriff et al., 2015. Investigating suspended sediment dynamics in contrasting
agricultural catchments using ex situ turbidity-based suspended sediment monitoring. Hydrology & Earth System Sciences. 19: 3349-3363
• Sherriff et al., 2015. Uncertainty-based assessment of tracer selection, tracer non-conservativeness and multiple solutions in sediment fingerprinting using synthetic and field data. Journal of Soils & Sediment.
• Sherriff et al., 2016. Storm event suspended sediment-discharge hysteresis and controls in agricultural watersheds: Implications for watershed scale sediment management. Environmental Science & Technology. 50: 1769-1778
• Shore et al., 2014. An agricultural drainage channel classification system for phosphorus management. Agriculture, Ecosystems & Environment. 199: 207-215
• Vero et al., (In Review) The Beast from the East: Impact of an atypical cold weather event on hydrology and nutrient dynamics in Irish catchments