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