Michael Bruen, Mary Kelly-Quinn, John O’Sullivan, Jonathan Turner,

Elizabeth Conroy, Anna Rymszewicz, Damian Lawler, John Wallace.

19th May 2015

SILTFLUX Data

Workshop No. 2

Siltflux project objectives and targets

1. Increase knowledge and understanding of silt flux in rivers to help set standards for suspended solids flux and concentrations for the protection of sensitive catchments in Ireland.

2. Understand the relationship between concentrations/flux of silts and the potential for deposition and ecological impacts in different types of rivers, and under variable landuse pressures.

3. Assess the benefits of silt reduction that enhancement measures can achieve ( Workshop No. 3) .

Sediment Database Structure

Sediment yields in Ireland: 0.03-0.44 tonnes ha-1 year-1

SILTFLUX Review of Irish Sediment Data

Catchment Area (km2) Sediment yield

(t ha-1year-1) Study period

Reference

Srahrevagh 0.072-0.204 0.172-0.272 2004-2005 Rodgers et al., 2008, 2011 Mount Stewart 7.52 0.067 2011-2012 Thompson et al., 2014 Dunleer 9.4 0.15 2009-2010 Melland et al., 2010 9.4 0.135 2010-2011 Melland et al., 2010 Castledockrell 11 0.177 2009-2010 Melland et al., 2010 11 0.031 2010-2011 Melland et al., 2010 Dripsey 15.24 0.161 2002 Kiely et al,. 2007 15.24 0.098 2003 Kiely et al., 2007 Glenamong 17.91 0.16 2001 May et al., 2005 Mattock 20.96 0.44 2011-2012 Thompson et al., 2014 Clarianna 29.8 0.085 2002 Kiely et al., 2007 The Oona 84.5 0.29 2001-2002 Kiely et al., 2007 84.5 0.41 2002 Kiely et al., 2007 Owenabue 103 0.256 2009-2010 Harrington & Harrington 2013 Bandon 424 0.142 2010-2011 Harrington & Harrington 2013

Irish Sediment Database – current status

Hypothesis Validation of Measurement Methodology Hypothesis : That suspended sediment concentrations could be estimated from surrogate measurements, e.g. turbidity. This consists of two parts; (i) Determine if there is a strong relationship between turbidity

and suspended sediment concentrations. (cf. previous presentation this morning)

(i) Quantify the relationship and develop an equation for use in

converting turbidity measurements to suspended sediment measurements for each site.

This is predicated on the ability to obtain reliable, cost-effective, continuous measurements of turbidity.

Measurement methodology

Comparison of direct, laboratory measured, suspended sediment

values with corresponding turbidity measurements. (i) In the field (at selected sites) – using auto-samplers (triggered

by text message) to take samples from river for a range of flow conditions. Samples were analysed in the laboratory and results compared with contemporaneous turbidity readings recorded from instruments submerged in the water at the same location.

(ii) In the laboratory – using specially prepared samples with a known concentration of suspended sediment and a variety of turbidity sensors.

WP3: Catchment data – SS Flux calculation

WP3: Catchment data – Discharge

Small Catchment Special structure e.g. flat-vee weir Large Catchment Hydrometric station (EPA, OPW, ESB) Own rating Flow gauging

Sediment data • Turbidity • Water Samples

(ISCO) + Laboratory analysis

• Water Levels • Data from

Hydrometric unit

(EPA, OPW, ESB)

River

Typology

Land Use

Pasture Tillage

31, 32 Clodiagh (x2),

Camlin

Glyde

12 Slaney

(Rathvilley,

Gibstown)

Urrin

WP3 & WP4: Current UCD sites

• 7 sites with continuous turbidity readings • 2 sites with automatic water samplers

River

Typology

Land Use

Pasture Tillage

31, 32 Clodiagh (x2),

Camlin

Glyde

12 Slaney

(Rathvilley,

Gibstown)

Urrin

WP3 & WP4: Current UCD sites – data presented today

• 7 sites with continuous turbidity readings • 2 sites with automatic water samplers

Slaney catchment

Catchment Slaney

Area (km2) 207.84

Typology 12: siliceous, medium slope

Land use Pasture

Slaney - Bedrock

Slaney - Typology

Slaney – Land Use

UPSTREAM: Pasture: 22.9% DOWNSTREAM: Pasture: 53.5%

Catchment view and instrumentation at u/s site

Instrumentation at d/s site (inside water treatment plant)

Slaney – Upper and Lower Reaches

Sediment peak preceding water level peak

Dep

th (

m)

SSC

(m

g/l

), T

urb

idit

y (N

TU)

Slaney targeted at storm dynamics

Slaney 12th – 14th Feb 2014 D

epth

(m

)

Turb

idit

y (N

TU /

SSC

(m

g/l

) Max SSC (mg/l)recorded: Gibstown: 123 mg/l Tuckmill: 212 mg/l Rathvilly: 145 mg/l Tullow: 131 mg/l

0

100

200

300

0.4

0.8

1.2

1.6 Tuckmill

0

50

100

150

0.9

1.3

1.7

2.1

12/02/2014 00:00 14/02/2014 00:00 16/02/2014 00:00

Tullow 0

100

200

300

0.5

0.9

1.3

1.7 Rathvilly

0

50

100

150

200

0.4

0.8

1.2

1.6

2 Gibstown

SSC = 0.71 + 0.633 Turbidity R2 = 0.88 N = 84 p-value <2e-16

SSC = 1.17 + 0.658 Turbidity R2 = 0.88 N = 126 p-value <2e-16

River Slaney – combined storms – all data to May 2014

WP3 & WP4: Turbidity vs SSC correlations

Slaney Flow and Flux

UCD project site - Camlin

Catchment size: 92.1 km2

Land use: 86.45% Pasture

WP3 & WP4: Current project sites - Camlin

Flow data: EPA Kilnacarrow station

WP3: SS Flux calculation – Example for Camlin

Glyde catchment

Catchment GLYDE

Area (km2) 345.27

Typology 31 : calcareous, low slope

Land use Tillage

Glyde

Glyde Bedrock

KILLANNY: Pasture: 87.14 % LAGAN: Pasture: 84.3 % DOWNSTREAM: Pasture: 69.57% Agr. with natural veg. 4.63 Complex cultivation patterns : 4.46 Non-irigated arable land: 17.13%

Glyde – Land Use

Summary

1. Glyde behaviour different from other rivers

2. Generally good SSC vs Turbidity relationships, but more complex than originally presumed when high values are targeted

3. Most suspended sediment on rising limb of storms

4. Much Suspended sediment transport in flux pulses