Presentation given at the 2nd SILTFLUX workshop on 19/05/2015 at UCD. Authors: Michael Bruen, Mary Kelly-Quinn, John O'Sullivan, Jonathan Turner, Elizabeth Conroy, Anna Rymszewicz, Damian Lawler, John Wallace

1. 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

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) .

3. Sediment Database Structure

4. 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-1
year-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

5. Irish Sediment Database – current status

6. 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.

7. 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.

8. WP3: Catchment data – SS Flux calculation

9. WP3: Catchment data – Discharge
Small Catchment  Special structure
e.g. flat-vee weir
Large Catchment  Hydrometric station
(EPA, OPW, ESB)
 Own rating  Flow gauging

10. Sediment data
• Turbidity
• Water Samples
(ISCO)
+ Laboratory
analysis
• Water Levels
• Data from
Hydrometric
unit
(EPA,
OPW,
ESB)

11. 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

12. 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

13. Slaney catchment
Catchment Slaney
Area (km2) 207.84
Typology 12: siliceous, medium slope
Land use Pasture

14. Slaney - Bedrock

15. Slaney - Typology

16. Slaney – Land Use
UPSTREAM:
Pasture: 22.9%
DOWNSTREAM:
Pasture: 53.5%

17. Catchment view and
instrumentation at
u/s site

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

19. Slaney – Upper and
Lower Reaches

20. Sediment peak
preceding water
level peak
Depth(m)
SSC(mg/l),Turbidity(NTU)
Slaney targeted at storm dynamics

21. Slaney 12th – 14th Feb 2014Depth(m)
Turbidity(NTU/SSC(mg/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

22. 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

25. Slaney Flow and Flux

26. UCD project site - Camlin
Catchment size: 92.1 km2
Land use: 86.45% Pasture

27. WP3 & WP4: Current project sites - Camlin
Flow data: EPA Kilnacarrow station

29. WP3: SS Flux calculation – Example for Camlin

30. Glyde catchment
Catchment GLYDE
Area (km2) 345.27
Typology 31 : calcareous, low slope
Land use Tillage

31. Glyde

32. Glyde Bedrock

33. 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

36. 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