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Peatlands and water quality: degradation,restoration and the Water Framework Directive
VNN Workshop. Leeds, 9th May 2012
Tim Allott
Martin Evans (UoM), James Rothwell (UoM), Chris Evans(CEH), Don Monteith (CEH), Tia Crouch (MFF), Jon Walker
(MFF), Ewan Shilland (UCL), Rick Battarbee (UCL)
A starting point: the River Ashop, Derbyshire
• 28 km2 catchment
• Degraded peatland headwaters
• Low pH
• Elevated metal concentrations(e.g. Lead, zinc, copper)
• High DOC / colour
• High suspended sediment load(POC/FPOM)
• Impoverished fish community
• WFD ‘fail’ on fish, zinc, copper
• Current status ‘Moderate’
• Overall objective ‘Good status’by 2027
VNN Workshop. Leeds, 9th May 2012
Impacts of peat degradation and restoration onwater quality?
• Degraded peatland headwaters
• Restoration via ditch blocking, re-vegetation and gullyblocking
Direct WFD concerns
• Low pH
• Specific pollutants (e.g. zinc, arsenic, etc)
• Biological quality elements (e.g. fish, invertebrates)
• (Ammonia, phosphate, DO, other specific pollutants)
Indirect WFD concerns
• High DOC / colour
• High suspended sediment loads (POC/FPOM)
VNN Workshop. Leeds, 9th May 2012
Intact peatlands and water quality regulation
• Oligotrophic – lownutrientconcentrations
• High water tableconditions
• Acidic
• Accumulating peat(organic matter)
Intact accumulating peats retain pollutants• Reduction of deposited SO4,NO3
• Storage of deposited metals
Drainage waters•Moderate DOC and organic acidity•Low POC•Low metals•Low nutrient export
VNN Workshop. Leeds, 9th May 2012
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Intact
Gullied
Peat degradation
Erosion, drainage and water table change – physicaland hydro-chemical effects
08/08 09/08 10/08 11/08 12/08
VNN Workshop. Leeds, 9th May 2012
Degraded peatlands compromise water quality
• Gully erosion and bare peat
• Grips and peat drainage
• Water table drawdown
• Reduced peat accumulation
• Aerobic decomposition
Degraded peats and pollutants• Reduced/zero C, SO4,NO3, NH4, metalaccumulation• Transformation from sink to source
Drainage waters• High POC• Increased DOC• Increased SO4 and NO3
• Increased acidity• Elevated metals and toxicsubstances
Image from Holden et al (2007)
VNN Workshop. Leeds, 9th May 2012
Peatland restoration and water qualityresponses
• Grip / drain blocking
• Gully blocking
• Re-vegetation of bare peat
• Stabilization of eroding/ditched peat
• Raising water table conditions
Known/likely impacts on:
• Suspended sediments ?
• Metals and toxic substances ?
• DOC ?
• Acidity ?
VNN Workshop. Leeds, 9th May 2012
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0.001 0.01 0.1 1 10 100 1000
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Re-vegetation shuts down suspended sedimentproduction and release
= data from intact reference site
VNN Workshop. Leeds, 9th May 2012
Evans M and Worrall (2009) NE Report
Re-vegetation shuts down suspended sedimentproduction and release
VNN Workshop. Leeds, 9th May 2012
SedimentLoads gC m2 a-1
Joseph South 4.07
Joseph North 1.43
Trenches North Hi 157.64
Trenches South 804.42
Control 1.87
Evans M and Worrall (2009) NE Report
Drain and gully blocking reduces suspendedsediments/FPOM
• Drain blocking significantly reducessediment yields (Holden et al 2007;Wilson et al 2011)
• Gully blocking traps FPOM (Evans M etal 2004)
• Drain blocking, FPOM changes andimproved stream biodiversity(Ramchunder et al. 2012)
VNN Workshop. Leeds, 9th May 2012
Peat storage of atmospherically derived metalsand toxic substances
VNN Workshop. Leeds, 9th May 2012
Metal release from degraded peatlands:sinks into sources
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Data from headwaters of the River AshopRothwell et al (2012) Env. Poll.
VNN Workshop. Leeds, 9th May 2012
• Outputs > inputs• Significant export from the headwater peats• Contrasting controls for different metals
Peatland restoration and reductions in metalrelease
Limited empirical evidence, but..
• Reduced suspended sediment andFPOM release will reduce metalexport
• Three potential mechanismsassociated with re-wetting:– Reduced oxidation/acidity would reduce
metal release (e.g. Zn, Ni)
– Reduced DOC would reduce export ofbound metals (e.g. Pb, Cu)
– Redox changes might increase therelease of redox sensitive metals (e.g.As, Fe, Mn)
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VNN Workshop. Leeds, 9th May 2012
VNN Workshop. Leeds, 9th May 2012
Degradation increases sulphate / nitraterelease and acidity
• Oxidation of stored sulphur and nitrogen
• Evidence from spatial comparisons (e.g. Daniels et al 2008), andindirectly from drought response studies (e.g. Clarke et al 2005)
• Land management impacts superimposed on a long-term historyof acid deposition
Daniels et al (2008)Clarke et al (2005)
Degradation, restoration and DOC/colour
• Increasing reports that ditch blockingreduces DOC (e.g. Wallage et al 2006;Armstrong et al 2010; SCaMP 2011; Wilson et al2011)
• But a lack of consistent behaviourbetween systems and over the(generally) short time periods of study
• Evidence of (transient?) DOC increasesafter blocking (e.g. Worrall et al 2007)
• Evidence that in some cases re-wettingmight increase DOC loss (e.g. Daniels et al.2008 study of catchments with significant storesof sulphur)
• Need fuller understanding of processcontrols in order to generalise/model
Wallage et al (2006)
VNN Workshop. Leeds, 9th May 2012
Daniels et al. (2008)
Blackstone Edge Reservoir
Climate change impacts
DROUGHT
Tipping, Rothwell et al. 2010. Environ. Pollut., 158: 1521-1529
VNN Workshop. Leeds, 9th May 2012
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)Degraded systems asclimate change
analogues?
Long term monitored data
• Crucial context for water qualityimpacts and catchmentmanagement
• Regional / national patterns
• Long term drivers (climate andatmospheric deposition)
See Acid Waters MonitoringNetwork website and reports
VNN Workshop. Leeds, 9th May 2012
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Upland waters: aqua incognita?
• 82% of GB river length lies withincatchments of < 10km2
• Of the upland river length, 97% lies incatchments < 10 km2
• Not many EA monitoring sites above300m!
• Much upland policy is based on asmall, disconnected and financiallyvulnerable set of monitoring sites(e.g. AWMN sites)
• Require increased monitoring, bothinvestigative and surveillance
VNN Workshop. Leeds, 9th May 2012
?
Investigative monitoring: Bamford/Ashopcatchment metals study (EA/STW/Moors for the Future)
VNN Workshop. Leeds, 9th May 2012
?
ENVIRONMENTAL CHANGE RESEARCH CENTRE
An Upland Waters Monitoring Network for the UK
(based on a science partnership of UCL, CEH, QMUL and SG; supported byDefra, DOENI, WG, SG, CCW, EA, Forestry Commission, CEH and ENSIS Ltd)
The UK Upland Waters Monitoring Network
Plans and Proposals
1. To build on (and replace from 2013) the Acid Waters MonitoringNetwork of 24 lake and stream sites across the UK
The UK Upland Waters Monitoring Network
Plans and Proposals
2. To add new sites conforming strictly to AWMN protocols for water chemistryand biology (diatoms, aquatic plants, macro-invertebrates, fish) in higheralkalinity regions non sensitive to acid deposition
3. To add a small number of non-AWMN “associated” sites where high qualitylong term data-sets already exist but do not conform strictly to AWMN protocols
4. To complete the installation of temperature loggers and flow and water-levelloggers at existing AWMN sites
5. To introduce additional protocols to AWMN sites for monitoring nutrients (e.g.low detection level TP and chl a), carbon export (e.g. POC in streams andsediment traps) and catchment land-cover change (e.g. repeat fixed pointphotography)
For further information see www.awmn.defra.gov.ukor contact Rick Battarbee or Ewan Shilland
Summary points
• Key upland WFD concerns: acidity, specific pollutants(metals), biological quality, DOC/colour, suspendedsediments/FPOM
• Peat degradation impacts all these!
• Peat restoration has clear and demonstrable benefitsfor suspended sediments
• Less consensus over other restoration related WQimprovements than policy/practitioner communitywould like (timescales, variation between case studydata, lack of data in many cases)
• Key role of monitoring and improved processunderstanding
VNN Workshop. Leeds, 9th May 2012