Tim Allott


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Tim Allott

  1. 1. VNN Workshop. Leeds, 9th May 2012 Peatlands and water quality: degradation,restoration and the Water Framework Directive 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)
  2. 2. VNN Workshop. Leeds, 9th May 2012A 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
  3. 3. VNN Workshop. Leeds, 9th May 2012Impacts of peat degradation and restoration onwater quality? • Degraded peatland headwaters • Restoration via ditch blocking, re-vegetation and gully blocking 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)
  4. 4. VNN Workshop. Leeds, 9th May 2012 Intact peatlands and water quality regulation • Oligotrophic – low nutrient concentrations • High water table conditions • Acidic • Accumulating peat (organic matter) Drainage watersIntact accumulating peats retain pollutants •Moderate DOC and organic acidity• Reduction of deposited SO4,NO3 •Low POC• Storage of deposited metals •Low metals •Low nutrient export
  5. 5. VNN Workshop. Leeds, 9th May 2012Peat degradationErosion, drainage and water table change – physicaland hydro-chemical effects 08 September 07 November 07 December 08/08 2008 09/08October 2008 09 August 2008 08 10/08 2008 11/08 2008 12/08January 2009 06 -100 0 Water Table Depth (mm) 100 200 300 400 Intact 500 Gullied 600
  6. 6. 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 Image from Holden et al (2007) Drainage waters • High POC • Increased DOCDegraded peats and pollutants • Increased SO4 and NO3• Reduced/zero C, SO4,NO3, NH4, metal • Increased acidityaccumulation • Elevated metals and toxic• Transformation from sink to source substances
  7. 7. VNN Workshop. Leeds, 9th May 2012Peatland 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 ?
  8. 8. VNN Workshop. Leeds, 9th May 2012 Re-vegetation shuts down suspended sediment production and release 10000 1000 SSC m g/l 100 10 1 0.001 0.01 0.1 1 10 100 1000 Q Ls-1km-2= data from intact reference site Evans M and Worrall (2009) NE Report
  9. 9. VNN Workshop. Leeds, 9th May 2012 Re-vegetation shuts down suspended sediment production and releaseSedimentLoads gC m2 a-1Joseph South 4.07Joseph North 1.43Trenches North Hi 157.64Trenches South 804.42Control 1.87 Evans M and Worrall (2009) NE Report
  10. 10. VNN Workshop. Leeds, 9th May 2012Drain and gully blocking reduces suspendedsediments/FPOM • Drain blocking significantly reduces sediment yields (Holden et al 2007; Wilson et al 2011) • Gully blocking traps FPOM (Evans M et al 2004) • Drain blocking, FPOM changes and improved stream biodiversity (Ramchunder et al. 2012)
  11. 11. VNN Workshop. Leeds, 9th May 2012Peat storage of atmospherically derived metalsand toxic substances
  12. 12. VNN Workshop. Leeds, 9th May 2012 Metal release from degraded peatlands: sinks into sources Data from headwaters of the River Ashop Rothwell et al (2012) Env. Poll. 08 September 07 November 07 December 09 August 2008 2008 08 October 2008 2008 2008 06 January 2009 -100 0W a t e r T a b le D e p t h ( m m ) 100 200 300 400 500 600 • Outputs > inputs • Significant export from the headwater peats • Contrasting controls for different metals
  13. 13. VNN Workshop. Leeds, 9th May 2012 Peatland restoration and reductions in metal release Limited empirical evidence, but.. • Reduced suspended sediment and FPOM release will reduce metal export • Three potential mechanisms associated with re-wetting: – Reduced oxidation/acidity would reduce metal release (e.g. Zn, Ni) 09 August 2008 -100 08 September 2008 08 October 2008 07 November 2008 07 December 2008 06 January 2009 – Reduced DOC would reduce export of 0 bound metals (e.g. Pb, Cu) – Redox changes might increase theW a t e r T a b le D e p t h ( m m ) 100 200 release of redox sensitive metals (e.g. 300 As, Fe, Mn) 400 500 600
  14. 14. VNN Workshop. Leeds, 9th May 2012 Degradation increases sulphate / nitrate release and acidity• Oxidation of stored sulphur and nitrogen• Evidence from spatial comparisons (e.g. Daniels et al 2008), and indirectly from drought response studies (e.g. Clarke et al 2005)• Land management impacts superimposed on a long-term history of acid deposition Clarke et al (2005) Daniels et al (2008)
  15. 15. VNN Workshop. Leeds, 9th May 2012 Degradation, restoration and DOC/colour• Increasing reports that ditch blocking reduces DOC (e.g. Wallage et al 2006; Armstrong et al 2010; SCaMP 2011; Wilson et al 2011)• But a lack of consistent behaviour between systems and over the (generally) short time periods of study• Evidence of (transient?) DOC increases Wallage et al (2006) after blocking (e.g. Worrall et al 2007)• Evidence that in some cases re-wetting might increase DOC loss (e.g. Daniels et al. 2008 study of catchments with significant stores of sulphur)• Need fuller understanding of process controls in order to generalise/model Daniels et al. (2008)
  16. 16. VNN Workshop. Leeds, 9th May 2012 Climate change impacts 08 September 07 November 07 December 09 August 2008 2008 08 October 2008 2008 2008 06 January 2009 -100Degraded systems as 0 W a te r T a b le D e p th (m m ) climate change 100 200 analogues? 300 400 500 600 DROUGHTBlackstone Edge Reservoir Tipping, Rothwell et al. 2010. Environ. Pollut., 158: 1521-1529
  17. 17. VNN Workshop. Leeds, 9th May 2012 Long term monitored data • Crucial context for water quality impacts and catchment management • Regional / national patterns • Long term drivers (climate and atmospheric deposition) 10 9 Dissolved Organic Carbon concentration (mg l-1) 8 7 6 5 4 3 2See Acid Waters Monitoring 1Network website and reports 0 1988 1993 1998 2003 2008
  18. 18. VNN Workshop. Leeds, 9th May 2012Upland waters: aqua incognita? • 82% of GB river length lies within catchments of < 10km2? • Of the upland river length, 97% lies in catchments < 10 km2 • Not many EA monitoring sites above 300m! • Much upland policy is based on a small, disconnected and financially vulnerable set of monitoring sites (e.g. AWMN sites) • Require increased monitoring, both investigative and surveillance
  19. 19. VNN Workshop. Leeds, 9th May 2012Investigative monitoring: Bamford/Ashopcatchment metals study (EA/STW/Moors for the Future) ?
  20. 20. ENVIRONMENTAL CHANGE RESEARCH CENTRE An Upland Waters Monitoring Network for the UK (based on a science partnership of UCL, CEH, QMUL and SG; supported by Defra, DOENI, WG, SG, CCW, EA, Forestry Commission, CEH and ENSIS Ltd)
  21. 21. The UK Upland Waters Monitoring Network Plans and Proposals1. To build on (and replace from 2013) the Acid Waters MonitoringNetwork of 24 lake and stream sites across the UK
  22. 22. The UK Upland Waters Monitoring Network Plans and Proposals2. 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 deposition3. 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 protocols4. To complete the installation of temperature loggers and flow and water-levelloggers at existing AWMN sites5. 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.uk or contact Rick Battarbee or Ewan Shilland
  23. 23. VNN Workshop. Leeds, 9th May 2012Summary points • Key upland WFD concerns: acidity, specific pollutants (metals), biological quality, DOC/colour, suspended sediments/FPOM • Peat degradation impacts all these! • Peat restoration has clear and demonstrable benefits for suspended sediments • Less consensus over other restoration related WQ improvements than policy/practitioner community would like (timescales, variation between case study data, lack of data in many cases) • Key role of monitoring and improved process understanding