Lake Restoration in the UK: lessons from the CEH case studies

Transcription

1 Lake Restoration in the UK: lessons from the CEH case studies Linda May, Bryan Spears, Sebastian Meis, Bernard Dudley, Stephen Maberly, Laurence Carvalho, Iain Gunn, Dave Carss, and Ian Winfield

2 Why is lake restoration important? Improving our understanding of restoration and recovery processes Providing the evidence base to support decision makers

3 Why is lake restoration important? Regulation Climate

4 Direct impacts: degradation of water quality Pollution Good water quality Bad water quality

5 Indirect impacts: loss of wildlife habitat & amenity value POCHARD BROWN TROUT GREAT CRESTED NEWT OTTERS

6 Impacts of pollution on lake water quality Degradation? Recovery Good water quality Bad water quality Recovery is not the reverse of degradation!

7 CEH s aim To provide the scientific evidence that helps lake managers to: Identify water quality problems Diagnose the causes (correctly!) Set restoration targets Manage the recovery process Based on a series of case studies. Evidence based management decisions are the key to success

8 CASE STUDY 1: Loch Leven (natural recovery) Cost of Scum Saturday (1992): 1M CEH data: May & Spears (2012) Loch Leven: 40 years of scientific research. Dev. in Hydrobiology. (10 papers).

9 CASE STUDY 1: Loch Leven (natural recovery) 300 Catchment P sources reduced by 60% Chemical recovery took > 15 years Slow recovery driven by release of legacy P from sediment stores Target Water column TP conc. (µg l -1 ) Recovery delayed by internal recycling of legacy P Recovery delayed by internal recycling of legacy P Cost of scum Saturday : 1M P input 60% P input reduced by 60% May & Spears (2012) Loch Leven: 40 years of scientific research. Developments in Hydrobiology. (10 papers).

10 CASE STUDY 1 : Loch Leven (natural recovery) Pochard Pochard Scotland Loch Leven Scotland Macrophyte growing depth (m) Large fish (ind. ha -1 ) 30 Annual P input to lake (tonnes) Large fish (individuals ha ) Year

11 CASE STUDY 2: Loch Flemington (managed recovery) x Long history of eutrophication P inputs from WWTW, agriculture & pig farm Cyanobacterial blooms in summer Natural recovery unlikely; no surface outflow Total phosphorus (µg L -1 ) SEPA pre-application data (average ) CEH pre-application data (May March 2010) 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

12 CASE STUDY 2: Loch Flemington (managed recovery) Phoslock controlled release of legacy P from lake sediments Potential to speed up chemical recovery from eutrophication demonstrated Ecological recovery still being monitored Total phosphorus (µg L -1 ) t of Phoslock, March 2010 SEPA pre-application data (average ) CEH pre-application data (May March 2010) CEH post-application data (March February 2011) Other P binding products under development, e.g. from waste products Average P concentration Before application 74 µg P l -1 After application 37 µg P l -1 WFD target 32 µg P l -1 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Meis (in prep) Investigating forced recovery from eutrophication in shallow lakes. PhD thesis, Univ. Cardiff. Submission 2012.

13 CASE STUDY 3: Loweswater (stakeholder involvement) Annual mean chlorophyll a (mg m -3 ) S3 S2 S3A S2A S1 S1A S5 S5A S4 M:P Moderate/Poor WQ S4A status Good/Moderate WQ status G:M High/Good WQ status H:G Phosphorus load (kg SRP y -1 ) Norton et al. (2011). Using models to bridge the gap between land use and algal blooms: an example from the Loweswater catchment, UK. Environmental Modelling and Software.

14 CASE STUDY 4: Loch Fitty (extreme restoration) Aim: to de-water, extract coal, solve pollution problems and rebuild to meet water quality targets But: causes of problem need to be properly identified and advice needs to be based on sound scientific evidence May et al. (2011). An assessment of recovery targets, endpoints and timelines associated with the proposed restoration of Loch Fitty (Fife). Report to Scottish Coal Company Limited (SCCL). 81pp.

15 CASE STUDY 5: Kinghorn Loch (multiple pollutants) PO 4 -P (mg/l) PO 4 -P (mg l -1 ) Polluted by red mud from an aluminium works 1950s to 1983; recovery since Arsenic (µg l -1 ) As (ug/l) Symptoms: algal blooms, fish kills, less macrophytes and macroinvertebrates 30 years of data enables recovery from multiple pressures to be investigated Initial results suggest that chemical recovery is slow (decades) and pollutant specific Ecological response still being investigated Kinghorn Loch Users Group Vanadium V (ug/l) (µg l -1 )

16 Accumulating knowledge from multiple case studies Loch Flemington (NERC/Phoslock ) Rescobie & Balgavies Lochs (Hutton/SEPA/SAC) Rouken Glen Pond (East Renf. Council) Clatto Reservoir (Phoslock /NERC/Dundee City Council Kinghorn Loch (Fife Council/SEPA/NERC) Loch Fitty (SEPA/Scottish Coal) Haining Loch (Tweed Forum) Loweswater (NERC Relu) Bassenthwaite (EA) Esthwaite (EA; EU; NERC) Shropshire/Cheshire meres (NE; EA) Loch Leven (NERC/SNH/SEPA/EU) Linlithgow Loch (Linlithgow Council/Historic Scotland) Coldingham Loch (Owner) Hornsea Mere (NE) Alderfen Broad (EA) Moor Loch Llangorse Lake (CCW) helps inform future decision making

17 Delivering decision support tools for water managers Are monthly monitoring data available? Y Is algal N-limitation apparent? TP Does the site fail WFD for TP and Chl? No Continue monitoring Y N Both N Is algal P-limitation apparent? Investigate trophic interactions Y Is there evidence of external P loading? Y Reduce external P load Consider N control N Is there evidence of internal P loading? N Site specific study required Y Is product flush-out likely? Is there an outflow and a Y source of TP replete water? Y Consider flushing N N Is the loch very shallow? Are protected species present? N Consider dredging N Y Spears et al., Report to the Environment Agency (2011) Consider P capping Allow natural recovery

18 Information available via the CEH website

19 Thank you for your attention!