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Tom Nisbet, Huw Thomas, Nadeem Shah & Samantha Broadmeadow
Forests & Water - An Assessment of Water
Services and Dis-benefits
16 September 2015 2
Past Focus on Upland Conifer Afforestation
Forest Hydrology Research
16 September 2015 3
Forestry as a Potential Pressure
• Canopy interactions can enhance pollutant capture, e.g. acid deposition;
• Greater canopy evaporation can reduce water resources;
• Management practices disturb soils and can increase pollutant inputs and losses to water;
• Excessive canopy shade and inputs of brash can damage riparian and aquatic habitats.
16 September 2015 4
• Partnership based, catchment focus and long-term;
• Impacts of forests and forestry management on water yield and extreme flows (e.g. Coalburn, Plynlimon, Balquhidder, Blackwood, TADPOLE);
• Impacts of forestry on soil and water acidification (e.g. Llyn Brianne, Loch Dee, Loch Ard, UKAWMN);
• Impacts of cultivation, drainage, roading, fertiliser, pesticides and harvesting on water quality (e.g. Coalburn, Plynlimon, Balquhidder, Glen Orchy);
• Impacts of developments in forestry practice (e.g. SRC, SRF, stump harvesting, CCF);
• Evaluation of BMP/countermeasures.
Nature of Research:
Quantifying Impacts
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Pressures are Manageable
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Current Research
• Effectiveness of good practice measures at Halladale;
• Impacts of energy forestry on water resources at Sibster, Alyth and Squerryes Estate;
• Impact of deforestation on nutrient release to waters at Flanders Moss;
• Long-term impact of forestry on acidification in Wales.
Halladale: Turbidity 01.01.1995 - 01.01.2011
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1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Tu
rbid
ity (
NT
U)
Lower Halladale
Middle Halladale
Bealach Burn
Upper Halladale
Allt a Bhealaich
BBLFperiods of cultivation
47 27 37 29
Mean annual pH for ten forest and two moorland streams
July 1991 -Dec 2012
4.5
5.0
5.5
6.0
6.5
7.0
7.5
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
Forest Moorland
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Woodland can improve water status by:
• Protecting the soil and reducing sediment delivery;
• Removing/reducing applications of fertiliser and pesticides;
• Intercepting pollutant pathways and retaining pollutants;
• Protecting river banks and increasing channel diversity;
• Moderating the riparian microclimate.
Woodland & WFD
16 September 2015 8
Woodland can reduce flood risk by:
• Reducing the volume of flood water by increasing evaporation;
• Slowing the rate of runoff from the land by increasing soil infiltration;
• Enhancing floodplain storage and delaying the flood peak by increasing hydraulic roughness;
• Reducing sediment delivery and siltation, increasing conveyance.
Woodland & FRM
9
Demonstrating how woodland creation and management can reduce flood flows:
Slowing the Flow at Pickering
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19
32 36 40 44 48 52 56 60 64
Discharge,cumecs
Hours since midnight (00:00) on 5th November, 2000
Test runs for the November 2000 flood, highlighting results for the first flood on 6th-7th November.
See text for explanation of the crims and debris dam sections used in each case.
Baseline
Case 1
Case 2
Case 3
Case 4
Case 5
Case 6
Case 7
Case 8
Planting 50 ha of riparian woodland and installing 100 LWD dams could reduce 1 in 25 year peak by 4% (21% of margin)
16 September 2015
National, Regional & Catchment Mapping:
Opportunity Mapping
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16 September 2015 11
• Improved models to better reflect and integrate woodland processes;
• Continued development of modelling and mapping tools to aid targeting of woodland creation for water plus other services, while minimising risks;
• Catchment-scale studies to quantify and demonstrate the impact of targeted woodland creation;
• Development of methods and metrics for valuing woodland water services.
Research Needs
16 September 2015 12
Conclusions:
• Research and monitoring continue to drive the development of good practice measures to ensure that forests and forest management protect the water environment;
• There is increasing evidence to support targeted woodland creation to reduce flood risk, tackle diffuse pollution and alleviate thermal stress, as well as deliver other ecosystem services;
• Further research is required to underpin the development and implementation of markets for woodland-water services.
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