Tom Nisbet, Huw Thomas, Nadeem Shah & Samantha Broadmeadow

Forests & Water - An Assessment of Water

Services and Dis-benefits

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Past Focus on Upland Conifer Afforestation

Forest Hydrology Research

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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.

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• 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

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6.5

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7.5

1991

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2000

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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

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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

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Demonstrating how woodland creation and management can reduce flood flows:

Slowing the Flow at Pickering

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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)

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National, Regional & Catchment Mapping:

Opportunity Mapping

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• 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

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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.