NA14 Freshwater bodies affected by diffuse pollution due to agriculture

Diffuse pollution, arising primarily from agricultural sources, constitutes a significant pressure on Scotland’s rural water environment[1]. Soil erosion and run-off result in suspended sediments, nutrients (fertiliser), and toxins (pesticide) entering neighbouring water bodies and reducing water quality. Water quality is closely linked to both land use and climate; with projected changes in both these factors it is important to assess the future risk in order to protect water quality (Towers et al, 2012).

Climate change has the potential to increase diffuse pollution from agricultural land in a number of ways e.g. (DEFRA, 2012):

• Higher intensity rainfall events and an increased risk of flooding will increase erosion and result in greater run-off and suspended solids washing off the fields, especially where ground is bare and unprotected by crops.
• Lower summer flows will reduce the dilution capacity in rivers and, as a consequence, the pollutants will become more concentrated.
• Warmer standing waters receiving high nutrient run-off as a result of greater intensity rainfall events could exacerbate algal blooms and eutrophication and increase loading of pollutants to the sea.
• Indirectly, climate induced changes in land use (e.g. more land being viable for farming, or improvements in the conditions of land already used for agriculture which result in increased intensification) could result in an associated increase in the use of fertilisers and pesticides, and land exposed to tillage and the use of heavy machinery.

The increased risk of diffuse pollution from agricultural land will potentially make it harder to meet the requirements of legislation (Scotland Rural Development Programme (SRDP); Good Agricultural and Environmental Conditions (GAEC) standards) and associated economic support and incentives.

Monitoring diffuse pollution due to agriculture provides both a direct measure of the impact on the water environment as well as an indirect measure of agricultural soil erosion and the loss of nutrients. The indicator draws on SEPA’s assessment of all pressures affecting Scotland’s water bodies. This identifies individual waterbodies under pressure from diffuse pollution due to arable, livestock and/or mixed farming.

Related indicators:

NA10 Soil erosion risk

NA12 Agricultural production methods which reduce erosion risk (Proportion of arable land using reduced/zero tillage; soil cover)

NB24 Proportion of water bodies not meeting Good Overall Status

NB33 Progress towards the environmental objectives of the River Basin Management Plans

SEPA assess pressures on (level and source) and quality of water bodies (hydrological units within each river basin district) under the EU Water Framework Directive (WFD). Under this process, the presence of diffuse pollution due to livestock farming, arable farming and/or mixed farming is monitored. Table 1 shows the latest figures for Scotland’s waterbodies found to be under pressure from diffuse pollution originating from one of these sources.

 Table 1:  Proportion of water bodies under pressure from diffuse pollution due to agriculture, 2014 (SEPA).

Overall this equates to just over 8% of all water bodies in Scotland currently being under pressure from diffuse pollution due to agriculture. The overall status of each water body is also assessed (as high, good, moderate, poor, or bad). Of those water bodies identified as under pressure due to diffuse pollution from agricultural sources, the vast majority are also, as a consequence, at less than good status.

Adaptation / policy drivers

The primary legislative driver for improving water quality is the EU Water Framework Directive (WFD) that led to the Water Environment and Water Services (Scotland) Act 2003 (WEWS Act). The WEWS Act provides powers to regulate water activities, including wetlands and groundwater as well as rivers, lochs, transitional waters (estuaries) and coastal water. River basin management planning (RBMP) in Scotland sets out how these improvements to Scotland’s water environment will be phased, and targets have been set for each waterbody for the time periods 2009-2015, 2015-2021 and 2021-2027.

Fundamental to the RBMP process is the legislative framework intended to ensure action on the most significant pressures on the water environment, supported by economic incentives, funding, and education to promote, encourage and support action. Working with farmers is part of a co-ordinated national level approach to reduce the risk of diffuse pollution. A partnership approach to reducing rural diffuse pollution is led by the Diffuse Pollution Management Action Group (DPMAG). In addition to its national strategy, DPMAG targets ‘Priority Catchments’ where a particular focussed approach is needed (SEPA, 2015)

Midway RBMP assessment in the Scotland and Solway River Basin Districts (RBD) identified good progress with regard to many measures, but also identified that targets for improvement were likely to be missed in a number of areas including rural diffuse pollution (SEPA, 2013a/2013b). The Second RBMPs identify that rural diffuse pollution remains by far the most significant pressure on water quality (Scottish Government, 2015a; Scottish Government & Environment Agency, 2015)

Table 2 shows that between 2008 and 2012 there was an increase in the overall number of waterbodies identified as under pressure from diffuse pollution due to agriculture. However, over this period there was also a considerable increase in the level of understanding of the water environment, as well as changes in assessment methodologies and environmental standards. One consequence of improvements to understanding and assessments is that real environmental change cannot be identified simply by comparing classification results across this period (SEPA, 2014a).  Over the second period (2012 to 2014) however, there was a significant decrease in affected water bodies that can be attributed to real environmental change.

Between 2009 and 2014, a targeted approach was taken with priority catchments being identified for the first RBMP. Around one example of poor practice was found per kilometre, and land managers were engaged with in order to highlight the necessary improvement measures. However, in the Scotland RBD, 6% of all water bodies had been identified for improvement of water quality, but only 3% were identified as likely to achieve this by 2015, largely due to rural diffuse pollution where over half the planned improvements were not on track. Rural diffuse pollution was also the main reason for failure in the Solway RBD (SEPA, 2015b). Contributing farming practices were more numerous and widespread than had been originally estimated, with multiple sources often on single farms. It therefore took longer than anticipated to improve understanding and to work with land managers to reduce these risks (SEPA 2013a; 2013b; 2013c).

Table 2 Number, area/length and proportion of water bodies under pressure from diffuse pollution due to agriculture, 2008-2014 (SEPA).

It is expected that pressure on Scotland’s water resources will increase in future as a result of both climate change and land use change. The predicted increase in arable area is likely to increase the risk of transport of sediments and associated pollutants to water bodies and therefore it will be necessary to continue to develop measures and incentives to encourage cultivation and land management techniques aimed at reducing this risk (Towers et al, 2012).

The current RBMPs have taken a ‘revised and strengthened approach’ to tacking rural diffuse pollution (Scottish Government, 2015b). Under the latest (2015-2027) RBMPs, work in the existing 14 rural diffuse pollution priority catchments will continue to ensure that good land management practices are strengthened and maintained and this will be expanded to take in 43 new catchments as well. In addition, SEPA will investigate and confirm the sources of pollution in 64 smaller, rural diffuse pollution focus areas and then work with land managers to put in place the appropriate measures for completion before 2027 (Scottish Government, 2015a).

There has been considerable progress made to implement the measures generated by the first cycle RBMPs. Figure 1 sets out the general framework for the delivery of the programme and planned reduction of pressures on the water environment.

Figure 1 Process of achieving objectives by reducing pressures on the water environment (Source: SEPA, 2009)

Over the course of the first RBMPs, SEPA has also improved the baseline knowledge of the pressures and impacts on the water environment which has resulted in changes in classification unrelated to any measures that have been implemented on the ground (SEPA, 2013a). The Limitations section provides further information.

However, the majority of the decrease in the number of water bodies under pressure due to rural diffuse pollution is due to the delivery of this policy and management programme rather than other factors, such as change in baseline knowledge or changing climatic pressure over this period.

Figures are presented as percentages of total number and area/length of water bodies for each type of water body. This is partly due to changes in numbers of unique water bodies included in WFD reporting between 2008 and 2012 (in part due to change in methodology). 

SEPA has been progressively improving the understanding of the state of the water environment in Scotland, and since 2009 a number of changes have occurred to the way data is collected and analysed:

• increasing the amount of environmental data on which the assessments are based;
• developing and refining the models used to interpret data and make assessments;
• and refining the delineation of bodies of groundwater and surface water to ensure there are not significant differences in environmental quality in different parts of the same water body (SEPA, 2013a)

There are therefore some changes within the data over this period that reflect a change in understanding rather than an actual change in the water bodies.  The formal directions on the classification of water bodies also changed for 2013 onwards.

All the groundwater bodies were radically redefined in 2012, therefore 2008 data is not provided here as comparison would be misleading.

Waterbodies may be impacted by multiple pollution sources, in addition to agriculture (arable, livestock and/or mixed farming), and may also be subjected to other pressures due to physical condition of the water environment, pressure on water flows and levels, restrictions to fish migration and pressure due to the presence of invasive species.

Brown, I et al (2012) Climate Change Risk Assessment for the biodiversity and ecosystem services sector [online] UK CCRA. Available from:  https://www.gov.uk/government/policies/adapting-to-climate-change (accessed August 2015)

DEFRA (2012) UK Climate Change Risk Assessment 2012: A climate change risk assessment for Scotland. Available online at: http://randd.defra.gov.uk/

Scottish Government (2015a) The river basin management plan for the Scotland river basin district: 2015–2027. Available online at: http://www.sepa.org.uk/media/163445/the-river-basin-management-plan-for-the-scotland-river-basin-district-2015-2027.pdf

Scottish Government (2015b) Appendices to the river basin management plan for the Scotland river basin district: 2015 – 2027. Available online at: http://www.sepa.org.uk/media/163444/appendices-to-the-river-basin-management-plan-for-the-scotland-river-bsin-district-2015-2027.pdf   

Scottish Government & Environment Agency (2015) The river basin management plan for the Solway Tweed river basin district: 2015 update. Available online at: http://www.sepa.org.uk/media/218890/rbmp_solway_tweed_2015.pdf 

SEARS (no date) Reducing the risk of water pollution: Diffuse Pollution General Binding Rules: explained. SEARS. Available at:  http://www.sepa.org.uk/regulations/water/diffuse-pollution/diffuse-pollution-in-the-rural-environment/  (accessed July 2015)

SEPA (2009) The river basin management plan for the Scotland river basin district 2009–2015

Chapter 3: Achieving our environmental objectives. Available online at: https://www.sepa.org.uk/environment/water/river-basin-management-planning/publications/

SEPA (2013a) Current condition and challenges for the future: Scotland river basin district. Available online at: https://www.sepa.org.uk/environment/water/river-basin-management-planning/publications/

SEPA (2013b) Current condition and challenges for the future: Solway river basin district. Available online at: https://www.sepa.org.uk/environment/water/river-basin-management-planning/publications/

SEPA (2013c) Delivering the programme of measures in the first River Basin Management Plan: A progress report for the Scotland River Basin District 2012. Available online at: https://www.sepa.org.uk/environment/water/river-basin-management-planning/publications/

SEPA (2014a) A public consultation to inform the development of the second river basin management plan for the Scotland river basin district. Available online at: https://www.sepa.org.uk/environment/water/river-basin-management-planning/publications/

SEPA (2015) DPMAG [online] Available from: http://www.sepa.org.uk/environment/water/river-basin-management-planning/who-is-involved-with-rbmp/dpmag/ SEPA [accessed October 2015]

Towers, W., Dunn, S., Dawson, J. & Sample, J. (2012) Research Summary: The potential risks to water quality from diffuse pollution driven by future land use and climate change [online] Aberdeen: CREW Centre of expertise for waters. Available from: http://www.crew.ac.uk/call-down/potential-risks-water-quality-diffuse-pollution-driven-future-land-use-and-climate-change  (accessed July 2015)