The James Hutton Institute
This page is no longer updated. The Macaulay Land Use Research Institute joined forces with SCRI on 1 April 2011 to create The James Hutton Institute.
THE STATE OF SCOTLAND'S FARMED ENVIRONMENT 2005
8. FRESHWATER
Pollution
The recently produced “characterisation report” (associated with the implementation of the Water Framework Directive), identifies where the water environment is at risk of being harmed and although there are problems, the majority of Scotland 's rivers are of high quality. Forty-three per cent of the water bodies in the Scotland river basin district are at risk of being harmed - this compares to over 80% of waters in most of Europe . In addition, most of Scotland 's river water bodies are of good quality: 72% are not affected by pollution; 73% are not affected by abstractions or dams; 66% are not affected by engineering works. The length of both poor (1,077km to 717km) and seriously polluted (91km to 51km) rivers in Scotland fell between 1999 and 2004. Leaking silos and silage effluent tanks, escape of animal slurry, pollution by chemicals, fuel oil, farm drainage and others can contribute to the pollution of water. There has been a significant reduction since 2000 in the number of reported point-source pollution incidents involving agricultural sources.
There remain, however, concerns about agriculture-related diffuse pollution. Nitrogen fertilizer is generally applied to crops as a combination of nitrate and ammonium compounds. Whilst ammonium ions are adsorbed onto soil particles, nitrate ions are highly mobile in soils and can be easily leached to ground or surface waters. Nitrogen applications to agricultural land in Scotland have ranged between 114 and 127 kg/ha between 1986 and 2003 and the rates of application to tillage crops in Scotland is around 40% less than in England and Wales because of cropping differences. Nonetheless nitrate concentrations in surface waters in Scotland are strongly correlated with proportion of arable land in their contributing catchments. Thus diffuse nitrate pollution has probably been driven by past changes in farming practices, and particularly the switch from mixed farming to cereal farming that occurred over much of eastern Scotland in the 1980s. The EC Nitrates Directive (91/676/ EEC) now provides a framework to protect water bodies from agricultural nitrate pollution. This includes the designation of Nitrate Vulnerable Zones, where mandatory practices of fertiliser use are implemented. Whilst improved nutrient management and the introduction of landscape features like buffer strips may help reduce contemporary losses of nitrates from agricultural soils, it is believed that it will take some time for these improved management measures to have a significant effect.
Phosphate fertilizer is also applied to agricultural land. In contrast to nitrogen, phosphorus is strongly adsorbed onto the fine particles in soil and consequently water pollution only occurs where these particles are washed into streams via erosion by surface water runoff, often during heavy rainfall events. Soil erosion in arable soils in Scotland is thought to have increased since the 1980s in association with changes in arable cropping practices. Although applications of phosphate to agricultural land in Scotland has been around 40 to 45 kg/ha since 1983, changes in agricultural practices have locally increased the loss of soil particles to surface waters. Thus phosphate pollution may be strongly associated with increased soil erosion. Excess phosphorus in freshwaters can lead to localised eutrophication. This may adversely affect the freshwater biota, and the quality of private water supplies.
Besides agriculture the main sources of phosphorus are outputs from sewage treatment works. Orthophosphate concentrations in surface waters provide an indicator of trends in total phosphorus. SEPA data show significant drops in the average organophosphate concentrations in both their South East and South West areas. Between 1993 and 2001 the percentage of sites across Scotland with mean concentrations <25 µg P/l and =125 µg P/l averaged 45% and 16% respectively. By 2004, the percentage of sites with mean concentrations <25 µg P/l had increased to 58% and the percentage of sites =125 µg P/l had fallen to 7.5%. These data probably reflect significant improvement in water quality principally through improved sewage treatment, however diffuse phosphate pollution form agriculture remains a concern. Under the Urban Waste Water Treatment Directive ( UWWTD) (91/271/ EEC), the Ythan Estuary, Dean Water, South Calder Water, River Almond, the lower part of the River Don and their respective catchments are all designated sensitive areas. Discharges into waters that have been designated as sensitive require additional treatment to remove nutrients. SEPA forecasts that agricultural activities will still be the largest polluting sector by 2012.
Shallow groundwater sources are especially at risk of contamination by faecal coliforms from livestock waste material. For example, of 1750 private water supply samples tested from Aberdeenshire between 1992-98, 30% failed on the basis of faecal coliforms, 41% failed on total coliforms and 15% failed on nitrate levels (Reid et al, 2003). However, progress is being made with regard to bathing water quality. Under the EU Bathing Waters Directive, some 60 bathing waters around the Scottish Coast are regularly monitored by SEPA. In 2005 95% (57 out of 60) of the Scottish bathing waters met European standards, and for the first time ever all recognized bathing waters on the west coast met the required standards. This provides evidence that the collaborative work of many Scottish agencies and land management interests to reduce diffuse pollution impacts is having a positive effect.
The Water Framework Directive (2000/60/EC)(WFD) is a wide-ranging and ambitious piece of European environmental legislation which became law in Scotland at the end of 2003 through the Water Environment and Water Services ( Scotland ) Act 2003 (WEWS). The Directive establishes a new legal framework for the protection, improvement and sustainable use of surface waters, transitional waters, coastal waters and groundwater across Europe in order to:
- Prevent deterioration and enhance status of aquatic ecosystems, including groundwater
- Promote sustainable water use;
- Reduce pollution; and
- Contribute to the mitigation of floods and droughts.
In Scotland , this work is being taken forward by SEPA, in conjunction with the Scottish Executive, in line with the timetable for action set in the Directive.
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