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Title: Risk Assessment Methodology for Determining Nutrient Impacts in Surface Freshwater Bodies
Author: Laurence Carvalho
Author: Stephen Maberly
Author: Linda May
Author: Colin Reynolds
Author: Mike Hughes
Author: Richard Brazier
Author: Louise Heathwaite
Author: Shuming Liu
Author: John Hilton
Author: Duncan Hornby
Author: Helen Bennion
Author: Alex Elliott
Author: Nigel Willby
Author: Rachael Dils
Author: Geoff Phillips
Author: Linda Pope
Author: Ian Fozzard
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1076, Representation ID: 332, Object ID: 2347; Environment Agency Project ID:EAPRJOUT_1450, Representation ID: 500, Object ID: 2604
This report summarises the development of a number of methodologies required for carrying out this initial risk assessment for lakes required under the EU Water Framework Directive (WFD), specifically in relation to nutrient pressures. It provides a number of approaches of increasing sophistication for assessing the magnitude of diffuse and point-source nutrient pressures and develops a nutrient classification for different lake types that can be applied to assess the impact of these pressures. Approaches to ecological classification for phytoplankton composition and abundance in lakes and slowmoving rivers are also outlined, as phytoplankton is considered the biological quality element most sensitive to nutrient pressures. An initial risk assessment using the recommended guidance for a tier 1 approach was carried out on all lakes in Great Britain >1 ha in size (>14,000 lakes). Overall 51% of sites are predicted to not meet the Total Phosphorus (TP) targets identified for high or good status and must, therefore, be considered at risk. Of the six lake ecotypes examined, very shallow, medium alkalinity lakes (equivalent to “mesotrophic lakes” under the Habitats Directive) appear to be at greatest risk (92 % of GB sites). There were also major regional differences in numbers of sites at risk. Scotland has by far the fewest sites at risk (18%), England by far the most (88%), with Wales having an intermediate percentage (56%). A large number of sites were also identified as “unknown” status, predominatly peaty lochs in Scotland. There is a high probability that most of these sites are not at risk from nutrient pressures, being largely present in the more undisturbed parts of northern Scotland. Further work is required not only to establish reference nutrient conditions for peaty, marl and brackish lake ecotypes, so their nutrient classification can be developed, but also the ecological impact of nutrient pressures in these lake types requires much further study. In summary it does, therefore, appear that a large number of sites in GB are at risk from nutrient pressures. The risk assessment process outlined above is, however, just the first step in a tiered process in identifying sites at risk. Those identified require further investigation, both monitoring and modelling using the more sophisticated approaches outlined in this report.
Publisher: Environment Agency
Subject Keywords: Water Framework DirectiveLakesPhytoplanktonEutrophicationPhosphorusRiversDiffuse pollutionNutrientsLakesEnvironmental factorsRisk managementFreshwater ecology
Extent: 220
Total file downloads: 292

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