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ANNEX A: PROPOSED STANDARDS AND CONDITIONS - DETAIL
This Annex sets out the numerical proposals for the first set of environmental standards and conditions for the Water Framework Directive. The proposed standards are compared with existing standards where they exist.
More information on the methods used to develop the standards, and the information on which they are based, can be found from the UKTAG report, or from the technical documents which support it. These documents can be found on the UKTAG website at www.wfduk.org .
The earlier part of this consultation paper summaries these proposals, and sets out proposals for their use in Scotland (see section C).
The proposed standards are set out in three sections in this Annex:
1. Water quality(physico-chemistry) - for rivers, lochs, transitional and coastal waters;
2. Water resources(hydrology) - for rivers and lochs only; and
3. Physical shape(morphology) - for rivers only.
Typologies
Ecology in water bodies can vary with factors like geology and altitude or loch depth, and so the biological responses to some external pressures, like nutrient conditions, may also vary between different types of river, or different types of loch.
UKTAG has investigated where variations in the characteristics of water bodies affect the sensitivity of the ecological communities to external factors. UKTAG has therefore set standards at different values for different types of a given water body, to reflect the varying needs of the ecology. These typologies are set out at the beginning of each section in this Annex.
General notes to tables:
'High' refers to the boundary between 'good' and 'high' classes: for 'high' ecological status, water must equal or better the standard.
'Good' refers to the boundary between 'moderate' and 'good' classes: for 'good' ecological status, water must equal or better the standard.
5-percentile This refers to the value in a dataset where 5% of all the dataset are equal to or below the value ( i.e. 95% of the dataset are higher). For standards, this would mean that, for instance, oxygen levels must not drop below the defined standard for more than 5% of the time.
10-percentile Similarly, this refers to the value in a dataset where 10% of all the dataset are equal to or below the value ( i.e. 90% of the dataset are higher). Here, this is used to mean that to meet e.g. the 'good' dissolved oxygen standard, oxygen levels must not drop below the defined standard for more than 10% of the time.
90-percentile This refers to the value in a dataset where 90% of all the dataset are equal to or below the value ( i.e. 10% of the dataset are higher). Here, this is used to mean that to meet e.g. the 'good' BOD standard, BOD levels must not be higher than the defined standard for more than 10% of the time.
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