« Previous | Contents | Next »
Listen
1. Classification
The WFD is much broader in its scope than previous legislation, and requires us to focus on both the ecological and chemical status of surface water bodies.
- Ecological status describes the degree to which human uses of the water environment have altered the structure and functioning of aquatic plant and animal communities. The Directive sets out five status classes: 'high', 'good', 'moderate', 'poor' and 'bad'. 'Good' ecological status means that human activities have had only slight impacts on the ecological characteristics of aquatic plants and animal communities.
- Chemical status describes whether the water contains safe levels of certain toxic chemicals that have been identified as of particular concern across Europe because of their toxicity, persistence and ability to accumulate in the bodies of plants or animals. These include the chemicals known as ' priority substances' and ' priority hazardous substances' as well as others identified under the Dangerous Substances Directive. The chemical classification is simple: water which contains too high a concentration of the listed pollutants cannot be classified as 'good'. The Directive therefore sets out just two status classes: 'good' and 'failing to achieve good'. Standards for these substances are being developed by the European Commission for use in all Member States.
The WFD requires us to aim to achieve at least 'good' status in both ecological and chemical terms. This is described in more detail below.
The Directive also requires us to consider the status of groundwaters, and requires groundwater bodies to aim for 'good' status in both quantitative and chemical terms. We expect to consult on proposals for groundwater standards and how they will be used during 2007 ( see section D), so groundwater is not discussed in more detail here.
Standards and classification
The Directive requires that monitoring and assessment methods are developed to classify the ecological status of Scotland's surface water bodies.
The first step in this process is to identify characteristics of the ecosystems that can be monitored and related back to the Directive's descriptions of the ecological conditions expected for each status class. This means defining, for instance, the composition and abundance of fish, invertebrates and plant communities that would be found in different types of rivers, lochs, estuaries and coastal waters in the absence of even minor human disturbance. We can then determine the changes from those conditions that would be expected for water bodies at 'good', 'moderate', 'poor' and 'bad' status.
The second step is to look at the characteristics of the water environment that are needed by aquatic communities in the different status classes. These characteristics include:
- physico-chemistry - e.g. oxygen levels, acidity, temperature and the concentration of chemicals listed as 'specific pollutants' in the UK ( see section D). These substances are known to harm ecology and are of specific concern in the UK because they are discharged to the water environment 'in significant quantities' 1.
- hydrology - e.g. water flows and levels; and
- morphology - e.g. physical shape of the watercourse, bank vegetation.
The environmental standards discussed in this paper have been developed in conjunction with the biological classification methods. This is to ensure that the standards describe the environmental conditions needed by aquatic plants and animals at 'high' or 'good' status.
The composition of plant and animal communities in our rivers, lochs, estuaries and coastal waters varies with the characteristics of those waters. The environmental conditions needed to support these different communities can also vary. Consequently, most of the standards in this report are specific to particular types of waters.
Each environmental standard has been set at the minimum level that the available scientific evidence indicates is necessary to protect aquatic plants and animals. This means, for example, that if the environmental standard for 'good' status oxygen levels was failed, adverse impacts on the condition of aquatic animals or plants would be likely.
Uses of classification
SEPA will begin monitoring using the new biological tools from December 2006. However, several years' data will be needed to fully classify all Scotland's water bodies into the new WFD status classes. Classification decisions will take account of biological monitoring results as well as information on whether the environmental standards are being met. SEPA will produce as good a picture as possible of the status of our water bodies by December 2009, to form part of the first River Basin Management Plan, as required by the Directive.
As information on the ecological status of our water bodies is gathered, the scientific understanding of the environmental conditions needed to support the achievement of 'good' status is likely to improve. Where the information provided from classification or other sources suggests that an environmental standard for a water body type may be too stringent or too lax, we expect SEPA to coordinate a review of that standard and, if appropriate, come forward with proposals for revisions.
Revisions to environmental standards will be taken into account during updates of the River Basin Management Plans. However, we do not propose to introduce new or revised standards during a planning cycle.
Heavily Modified and Artificial Water Bodies ( HMWBs and AWBs)
In some cases, substantial alterations made for activities like navigation, water storage, flood defence and land drainage will mean that a water body cannot reach 'good' ecological status. Where certain criteria are met, the WFD allows such water bodies to be designated as heavily modified water bodies ( HMWBs). Other water bodies, such as canals, which have been created where no natural water body previously existed, will be designated as artificial.
More information on how these water bodies will be identified is set out in our paper on objective setting 2.
The objective for heavily modified and artificial water bodies is to aim to achieve 'good' ecological potential by 2015 rather than 'good' ecological status. Alternative objectives may be set where making the improvements needed for 'good' ecological potential would be technically infeasible or disproportionately expensive.
Water quality standards will usually be directly applicable to HMWBs. For example, environmental standards for toxic pollutants are not dependent on whether a water body is heavily modified or artificial.
Depending on the modifications or the artificial characteristics, the environmental standards for water flows and levels and for the physical structure of water bodies may not be directly applicable. A water body would not be designated as heavily modified if all such standards could be achieved without significant adverse impacts on the relevant use of the water body.
« Previous | Contents | Next »