About the Water Framework Directive

The purpose of the Water Framework Directive is to establish a framework for the protection of inland surface waters, estuaries, coastal waters and groundwater. The framework for delivering the Directive is through River Basin Management Planning.  The UK has been split into several River Basin Districts (RBDs). Each River Basin District has been characterised into smaller management units known as Water Bodies. The surface Water Bodies may be rivers, lakes, estuary or coastal.

River Basin Districts in the UK

Source: WFD UK Technical Advisory Group

To achieve the purpose of the Directive of protecting all Water Bodies, Environmental Objectives have been set. These Environmental Objectives are reported for each water body in the River Basin Management Plan (RBMP). The progress towards delivery of the objectives will be reported on by the relevant competent authorities at the end of each six year River Basin Planning cycle.

It is recognised in the Directive that physical alterations support the socio-economic use of a water body for a particular purpose (for example, water storage, flood defence or navigation). In this case the water body may be designated as a Heavily Modified water body (HMWB). Artificial Water Bodies (AWBs) are those Water Bodies which have been constructed for a specific use (for example, a reservoir). Any of the surface water body types (rivers, coastal, lake or transitional) can be designated as Heavily Modified or Artificial. AWBs and HMWBs are subject to alternative environmental objective than ordinary Water Bodies hence they have been clearly identified in each RBD and will be classified differently.

The achievement of the Environmental Objectives is dependent upon the current Ecological Status or Ecological Potential (for HMWBs and AWBs) of the water body.

Ecological Status
Ecological Status is classified in all Water Bodies, expressed in terms of five classes (high, good, moderate, poor or bad). These classes are established on the basis of specific criteria and boundaries defined against biological, physico-chemical and hydromorphological elements. Biological assessment uses numeric measures of communities of plants and animals (for example, fish and rooted plants). Physico-chemical assessment looks at elements such as temperature and the level of nutrients, which support the biology. Hydromorphological quality looks at water flow, sediment composition and movement, continuity (in rivers) and the structure of physical habitat.

The overall Ecological Status of a water body is determined by whichever of these assessments is the poorer. For example, a water body might pass ‘Good Status’ for chemical and physico-chemical assessments, but be classed as ‘Moderate Status’ for the biological assessment: In this case it would be classed overall as ‘Moderate Ecological Status’. To achieve the overall aim of good surface water status, the Directive requires that surface waters be of at least Good Ecological Status and Good Chemical Status. To achieve High Status, the Directive requires that the hydromorphological Quality Elements are also in place. For lower classes, although hydromorphological quality is not explicitly required, it is a supporting element of the biological and in some cases physico-chemical status and must therefore be taken into account.

Ecological Potential
For HMWBs and AWBs, a separate classification process applies because these water bodies cannot reach good ecological status due to socio-economic uses. We identify whether a HMWB or AWB meets its Ecological Potential or not by:

  • Identifying the impacts affecting the water body;
  • Identifying the mitigation measures necessary to ensure the hydromorphological characteristics of a water body are consistent with Good or Maximum Ecological Potential; and
  • Assessing whether those measures have been taken.

Where all applicable mitigation measures have already been taken or screened out, the water body can be classified as Good Ecological Potential or better. Where one or more applicable mitigation measure(s) remains to be taken, the water body will be classified as Moderate Ecological Potential (MEP) or worse. This will then be combined with the outcomes from other assessments to give an overall classification.