Indicator 6.3.2 Proportion of bodies of water with good ambient water quality

Percentage of UK surface water bodies awarded ‘Good’ or ‘High’, by water body type, under the Water Framework Directive

This indicator shows the percentage of surface water bodies in the UK awarded a good or high surface water status classification under the Water Framework Directive (WFD). The purpose of the WFD 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. 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. Surface water status is measured by both its ecological and chemical status. It is assessed against the scale of high, good, moderate, poor and bad. The results published each year relate to data reported in that year under the Water Framework Directive.

United Kingdom

Percentage (%)

Figures are based on numbers of surface water bodies classified under the Water Framework Directive (WFD) in England, Wales, Scotland and Northern Ireland. Includes rivers, canals (Northern Ireland does not report on canals), lakes, estuaries and coastal water bodies. Surface water status is measured by both its ecological and chemical status. It is assessed against the scale of high, good, moderate, poor and bad.

The ecological status of surface waters is assessed according to the following criteria

- Biological quality measured by composition and abundance of specified elements such as fish, benthic invertebrates, aquatic flora;

- Hydromorphological quality measured by reference to elements such as river continuity, channel patterns, dynamics of flow or substrate of the river bed;

- Physico-chemical quality measured by reference to elements such as temperature, oxygenation, pH, nutrient conditions and the concentrations of specific pollutants (synthetic and non-synthetic).

The chemical status quality of surface waters is measured by reference to environmental quality standards for chemical substances at European level. These standards specify maximum annual average concentrations for specific water pollutants. The specific requirements differ depending on which type of surface water body is being monitored. Chemical status is measured as either good or fail. If part of a water body fails on any one of the criteria monitored, it will fail to achieve or lose good status. This is described as the "one out all out" approach.

The results published each year relate to data reported in that year under the WFD; data reported in a given year relate to data collected over the previous year (for Scotland) and previous 3 years (for England, Wales and Northern Ireland).

Some small differences exist in the way the administrations and environment agencies implement the methods and tools for assessing water body status. The introduction of new Water Framework Directive (WFD) monitoring data and classification standards (including a new baseline adopting all of the new standards, tools, designations and water body boundaries) in 2014 has led to a step change in the number of water bodies assessed as being in each status class in following years.

The formal reporting of new standards in cycle 2 of WFD has used the second cycle plans published in 2015. The introduction of reporting the cycle 2 standards has differed amongst the UK countries. The percentage of water bodies in each status class has been calculated based on the total number of water bodies assessed in each year. The number of water body assessments included varies slightly from year to year. The reductions in the number of assessments made in 2015 and 2016 were primarily due to Wales and then England adopting the monitoring and classification standards laid down in Cycle 2 of the WFD. This resulted in the removal of a number of water bodies that were below the 10km2 catchment area in line with WFD guidance.

While data is available from 2009, it is not reported here because data from 2015 onwards are not directly comparable to those in earlier years. Data from 2009 is available from the Joint Nature Conservation Committee's website.

For a broader view of the condition of the water environment, see indicator B3 in the Outcome Indicator Framework for the 25 Year Environment Plan 2021 update.

Data follows the UN specification for this indicator. This indicator has been identified in collaboration with topic experts.