The Water Framework Directive is a piece of European legislation that states that all UK waterbodies (rivers, lakes, seas) must be in ‘good ecological status’ by 2027.
The ‘ecological status’ of a stretch of river is measured by looking at a number of things which affect the health of a river, including:
• Invertebrate populations
• Fish populations
• Pollutants (e.g. phosphate or ammonia)
• Oxygen content
For each category, the river is graded either Bad, Poor, Moderate, Good or High. The entire stretch of river takes its classification from the worst result in these categories; for example, if the river is achieving ‘Good’ status for everything except its fish populations, which are classed as ‘Bad’, the entire stretch will be classified as ‘Bad’. This ensures that work can be targeted towards tackling the reason (or reasons) a river is failing to meet Good Status, e.g. its fish populations. The projects outlined in this Catchment Management Plan will help to move the river into Good Ecological Status.
The Environment Agency also routinely measure flow levels as part of their assessment of the river’s Water Framework Directive status. The results of these flow measurements are shown in the chart.
If the river has ‘passed’ the assessment (shaded green), there is enough water in the river to sustain its ecology. If it has ‘failed’ (red), there is not enough water to support its ecology.
The chart below shows the most recent (2012) Water Framework Directive classifications for the Mimram.
Section of river
Criteria failing to reach Good Ecological Status
(i.e. ranked Moderate, Poor or Bad)
St Pauls Walden to Welwyn
Welwyn to confluence with the Lea