Assessing the health of our rivers
Find out why our rivers are failing to meet a healthy status under our water environment regulations
Introduction
This extra section explains how the government measures and assesses the health of our rivers, along with all water bodies. Warning: it's complicated! We try and make it as clear as possible, but this is a complex process that is built on decades of scientific research. Treat this as an introduction.
The quality of our water environment in the UK is assessed following the EU's Water Framework Directive, an approach that aims for good status for all surface waters (rivers, lakes, estuaries and coasts) and groundwater.
Rivers are very complex systems and, just like human health, there are many parameters that we can measure. They are assessed using a wide range of indicators, shown below, that allow us to determine both ecological and chemical health.
If any of these indicators fails to reach good status for a particular stretch of river then the overall classification will also fail to reach good. This ‘one-out all-out’ approach embeds the precautionary principle into protection of our freshwater ecosystems.
In England, the Environment Agency is responsible for monitoring the ecological and chemical status of our rivers. The resulting status classifications and the information behind them can be viewed on the Catchment Data Explorer .
Ecological health
Just 14.55% of our river water bodies in England are in good ecological health. Below, we unpack some of the different elements that make up ecological health. You can zoom in and find out how your river measured up against the different indicators that contribute towards ecological health.
Biological quality 🐟
This measures if the river supports healthy, diverse communities of plants and wildlife.
Less than 1/3 of our river waterbodies in England are currently supporting healthy communities of plants and wildlife.
The classification of biological quality in rivers is determined based on:
Fish are used as indicators of water quality and hydromorphological condition, as well as longitudinal connectivity in rivers. The abundance, diversity and age structure of fish communities can tell us a lot about how healthy a river is and whether or not important species are still thriving.
Aquatic invertebrates, such as flies or bugs, are incredible indicators of water quality. Invertebrates are very sensitive to different types of pollution, so we can detect issues with water quality by looking at the composition and abundance (or absence) of different species.
This is an assessment of the aquatic flora (plants, mosses and algae) growing in the river and this can tell us how well the river is working. They can indicate the impact of increased nutrients in rivers and are also influenced by other pressures such as channel engineering, water abstraction, flow impoundment or acidification.
Physico-chemical quality 🔬
These include physical and some chemical properties of the water in a river. 39% of rivers have good indicators of physico-chemical quality but more than half of our rivers, 57%, fail.
You can explore by some of the element level classification below:
Specific pollutants 👩🔬
This shows rivers contaminated with substances that can have a harmful effect on biological quality. Only a small proportion (3%) of rivers are failing this indicator. But worryingly, 58% of river water bodies haven't been assessed for specific pollutants, so we have a low level of confidence in this.
Here's the list of specific pollutants:
- 2,4-dichlorophenol
- 2,4-dichlorophenoxyacetic acid (2,4-D)
- arsenic
- carbendazim
- chlorothalonil
- copper
- cyanide
- diazinon
- dimethoate
- glyphosate
- iron
- linuron
- Manganese
- mecoprop
- pendimethalin
- permethrin
- phenol
- toluene
- triclosan
- un-ionised ammonia
- zinc
Supporting Elements
There are a number of other supporting elements which are not assessed for all waterbodies, but which can help inform the health assessment and pin down the issues impacting on overall health. To explore these please visit the Environment Agency's Catchment Data Explorer .
Chemical health
0% of our rivers are considered to be in good chemical health. This is where our river water bodies are failing. When we start digging into a long list of chemicals that are known to cause harm, we find that at least some are present in all of our rivers.
A healthy river should be free of contaminants.
Priority substances 🧪
This assesses whether rivers are contaminated with chemicals that present a significant risk to or from the aquatic environment. Only 6% of river water bodies are failing this.
The Priority Substances are identified to be of European Union-wide concern, and each has an associated Environmental Quality Standard (EQS) to protect against long-term chronic and short-term acute pollution, such as limits on concentration.
The EQS is set to protect not only freshwater and marine ecosystems but to safeguard human health which may otherwise be at risk via drinking water or ingesting food from aquatic environments. (Note that this doesn't include monitoring bacterial water quality. Faecal indicator organisms such as E.coli can present a human health risk but the Environment Agency only monitor for this at designated bathing waters, so the Wharfe is the only river in the UK where this is a statutory requirement).
Examples of priority substances include:
- Lead and other heavy metals and their compounds. These mostly come from industrial sources many of which are no longer active. However, metal particles from car brakes also contribute to the problem
- A number of herbicides and pesticides used in agriculture and our gardens. These products are widely used and tiny amounts of them can cause significant problems for the quality of our drinking water requiring expensive and carbon intensive treatment to remove them.
Priority hazardous substances ☢️
This is where all of our rivers are failing.
Some chemicals have been designated as priority hazardous substances due to their toxicity, their persistence in the environment (they take a very long time to breakdown) and bioaccumulation in plant and animal tissues, or an equivalent cause for concern.
These persistent chemicals are now widespread and this means that none of our rivers in England are considered to be in healthy state. Of all the chemicals assessed, it is primarily three pollutants that are cause the greatest number of failures:
- PBDEs (polybrominated diphenyl ethers) - a group of brominated flame retardants;
- Mercury and its compounds; often airborne from coal-fired power stations, manufacturing, industry and even crematoriums.
- PFOS (perfluorooctanesulfonic acid and its derivatives) - a group of per-fluorinated chemicals which have been widely used because of their non-stick, water repellent and oil resistant characteristics including in fire-fighting foams and textiles.
It is now internationally recognised that these chemicals are hazardous and their use is now highly regulated or banned. However, these persistent chemicals take many decades to degrade and will continue to enter the environment from legacy sources, such as the breakdown and disposal of old products or atmospheric deposition.
Other pollutants ⚗️
We have a very low level of understanding of other chemicals present that are likely to cause pollution, as only 1 in 10 river water bodies has been assessed.
Other pollutants include:
- Aldrin, dieldrin, endrin & isodrin
- Carbon tetrachloride
- DDT total
- Para-para DDT
- Tetrachloroethylene
- Trichloroethylene
This data has revealed that numerous chemicals, including those that are persistent, bio accumulative and toxic, are now ubiquitous in our rivers. Dr Rob Collins, The Rivers Trust’s Head of Policy and Science said:
In addition to the urgent threat to wildlife, river pollution impacts on people and businesses too, representing a chemical time-bomb which we have detonated for the next generation. It is our responsibility to stop polluting now, and every sector from agriculture to transport has a role to play.
And it doesn't stop there. Neither the Priority Substances nor Priority Hazardous Substances include a number of ‘emerging’ contaminants that may present a risk to our freshwater ecosystems but for which information remains limited. These include pharmaceuticals, personal care products and microplastics.
Moreover, the assessment of chemical status evaluates each contaminant in isolation and does not account for the cocktail of chemicals found in our rivers. In combination, some mixtures have been shown to to cause even more harm, resulting in a greater cumulative negative effect on aquatic life.
What next?
Under our water environment regulations, all waterbodies (stretches of rivers, lakes, estuaries) which do not achieve 'Good' status are investigated by the Environment Agency to assess the reasons why. The resulting dataset is referred to as 'RNAGS', which stands for 'Reasons for not achieving Good status'. To find out why your river is not healthy then head back to the State of the Rivers main report and continue to the section ‘How did we get into this mess?’.
