How does this vary by location?

Pollution trends affecting freshwater ecosystems and resources significantly vary between developed and developing countries.

In developing countries, investment in wastewater treatment or regulatory control struggles to keep pace with growing population and resource demands.

As well as controls on point-source discharges of pollution, in Europe, regulatory instruments such as the Urban Wastewater Treatment Directive (91/271/EEC) and Water Framework Directive (WFD 2000/60/EC) have been applied to reduce issues of water pollution with varying degrees of success.

The Water Framework Directive (WFD) identifies variations in ecological status using biological indicators as ‘quality elements’ that guide programmes of measures to improve river basin management. However, large numbers of water bodies are still failing to reach good ecological status for a range of reasons.

In the UK, roughly two thirds of water bodies have failed to reach good ecological status so far. Pollution from agricultural sources (nutrients and sediments) and point sources, such as combined sewer overflows and incidents from industrial or wastewater treatment plants remain an issue.

Rural and urban waters in the UK

Notwithstanding overall pollution status in the UK, some evidence suggests that there are contrasting trends in rural and urban rivers.

From the early 1990s onwards, the Urban Wastewater Treatment Directive imposed tighter controls on the performance of wastewater treatment works to reduce insanitary, organic pollution inputs to the urban river network. Simultaneously, traditional urban industries associated with the former coal-field based economy were in decline.

The analysis of large-scale long-term data from thousands of samples collected by the UK’s water regulators showed that the number of clean water organisms in urban river systems has increased significantly between 1990 and 2010.

This includes iconic organisms – indicative of clean, fast-flowing waters – such as Atlantic salmon Salmo Salar and the Dipper Cinclus. These species have returned widely to urban reaches of rivers such as the Taff, Tawe, Calder, Weir and Tyne.

Paradoxically, however, this means they’re also exposed to new emerging pollutants such as microplastics or complex pollutants (e.g. flame retardant chemicals) that still occur in urban systems.

In many rural UK rivers, by contrast, there are concerns that nutrient, sediments, pesticides and other pollutant concentrations are increasing. These pollutants come from diffuse sources, where agro-chemicals are applied to increase production, and can be the result of an increasing number of intensive livestock units (e.g. poultry sheds).

These issues are under increasing scrutiny from researchers and regulators but illustrate the need to balance the protection of water resources with their exploitation for human needs.

Over to you

• What is the state of water bodies near you?
• If you live in Europe, do you think that they have reached a good ecological status?

Let us know in the comments.