The River Thames dataset is the world’s longest continuous water quality record, providing an invaluable historical perspective on how human activity and policy can affect rivers, and sets a new benchmark for assessing modern water quality challenges.

Photo credit: Nicole Rathmayr

Over the past 40 years, concerted efforts to improve wastewater treatment and agricultural practices have led to an 80% decrease in phosphorus loads in the River Thames. However, new research, spanning a 150 year data set, has unfortunately shown that algal blooms still persist.

According to the study, rising river temperatures driven by climate change are increasing the risk of both spring diatom blooms and summer cyanobacterial blooms. Despite huge successes in reducing phosphorus loads in the River Thames, phosphorus concentrations remain above levels that would limit algal growth and rising water temperatures are now increasing the potential for algal blooms in the river.

These blooms can have significant impacts on the health of rivers; shading out and suffocating aquatic life; removing oxygen in the water during decomposition; and introducing potentially toxic cyanobacteria. These algal blooms also represent an economic cost, requiring extensive drinking water treatment and limiting recreational activities such as sailing, fishing and swimming. The study warns that “water quality management is now ‘treading water’ in a warming climate”.