River creatures thrive as sewer improvements pay off
Sustained efforts to reduce sewage pollution have brought improved river water quality - as indicated by increasing numbers of snails, shrimps and other river creatures, the Environment Agency has said as it released biological water quality data.
Snails, worms and shrimps living on the riverbed are very sensitive to pollution and populations can decline in response to low levels of some pollutants that escape detection through chemical sampling. Counting the insects therefore provides an indicator of river health called "biological quality."
Results of the latest biological quality survey show an improvement in river health over the last five years, with 72% of rivers in 'good condition' as compared to 69% in 2000. The river creature counting sessions also identified more species that can only live in clean rivers, such as mayflies, than in previous years.
But river water quality degraded in some parts of the country, such as the Anglian region where lower river flows have led to a 6% deterioration since 2000, the survey showed.
Tricia Henton, environmental protection director at the EA, said that the EU Water Framework Directive would drive further improvements and also require new methods of measuring the ecological health of rivers.
"Run-off from urban and agricultural land is the most widespread pollution risk across England and Wales and we face a major challenge in addressing these to meet new EU standards.
"We will take action where needed to meet the Water Framework Directive targets by 2015," she said.
But as the survey was conducted before the summer's drought, it does not factor in its effects. These are likely to have been particularly severe for riverbed creatures and water quality in the south and east as pollutants accumulated and natural cleaning mechanisms slowed down in this summer's low river flows.
"The current drought is affecting water quality, where very low river flows have caused oxygen levels to plummet and increased pollution. This has left fish struggling to breathe and insects unable to breed as they are stranded in dried up river beds," said Tricia Henton.
"But diffuse pollution is still a problem and measures need to be taken to tackle it. Reducing pollution by designing and building better drainage for housing and roads, treating contaminated land and encouraging good agricultural practices will all help improve the quality of water," she said.