Public Domain

Project of the Week 22: Outfall Safari

Recently, DITOs hosted a Discovery Trip on the subject of environmental citizen science in the UK. This was attended by a small group of international academics and decision makers. We spent two days meeting with amazing practitioners, discussing and sharing approaches and lessons learnt, and visiting some of the impressive sights that London has to offer! Among the many citizen science projects we learned about, one particularly inspiring and local example was introduced to us by Joe Pecorelli of the Zoological Society London (ZSL). As well as offering a fun and interesting activity to local residents, this scheme has managed the rare feat of translating citizen science into policy impact: the Outfall Safari project.

What does this project do?
It trains citizen scientists to assess river outfalls for pollution. A river outfall is where a pipe meets a river. This pipe is connected to the drains you find in roads and gardens which collect rainwater - not sewage. However, these can sometimes be misconnected to sewage pipes, so the sewage is not sent to a treatment works but empties into a river instead.

An Outfall Safari involves training teams of volunteers how to assess river outfalls for pollution. Outfall Safaris are run over a one month period and coordinated to avoid any overlaps in the lengths of river surveyed and also to avoid surveying within 48 hours of rain in the catchment, as rainwater can wash away evidence of pollution! The data is sent directly to ZSL for analysis and then reported to the Environmental Agency and Thames Water. Thames Water, The Highway Agency and Local Authorities are responsible for identifying the sources of pollution and enforce any rectification of misconnections.

What do I have to do?
Sign up to become a volunteer and go through training with ZSL or one of their project partners. Once trained, volunteers walk the riverbanks in groups, armed with a specially created app that allows them to geolocate, photograph and assess outfalls for evidence of pollution. The assessment gives outfalls a score between 0 and 20. A score of 0 means they are not polluting at the time of the survey whereas 20, the highest score, means they are visibly impacting the river based on evidence such as discoloured water, sewage fungus, bad smells and sanitary products at the outfall.

Where can I find out more?
ZSL's main Twitter account and ZSL's marine and freshwater conservation Twitter account
ZSL's Facebook page on marine and freshwater conservation
ZSL news story: Improving London's Rivers
Thames21's news story about Outfall Safari
ZSL's report on outfall pollutions in London Rivers (which has been used by the Environment Agency, Greater London Authority and Thames Water!)

You may also be interested in:
Thames21, a local river conservation group
London Wildlife Trust
Investigation and rectification of drainage misconnections - Good Practice Document
Further information on pipe misconnections
Position on Misconnections by the Catchment Partnerships in London Group

The image below is where pipe misconnection has taken place:

Individual river Outfall Safari reports, with details of the methodology, are available from this ZSL page.

What’s the Citizen Science Project of the Week?
Citizen Science Project of the Week is a regular Monday feature at Doing It Together Science. What project would you like to see featured? Please let us know on the contact form, Facebook page or email us at Please put "Project of the Week" in the subject line and send us a link to the project, some information about it and why you'd like it featured. If you want us to, we'll credit you and tag you on Facebook!

More details
The rivers and streams of Greater London total over 600km in length (excluding the main stem of the River Thames). Based on this total length, the Outfall Safari data for the 142km of river surveyed has been scaled up. This shows there could be as many as 1,483 polluting outfalls in Greater London and of those, 1,121 could score ≥ 4 (recall that a score of 0 is no pollution, and 20 is major pollution). Collectively this represents a substantial pollution issue that is degrading the health of rivers in the capital. The Outfall Safari data does have its limitations – it might not detect for instance outfalls that pollute intermittently, particularly if relatively long-lasting pollution indicators such as sewage fungus are not present. Therefore, the issue of polluted surface water outfalls might be even more extensive than the Outfall Safari data shows.

ZSL has a number of other active projects working to conserve and enhance the rich ecosystem of the Thames River catchment area. These projects rely on the passion and dedication of citizen scientists working in the field to help improve the rivers in and around London!

Based on the results of the data collected by the project volunteers, ZSL put out a report that calls for action from both policy makers and water management companies to ensure that they are doing their part in protecting London's rivers from the pollution threat of misconnected pipes.

Many thanks to Joe from ZSL for guiding us through the Outfall Safari experience! Here he is below at the Discovery Trip (please let us know if are interested in citizen science and policy and would thus like to come on such a trip).