London’s Rivers

London’s Rivers is a community-based river stewardship project which brings together ZSL, local organisations, trained citizen science volunteers and the Environment Agency to work in partnership to improve rivers in the capital for both wildlife and people.

The River Monitoring Initiative (RMI) method used in the London’s rivers projects was developed nationally by the Riverfly Partnership. ZSL is currently coordinating the RMI on the River Crane and Hogsmill River, the first two rivers to join the project. The RMI sampling method is based on long established principles of water quality monitoring, in which families of river invertebrates are allocated scores according to their sensitivity to pollution. When pollution enters a river the highest scoring taxa are the first to be lost and the average score falls. The RMI scoring system is based on only eight families of invertebrates and is a simplified version of the technique that the Environment Agency themselves use. 

The river sites to be monitored are agreed in advance with the Environment Agency as are trigger levels for each site. The trigger level is the minimum acceptable score for a sample from a particular site. A sample that scores below the trigger level is first checked by ZSL freshwater ecologists before being reported to the Environment Agency for further investigation.

Citizen science volunteers being trained in the RMI sampling method on the River Crane
Citizen science volunteers being trained in the RMI sampling method on the River Crane

Why London's rivers need our help

The rivers and streams of London are a priority habitat in the London Biodiversity Partnership’s, Biodiversity Action Plan yet they are currently classified as being in ‘poor’ or ‘bad’ condition. They do not achieve their potential either as a wildlife habitat or as a natural resource for Londoners and they need our help now.

This project is timely as it supports the new way rivers are managed in the UK. DEFRA’s new approach to river management, of working in catchment partnerships, has been adopted as a result of the European Union’s Water Framework Directive. Locally focussed decision making and positive community action are at the core of this new approach. The RMI helps provide the evidence needed to underpin this local decision making and strengthens relationships between the Environment Agency and trained volunteer groups. 

In recent years most rivers in the capital have been monitored infrequently. The RMI scheme, by sampling at a larger number of sites in a single river catchment, on a monthly basis will mean the project’s rivers are being monitored more frequently and more widely. This increased surveillance will mean there is more chance of detecting pollution events.  In addition when pollution events happen, action will be taken at the earliest opportunity thus increasing the chances of finding the source and bringing the polluter to account.

Project information

People involved

ZSL’s Joe Pecorelli is the manager of the London’s Rivers project.


  • The Riverfly Partnership
  • Thames 21
  • Friends of River Crane Environment
  • London Wildlife Trust
  • Thames Anglers Conservancy
  • Friends of Yeading Brook
  • South East Rivers Trust
  • Kingston University
  • The Environment Trust for Richmond upon Thames
  • Epsom and Ewell Borough Council
  • The Lower Mole Project.

Kindly funded by:

  • The Crane Valley Partnership
  • The Peoples Postcode Lottery