What is Riverfly Monitoring?

Riverfly monitoring is fantastic way to record the health of our river ecosystems, monitor local wildlife and enjoy time in nature. Carrying out riverfly monitoring also enables large scale recording and reporting of pollution incidents. Serious pollution incidents can occur in our watercourses, spelling disaster for river ecology.  Regular monitoring is the best way of identifying such incidents early and enable a rapid response.

The Angler’s Riverfly Monitoring Initiative (ARMI) was launched by the Riverfly Partnership in 2007 to enable anglers an other interested groups to actively monitor and protect their local rivers.  It helps rivers to be monitored more widely and at greater frequency than is possible by the Environment Agency alone.

The ARMI monitoring technique involves pairs of volunteers taking 3-minute kick samples from the river bed each month, and recording the presence and abundance of eight pollution-sensitive invertebrate groups. The focus of the sampling is on ‘riverflies’ - mayflies, stoneflies and caddisflies. If invertebrate numbers drop below expected levels the Environment Agency are informed and will take action to investigate the suspected pollution incident.  The Riverfly data held by each river group will also allow for long-term changes to be identified, and the regular presence of volunteers on the river will discourage potential polluters.

ARMI is already used widely in the UK as a 'neighbourhood watch' for rivers, practiced by anglers, environmentalists and community groups. It has proven effective in identifying pollution incidents and ensuring action is taken. In several cases this has led to prosecution of polluters by the statutory authorities and has prevented similar future incidents. ARMI will be recognised on all Water Framework Directive River Basin Management Plans in England and Wales.

Get involved in Riverfly Monitoring!

Riverfly monitoring groups are active on the following rivers in the Colne catchment:

Colne - Friends of Oxhey Park/North Harrow Waltonians Angling Soc./Bath Road Piscatorial Soc.

Ver – Ver Valley Society & Redbournbury Fishery

Gade - The Friends of Gadebridge Park/Friends of Croxley Common

Bulbourne - The Box Moor Trust

Chess – River Chess Association

Misbourne – Chiltern Society & Misbourne River Action


Alternatively you can contact the Riverfly group coordinator Lara Clements at This email address is being protected from spambots. You need JavaScript enabled to view it. if you are located in Buckinghamshire, Berkshire or Hertfordshire and would like to get involved in Riverfly Monitoring within the Colne Catchment.

The Chilterns, Hertfordshire & Middlesex Riverfly Hub

The Chilterns, Hertfordshire & Middlesex Riverfly Hub is a partnership, set up in 2014 to provide ARMI training to anyone wishing to monitor the health of rivers in the Hertfordshire, Middlesex and Chilterns areas.  Jointly led by the Chilterns Chalk Stream Project and Herts & Middlesex Wildlife Trust, the Hub coordinates Riverfly Monitoring across the area with the ultimate aim of setting up and supporting riverfly monitoring on every river in the Chilterns (including the Colne) and Hertfordshire.

The hub is able to provide training for volunteers through an annual programme of training workshops run by its five Riverfly Partnership accredited ARMI instructors. For more information, or to register your interest in becoming a Riverfly monitor, please contact the hub’s coordinator This email address is being protected from spambots. You need JavaScript enabled to view it..

You can see their first ever annual riverfly newsletter here Chilterns and Hertfordshire  Annual Riverfly Newsletter

The Herts & Chilterns Riverfly Hub is being supported by grants from Affinity Water, Natural England via the Lea Catchment Nature Improvement Area and the Chilterns Chalk Streams Project. The hub’s partners are:

 Riverfly logo small 1CCSP logoHMWT logoRiver Chess AssFriends ot Mimram logoColne-Valley-FisheriesAffinity Water logoHCC small copyEA logo

Design by LTD Design Consultants and build by Garganey Consulting. From an original concept by the Herts and Middlesex Wildlife Trust.