Monitoring the river flies, or rather the larvae forms of river flies, is one of the key techniques in measuring and monitoring the health of a river. This is because different freshwater invertebrates have varying tolerances to water pollution and unlike fish species, they are unable to easily move away from a pollution event.
The ARMI Riverfly Monitoring programme is co-ordinated by The Riverfly Partnership and has been developed to identify both key species and methodology that could be consistently and successfully used by volunteer citizen scientists.
An ARMI Riverfly survey consists of three parts, repeated at regular (typically monthly) intervals;
- Collect a sample
- Analyse the sample for indicator species
- Record the results
Collect a sample
A 3 minute kick sample is taken at the site that is representative of the location, typically by section and including all the ‘environment types’ proportionate to their prevalence at the site. Large rocks are also checked for larvae and added to the sample.
Analyse the sample for indicator species
The sample is then analysed on the river bank by separating the indicator species for counting. The invertebrate species or groups to be identified are as follows;
- Cased Caddis
- Caseless Caddis
- Blue Winged Olives
- Flat bodied upswings
- Burrowing mayfly
- Gammarus (freshwater shrimp)
Record the results
The survey data is then entered onto the riverflies.org website, the presence and proliferation of each invertebrate category contributing to a ‘score’ for the survey on that date. These scores can be compared against other sites to see relative improvement or deterioration of a site against its neighbours. Additionally, when sufficient data has been collected, the Environment Agency will assess a trigger score level, providing an alarm point at which an environmental incident can be triggered, should the score fall below it.
Friends of the Rib & Quin now has in place five active Riverfly sites, with a sixth soon to be added, all located at sites not part of the current Environment Agency testing regime. They are;
Buntingford – Watermill, River Rib
Buntingford – Aspenden Road Bridge, River Rib
Braughing – Gravelly Lane, River Quin
Standon – A120 bridge, River Rib
Latchford – River Rib
Cold Christmas – River Rib
Adding in five further EA sampling sites, there are now eleven survey points in our catchment, though there is room for plenty more!
At this very early point, looking at average scores across very limited FORQ data and EA surveys over the last decade, the following table emerges;
|FORQ Buntingford Watermill, Rib||5|
|FORQ Buntingford Aspenden Road, Rib||4.6|
|EA Westmill, River Rib||7.5|
|FORQ Braughing Gravelly Lane, River Quin||8.5|
|FORQ Standon A120 bridge, River Quin||9|
|FORQ Latchford, River Rib||10.5|
|EA Barwick Ford||10.75|
|FORQ Cold Christmas, River Rib||9|
|EA Wadesmill, River Rib||11|
|EA Chapmore End, River Rib||10.71|
|EA Bengeo Hall, River Rib||10.41|
At this stage, very little can be concluded or observed from these results, aside perhaps from a north to south rise in scores. However, as our data sets continue to increase, the patterns of Riverfly numbers and the underlying indicative score for each site will become more evident, providing a baseline for the measurement of river improvement initiatives as well as an alarm to pollution incidents that impact the health of the river.
All surveys completed by Friends of the Rib & Quin are posted to this website as blog posts and can be viewed here. Data from our rivers as well as those for all Riverfly monitoring sites can also be viewed on the Riverflies.org website and in particular through their Data Explorer. Choose either Rib or Quin from the River pull down menu and press search.
If you are interested in learning more about Riverfly monitoring or train as a volunteer surveyor, drop us a line at FORQcomms@gmail.com