Monitoring the ecological status of the worth -part two - Riverfly monitoring

​A few months ago we posted a blog about how we use electrofishing to monitor the fish population in the Worth and hence the ecological status of the river. This blog looks at another way of assessing the river ecology.

Kick sampling amoungst the debris in North Beck

 Riverfly monitoring is a way of checking water quality and can be an important first pointer of pollution. It is a nationwide volunteer citizen science scheme run by the Fresh Water Biological Association, monitoring on the Aire and it’s tributaries is co-ordinated by the Aire Rivers Trust.
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Monitoring involves taking monthly kick samples and examining the results to see which invertebrates are in the river. A kick sample is taken​by kicking the river bed and catching in a

Checking a sample taken near Marriners Walk.

downstream net any bugs dislodged from under the stones. Monitors are looking for eight particular bugs which are especially sensitive to water quality, the counts are scored on a system established by the Anglers Riverfly Monitoring Initiative (ARMI) a drop in numbers below a certain trigger level may indicate pollution, resulting in further investigation by the Environment Agency.  Monitoring results over time can also be a general indicator of trends in water quality.Riverfly monitoring has been happening on the Worth since 2016. Initially by RWF founder Phil Sheridan who worked as a one man band at Aireworth Grove until the Aire Rivers Trust took over co-ordination for the Aire  and started training volunteer monitors in 2022. A number of RWF members are now trained and monitor sites up and down the Worth and it’s tributaries, we find it a useful way of checking water quality in the catchment.
There are now samples sites at various locations along the Worth and tributaries:

• Aireworth Grove
• North Beck, Beck St by Morrisons
• The Walk
• Damems Nature Reserve (currently not monitored)
• North Beck, downstream of Stells Mill/Holme Mill Lane (currently not monitored)
• River Worth at the Vale Farm confluence
• Bridgehouse Beck at the Vale Farm confluence
• Bridgehouse Beck, Riverside Walk, Haworth (currently not monitored)
• Bridgehouse Beck, below Oxenhope Sewage Treatment Works
• Bridgehouse Beck, below Oxenhope Train Station

So what have the results told us so far? Sam Riley-Gunn of the Aire Rivers Trust (ART) and Riverfly co-ordinator  for the Aire catchment sums up the 2025 results:

Across the catchment the River Worth shows a strong central tendency in its 2025 average ARMI scores compared to those of the wider Aire Catchment. Indicating there are not severe pollution problems across the sampled tributaries of the Worth.
Sampling takes place just above the confluences of the three main tributaries of the river: Brighouse Beck, Upper Worth and North Beck.  North Beck demonstrates the healthiest invertebrate counts at Keighley Morrisons. However the data set for North Beck is limited to one sampling site and additional regular data from Dean and Newsholme Becks would be very beneficial to confirming the health of this tributary.

A heptagenid nymph (Flat Bodied Stone Clinger) - one of the indicator bugs monitors are looking for.

The main stem of the lower Worth running through Keighley scores on or above average for the Aire catchment which is positive. Bridgehouse Beck presents some limited concern. The site at its confluence with the Worth at Mytholmes returns a score just below the all Aire average and returned a confirmed trigger level breach in August 2025, during a period of extreme drought. This is likely due to high nutrient inputs from land-based run-off at the sampling site. ​

ART and RWF are both keen to extend  monitoring on the Worth, these flyers give more information. If you would like to get involved in maintaining the water quality of the Worth get signed up now.
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