Surveying the Nidd and its tributaries

What did we do and what did we find?

On the 3rd August 2023 ten teams of citizen scientists took water samples from 45 sites along the full length of the River Nidd and some of its major tributaries at approximately the same time on the same day. The samples were analysed by Simplex Ltd for the faecal bacteria E. coli.


The Activity was organised by Nidd Action Group with the help and support of Yorkshire Dales Rivers Trust, the University of Leeds, Bilton Conservation Group and numerous individual volunteers. We would like to thank Rick Battarbee & Malcolm Secrett (Ilkley Clean River Group) and the Environment Agency for their help with project planning and Woodleigh Impact for funding the laboratory analysis.

The results showed:

The concentrations of E.coli were high, with only a handful of sites meeting the sufficient level for inland bathing water.

  • in the upper catchment, down to Birstwith the concentrations of E. coli were much lower than in the middle and lower catchment .
  • E.Coli concentrations rose below Killinghall STW and stayed high, with the most extreme value at the Nidd Viaduct, below the confluence of Oak Beck and the river Nidd


  • Knaresborough sampling locations had concentrations well above the levels deemed sufficient for inland bathing water.
  • From Hunsingore down to Moor Monkton the concentrations of E.Coli doubled between each sampling site, reaching a maximum just before the Nidd meets the Ouse.
  • The tributaries in the middle and lower Nidd Catchment all had high concentrations of E.coli – Ripley Beck, Oak beck, Bilton Beck (extremely high) and Crimple Beck.

We concluded:

  • The extremely high levels of E.coli will have been influenced by earlier rain, due to wash off from agricultural land as well as the discharge of treated sewage and any storm water overflow (SWO).
  • The pattern of relatively low concentrations in the hills mirrors that found in the Wharfe (iWharfe reports for 2020 and 2021)
  • Further investigation is needed around the ‘Spikes’ of exceptionally high concentrations below Killinghall STW, at the Nidd viaduct, below Oak Beck (home of Harrogate North STW) and at the very bottom of the Nidd from Hunsingore onwards, where flooded agricultural land and a variety of STWs, including Harrogate South, are located.
  • Sites that need further testing are Bilton beck – Woodfield Road, Ripley Beck, Oak Beck and Crimple Beck which all showed high concentrations of E.Coli.

Follow up work:

  • Analysis of the laboratory results from nutrient chemistry samples taken. These may help to identify the source and nature of pollution throughout the Nidd and its tributaries.
  • Dry weather sampling, planned for October, should test whether the pattern and significant locations observed in this survey are consistent
  • Work with the EA and others to increase our understanding of E.Coli concentrations in the Nidd Catchment.