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Working towards a cleaner Wharfe – a closer look at water quality testing at Ilkley’s bathing water

Posted by: , Posted on: - Categories: Environment Agency, Sustainability, Water

In December 2020, a stretch of the River Wharfe at Cromwheel, Ilkley, in Yorkshire was designated a bathing water by Defra,the first section of a river in the country to become a bathing water. Yorkshire’s Bathing Waters lead Claire Campbell looks at the intensive testing and monitoring which has helped identify factors influencing water quality in the river.

Increasing interest in the use of England’s rivers for recreation saw the River Wharfe at Cromwheel become the first section of a river in England designated a bathing water site.

This means that aside from water quality testing aimed at monitoring the ecological health of the river, we now monitor it under Bathing Water Regulations 2013.

At bathing waters across the country, compliance samples are taken between May and September, testing for faecal bacteria – E. coli and Intestinal enterococci. At the end of the season each bathing water is given a classification of Excellent, Good, Sufficient or Poor based on a rolling average of the last 4 years of results.

The image shows the River Wharfe at Cromwheel, with an Environment Agency officer in the water taking a water sample, and another standing on the river bank taking notes.
Environment Agency water quality testing at Cromwheel, on the River Wharfe at Ilkley

Traditional water quality assessment of our rivers, including the River Wharfe, is carried out in line with the requirements of the Water Framework Directive (WFD), the legislation used to determine the ecological status of waterbodies such as rivers, lakes, estuaries, coastal sites and groundwaters. This shows the River Wharfe to be of generally good quality for fish and wildlife.

In contrast, bathing water standards are based on public health protection measured by bacterial indicators that wildlife are largely insensitive to. Over each of the three seasons since Cromwheel was designated as a bathing water, it’s been classified as ‘Poor’ for bathing water quality.

But three years on from its designation - after comprehensive testing and analysis - we now know much more about what drives the bathing water quality changes.

The image shows a photograph of the River Wharfe at Cromwheel, with a view to the suspension bridge across the river.
The River Wharfe at Ilkley, looking from Cromwheel to the suspension bridge.

Water quality investigations

 In response to the poor results of a number of samples taken during the first bathing water season for Cromwheel, in 2021 we started an investigation into the bacteria used to assess bathing water quality.

This included intensive half-hourly bathing water sampling across three days at Cromwheel and upstream at Bolton Abbey. This was supported by continuous water quality monitors at Grassington, upstream of Addingham, and Cromwheel, and a fixed bacteria monitoring unit at Cromwheel.

Initial findings pointed towards wet weather as a significant influencing factor in the bathing water quality at Cromwheel.

In response to local concerns about water quality we also took the opportunity to reassess the ecological health of the river during 2021, carrying out comprehensive water sampling and invertebrate, microalgae and plant surveys from Kettlewell through to Tadcaster.

We updated the WFD classifications of the seven waterbodies which make up the main river. Our results show invertebrates, ammonia, and dissolved oxygen to be at the highest status, which is positive, but it did show that nitrates and phosphates from farming in the catchment impact on water quality. These increase the growth of algae and plants in the river which can cause problems for fish and invertebrates.

Building on this insight, we secured funding to carry out more detailed water quality investigations spanning 2022 and 2023.

More intensive monitoring days took place at Cromwheel, Bolton Bridge and Burnsall with additional continuous water quality monitors installed at various locations up the Wharfe.

In 2023 extra sampling focused on a number of larger tributaries between Addingham and Kettlewell on the River Wharfe, prioritised as having the greatest potential impact on the bathing water, and at a number of smaller streams between Addingham and Ilkley chosen due to their close proximity to the Cromwheel.

We also sampled upstream and downstream of several Yorkshire Water sewage treatment works upstream of the Cromwheel at Hebden, Grassington, Burnsall, Beamsley and Draughton and added another fixed bacterial unit at Burnsall.

Volunteer Citizen Scientists played a crucial role in supporting our water testing efforts, contributing 104 volunteer days in 2023. Their involvement, co-ordinated by the Yorkshire Dales Rivers Trust with support from Yorkshire Water, demonstrated the power of community involvement in supporting the bathing water investigations on the Wharfe.

Over the three summers we have collected in excess of 750 investigatory bacteria samples along the River Wharfe and its tributaries.

What the investigations revealed

The image shows the lid of a water sampling bottle, which has the date, time and location written on it. This is one of the bathing water samples taken from the River Wharfe at Ilkley.
One of the bathing water samples taken from the River Wharfe at Ilkley.

The findings from the three-year analysis sheds light on the complex dynamics influencing water quality at the River Wharfe bathing water.

We now know that rainfall anywhere in the Wharfe catchment is a driving force behind periods of reduced bathing water quality;

After rain, bacterial levels at all sampling sites, from Kettlewell to Cromwheel, are elevated, indicating that activities across the whole Wharfe catchment are impacting on bathing water quality, and none of the four upstream sites tested met the bathing water standards in 2022 and 2023.

Microbial Source Tracking (MST) analysis – a technique that differentiates between human and non-human sources of faecal contamination in water samples – provided valuable insight into the sources of contamination.

During dry conditions at Cromwheel, there are similar levels of bacteria from both human (water company sewage discharges and private septic tanks) and agriculture (cows and sheep) sources. Following rainfall, which leads to increased run off of water from the land in the catchment, this distribution changes, with the amount of bacteria from cows and sheep becoming much more significant than sewage and keeping bacteria levels high in the river for over 48 hours after the rain.

The analysis shows that while sewage inputs close to Cromwheel have a short-lived impact on bathing water quality, the catchment-wide agricultural input from further upstream leads to longer term high bacterial levels in the river.

What’s next for the Wharfe?

We have shared our findings with a number of stakeholders in the Wharfe catchment including Ilkley Clean Rivers Group, Yorkshire Water, the National Farmers Union, Yorkshire Dales Rivers Trust and Catchment Sensitive Farming officers.

Yorkshire Water is to improve the sewer network as part of country-wide investment from water companies.

Event Duration Monitoring now means we know how often and for how long storm overflows are used, with the number monitored increasing from 7% in 2010 to 100% now.

We’ve increased compliance checks on water company assets and the number of officers dedicated to regulation. This includes all 11 Yorkshire Water Sewage Treatment Works in the catchment above Cromwheel, Ilkley Sewage Treatment Works downstream, storm overflows within the catchment and pumping stations within 5km upstream of Cromwheel.

A number of private discharges have been inspected to check compliance with permits such as fish farms, private sewage treatment plans and trade sites.

Our agriculture team is providing advice to farmers in the Wharfe catchment on slurry and manure management and checking compliance with the regulations, and offering guidance on access to grants to make improvements.

With partners, we’ve also been using the sampling results to inform other work taking place on the catchment around natural flood management and river restoration.

The journey to improving bathing water quality at Cromwheel is complex and needs a co-ordinated effort from the whole community and partners - including the water company, farmers, land managers, tourist sites and residents - to identify and progress action to improve the bathing water quality.

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1 comment

  1. Comment by ian gregory posted on

    I just don’t understand why you would ever want to encourage people to swim in our rivers. Makes no sense at all.


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