The UK has only one stretch of river designated as a bathing water, on the River Wharfe at Ilkley, West Yorkshire. The designation was granted by the Department for Environment, Food and Rural Affairs in December 2020 following an application led by the Ilkley Clean Rivers Campaign.

The designation means the quality of the water has to be monitored regularly during the bathing season. The Environment Agency took weekly samples of the water quality between 1 May and 30 September 2021 at Cromwheel, a site close to the town centre where bathing is popular. “Once a bathing water is designated, we have to monitor it,” explains Martin Christmas, environment manager at the Environment Agency.

The samples were measured for levels of intestinal enterococci and escherichia coli (E. coli), and resulted in the water quality receiving an overall rating for the season of ‘poor’, meaning bacteria levels were so high that it was deemed unsuitable for bathing.

The application for Bathing Water Status at Ilkley was driven not by a desire to encourage river swimming and bathing in the town but to put pressure on the local water company, Yorkshire Water, to stop discharging untreated sewage into the river from the town’s sewage treatment works and emergency/storm outfalls.

All water companies are permitted to do this in emergencies when the sewer system is overloaded, but the Ilkley Clean Rivers Campaign argued that this was happening far more frequently than it should. Yorkshire Water itself acknowledged that there were 40 spills from a combined sewer overflow (CSO) close to the bathing water site in 2020. A citizen science project in 2019 led by Professor Rick Battarbee, director of the Environmental Change Research Centre, University College London, helped to identify the state of the river and the principal pollution sources. 

The Ilkley Clean Rivers Campaign used the information collected on water quality to lobby for this stretch of the River Wharfe to be granted Bathing Water Status so that the Environment Agency would be required to run regular water quality tests at the site and the poor condition of the water would be recognised.

Ilkley is a market town with a population of just under 15,000. Most of the town’s sewage is captured in combined sewers and taken to a treatment works on the south-east side of the town, downstream of the bathing water site. In the 1km section of river upstream of the designated bathing water, there is a CSO (Rivadale View) and a sewage pumping station (Bridge Lane SPS). When these outfalls are operating, they discharge diluted effluent into the river.

Upstream of the town, River Wharfe catchment consists of hillsides scattered with springs and old mine workings. The catchment is mostly rural, with several small villages, including Kettlewell and Grassington, and is primarily a mixture of low-intensity livestock farming. Before reaching Ilkley, the Wharfe flows through the village of Addingham.

Although the campaign group has focused on sewage discharges into the river, there are other issues that affect the water quality at Ilkley, including significant inputs from various sources, especially farming. The location of the town, in a steep-sided valley, means water pours down the hills quickly when it rains, depositing run-off from fields into the river and overloading storm sewers in the town.

At the end of 2020, Yorkshire Water formed the Wharfe Partnership to address the wide range of factors affecting the river at Ilkley. The partnership aims to bring together stakeholders and landowners across the catchment to coordinate the work required to improve the health of the river.

It includes the Environment Agency, the National Trust, Yorkshire Wildlife Trust, Yorkshire Dales Rivers Trust, Bradford Council, the Country Land and Business Association and the Devonshire Group, which owns estates in the catchment. The partnership is chaired by Ilkley resident Roger Falconer, emeritus professor of water and environmental engineering and founding director of the Hydro-environmental Research Centre at the School of Engineering, Cardiff University.

Falconer thinks the bathing water designation is positive for the region but that it is important to understand the complexities of the issues and the whole catchment. “We shouldn’t just look at an isolated reach,” he says. “We need engineers to model the whole river and plan the best solutions.”

Yorkshire Water is tackling some of the issues associated with its own infrastructure, and in January 2022 announced plans to spend up to £13m on its wastewater network and treatment works upstream of the bathing water site. The company has been modelling the catchment around Ilkley to understand the factors that influence water quality. It found that during periods of dry weather, the main contributors to background bacteria were agricultural operations, local domestic waste patterns, misconnections and its own treatment works at Grassington, Draughton and Beamsley.

As a result, it plans to enhance disinfection of the final effluent that goes into the river at the Grassington, Draughton and Beamsley works. It intends to investigate misconnections in the catchment and reroute the sewer network in some areas of Ilkley to reduce discharges from storm overflows. A project is also under way to upgrade the Rivadale CSO.

Ben Roche, director of wastewater at Yorkshire Water, says: “Our modelling indicates that acting upstream of the bathing water, at our treatment works at Grassington, Draughton and Beamsley, will deliver the greatest benefit in terms of improving water quality via our assets. We are also assessing the pumping station at Addingham and considering green and sustainable solutions.”

A smart wastewater network pilot for Ilkley will also begin this year. It will trial the use of monitoring, analytics and control solutions to understand the sewer network from homes to treatment works and treated discharges back into the environment. It is hoped that the pilot will offer real-time, end-to-end management and control of wastewater assets, reducing intermittent discharges from CSOs and sewer flooding, identifying areas for investment and improving energy efficiency to reduce carbon emissions.

Still, Yorkshire Water’s modelling indicates that pollution is entering the watercourses from a variety of sources, including misconnections and agricultural land that the river and its tributaries run through. Roche says: “It is important that other landowners and stakeholders take action to ensure water quality is improved in the future, with the ultimate aim of improving the bathing water classification.”

The company says it will do more modelling to increase data and improve the understanding of all of the factors that influence water quality in the river.

In addition to Yorkshire Water’s monitoring and the Environment Agency’s bathing season sampling, the citizen science project managed by Battarbee has been taking samples from sites upstream of Ilkley, including on tributary streams draining agricultural catchments, on the main river upstream and downstream of outfalls from small village treatment works, and upstream and downstream of a CSO serving the village of Addingham.

The data showed that concentrations of E. coli in the main river during dry weather conditions were relatively low, but in wet weather two scenarios caused elevated concentrations.

First, on 23 August 2021, the day after a long spell of dry weather followed by heavy rain, concentrations of E. coli in the main river rose to more than 2,000 colony forming units (cfu) per 100ml. At the same time, concentrations in the tributary streams were the highest recorded, suggesting that the relatively high concentrations in the main river were mainly of agricultural origin, probably caused by faecal bacteria resuspension from stream and riverbed sediments and the inwash of livestock faeces and contaminated soil.

Second, there were two occasions when, after heavy, prolonged rainfall, the capacity of the storm tanks at the Addingham pumping station were exceeded and the CSO discharged untreated effluent into the local stream and from there into the Wharfe.

Battarbee concludes that a number of different sources of faecal bacteria will have to be controlled if the River Wharfe in Ilkley is to become fit for swimming, including reducing discharge of untreated sewage from CSOs, treating the final effluent from treatment works and controlling diffuse sources of faecal bacteria pollution from farmland.

“Although some of these solutions inevitably require hard engineering, for example the de-combination of old combined sewer networks, others are nature-based and capable of providing multiple environmental benefits,” he says. “Structured wetlands can be used for effluent treatment, rain gardens in urban areas reduce surface water run-off into sewers, and fenced riparian buffer zones in agricultural catchments limit the access of cattle and sheep to streams and riverbanks. 

“Each of these solutions not only reduces faecal bacteria contamination in watercourses but also reduces nutrient pollution, creates wildlife habitat and mitigates carbon emissions. Such co-benefits need to be taken into account when considering the cost of cleaning up.”