Raw sewage released 1,500 times into River Lune and Morecambe's sea in 2022

Storm overflows normally happen when the sewage system is at risk of being overwhelmed – such as after heavy rain or during higher levels of ground water.

In these cases, water companies may need to release excess water and sewage into rivers and the sea, to prevent water backing up into the streets and people's homes.

This has an impact on the quality of natural water sources, with some charities alleging storm overflows are being misused and under reported.

Figures from the Environment Agency show storm overflows were used 1,459 times within Lancaster's local authority boundaries in 2022, discharging for a total of around 13,653 hours.

All of these spills were from United Utilities' network.

These figures may not provide a full picture of the amount of water pollution in the area – Lancaster may also be impacted by overspills from areas with which it shares water sources.

The Rivers Trust said it was particularly concerned by storm overflows being used during hot periods.

Tessa Wardley, director of communications and advocacy at the charity, said: "Discharging untreated sewage in dry weather is bad for both human health and river health – lower river flows mean more concentrated pollutants at a time when more people want to enjoy their rivers.

"Although a problem in their own right, these discharges are also the ‘canary in the coalmine’ pointing to greater problems in our sewerage and river systems. This could be blockages in the system, ground water seeping into broken pipes, misconnections or just poor management choices."

She urged "robust, urgent action" on sewage and river management.

United Utilities saw 69,245 overspills across its network in 2022 – although 13% of the company's facilities did not report overspill data last year.

Water minister Rebecca Pow said the amount of sewage pumped into rivers is "utterly unacceptable", adding the Government has a plan to tackle pollution.

She said: "Targets set by the Government to reduce storm overflows are very strict and are leading to the largest infrastructure programme in water company history – £56 billion over the next 25 years.

"Shortly, water companies will also publish action plans for every storm overflow in England, something the Environment Secretary has personally pressed for.”