Villagers surrounding a “unique” body of water have raised the alarm over an ‘emergency’ that is seeing sewage discharged into it.

Residents living near the Pillhill Brook Chalk stream, which passes through villages including Thruxton, Monxton and Abbotts Ann, are “incensed” following Southern Water pumping treated sewage into the water.

The water company says that this process, known as overpumping, is only carried out in emergency situations, but residents say this ‘emergency’ instead results from a lack of investment in the area’s sewers, and has continued for over a decade.

Simon Cooper, who runs a flyfishing business in the area, said that this continuing pumping was “doing devastating damage” to the water.

Southern Water did not respond to a request for comment.

Chalk streams are described by the WWF as a “unique” habitat, most of which are only found in southern England. They provide clean water sources from underground aquifers, as well as providing habitats for a variety of organisms.

Pillhill Brook is one example, rising near Fyfield and flowing through to Upper Clatford, near where it joins the River Anton, which in turn connects with the River Test.

Recently, signs have started appearing along the brook from Southern Water, warning residents to “please avoid contact with the water” as “surplus wastewater” is being released into the stream. During this process, sewage is screened with filters, a settlement tank and UV light to kill bacteria, in order to dilute the amount of sewage entering the water.

However, Toby Wyles, who owns land adjoining the brook, said that this activity is “very troubling”.

“These are very precious, these chalk streams, and very rare in the world. Releasing nitrate and other grey water into these streams is not a good idea. They are allowed to do it by law in emergencies, but it hasn’t rained now for around five weeks. This is not a flood emergency.”

He accused Southern Water of “trying to get around their obligations of treating sewage” after a lack of investment in the sewage infrastructure, and said that the area’s fishing economy “could be damaged” by sewage in the water.

Simon, who owns Fishing Breaks, is one of these individuals. He downplayed concerns over the impact of overpumping sewage in the short term, but was worried for the future.

“In the immediate short term the occasional bit of sewage, though annoying and unpleasant, isn’t the end of the world,” he said. “In the long term, poor sewage treatment is doing devastating damage not just to chalk streams but to rivers up and down Britain.”

“Pillhill Brook is very special because it’s relatively unspoiled and it hasn’t changed an awful lot. It’s home to native white clawed crayfish and there are very few colonies of those left in the UK, they’ve been wiped out by signal crayfish, loss of habitat and pollution.

“It’s just a crying shame that the perfect little chalk stream that can’t take this volume of water is essentially being destroyed. It just strikes me as unnecessary.”

The concerns raised by residents have made their way to parish councils, with six councils up and down the brook banding together to demand change from Southern Water.

They want the company to agree six commitments in the area, the first of which is “major capital investment” in the area’s sewerage systems. Southern Water spent £500,000 on the area in the early 2010s, but since then, the company has resorted to using tankers to pump excess sewage to prevent it backing up into residents’ homes.

The use of tankers, as well as overpumping, is authorised in emergencies to prevent the loss of service or flooding. Tim Grimshaw, a representative of the parish councils, said that this justification didn’t hold.

“They do overpumping and tinkering under the guise of emergency works,” he said, “and we’re calling them temporary works as they can’t be an emergency after some 12 years of continued crisis by Southern Water each winter when they get infiltration into their pipes. As local residents, it doesn’t seem reasonable.”

He said residents were being affected by these works, with floodlights and exhaust fumes from traffic “getting worse” as Southern Water became “more aggressive in their operations”.

However, Tim pointed out that Southern Water has made some steps to engage with the community so far. He said that extra signs warning of overpumping had been put out since concerns were raised by the councils, and they had been “very open” in his experience.

Meanwhile, the parish councils are co-ordinating their response, and asking for the company to be held to account. For instance, the infiltration reduction plan for the area, which is designed to set out the steps to improve the situation, is meant to be updated yearly. However, it has not been reviewed since 2018.

“Utilities have got to be more answerable towards all stakeholders, rather than just shareholders and a regulator,” said Toby. “They’ve got to think about the people that live in the areas they serve rather than just a return on capital.”

The councils, meanwhile, are liaising with Hampshire County Council and MP Kit Malthouse on the issue, with the latter describing it as “an ongoing and complex issue which needs to be resolved for local residents”.

However, Simon Cooper said that Southern Water alone is not capable of rectifying the issue, and that systemic change is needed.

He said: “You have to feel a certain sympathy for them [Southern Water]. They’re greatly constrained by what they can do in prices. We all pay £200-300 a year for energy bills so we can have green electricity, but Southern Water don’t get a similar subsidy to get purer rivers, and somehow that needs to change.

“People need to understand that ultimately consumers are going to have to pay more, and the lead for that has to come from government.”

An Environment Agency spokesperson said: “Water companies have a legal duty to avoid pollution. The Environment Agency does not license the discharges made by Southern Water into Pillhill Brook, which are a result of the sewer network being overloaded by groundwater infiltration. Discharges to the brook should only occur under exceptional high flows in order to protect homes from sewer flooding.”

“Although highly diluted, Southern Water must monitor and sample any discharges to the brook as well as use disinfection. We have required Southern Water to implement an infiltration reduction plan to reduce infiltration, so that these discharges are not required in the future.”

Southern Water were contacted for comment.