The UK’s rivers face “a horror story that just gets worse and worse” amid fears the country is heading for a drought, a campaign group has said.

Charles Watson, founder and chair of River Action, said reduced water levels meant the UK’s rivers would become more polluted and urged the Government to act to prevent an “ecological emergency”.

He said the country’s rivers faced “a classic tipping point”, adding: “We have not seen a situation like this.”

River Action has so far largely focused on the issue of pollution, raising concerns about the impact of intensive farming on waterways such as the River Wye.

Agricultural pollution harms rivers through a process called eutrophication, in which nutrients washed from fields into waterways cause algal blooms that harm or kill plants, fish and other wildlife.

But Mr Watson said falling water levels added a new dimension to the threat to the UK’s rivers.

He said: “The flows are drying up, which is disastrous for wildlife.

“If the flows really slow down, the ecology of the rivers is being killed and, meanwhile, the concentration of the pollution that’s all still there (will increase).”

Using the example of the River Wye, he said the river’s salmon population was only saved during July’s heatwave by Natural Resources Wales’ decision to open the Caban Coch reservoir, feeding the Wye and raising its water levels.

Mr Watson said: “You can do that once. You can’t do that every time there’s a drought.”

According to the Environment Agency’s monitoring equipment at Hereford Bridge, the river’s water level had fallen to just 0.04 metres on Tuesday afternoon, well below the top of its normal range of 3.3m.

Urging the Government to take action, he said water companies had been too slow to stop leaks and criticised a request by Southern Water to take more water than normally allowed from the River Test in Hampshire.

Mr Watson added: “We know how to do emergencies. We stopped the banking system from collapsing, we handled the pandemic, we’ve supported the Ukrainians – why the hell can’t we deal with this ecological emergency?”

Prolonged dry weather and high temperatures have prompted South East Water, Southern Water and Thames Water to announce hosepipe bans to conserve water, while the UK Centre for Ecology and Hydrology forecasts exceptionally low water levels in southern, central and eastern England until October.