Britain’s network of canals and rivers is under strain from funding shortfalls and growing climate pressures, campaigners warn.

Three-quarters of the country’s waterways face financial peril, according to the Inland Waterways Association (IWA), an independent charity advocating for Britain’s canals and rivers, as the country braces for heavier winter rainfall and intensifying summer droughts.

The IWA has published a first-of-its-kind climate risk map showing that 99% of navigable waterways will face heightened risk under a predicted 2C global heating scenario.

Areas of concern include the Pennines and the Midlands, where higher-ground reservoirs feed several canal systems and where droughts are expected to worsen. Sections of the Leeds and Liverpool canal were closed from May to September due to low water levels.

Waterways provide free public access to nature for more than 10 million people, save the NHS an estimated £1.5bn annually, support more than 80,000 jobs and act as green corridors for wildlife, according to the Canal & River Trust (CRT).

The trust manages about 2,000 miles of waterways, including roughly 80% of Britain’s navigable canals. Nearly 80% of local authorities have a navigable waterway in their area.

The collapse of the Bridgewater canal embankment at Dunham Massey on New Year’s Day this year highlighted the network’s vulnerability. Despite being well maintained, a large section gave way after heavy rainfall, flooding neighbouring fields and a nearby sewage works.

Nearly 1,000 people were evacuated from their homes and stabilisation has cost about £400,000, with full permanent repair costs unclear. Charlie Norman, the IWA’s director of campaigns, described it as a warning. “Infrastructure can fail catastrophically even when well maintained. Climate pressures alone are enough to cause serious damage.”

Norman said underfunding compounded the impact of rising climate pressures. “Decades of erratic government support along with more frequent extreme weather events have left many waterways vulnerable to breaches, closures and mounting maintenance costs,” he said. “This year’s drought led to the closure of dozens of canals across the country, affecting wildlife, tourism, businesses, and people living on the canals.”

A Defra spokesperson said: “Our canals and rivers provide a wide range of benefits, such as connecting people to nature. That is why we are investing more than £480m of grant funding to the CRT to support essential infrastructure maintenance of our much-valued waterways.”

The spokesperson said navigation authorities had independent responsibility for maintaining canal networks, safety and resilience against climate change.

The CRT receives the largest share of government funding for waterways but rising climate-related demands mean state support remains insufficient to maintain its network.

Campbell Robb, the CRT chief executive, said: “Emergency repairs alone cost our charity £10m last winter after eight named storms. We need the support of the public in the unrelenting task to look after and keep the canals open and thriving, including more people volunteering and donating money. The government recognises the role it also needs to continue to play to help our charity keep the network open and safe.”

After the CRT, the remaining 20% of the canal network and about 3,000 miles of navigable waterways are overseen by authorities including the Environment Agency, Scottish Canals, the Broads Authority, and smaller independent bodies.

For its risk map, the IWA graded navigation authorities from severe deficit (red) to financially stable (green). About 75% fell into red or amber categories, including the Environment Agency and the Cam Conservancy, which acknowledged it could not meet all its commitments.

Stoppages, such as at Jesus Green and Baits Bite Lock on the River Cam, show how network isolation harms local businesses and navigation. David Goode, the chair of the Cam Conservancy, said: “Even in a good year our fees barely cover running costs.” He called a £500,000 contribution from the local mayor towards the £1.6m Baits Bite Lock stabilisation a “life-saver” but added: “One-off grants won’t solve longer-term problems.” Jesus Green Lock remains indefinitely closed.

In addition to closures and climate damage, rising litter is a daily challenge. Elena Horcajo spends two hours each morning collecting waste along the Regent’s canal after the CRT removed towpath bins, citing untenable maintenance costs. The trust now relies on reactive litter clearance using staff and volunteers, but Horcajo says CRT-led volunteer clean-ups fail to manage the problem.

The IWA is calling for a government review to define sustainable, long-term funding. Norman said: “Millions now will save billions in the future.”

He said increased government investment would allow authorities to reinforce infrastructure, reduce flood risk and support water transfer schemes to alleviate drought, protecting navigation, heritage, economic activity and environmental benefits.

“Without intervention, this vital, historic network faces irreversible decline by 2050,” Norman said.