The Environment Agency has recommended reservoir safety legislation be reviewed to take into account the impacts of climate change and ageing reservoirs - the average age of UK dams is 110 years.
Chief Executive Barbara Young said overall compliance with the Reservoirs Act 1975 had improved since the Environment Agency became the enforcement authority in 2004, but there was still work to be done.
"Dams and reservoirs store large amounts of our nation's water, but if owners don't monitor their condition and repair them when necessary, the huge amounts of water that they hold can threaten life and property.
"Reservoir undertakers are responsible for the safety of dams, including appointing supervising engineers, arranging inspections, and carrying our work where necessary. We're in charge of making sure they do this.
"When we took over as the enforcement authority from local authorities, we faced a huge task. There was a significant backlog of non-compliance potentially placing people and property at risk, where some 379 reservoirs had no supervising engineer and 202 had inspection reports overdue.
"Since then, failure to carry out regular safety inspections has been cut by 80%, and over the past two years, we've issued 118 notices and prosecuted the undertakers at two reservoirs for failing to comply with the Act," she said.
Young said that even with greater compliance, the risk of dam failure was likely to increase because of more extreme weather events with climate change and an ageing reservoir stock.
"Because of these issues, and along with our experiences over the past three years, we believe a review of the legislation is timely," Young said.
The Environment Agency proposes:
- Better enforcement powers for emergency flood plans. Engineers do not currently have to sign off an emergency flood plan.
- Money to act on reservoirs with no owners. Currently there are at least two reservoirs in England that have no legally responsible reservoir undertaker.
- Mandatory post-incident reporting. It is Currently a voluntary system and reservoir undertakers don’t always inform the Environment Agency about emergency incidents at their reservoirs. It would be in the public interest for all emergency incidents to be reported for lessons to be learnt and information to be disseminated to the industry.
- Better definition of a reservoir within the Act. Currently the definition is volumetric, based on a minimum capacity of 25,000 cubic metres of water above ground. The definition of reservoirs should take into account the nature of the downstream community and possible consequences of a reservoir failure or dam breach.
About 80% of the dams across England and Wales are made of clay and earth. The oldest dams were built in the 12th century, and many were built during the Victorian era. Two dams failed in 1925, but there has been no loss of life since 1930 when the Reservoir (Safety Provisions) Act was passed.
The Ulley dam was in danger of collapse during freak rainfall during the summer.