England is facing water supply shortages by 2050 unless rapid action is taken to curb water use and wastage, the Environment Agency has warned.
Its new report says enough water to meet the needs of 20 million people is lost through leakage every day.
Population growth and the impact of climate change are expected to add to supply pressures.
The agency wants people to have a personal water target and has urged them to use water more wisely at home.
The study, the first major report on water resources in England, says that population growth and climate change are the biggest pressures on a system that is already struggling.
In 2016, some 9,500 billion litres of freshwater were taken from rivers, lakes, reservoirs and underground sources, with 55% of this used by public water companies, and 27% going to the electricity supply industry.
But in addition to the 3 billion litres a day that are wasted through leakage, there is a considerable price being paid in terms of the sustainability of these supplies.
According to the Environment Agency, extraction of groundwater – the water beneath the earth’s surface – is not at a sustainable level for 28% of groundwater bodies and up to 18% of surface waters.
A year earlier in 2016, unsustainable extraction meant that at least 6% and possibly up to 15% of river water bodies did not achieve “a good ecological status or potential”.
The majority of chalk streams also failed to meet that standard, with over extraction of water being responsible in a quarter of the streams that were tested.
“We need to change our attitudes to water use,” said Emma Howard Boyd, the Environment Agency chairwoman.