The water shortages already threatening East Anglia's parched countryside could worsen drastically in future unless urgent action is taken to mitigate the twin threats of climate change and population growth.

That stark warning comes in an Environment Agency (EA) report which suggests river levels could plunge by as much as 80pc if rainfall dries up and demand for water continues to rise unchecked by 2050.

The spectre of the regions's finest waterways being reduced to muddy trickles is the most pessimistic scenario among several analysed in the report, with other models predicting less severe outcomes.

Nevertheless, it says uncertainty over future supplies means crucial strategic decisions must be made now in order to conserve precious water resources – particularly in agricultural heartlands like East Anglia.

The Anglian region receives only 600mm of rainfall a year, less than 70pc of the national average, yet has more abstraction licences for domestic and industrial use than anywhere else in the country.

Although the area's dependence on more stable groundwater supplies makes it more resilient to changes in river flows, shortfalls could have potentially disastrous effects on industry, homes, ecology and tourism.

Experts say a change of public attitude is needed to reduce domestic wastage, while water companies and industrial users must maximise efficiency to stretch available resources.

Even desalination plants that transform seawater into drinking water could be considered if supplies run dangerously low.

Richard Thompson, EA's water resource planning manager for the East Anglian region, said: 'The first thing I would say is don't be alarmed. We are used to dealing with drought and dry weather in this part of the country and we have got a lot of ways we can manage our resources. But we need to make sure we make plans for the future and that involves everybody trying to use less water and securing more supplies to balance the needs of people, the environment and business – and agriculture is a key part of that.

'The East of England may not have the same population pressures in terms of the people currently living here, but what it does have is a hugely important agricultural industry which needs reliable supplies of water to irrigate its crops.'

Farming industry leaders said they were concerned about finding enough water for the next 30 weeks – let alone the next 30 years – as the ongoing drought brought the longer-term concerns into focus.

A drought summit between the East Anglian branch of the National Farmers' Union (NFU) and the EA earlier this month heard that irrigation restrictions were 'highly likely' during the 2012 growing season unless there is substantial rainfall in the next few months.

The NFU's senior policy advisor Paul Hammett said better communication and flexibility between farmers and EA officers on local licensing and cropping decisions could help them meet those challenges.

'Farmers have made fantastic progress since the droughts of the early 90s,' he said. 'But there is more that needs to be done. Farmers recognise the scale of the challenge and they are doing something about it – developing partnerships with other users, developing skills in more efficient use of water, and building their own reservoirs to control their own supplies.'

The EA report, named The Case for Change – Current and Future Water Availability, predicts warmer and drier summer weather, particularly in the south-east of England, causing rivers and reservoirs to dry up. Meanwhile, a forecast population growth of 9.6 million in England and Wales by the 2030s will produce a leap in demand, exerting severe pressure on already-stretched supplies.

The report says reducing the public's lavish usage of water for washing, flushing and cooking will be crucial – although 'demand management' alone will not be enough.

Mr Thompson said: 'What we are asking people to do is take simple steps, like taking a shorter shower, turning the tap off when they clean their teeth, or replace their taps and showers with water-efficient devices.

'At the same time, the water companies need to address leakages and farmers are already investing in winter storage reservoirs so they can take water when river flows are higher.'

John Clare from Anglian Water said millions of pounds were already being invested to improve the efficiency of the region's infrastructure.

'The potential impacts of climate change and population growth are by far the biggest challenges we face,' he said.

'The EA's timely report highlights the kind of future we could face if we ignore the dangers, but there is no reason why the future cannot be one in which our region continues to thrive, with enough water to supply our homes and businesses, keep our rivers flowing and our wetlands wet.

'To make that happier future a reality, we all need to see water as the precious, shared and finite resource it is and do all we can to conserve it.'