Water suppliers are being encouraged to consider projects reminiscent of the Romans or Victorians as they prepare to cope with growing demand

A new era of building pipes and canals to divert water from rivers and aquifers across Britain is being proposed as concern mounts about how to keep the taps flowing in drought-prone regions of the country.

After the driest spring for a century left this year's crops dying in parts of England, and the threat of bans on hose pipes and car washes becomes an annual summer event, experts say around four major transfer projects could be approved in the coming years as water companies struggle with growing demand and falling supplies.

To make way for the return of such big engineering schemes - reminiscent of the Romans or Victorians - the government's water white paper, due to be published in the coming weeks, is expected to include changes to regulation to allow companies in water-rich areas to make money from selling it to drier regions.

However the plans are likely to meet stiff opposition from those worried about how wildlife will survive, the impact on the landscape, and the cost and greenhouse gas emissions that will come from the energy required to pump water over vast distances.

One of the most controversial proposals is a huge project to move water from the River Severn. It would be transported more than 100 miles from mid-Wales or the west of England into the Thames, in order to supply London and the south-east of England. A recent public inquiry into Thames Water's investment plans has ordered the company to reconsider this scheme.

The most likely schemes will involve transfers between neighbouring regions, which water suppliers are being encouraged to reconsider as they prepare the next round of investment plans to meet demand over the coming decades. These ideas will be considered alongside "soft" measures to reduce demand and repair leaking pipes, and other investments such as building new reservoirs or "recycling" sewage water.

Other grand designs that could be revived, however, include bringing supplies from ground water in south Wales, from Birmingham via the Oxford canal, and from the Kielder reservoir in Northumberland in the north-east of England - down to the east and south-east of England, where the need is greatest.

In a sign of the opposition companies are likely to face from local communities and environmental groups, however, the Countryside Council for Wales warned that the land around the possible mid-Wales source of water for transfer from the Severn to the Thames was home to many protected species including important bog and heathland, and hen harriers, peregrine falcons and merlins.

The RSPB said it would consider small inter-regional transfers against the damage that could be done by alternative sources of water, but it had concerns about water levels in the rivers left behind, mixing water qualities, alien species moving further afield, and climate change leaving schemes redundant when rainfall patterns change.

About 5% of water supplied to homes and businesses in the UK comes from water piped in from outside the immediate area, but such schemes have fallen out of favour in the last decades as concerns have risen about the environmental impact on the areas donating the water, the cost and energy use.

However there are several signs that times are about to change again, with companies, regulators and politicians increasingly concerned about how to meet the growing needs of an increasing population, forecasts of less rain at the important times to recharge rivers, reservoirs and underground storage, and new regulations to protect the habitat of rivers from too much abstraction.

The Environment Agency's policy, updated as recently as July 2011, says that the "cost and environmental impact of large-scale transfers of water … mean that such proposals are unlikely to be necessary". However at a conference hosted by the Royal Academy of Engineering in late October, Trevor Bishop, the agency's head of water resources, signalled a new approach, telling the Guardian that large-scale transfers "are an inherent part of our water resources today; there's every possibility they might provide a part of our future".

At the same conference, Yvette de Garis, Thames Water's head of environment and quality strategy and regulation, told the audience that new information meant that Britain's largest water supplier was also reconsidering its decision to rule out the Severn-to-Thames transfer in its last major investment plan, published in 2009. The next plan, which also covers demand management, fixing leaks and other small schemes, is currently being written. "We are undertaking this appropriate assessment on the Severn estuary to see whether those options can be included," de Garis told the conference. "I have to say that it is my expectation that they probably can be, because the data that we have to date is unlikely to show an adverse impact."

De Garis added a note of caution, however, saying that as well as strong objections from local communities, European legislation protecting habitats and water quality could make transfers impossible in future years.

Ofwat, the national water regulator, said it was also working on changes which would make it easier and more attractive to build big water transfer schemes. In a statement, the regulator said that its own research suggested £960m could be saved over 30 years if there were more connections between supplies.

"We need to look at a range of measures to keep the taps running," it said. "Water trading is a way of moving water from where it is plentiful to where it is scarce, helping meeting increasing demand for water where it is needed while protecting water resources in the environment and the associated wildlife. As well as protecting the environment, water trading connects up water networks and resources [and] thus increases the resilience of supply to droughts or system failures."

Supporters, however, say there are also benefits to transfers, for example if areas which usually experience droughts at different times can be linked up, and different water qualities can be improved by better water treatment. "What's needed is someone to look at these water transfer schemes with the imagination of good engineers," said John Lawson, a consultant who has been promoting the Severn-Thames scheme.

Phil Burston, senior water policy manager for the RSPB, said: "I wouldn't say we are in favour [of the smaller schemes] … but we'd definitely be opposed to large inter-basin transfers, or even resurrecting the concept of a national grid, which rears its ugly head from time to time. If we're going to see in the next generation of plans a large number of large-scale plans, that's definitely going back to old-style thinking."