A family has pleaded to be "treated fairly", after being told their property may disappear under a proposed reservoir.
The Authers have spent £1m developing Bramble Grange B&B
Helen and Mike Authers have spent £1m developing their 18-acre Bramble Grange B&B and home near Abingdon since they bought it three and a half years ago.
But it will be subject to a Compulsory Purchase Order (CPO) should Thames Water's proposed Oxfordshire reservoir get the go-ahead.
The £1bn reservoir would be the biggest built in the UK for 25 years.
While the Authers do not oppose the reservoir if a need for it can be demonstrated, they said the proposal hangs over them like a cloud.
"It's a bit demoralising," said Mrs Authers.
"We put the development work on hold when we were told about the CPO before Christmas, but we've restarted it now.
"We're doing the work but it could be gone in five years.
"We've been told Thames Water will buy the house at market value but there's been no mention of compensation.
"We would incur costs, then we've got horses to move and a business we would lose."
As local people, the Authers knew about the reservoir when they bought the property, but they said they approached Thames Water at the time to be told it was not on their five-year plan.
Now they say they feel trapped, unable to sell their home and with a daughter due to start secondary school in two years time.
Mrs Authers added: "I cannot plan for anything at the moment.
"If there's a need for the reservoir then fine, all we are asking is that we are treated fairly and considerately."
A spokeswoman for Thames Water said that up to 20 properties could be affected by CPOs.
She added: "We are saying, 'we want to by your property, do you want to sell?' We'll offer market value for them."
While she could not comment about possible compensation, she said each property would be assessed on a case-by-case basis.
The Vale Reservoir Group - named Fluvius - has already been set-up to represent the interests of people affected by the proposal.
Spokesman Jeremy Scott said: "There's going to be terrible upheaval.
"We believe the reservoir is coming.
"We did a survey and 78% would not oppose the reservoir provided suitable compensation was made."
'State of limbo'
They said a survey conducted by Steventon Parish Council showed there were "massive concerns about the impact of road traffic" and identified the desire for new facilities - such as fishing and sailing venues.
But as Oxfordshire county councillor Ian Brown pointed out, many people are likely to remain in a "state of limbo" until a final decision is reached.
He said: "There are very few people willing to put a bet on buying land out in the reservoir area at the moment."
Ed Vaizey, the MP for Wantage and Didcot, opposes the plan on the basis that he would prefer to see £1bn spent on trying to stop leaks.
Thousands of Vale of White Horse residents will receive a leaflet - entitled "Water for future generations - Upper Thames Major Resource Development" - inviting them to visit an exhibition about future water needs.
Councillor Jerry Patterson, leader of the Vale of White Horse District Council, urged residents to attend the exhibitions.
He added: "This is probably the most significant development the Vale council has ever had to face."