Drought, population growth, profit and politics are turning water into a very precious commodity in the Rio Grande river basin on the US-Mexico border.
And tensions are increasing on both sides - between an impoverished part of Texas and a Mexican city already very dangerously low on water reserves - over who has water, and who is suspected of having it.
El Paso's citizens are accused of not taking the problem seriously enough
The dispute stems from the fact that people are legally entitled to more water from the Rio Grande than is actually in the river itself.
"The drought that we're looking at, for this area of Texas and New Mexico - and Mexico - is what we call a river drought," said David Crowder, the environment correspondent of the El Paso Times.
"Right now the problem we're having is to do with the snowfall up in Colorado which feeds the Rio Grande river, which provides the water the farmers use in this area, and about half the water the city uses."
There's an old quote from Mark Twain, which goes: 'Whisky's for drinking, water's for fighting over'
Mr Crowder told BBC World Service's Politics Of Water programme that the problem was being exacerbated by people in the US who did not believe the problem was serious.
"There does seem to be a gap in people's understanding and belief of the reality of this drought, especially here in the El Paso area," he said.
"A lot of folks are saying: 'I have no interest in letting my lawn go brown this summer'."
But outside the city, Texan farmers are seeing their livelihoods threatened by the drought in an area that is economically dependent on agriculture.
"When you're out of [water], it becomes very valuable," said Johnny Stubbs, a farmer in the lower El Paso area.
"Anything that grows in this part of Texas is entirely dependent on irrigation water.
El Paso and Juarez are part of the same conurbation
"We're looking now at an initial allotment of 10-11% of what we would normally get."
The situation has become so bad that wells drilled during the 1950s and long since abandoned are being restored - although primarily as a stop-gap measure, as the water is saline and will eventually ruin the land.
The management of the Rio Grande is vastly complex - it is split between the governments of the US and Mexico, three American states, five Mexican states, 18 Native American nations, and several districts and municipalities.
Consequently, there is great concern about future disputes.
"Water has almost the same potential to be as divisive an issue as perhaps even immigration," said Fernando Marcias, a former senator who is now overseeing infrastructure projects along the river.
"In the future, [the problems] are going to be very severe.
The Bush administration "has changed priorities"
"In the next 20 years there are going to be very severe water shortages, especially if more recent drought conditions continue."
Mr Marcias added that the potential dispute continued all the way up to state level.
"The Mexican perspective is that they are very hopeful that with the Bush administration's familiarity with the relationship between the United States and Mexico that there would be movement on the water issue," Mr Marcias added.
"Some of the movement has not occurred because of the reprioritisation of the objectives of the US administration.
"But what's going on currently is a difference of opinion in terms of how to interpret some of the existing international treaties."
Over the border from El Paso is Juarez, three times the size of El Paso, but in effect part of the same bi-national metropolis, the biggest in the world.
As more and more people come to the region, the pressure on the water increases - especially on the Mexican side of the border.
Dispute of the future
"Two years ago, Juarez was advised that they had five years of water left," said the El Paso Times' David Crowder.
"There are areas of Juarez now where the wells that serve large neighbourhoods are starting to bring up briny [salty] water.
"It seems - at least on this side - that nobody's paying a great deal of attention to the situation."
The consequence of the strain Juarez puts on the Rio Grande is that Mexico has now run up a "water debt", owing the US millions of gallons of water.
And some Texan farmers even believe the country is hoarding water, although Mexico denies this and insists the debt can be repaid.
This type of dispute, which some fear may become more and more common in the future, as yet has no tried and tested solution.
"Why this issue is difficult is because we don't have rules for how to address this kind of scenario," explained Arturo Herrera, from the International Boundary Water Commission.
The Rio Grande is now completely dry at some points
But in a final twist, this scarcity of water may yet become a bonus for the Texan farmers.
Many in El Paso see the future as one where, with supplies harder to get at, the vast quantities of water currently used to irrigate the land could instead be turned into giant water banks.
The farmers could then cash in their water rights, leasing out the land and supplying towns and cities with the water that used to keep their crops alive.
In such cases, the less water there is, the higher the price they can charge.
But south of the border, there are many who cannot afford it even now.