Disappearing Water

They serve a strong brew at the Alamo coffee-house in Presidio, a small farming town near the US-Mexican border. They need to. Times are tough, says Terry Bishop, looking up from his second mugful. This land, next to the Rio Grande in Texas, has probably been continuously farmed for longer than anywhere in America, he says. Six hundred years minimum. It has been home to scalp-hunters and a penal colony; it has seen Comanche raids, Spanish missionaries, marauding Mexican revolutionaries and a population boom during a recent aliens amnesty. All that time, it has been farmed. But soon it will be back to sagebrush and salt cedar. Climbing the levee by the river at the end of his last field, Bishop shows me the problem. The once mighty Rio Grande is now reduced to a sluggish brown trickle.

In its middle stretches, the river often dries up entirely in the summer. All the water has been taken out by cities and farmers upstream. "The river's been disappearing since the 50s," says Bishop, who has farmed here virtually all that time. There has not been a flood worthy of the name since 1978. For 300km upstream of Presidio, there is no proper channel any more, he says. They call it the forgotten river. Bishop's land brings with it legal rights to 10m cubic metres of water a year from the river - enough to flood his fields to a depth of more than a metre, enough to grow almost any crop he wants. But in recent years he has taken only a quarter of that. Even when he gets water, "it's too salty to grow anything much except alfalfa."

But that is all a bit academic now. Yields got so low that the farm went bust. Bishop lets some fields to tenants, but most of them lie idle these days. The land is gradually returning to desert. And Bishop drinks a lot of coffee. This is the way of things in Presidio. The town was once a major farming centre. It used to ship in thousands of Mexican workers to harvest its crops. Bishop's farm alone once employed 1,000 people. But that has all ended and the unemployment rate among the town's permanent residents is almost 40%.

The only profitable business now is desert tourism. An old silver mine a few miles up the road has been turned into a ghost town, and a fort at Cibolo Creek is now an upmarket resort attracting the likes of Mick Jagger. Harvesting tourists, that's the game now, says Bishop.

On the map, the Rio Grande is the fifth longest river in North America and among the 20 longest in the world. Its main stem stretches 3,000km (1,900 miles) from the snowfields of the Colorado Rockies to the Gulf of Mexico, via New Mexico and Texas. It drains one tenth of the continental US and more than two-fifths of Mexico. The hub of human exploitation of the Rio Grande is the Elephant Butte reservoir near El Paso in Texas (about 300km upstream of Presidio). It was built in 1915 and changed the river for ever. The wild, untamed flow - which obliterated villages and once rode right through downtown Albuquerque - was ended for good and its waters were corralled for irrigation.

Today, Elephant Butte and its downstream sister, the Caballo, all but empty the river to supply El Paso and nearby farmers. More than 9 million people in the basin rely on the Rio Grande's waters. But it is the farmers who make most use of it. Four-fifths of the water in the river is taken for irrigation - most of it to grow two of the thirstiest crops in the world: cotton and alfalfa, a grain fed to cattle. And the wastage is huge. Only about 40% of the water reaches the crops, while evaporation in the hot sun takes more than two metres of water a year from the reservoirs - a total of around 300m cubic metres from Elephant Butte alone.

Usually a trickle of water gets through to the sea. But since the mid-1990s, a decade during which drought has gripped the basin, the flow has been at record lows. In 2001, it ceased altogether. A sandbar 100m wide completely blocked off the river from the Gulf of Mexico. The bar lasted for five months before summer flows washed it away. And for much of the next two years it returned. You could drive a car across the beach between the US and Mexico. The Rio Grande had, literally, run into the sand.

Rivers so often define our world. Is there a better book about America than Huckleberry Finn's journey on the Mississippi? Is there a better way of seeing London than taking a boat down the Thames to Greenwich? Some of the greatest human adventures have been along rivers: up the Orinoco to find El Dorado; or the search for the source of the Nile. Millions of Indians keep bottles of Ganges water in their homes, like holy water. We romance on the Blue Danube and the Seine; and fight over the Jordan and the rivers of Babylon. Yet something disturbing is happening.

The maps in an atlas no longer accord with reality: inland seas and lakes are disappearing; the old geography lessons about how rivers emerged from mountains, gathered water from tributaries and finally disgorged their bloated flows into the oceans are now fiction. Some of the great rivers of the world are disappearing: the Nile in Egypt, the Yellow River in China, the Indus in Pakistan, the Colorado and Rio Grande in the US - all trickling into the sand, sometimes hundreds of miles from the sea. Few of us realise how much water it takes to get us through the day. On average, we drink around five litres of the stuff. Including water for washing and for flushing the toilet, western Europeans use only about 150 litres each. In some countries suburban lawn sprinklers, swimming pools and sundry outdoor uses can double that figure. Typical per-capita water use in suburban Australia is 350l and in the US around 400l.

We can all save water in the home. But laudable though it is to take a shower rather than a bath, put a brick in the lavatory cistern and turn off the tap while brushing our teeth, we shouldn't get hold of the idea that regular domestic water use is what is really emptying the world's rivers.
Manufacturing the goods that fill our homes consumes a certain amount, but that is not the real story either. It is only when we add in the water needed to grow what we eat and drink that the figures really begin to soar. The numbers are mind-boggling: it takes between 2,000 and 5,000l of water to grow one kilo of rice. That is more water than many households use in a week. For just a bag of rice.

It takes 1,000l to grow a kilo of wheat, and 500l for a kilo of potatoes. When you feed grain to livestock for animal products such as meat and milk, the figures become yet more startling. It takes 11,000l to grow the feed for enough cow to make a quarter-pound hamburger; and between2,000 and 4,000l for that cow to fill its udders with a litre of milk. Cheese? A kilo of cheddar or brie takes about 5,000l.

As a typical meat-eating, milk-guzzling westerner, I consume as much as a hundred times my own weight in water every day. It is time, surely, to preach the gospel of water conservation - but don't buy one of those T-shirts with jokey slogans such as "Save water - bath with a friend". Good message, but you could fill 25 bath tubs with the water needed to grow the 250 grams of cotton used to make the shirt. Globalised markets mean that whenever you buy a T-shirt made of Pakistani cotton, eat Thai rice or drink coffee from Central America, you are influencing the hydrology of those regions - taking a share of the river Indus, the Mekong or the Costa Rican rains. You may be helping rivers run dry. The consequences are with us already. Back in Texas, the El Paso Times regularly alerts readers to the days when they can use public water on lawns, and the days they can't.

Jittery suburbanites are repairing old wells in the hope of capturing some private water from beneath their land. And in the unplanned shanty-town "colonias", where many Mexicans end up after crossing the river, thousands of people live without access to piped water at all - and that is a shock to find in the US, even in the desert. El Paso is buying up properties from local farmers to bag their rights to underground water reserves. Its "water ranches" are dotted all along the highway to Presidio, to exploit the subterranean aquifers - natural reservoirs of water trapped between layers of rock. But water-ranching will be only a temporary solution. The region's major aquifer, which lies beneath a vast area of Texas, New Mexico and the Mexican Chihuahua desert, is rapidly running dry because there is not enough rain to replace what is pumped out.

According to Mary Kelly, a leading environmentalist campaigning to save the river, pumping out this underground water could trigger the final and irreversible desiccation of the landscape. "Most of the recharge for the aquifer comes from seepage from the canals supplying the farms - which ultimately means it comes from the Rio Grande."

Downstream of El Paso, the river becomes a dribble of sewage effluent disappearing into remote scrub most of the way to Presidio. Hydrologically speaking, the Rio Grande pretty much ends here. Beyond Presidio, the river winds through dramatic canyons in the Big Bend National Park. But the flow is small and muddy. "We get about a sixth of the historical flow here," Dave Elkovitz of the park authority told me. A couple of weeks before my visit, the river dried up here for the first time in more than 50 years. Stagnant pools of water evaporated, leaving dry gravel beds and thousands of dead catfish. Starved of food, a troop of black bears headed back to Mexico. "We have treaties for the river," said Elkovitz. "But they allocate more water than actually exists. What good is that?"

The main treaty, signed in 1944, requires that one-third of the water flowing into the Rio Grande from six Mexican tributaries, much the largest of which is the Rio Conchos, is allocated to the US. The US can dry up the Rio Grande at El Paso as much as it wants, but, come hell or low water, the Mexicans have to deliver that quota. The treaty might have been fine 60 years ago when the rains could be relied upon, but what it means now is that northern Mexico is littered with irrigation areas living on borrowed time and water they owe to Texas.

Today, these districts are engaged in a major modernisation process to save water. Engineers are busy lining canals to prevent water seeping out of their porous bottoms. And they are installing perforated rubber piping to get water right to the plant roots rather than flooding fields. This $130m programme is being paid for mainly by the US government: the aim is to save 350m cubic metres of water a year. That volume close to the amount that Mexico should be sending down the Rio Conchos into the Rio Grande each year under the treaty terms.

"The Americans will get what we save," said one official. It sounds like a win:win situation: the Mexican farmers, I was told, would get greater water security, while the US gets its missing water. But there is a fallacy here: the modernisation will not actually make more water, and most of the savings are not real savings. The seepage will stop, but, says Kelly, that only means the aquifer will no longer be replenished.

As the canal water has failed in recent years, many farmers have come to rely on pumping underground water. But most of the underground water in the wells comes from seepage from the canals and fields. If the seepage is cut, the wells will dry up. According to Kelly, the modernisation plan will only hasten the aquifer's demise. The local irrigation engineers, and the people funding their work, seemed unconcerned by this prospect. But the tragedy is that to meet their immediate obligations to deliver water to Texan farmers, the Mexicans risk the loss of their vital underground water reserves.

Thanks to global trade, this is a scenario being played out the world over. Economists call the water involved in the growing and manufacture of products "virtual water". Every tonne of wheat arriving at a dockside, for example, carries with it in virtual form the 1,000 tonnes water needed to grow it. The world's virtual water trade is estimated to amount to be about 1,000 cubic kilometres a year, or 20 river Niles. Of that, two-thirds is in a huge range of crops from grains to vegetable oil, sugar to cotton; quarter is in meat and dairy products; and just a tenth in industrial products. This trade "moves water in volumes and over distances beyond the wildest imaginings of water engineers," says Tony Allan of the School of Oriental and African Studies in London, who invented the term "virtual water".

This hidden water export business is laying the fuse for a hydrological time-bomb. Mexico's virtual-water exports are emptying its largest body of water, Lake Chapala, which is the main source of water for its second city, Guadalajara. But the biggest net exporter of virtual water the US. It exports around a third of all the water it takes out of the natural environment. Much of that is in grains, either directly or via meat. The US is emptying critical underground water reserves, such as those beneath the High Plains, to grow grain for export. It also exports an amazing 100 cubic kilometres of virtual water in beef. Once upon a time, it was the cattle drives that made the Rio Grande famous in scores of westerns. One day soon, the movie house may be the only place you can find the river at all.

[This is an edited extract from When Rivers Run Dry, by Fred Pearce, published by Eden Project Books]