ON A WARM JULY AFTERNOON I am going to see the mouth of the Rio Grande for the first time. Sixteenth-century Spaniards called the stream Río de las Palmas; the bright forest of palm trees around the mouth was a landmark for navigators of the Gulf. In good years, the lowlands surrounding those groves would be marshes teeming with shellfish and minnows hunted by ibis and herons stepping sprightly in the brine. But today, as I ride eastward on Texas Highway 4, the most striking features ahead are airborne white swirls of sand and salt. Decades of clearing for agriculture and development have isolated the last native sabal palms to a small Audubon preserve outside Brownsville, and most of the wetlands have gone as dry as chalk. The sprawling river delta has been reduced to a nearly barren, eroded strip of earth, and some residents of Port Isabel are having trouble breathing because there's so much windblown grit in the air.
My guide is a pleasant man named Gilberto Rodriguez who grew up on a farm in Weslaco and now roams the lower Rio Grande as a watermaster specialist for the Texas Commission on Environmental Quality (TCEQ). In layman's terms, Rodriguez is an unarmed water cop; he spends much of his time checking pump gauges on the Texas side, making sure none of its farmers are drawing more water than they're allowed. For many Rio Grande Valley residents, the mere inference of such cheating sparks outrage, and Rodriguez tells me he often fears violence. "The hotter the water," he reflects, "the more hostile people become."
He is not referring to water temperature. Valley growers are livid over what they believe is Mexican theft of Rio Grande water in the northern state of Chihuahua. You might think the Rio Grande begins with snowmelt and rapids in the Rockies of Colorado and New Mexico and then marks the plains with graceful lines of cottonwood and willow as it claims its legacy as the Texas-Mexico border. Technically, that's true. But these days, dams in New Mexico, the thirsty and sprawling border cities of El Paso and Juárez, and giant tangles of nonnative salt cedars strangle the Rio Grande's once mighty flow by the time it enters Texas. In reality, the river's headwater today is Mexico's Río Conchos, which begins high in the Sierra Madres, crosses the Chihuahuan Desert, and revives the parent stream at Presidio and Ojinaga, above Big Bend. Roughly 50 percent of the water in the border stream now comes from the Río Conchos.
By terms of a 1944 treaty, two thirds of the Conchos flow belongs to Mexico; the remaining third is supposed to continue on to the United States. But in recent years, Mexico has amassed a huge "water debt." Instead of regularly releasing Río Conchos water downstream, Chihuahua has stored it in reservoirs and put it to the use of its towns and irrigating farmers. Texas farmers believe that their way of life is being sold upriver, and they're frustrated by the lack of action from the U.S. government. They calculate the loss to their fields at about 489 billion gallons of water and warn that the Valley economy could collapse. Their anger has embroiled Mexican president Vicente Fox in a domestic political furor that has soured relations with the U.S. Invoking the rhetoric of the war on terrorism, Texas agriculture commissioner Susan Combs, one of the farmers' key political advocates, has called Chihuahua "a rogue state." But the farmers' frustration and vituperation is aimed not only at Mexico. The conflict has also embarrassed Governor Rick Perry and President George W. Bush.
A dwindling supply of water is an issue for every citizen of Texas, but few residents have as desperate a case as Rio Grande Valley farmers. They've suffered a dry spell in the past decade that rivals the legendary drought of the forties and the fifties that turned most of Texas into a federal disaster area. Because the groundwater is brackish, the Valley gets no help from aquifers; the Rio Grande carries all the water there is. Every drop of Conchos water is vital, but that spigot too has been all but turned off.
Nowhere is this reality more clear than at the mouth of the Rio Grande, which is further consumed by mats of water hyacinth and hydrilla. At the terminus of Highway 4, Rodriguez and I jostle from pavement to loose sand. It's a pretty day at the beach. The white-capped waves are bright dark blue, and squadrons of brown pelicans fold their wings and smack beak-first into the surf, trying to catch dinner. Boca Chica, which means "small mouth," has none of the glitz and development of nearby South Padre Island, but families are out fishing, splashing, building sand castles. Ahead, a portable light tower has been erected. That landmark, Rodriguez tells me, is Mexico. Parked on the beach, hood pointed toward the surf, is a green-and-white SUV marked U.S. Border Patrol. For hours on end two agents sit and stare at beachcombers and the Gulf.
The agents represent the increased vigilance of Homeland Security, but their presence here also marks the death of a river. The riverbank they've parked beside is now a land bridge. It is not unlike other strips of sand and shell that the tide and currents lay out in the Gulf's endless construction of beaches becoming dunes becoming barrier islands. The difference is that this sandbar has obliterated a natural frontier between nations and left the mythic Rio Grande a tepid, stagnant shallow. It has too little push to cross the bar and reach the ocean.
On this day the pool trapped at Boca Chica looks blue enough, but its biological illness is indicated by crusts of salt that line the banks for hundreds of yards upstream and resemble icy slush. Freshwater inflow is an estuary's lifeblood, but these days the Rio Grande has little of that to give. I watch some Mexican boys skimming the stagnant pool