美国国家公共电台 NPR Mexico Worries That A New Border Wall Will Worsen Flooding（在线收听）

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President Trump has kept up the pressure to build a wall along the U.S.-Mexico border, though the administration now seems willing to wait until later this year so they can figure out where the funding for that wall is going to come from. But there may be another obstacle here.

Mexican engineers think construction of a massive barrier may violate a 47-year-old treaty on the shared waters of the Rio Grande. If Mexico protests, the fate of the wall could end up in an international court. NPR's John Burnett has this report.

JOHN BURNETT, BYLINE: Mexico is watching with growing alarm as the U.S. Department of Homeland Security moves ahead with its plan to dramatically extend a border barrier that's already caused serious flooding. The 1970 Boundary Treaty lays out the precise border between the U.S. and Mexico and sets rules for the Riverside territories.

The treaty states both U.S. and Mexican officials on the International Boundary and Water Commission must agree if one side wants to build any structure that would affect the flow of the Rio Grande or its floodwaters. The U.S. has already built nearly 700 miles of security fence, and Mexico has consistently opposed it, says Antonio Rascon, chief engineer of the Mexican side of the commission.

ANTONIO RASCON: (Through interpreter) For us, were not in agreement with construction of a wall in the floodplain that affects the transborder flow of water. In general, we have been complaining about the fence since 1992. We're talking 25 years. That's when they installed the first fence in San Diego, and it's been advancing and advancing.

BURNETT: In its 128 years of existence, the Boundary and Water Commission or IBWC has tried to resolve differences quietly with professionalism and diplomacy, but the bold plan for Trump's wall is straining that crossborder collegiality. With the earlier fence construction Mexico protested, the U.S. made some design modifications and the project moved ahead over Mexico's objections.

Homeland Security has not yet revealed what the new wall would look like or exactly where it would go, but some of the initial schematics - as high as 30 feet made of solid concrete - have prompted Mexico's side of the international commission to speak out for the first time to NPR. Rascon says Mexico will not stand for a treaty violation.

RASCON: (Through interpreter) A concrete wall that blocks transborder water movement is a total obstruction. If they plan that type of project, we will oppose it.

BURNETT: People familiar with river hydraulics say there's another way to understand a wall built in a floodplain. It acts like a dam. During torrential rains, these obstructions deflect water and worsen flooding. Stephen Mumme is a political science professor at Colorado State University who has studied U.S.-Mexico water diplomacy for nearly 40 years. He says concerns over floods on the border are well-founded.

STEPHEN MUMME: We have a history. We know they occur.

BURNETT: Over the past nine years, steel fencing along the Arizona-Mexico border has clogged with debris during the summer monsoon season. Floodwaters damaged Organ Pipe Cactus National Monument and coursed through the Lukeville, Ariz., port of entry. In the twin cities of Nogales in separate events, raging floodwaters killed two people, washed cars away, collapsed a section of the fence and caused millions in damages.

MUMME: It just walled up the water. It dammed up the water.

BURNETT: Even worse flooding is expected if the wall is built in the floodplain of the Rio Grande Valley of Texas. Homeland Security has long wanted to put a fence along the river in Starr County, Texas, a favorite crossing spot for smugglers of drugs and people, says Border Patrol Chief Ron Vitiello.

RON VITIELLO: That was a place where we thought a barrier made sense.

BURNETT: Two things blocked the project in Starr County. Congressional funding ran out and the Mexican side of the Boundary Commission resisted a fence in the floodplain. Today Starr County is one of the first places on the 2,000-mile border where Trump's wall is expected to resume. Everything is ready to go. The government has been seizing land along the river by eminent domain, and there are already blueprints where to build about 10 miles of fence. But Vitiello insists the U.S. will not bigfoot its Mexican neighbors.

VITIELLO: So if we go forward inside of the floodplain, then it will comply with our responsibility under the treaty.

BURNETT: Locals in this Starr County seat of Rio Grande City are not comforted by the government's assurances. What they're afraid of is a wall that would prevent the city from properly draining during, say, a hurricane blowing in from the Gulf of Mexico less than a hundred miles away. Gilbert Millan is the city's planning director. Alberto Perez is the city manager.

GILBERT MILLAN: The drainage system would obviously be impacted due to the dragging of debris from the water coming back to the riverbanks.

ALBERTO PEREZ: Or it might, you know, end up knocking down the wall because the water's got to get out of here somehow. And there's nowhere for that water to go when we have those floods.

BURNETT: At one point, the U.S. section of the Boundary and Water Commission sided with worried city officials and joined the Mexican section in opposing the Starr County wall. Then U.S. officials flipped 180 degrees.

SCOTT NICOL: And in early 2012, the U.S. section of IBWC said we respectfully disagree with our Mexican counterparts, and we approve these walls going up.

BURNETT: That's Scott Nicol, co-chair of the Rio Grande Valley Sierra Club. Nicol obtained through open records request thousands of federal documents that he shared with NPR. What they show is that U.S. officials changed their minds after being presented with a new plan for the Starr County border barrier that was commissioned by Homeland Security.

In an email to NPR, U.S. commissioner Edward Drusina writes (reading) after careful consideration of the state-of-the-art hydraulic model, I concluded there was no significant reason to object to Homeland Security proceeding with the construction of the fence.

Others including Mexico's chief river engineer Antonio Rascon still are not convinced.

RASCON: (Through interpreter) We've seen lots of pressure by Homeland Security so that this project moves forward. By the kind of wall they're planning would have drastic effects on transborder water flows.

MUMME: I think that showdown is coming. This is supposed to go forward on a bi-national co-operative basis, and that's not happening.

BURNETT: Again, water diplomacy expert Stephen Mumme.

MUMME: Mexico is asserting a treaty right under the 1970 Boundary Treaty is more likely than ever because of the heightened nationalism and the indignation about the United States fence and wall project.

BURNETT: To protest the border wall, Mexican officials on the Boundary and Water Commission in Juarez, Mexico, would first lodge a formal complaint with their counterpart across the river in El Paso. If they don't resolve it, the dispute goes to the State Department and its Mexican equivalent and finally to arbitration before a world court. Whether it gets that far may depend on how badly the United States wants to build Trump's wall in Starr County. John Burnett, NPR News, Rio Grande City, Texas.