Interior Secretary Ryan Zinke just acknowledged the elephant in the room.
“The Rio Grande, what side of the river are you going to put the wall?” he said, speaking at the Public Land Council’s Legislative Conference. “We’re not going to put it on our side and cede the river to Mexico. And we’re probably not going to put it in the middle of the river.” And therein lies one of the many problems with a fortified border wall, which seems to create more problems than it solves.
Access to the Rio Grande is a major issue for Texas agriculture. Ag in the Rio Grande Valley alone is an $1.6 billion industry. A massive wall cutting off access would annihilate hundreds of thousands of American jobs. Not only are thousands of Americans directly employed in Rio Grande Valley farming, hundreds of thousands of Americans are directly employed in businesses that serve those farmers. Banking, trucking, oil and gas, and service industries are all directly tied to Rio Grande Valley farming, which is directly tied to access to the river's water. When the water is cut off, hundreds of thousands of American jobs die.
You could pump water through the wall, but who will maintain the pumps? The fact it's a fortified wall prevents most everyone from accessing the other side of the pump. Do you really want to $1.6 billion worth of American jobs to depend on the speed of a government work order?
There's also the fact a massive wall would invalidate the complicated legal agreement currently governing Mexican and American use of Rio Grande water, which is what Zinke refers to when he mentions ceding the river to Mexico. A fence is not a property line, but it is fixed, while the Rio Grande shifts.
When it comes to international agreements over sharing the water from a constantly-shifting river, the construction of a wall could be construed by some courts as the most reliable indicator of a national border. Even with a buffer zone, a fence could cede parts of the river that shift south, which otherwise would have remained American territory.