"The Rio Grande, what side of the river are you going to put the wall? 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."
That may sound like he's suggesting the wall be built on Mexico's side of the river. Not true. That would amount to an invasion of Mexico, and the seizure of some of their territory -- and just like Mexico is not going to pay for the wall, they would never allow us to build it on their sovereign territory.
Zinke was pointing out just how complicated building a wall would be. If we built it on our side of the Rio Grande, then we would actually be ceding the river to Mexico (in effect, if not legally) -- because Mexicans would have free access to the river (right up to their side of the wall), while Americans would have their access to the river cut off.
Since the admission of Texas to the Union, the United States and Mexico have shared access to and water from the Rio Grande River. Trump's wall would fundamentally alter that. Is this what Americans want? Have the Washington politicians (other than Zinke) even thought about this?
After getting in trouble about repealing Obamacare, Trump stated that he didn't understand how complicated the issue was. I submit that building this silly wall is just as complicated an issue, and Trump has yet to understand that.
In addition to effectively ceding the river to Mexico, the wall would also affect border commerce, affect the region's environment, cost over $20 billion (at a time when we have trillions in debt), raise issues of eminent domain, and probably be ineffective in controlling the immigration of the undocumented. It's a simplistic idea that would create more problems than it would solve.