We, here on the west coast of USA, get a lot of our winter vegetable crops from California's Imperial Valley which is just north of the Mexican border and south of the Salton Sea. Unlike California's larger Sacramento / San Juaquin Valleys, it gets its irrigation water from the Colorado River. The larger valleys, to the north, get their water from mountain ranges inside California.
I recently had a conversation with someone that grew up in the Imperial Valley and he says it's a beautiful valley, but it's days as an agricultural valley may be numbered. It's productivity, for agriculture, is artificially created with irrigation water from the Colorado River and artificially propped up soils from tons of fertilizers.
I've been thinking they could save the agriculture, there, by desalinizing nearby seawater from the Gulf of California, in Mexico, or even the Pacific Ocean near San Diego.
The person, I was talking to thinks, instead, they may have to just let go of agriculture and let that valley return to desert. Agriculture could move to other places where soil and water conditions are naturally better, like some areas quite a ways farther south in Mexico where there could be more investment in agriculture.
It could help Mexico's economy, but we would be importing more food from there.
Artificial national borders are kind of problematic as well. We do live in a changing, global economy.