Actually Mexico threatened to take the US to international court during Nixon's presidency because the water coming out of the Colorado River into Mexico was so salty it was killing crops and un-drinkable.
The US agreed to make one of the biggest De-salination plants in the world just before the border and now the US pays about $300/ton to clean up the Colorado River before it flows into Mexico.
That says the plant is not currently operating. It also says that it's only "included" in the water sent to Mexico. I don't see any indication that it's used for anything close to the full volume of the Colorado River.
Thanks for the link! Didn't know it wasn't operating. My understanding is that the treaty says that the salt content should be less than X parts per million and when the Colorado River gets saltier than X, they can turn the plant on. This diverts some of the water out and returns it in with significantly less salt, thus reducing the total salt content of the river as a whole to a level less than X.
Basically, imagine you have a glass of chocolate milk. You take a teaspoon of chocolate milk out and put a teaspoon of regular milk back in, you will reduce the chocolate content of the glass. The glass is the river as a whole, the plant only treats the teaspoon.
> Actually Mexico threatened to take the US to international court during Nixon's presidency because the water coming out of the Colorado River into Mexico was so salty it was killing crops and un-drinkable.
That doesn't really answer how it would enforce anything; sure, in that case, the US may have chosen to do something, but if it hadn't, its not like winning a case at the ICJ would have forced the US to do anything.
The US agreed to make one of the biggest De-salination plants in the world just before the border and now the US pays about $300/ton to clean up the Colorado River before it flows into Mexico.