I ran the Rio Grande on Google earth. I thought the border was the middle of the river. When you look, in lots of places it’s hard to tell where the river is or was.
Somehow I learned of the controversy about a similar situation with Oklahoma and the Red River. There is considerable acreage made and lost by the meandering of the river. As I recall, there are (or were) some big legal battles of the new/lost acreage
“I thought the border was the middle of the river.”
I believe you are correct.
“There is considerable acreage made and lost by the meandering of the river.”
That is one of the big issues covered by the Treaty with Mexico, and administered by the implementing body (International Boundary and Water Commission). They also manage flooding and water use issues.
That is how they got involved - they are responsible for certifying that any American construction is not going to divert floodwaters into Mexico, or change the course of the river.
On the good side, if the court can drive a rapid approval of the design through the IBWC, then riverwall designs could potentially be built with 2020 money further upriver, where another 200 miles is needed. That would save a lot of landowner’s property, and conserve a lot of land acquisition costs.
One of the two injunctions on Fisher building this river wall, is in this case: https://www.freerepublic.com/focus/f-news/3800656/posts
The Bush appointed judge seems to be driving a rapid legal resolution, which may well end up validating the riverwall design, for use elsewhere along the 1,250 mile International border along the Rio Grande.