I know it's been stated that Santa Anna will be behind the wall, and a pretty huge swath of the reserve will be bulldozed. It doesn't really sound like the refuge will really exist any more post border wall. Local folks are also concerned because tentative plans would also cut off most folks from the river, which is obviously going to also affect agriculture in the valley.
Have to say this seems senseless to me. Apparently the rationale is that because the refuge is Federal property, no legal impediments can be raised to the work.
The Rio Grand is not the Amazon or even the Hudson, it is a fairly modest stream by the time it reaches South Texas. The border patrol uses air boats to patrol stretches of the river because it is too shallow for regular outboards. These make hellish noise, so that any migrant even thinking of crossing gets ample warning well before the boat comes into view.
With many miles of other crossing opportunities, it just seems pointless and willful to single out a nature preserve.