The Valley relies heavily on the Rio Grande for its water — and that could spell challenges as South Texas grows

The Rio Grande Valley’s growth runs on river water — a source that’s becoming increasingly unpredictable.

A new Texas A&M study shows that McAllen, Brownsville, and other South Texas metros depend more on the Rio Grande and its reservoir system than any other region in Texas.

That makes the Valley especially vulnerable to drought, cross-border disputes, and the realities of a strained binational supply.

The report, “Mapping Metro Water Use: Sources, Industries and Consumption,” by the Texas Real Estate Research Center, found that while groundwater provides about half of Texas’ total water use, roughly 90% of South Texas’ supply comes from surface water — nearly all of it drawn from the Rio Grande.