Who would control the Rio Grande?

No single country controls a river that forms an international border. The Rio Grande is already shared between the United States and Mexico under a treaty, and an independent Texas would take the U.S. seat in that arrangement, with more direct control over Texas water than Texas has today.

The Rio Grande is already a shared, governed river

For most of its length the Rio Grande is the boundary between Texas and Mexico, and it has been jointly managed for generations. Upstream, the U.S. portion is divided among Colorado, New Mexico, and Texas by the Rio Grande Compact. At the border, the water is shared with Mexico under the 1944 treaty and administered by the binational International Boundary and Water Commission. No one party owns the river now. It is governed by agreement, and that does not change at independence.

Texas takes the U.S. seat at the table

Today, on the U.S. side of the border arrangement, Texas water is represented by the federal government. The U.S. Section of the IBWC answers to Washington. On independence, Texas would step into that role for its own stretch of the river, dealing with Mexico directly as the neighbor that shares the water. That is more control for Texas, not less. The state whose farms and cities actually depend on the river would be the one negotiating for it.

Upstream and downstream, the rules carry over

The compact that divides the upper Rio Grande among Colorado, New Mexico, and Texas would convert from an interstate compact into an agreement between countries, the same as every other shared river. The 1944 treaty with Mexico carries over under international law. The result is that the Rio Grande keeps being managed by the same kind of agreements that manage it now, with Texas holding its own seat instead of being one voice inside a federal delegation.

Honest about the pressure on the river

The Rio Grande is a working river under real strain, from drought, from growth on both sides of the border, and from years when deliveries have run behind. None of that is created by independence, and none of it is solved by staying in the union. What independence changes is who answers for Texas water. An independent Texas would set its own priorities for the river and press its own case with Mexico directly, rather than hoping Texas ranks high enough on Washington's list.

The bottom line

The Rio Grande stays a shared, treaty-governed river, the way it already is. Independence puts Texas in the U.S. seat for its own stretch of the river, which means more direct control over Texas water, not a free-for-all and not a loss.