How would an independent Texas secure its water supply?

The same way it does today, and with more control, not less. Water in Texas is overwhelmingly governed by Texas already. Independence changes the label on a handful of agreements without changing the water itself.

Texas already manages its own water

The institutions that plan, allocate, and protect Texas water are state institutions. The Texas Water Development Board produces the State Water Plan and finances water projects. The Texas Commission on Environmental Quality administers water rights and quality. Groundwater conservation districts manage aquifers locally. River authorities manage the basins. None of that depends on Washington, and none of it disappears at independence. The day-to-day machinery of Texas water is built and run in Texas.

Shared rivers are managed by agreement, the way they already are

Some Texas rivers cross borders, and those are governed by agreements rather than by ownership. Inside the union, Texas already operates under interstate compacts for the rivers it shares with its neighbors, including the Rio Grande, Pecos, Canadian, Red, and Sabine. These are negotiated agreements that divide the water between states. On independence, agreements between U.S. states simply become agreements between countries. The substance of who gets what does not have to change. Only the legal category does, from interstate compact to international treaty, which is exactly how neighboring nations all over the world share rivers.

The 1944 Water Treaty with Mexico is an asset, not a problem

The Rio Grande and the Texas-Mexico water relationship are governed by the 1944 treaty on the waters of the Colorado and Tijuana Rivers and the Rio Grande, administered by the binational International Boundary and Water Commission. It is the agreement under which Mexico delivers Rio Grande water to the United States, on the order of 350,000 acre-feet a year averaged over five-year cycles, and Texas is the principal beneficiary on the U.S. side. Boundary and water treaties are precisely the kind that survive a change in sovereignty. Under the Vienna Convention on Succession of States in Respect of Treaties, opened in 1978, territorial and boundary regimes pass to a successor state rather than lapsing, and the International Court of Justice confirmed in its 1997 Gabcikovo-Nagymaros judgment, when Slovakia inherited a Danube water treaty from the former Czechoslovakia, that this principle reflects general international law. An independent Texas would step into the 1944 framework as a party in its own right, with its interests represented directly for the first time, instead of relying on federal negotiators in distant Washington to defend Texas water.

Shared aquifers follow the same logic

Some groundwater, including the Ogallala on the High Plains, sits beneath more than one state. Aquifers that cross borders are a common feature among neighboring nations and are handled through cooperative agreements, the same tool used for shared rivers. Nothing about independence requires Texas to drain or surrender a drop. It requires the same neighborly management that already exists, conducted between sovereigns.

Does Texas have enough?

Water is a real, long-term challenge in Texas, and it will be a challenge whether Texas is independent or not. The difference is who gets to solve it. Today, water policy for Texas competes for attention in a federal system juggling the priorities of fifty states. An independent Texas would set its own water strategy, fund its own infrastructure, and answer to its own people, without asking permission. Self-government does not create the water problem. It hands Texas the full set of tools to address it.

The bottom line

Texas already runs its own water. Independence converts a few shared-water agreements from domestic compacts into international treaties, gives Texas a direct voice in the Rio Grande for the first time, and leaves the state in firmer control of its most precious resource.