Texas groundwater rights follow the rule of:

Prior appropriation is the doctrine that governs surface water rights in Texas and many western states, operating on the 'first in time, first in right' principle where water rights are allocated based on the historical order of appropriation permits — this system applies to rivers, streams, and lakes in Texas but does not apply to groundwater, which is governed by the entirely separate rule of capture.

Riparian rights is the doctrine used in eastern states where landowners adjacent to a body of surface water have the right to make reasonable use of that water based on their land's proximity to the water source — Texas does not use riparian rights for either surface water or groundwater, having moved away from riparian doctrine for surface water in the early 20th century when it adopted prior appropriation.

Federal water law does not govern private groundwater rights in Texas; water law in the United States is primarily a matter of state law, and the federal government's role is generally limited to navigable waterways, federal lands, and interstate compacts — Texas groundwater on private land is exclusively governed by Texas state law under the rule of capture.