Tex. Water Code § 11.038

(a) A person who owns or holds a possessory interest in land adjoining or contiguous to a canal, ditch, flume, lateral, dam, reservoir, or lake constructed and maintained under the provisions of this chapter and who has secured a right to the use of water in the canal, ditch, flume, lateral, dam, reservoir, or lake is entitled to be supplied from the canal, ditch, flume, lateral, dam, reservoir, or lake with water for agricultural uses, mining, milling, manufacturing, development of power, and stock raising, in accordance with the terms of the person's contract.

(b) If the person, association of persons, or corporation owning or controlling the water and the person who owns or holds a possessory interest in the adjoining land cannot agree on a price for a permanent water right or for the use of enough water for irrigation of the person's land or for agricultural uses, mining, milling, manufacturing, development of power, or stock raising, then the party owning or controlling the water, if the person has any water not contracted to others, shall furnish the water necessary for these purposes at reasonable and nondiscriminatory prices.