30 Tex. Admin. Code § 297.32
A person seeking permission to use state water for domestic or livestock use from a reservoir constructed by the federal government for which no local sponsor has been designated nor permit issued or a reservoir permitted for storage solely for the purpose of optimum development of the project issued shall apply for authorization. If a request for domestic use is received, and upon investigation it is determined that an existing water supply system is reasonably available to the property, the request shall be denied. In considering the quantity of water to be used for domestic use, the commission will apply a standard of 125 gallons per capita per day unless persuasive reasons for a different daily allocation exist. See § 295.81 of this title (relating to Application).
30 Tex. Admin. Code § 297.32