Water rights are issued by the State of Texas with a small annual fee necessary to pay the costs of the permitting program at the issuing agency. In many cases the State of Texas has created special districts, such as the Brazos River Authority, to develop and manage surface water supplies.
The cost of building and maintaining dams and reservoirs, and all the other costs for managing water supplies, is not paid by the state and is not supported by any tax revenue. The revenue to pay those costs is covered by the sales price of water.
Water is not provided free of charge to the general public due to costs associated with the process of collecting, treating, transporting, and overseeing water quality and quantity. There are costs associated with water availability whether surface or ground water is the source.