Tex. Water Code § 60.103

The district shall prescribe fees and charges to be collected for the use of the land, improvements, and facilities of the district and for the use of any land, improvements, or facilities acquired under the provisions of this subchapter. The fees and charges shall be reasonable, equitable, and sufficient to produce revenue necessary to exercise the powers described by Section 60.101 and adequate to pay the expenses described by Section 60.105.