Tex. Water Code § 7.103

If it is shown on a trial of a defendant that the defendant has previously been assessed a civil penalty for a violation of a statute within the commission's jurisdiction or a rule adopted or an order or a permit issued under such a statute within the year before the date on which the violation being tried occurred, the defendant shall be assessed a civil penalty not less than $100 nor greater than $25,000 for each subsequent day and for each subsequent violation. Each day of a continuing violation is a separate violation.