(a) A retail public utility as defined by Texas Water Code, §13.002(19) and each entity from which the utility is obtaining wholesale water service for the utility's retail system shall report to the executive director when the utility or entity is reasonably certain that the water supply will be available for less than 180 days. The reporting must be accomplished by utilizing the online "PWS Drought Contingency Plan Reporting Form."(b) If reporting cannot be accomplished in accordance with subsection (a) of this section then the retail public utility or entity from which the utility is obtaining wholesale water service may report to the executive director by United States Postal Service mail, program electronic mail, or facsimile.