Any person purporting to act for any water right holder, in regard to diversion, transport, use, or impoundment of state water, or payment of a watermaster assessment, or for a contractual buyer, in regard to diversion, transport, use, or impoundment of state water, shall submit to the watermaster a document signed by such water right holder confirming such authority and specifying the duration of such authority.
30 Tex. Admin. Code § 304.44