(a) Except as provided by subsection (b) of this section, a certificate of adjudication, permit, certified filing or unadjudicated claim to appropriate state water is subject to all prior and vested riparian rights of others using water on the stream or other source of supply.(b) Except for water rights granted on the mainstem of the Rio Grande below the Amistad Reservoir (see, generally, Chapter 303 of this title relating to Operation of the Rio Grande) and certain uses exempt from permitting under Texas Water Code §§11.142, 11.1421 and 11.1422 (see, generally, Subchapter C of this Chapter), as between appropriators, first in time is first in right.(c) The time priority of an appropriation of water dates from the filing of the related application with the commission or as determined with a final decree in accordance with Texas Water Code §11.323. The application is considered filed after the application has been declared administratively complete in accordance with §281.17 of this title (relating to Notice of Receipt of Application and Declaration of Administrative Completeness) and filed with the chief clerk.