(a) The granting of an application for a new water right or an amended water right shall not cause an adverse impact to an existing water right as provided by this section. An application for an amendment to a water right requesting an increase in the appropriative amount, a change in the point of diversion or return flow, an increase in the consumptive use of the water based upon a comparison between the full, legal exercise of the existing water right with the proposed amended right, an increase in the rate of diversion, or a change from the direct diversion of water to on-channel storage shall not be granted unless the commission determines that such amended water right shall not cause adverse impact to the uses of other appropriators. For the purposes of this section, adverse impact to another appropriator includes: the possibility of depriving an appropriator of the equivalent quantity or quality of water that was available with the full, legal exercise of the existing water right before the change; increasing an appropriator's legal obligation to a senior water right holder; or otherwise substantially affecting the continuation of stream conditions as they would exist with the full, legal exercise of the existing water right at the time of the appropriator's water right was granted.
(b) Subject to meeting all other applicable requirements for an application to amend an existing water right, an amendment to a water right, except for the increase in the appropriative amount or diversion rate, shall be approved as provided by Texas Water Code §11.122(b) if the requested change will not cause such adverse impact on other water right holders or the environment of the stream of greater magnitude than under circumstances in which the water right being sought for amendment was fully exercised according to its terms and conditions as they existed prior to the amendment.
(c) If it is determined that a proposed amendment for a change in the diversion point may adversely affect existing water rights, the amendment, if approved, shall be subordinate only to such affected water rights and the amended water right shall otherwise retain its priority date.
(d) The burden of proving that no adverse impact to other water right holders or the environment will result from the approval of the application is on the applicant.
(e) In granting an application, the commission may direct that stream flow restrictions, return flows, and other conditions and restrictions be placed in the permit being issued to protect senior water rights.

Source Note: The provisions of this §297.45 adopted to be effective February 24, 1999, 24 TexReg 1162