30 Tex. Admin. Code § 297.51
When a water right is issued for appropriation by direct diversion or construction, modification or repair of a storage reservoir, or any work in which a time limitation is set by the water right for commencement or completion of construction, a water right holder shall commence and complete actual construction of the proposed facilities within the time fixed by the commission. Failure to commence or complete construction within the time specified in the permit or extension granted by the commission shall cause the water right holder to forfeit all rights to the permit, subject to the provisions of § 295.72 of this title (relating to Applications for Extensions of Time) and the provisions of § 297.74 of this title (relating to Forfeiture and Revocation of Water Right).
30 Tex. Admin. Code § 297.51