(a) The owner of a utility that supplies retail water service may not contract to purchase from an affiliated supplier wholesale water service for any of that owner's systems unless:
(1) the wholesale service is provided for not more than 90 days to remedy an emergency condition, as defined by utility commission or commission rule; or
(2) the utility commission determines that the utility cannot obtain wholesale water service from another source at a lower cost than from the affiliate.
(b) The utility may not purchase groundwater from any provider if:
(1) the source of the groundwater is located in a priority groundwater management area; and
(2) a wholesale supply of surface water is available.