The executive director shall prepare and issue not later than the 15th day after the last day of the permit year an annual certified report (written analysis) based on the investigation and monitoring, which will state the annual average percentages of surface water and groundwater provided to the purchaser by the seller of the alternative water supply for that permit year. The executive director's annual certified report shall be determinative and controlling for purposes of determining the percentages of surface water and groundwater in the alternative water supply pursuant to Water Code, §151.129.