A district shall have power to make findings upon each and all of the matters referred to in Section 31026. A finding by the board of directors upon the existence, threat or duration of an emergency or shortage or upon the matter of necessity or any other matter or condition shall be made by resolution or ordinance, and shall be prima facie evidence of the fact or matter so found, and such fact or matter shall be presumed to continue unchanged unless and until a contrary finding shall have been made by the board by resolution or ordinance. Such finding shall be received in evidence in any civil or criminal proceeding in which it may be offered, and shall be proof and evidence of the fact or matter found until rebutted or overcome by other sufficient evidence received in such proceeding. Copy of any resolution or ordinance setting forth any finding shall, when certified by the secretary of the district, be evidence that the finding was made by the district as shown by the resolution or ordinance and certification.