Upon the filing of the findings of fact at the final hearing of said petition, as set forth in the last preceding section, said judge, if he finds that the granting of said petition and the drainage of the lands in said irrigation district will be conducive either to the public health, welfare or convenience, or will increase the public revenue, or will be of special benefit to the majority of the acreage of the lands in said irrigation district, shall enter the decree of said court granting said petition. Thereupon a certified copy of same shall be filed in the office of the secretary of state: and from and after the date of said filing of said decree, said irrigation district shall be vested with all of such functions, powers and authority of a drainage district and its board of commissioners under the laws of this state relating to drainage districts. The function, powers and authority granted by this act shall be exercised by such irrigation district through its board of directors and so far as may be in the manner provided by the drainage district laws of this state.