In the interest of water conservation and land irrigation in that portion of Alabama known as the State of Alabama and for purposes of cooperation with any water authority or agency or any river area development authority or agency heretofore or hereafter created, there is hereby authorized and shall be established as provided in this article a state development agency constituting an irrigation district or districts for the State of Alabama. The agency, when incorporated in accordance with this article, shall be an instrumentality of the State of Alabama.