Right of way for ditches and canals; reservation in conveyances. There is granted over all the unimproved lands now or hereafter belonging to the state the necessary right of way for ditches, canals, and reservoir sites for irrigation purposes constructed by authority of the United States or otherwise. All conveyances of state land made after May 18, 1905, shall contain a reservation of such right of way and reservoir sites

ORS 541.240 — under Chapter 541.