Wash. Rev. Code § 87.03.130
Any district heretofore or hereafter organized and existing, may change its name by filing with the board of county commissioners of the county in which was filed the original petition for the organization of the district, a certified copy of a resolution of its board of directors adopted by the unanimous vote of all the members of said board at a regular meeting thereof providing for such change of name; and thereafter all proceedings of such district shall be had under such changed name, but all existing obligations and contracts of the district entered into under its former name shall remain outstanding without change and with the validity thereof unimpaired and unaffected by such change of name, and a change of name heretofore made by any existing irrigation district in this state, substantially in the manner above provided is hereby ratified, confirmed and validated.
RCW 87.03.130