Any water user, as defined in subsection (1) of section 42-5102, Idaho Code, or a representative thereof, within the district who possesses the qualifications required of electors under the general laws of the state shall be entitled to vote at any election held under the provisions of this chapter. A representative of a water user shall be so designated by written proxy signed by the water user except that the vote of a federal, state, or county government may be cast by an elected or appointed official of the agency, or his designee.