Section 7. Irrigation, power, electrical, agricultural improvement, drainage, and flood control districts, and tax levying public improvement districts, now or hereafter organized pursuant to law, shall be political subdivisions of the state, and vested with all the rights, privileges and benefits, and entitled to the immunities and exemptions granted municipalities and political subdivisions under this constitution or any law of the state or of the United States; but all such districts shall be exempt from the provisions of sections 7 and 8 of article IX of this constitution.