Cal. Wat. Code § 31615
Subject to such limitations as may be contained in the resolution declaring the improvement district to be formed, the board shall have the power in any year to cause taxes to be levied and collected in any improvement district to finance any project of such improvement district or to pay the principal of and interest on bonds issued by the district on behalf of such improvement district for the purpose of financing any project in such improvement district, and to pay the costs of administration, maintenance, and operation of any works or facilities of or for said improvement district. In the Cucamonga County Water District such tax may be levied on land only; but such restriction shall be applicable only within any improvement district formed within the district, and only so long as necessary to pay for the water facilities which may be constructed in such improvement district.
Ca. Water Code § 31615