Cal. Wat. Code § 43006
In addition to levying assessments or fixing tolls and charges under Part 9 (commencing with Section 46000) of this division, and in lieu either in whole or in part of calling such assessments, the board may fix tolls or charges for the use of water, including the use of groundwater, or for any other service of any type or nature whether or not related to water use, rendered by the district, and collect the same from all persons receiving the benefit of the water or other services. The tolls and charges shall be proportional, as nearly as practicable, to the services rendered. Such tolls or charges may be levied and collected in order to provide, in whole or in part, for the payment of amounts due to the state, the department, any other district, or the United States, whether for capital charges or service charges or otherwise, pursuant to contracts made in accordance with Chapter 6 (commencing with Section 44000) of this part, or in order to provide, in whole or in part, for the payment of the costs of a project or the principal of and interest on bonds or warrants of the district, or in order to provide a bond reserve fund to secure bonds of the district, or in order to provide for the operation and maintenance of a project pursuant to Section 47180, or to obtain funds for any lawful purpose of the district. The provisions of Sections 47181 to 47185, inclusive, shall be applicable to any such tolls or charges.
Ca. Water Code § 43006