Cal. Water Code § 31500

Whenever, in the opinion of the board, the public interest or convenience may require, it may order to be done in, under, or upon the whole or any portion of any one or more of the streets or public places of the district, or any property or rights of way owned by the district, any work or improvement for supplying or distributing an irrigation, domestic, or other water supply or for fire protection, or for collecting, treating, and disposing of sewage, waste, and storm waters, and provide that the cost thereof shall be assessed upon the lots and lands fronting on the streets or public places, or upon any district to be assessed therefor, which district need not be composed of lands contiguous to each other.