Cal. Water Code § 51440

When the district has obtained an irrigation system pursuant to Section 50910, and the charges for furnishing water and making water available have been fixed pursuant to Section 50911, which remain unpaid at the time the board orders an operation and maintenance assessment, the board may order that such charges be included as a part of the operation and maintenance assessment levied upon the parcels to which water has been furnished and when so levied, shall be a lien against the land.