Cal. Water Code § 46009

Every preliminary assessment is a lien upon the land affected until the full amount of the assessment is paid. The lien is prior to all other liens, except state, county, and municipal taxes and assessments, or taxes levied or assessed by or under statutory authority. The preliminary assessments shall bear interest at the rate of 7 percent per year and shall be collected in the same manner, together with the same penalties for delinquencies, as other assessments provided for in this division. Interest commences to run 30 days after filing of the assessment roll with the county treasurer of an affected county.