California Code, Water Code - WAT § 43007

If tolls or charges are levied and collected in order to provide, in whole or in part, for the payment of amounts due under more than one contract, such tolls and charges may be fixed, levied and collected in such a manner as to, as nearly as practicable, charge the lands served under a particular contract with the amounts due under such contract. The assessment commissioners appointed under Chapter 2 (commencing with Section 46150) of Part 9 of this division may apply this principle in determining the portion of the total benefits to accrue to the district under a particular contract which will be realized by each parcel of land in separate ownership in the district.