1.  At its regular meeting in February the board of directors shall fix the rate and levy an assessment upon the lands in the district, in accordance with the provisions of this chapter, which levy and assessment shall be sufficient to raise the annual interest on the outstanding bonds or any contractual obligation.

2.  At the expiration of 10 years after a bond issue or such other period as may be authorized, the board must increase the assessment as may be necessary from year to year to raise a sum sufficient to pay the principal of the outstanding bonds of that issue as they mature, and must increase the assessment in such amount as may be necessary from year to year to raise a sum sufficient to pay the principal of any outstanding contractual obligation, as such principal may be required to be paid under the terms of the contract.

3.  The board may levy a tax upon the lands in the district either upon the same pro rata basis as benefits may have been apportioned, or otherwise, as the case may be, in order to secure such funds as may be deemed necessary to replace any deficit that may occur in a fund created for the repayment of a district obligation by reason of tax delinquencies.

4.  The secretary of the board shall compute and enter in a separate column of the assessment book or books the respective sums to be paid as an assessment on the property therein enumerated.

5.  Except as otherwise provided herein, assessments made for any of the other purposes of this chapter shall be made and levied as above provided and entered in appropriate columns of the assessment book or books.