N.D. Cent. Code § 61-16.1-59.1
A water resource board shall establish a sinking fund for each issue of bonds, and the fund must consist of all drain assessments made for the bonds, all warrants funded, all assessments for the warrants, all accrued interest received on sale of bonds, all proceeds of bonds sold not actually expended for the drain, the reserve fund authorized for purchase of tax delinquent lands affected by the drain, all general tax levies for payment of obligations of the drain, and any other moneys that may be appropriated to the sinking fund. Separate sinking funds must be provided for each separate drain for which bonds have been issued. Until the purpose of the sinking fund has been fulfilled, moneys in the sinking fund may not be applied to any purpose other than payment of the bonds for which the fund was created.
N.D.C.C. § 61-16.1-59.1