(a) The treasurer shall maintain a construction and maintenance fund and an interest and sinking fund for the district and shall place money in those funds as required by this chapter or as the board by resolution directs. All other money received by the district shall be placed in a fund or funds as provided by the board.
(b) The amount of taxes collected that is necessary to pay the principal of and interest on the bonds as they mature shall be credited to the interest and sinking fund. All money received by the district from the sale of bonds shall be credited to the construction and maintenance fund.

(c) The treasurer shall pay from the construction and maintenance fund or from a fund or funds designated by the board the expenses, debts, and obligations of the district created after the filing of the original petition and incurred in the creation, operation, and maintenance of the district, other than the principal of and interest on bonds.
(d) The interest and sinking fund may be invested for the benefit of the district in bonds and securities approved by the attorney general.
(e) The construction and maintenance fund and interest and sinking fund shall be held for the purposes for which they were created. If money is improperly paid from either fund, the commissioners court may require the county treasurer to transfer to the fund from the district account the amount necessary to restore that amount.
(f) District funds shall be deposited in the county depositories in the manner required by law for county depositories. Interest collected on those funds belongs to the district.