(a) The money received from any sale, transfer, or lease of facilities as cash, or in the case of a sale or transfer involving revenue bonds, the money received as matured interest or principal on the bonds shall be used to pay the principal of and interest on water development bonds or to meet contractual obligations incurred by the board. The money shall be collected and credited to the proper special fund as is money received in payment of principal and interest on loans to political subdivisions under this code, taking into consideration the manner in which the facilities were acquired.
(b) When enough money has been collected to pay all outstanding indebtedness, including the principal of all state bonds and contractual obligations and the full amount of interest to accrue on these debts, the board may use any further amounts received from the sale, transfer, or lease of facilities to acquire additional facilities or to provide assistance to political subdivisions for water supply projects.