(a) In order to meet requirements of Title VI of the Federal Water Pollution Control Act, the board may direct the comptroller to transfer amounts from the water quality enhancement account to the state water pollution control revolving fund created by § 15.601 of this code to provide financial assistance pursuant to this chapter.
(b) In order to meet requirements of any federal legislation or federal agency program under which an additional state revolving fund, as defined in § 15.602 of this code, has been established, the board may direct the comptroller to transfer amounts from the water supply account, the flood control account, and the economically distressed areas account to such additional state revolving fund to provide financial assistance pursuant to this chapter.

(c) The board shall use the state water pollution control revolving fund in accordance with § 15.604(a)(4) of this code and the Federal Water Pollution Control Act, Section 603(d)(4), as a source of revenue to be deposited in accordance with this chapter for the payment of principal and interest on water quality enhancement bonds issued by the state, the proceeds of which are deposited into the state water pollution control revolving fund.
(d) In the event amounts are transferred to any additional state revolving fund, as defined in § 15.602 of this code, pursuant to Subsection (b) of this section, the board shall, to the extent permitted by the federal legislation or federal agency program under which such additional state revolving fund was established, use such additional state revolving fund as a source of revenue to be deposited in accordance with this chapter for the payment of principal and interest on water development bonds issued by the state, the proceeds of which are deposited into such additional state revolving fund.