(a) The board shall establish and collect rates and other charges for the sale or use of water, water connections, power, electric energy, or other services sold, furnished, or supplied by the authority. The fees and charges must be reasonable and nondiscriminatory and sufficient to produce revenues adequate to:
(1) pay all expenses necessary to the operation and maintenance of the properties and facilities of the authority;
(2) pay the interest on and principal of all bonds issued under this chapter as the interest and principal become due and payable;
(3) pay the principal and interest on any legal debt created by the authority;
(4) pay all sinking fund and reserve fund payments agreed to be made with respect to bonds and payable out of those revenues, as the payments become due and payable; and
(5) fulfill the terms of any agreements made with the bondholders or with any person on their behalf.
(b) Out of the revenues that may be received in excess of those required for the purposes specified in Subsection (a), the board may:
(1) establish a reasonable depreciation and emergency fund;
(2) retire, by purchase and cancellation or redemption, bonds issued under this chapter; or
(3) apply the excess revenues to any corporate purpose.

(c) The rates and charges of the authority may not be in excess of what is necessary to fulfill the obligations imposed on the authority by this chapter or other law. Nothing in this chapter shall be construed as depriving this state of its power to regulate and control fees or charges to be collected for the use of water, water connections, power, electric energy, or other service; provided, however, that this state pledges to and agrees with the purchasers and successive holders of the bonds and other written evidence of indebtedness issued under this chapter that this state will not limit or alter the power vested in the authority to establish and collect fees and charges that will produce revenues sufficient to pay the items specified in Subsection (a), or in any way impair the rights or remedies of creditors or bondholders, or of any person on their behalf, until the bonds and other written evidence of indebtedness, together with the interest on the bonds or indebtedness and the interest on unpaid installments of interest and all costs and expenses in connection with any action or proceedings by or on behalf of the bondholders and all other obligations of the authority in connection with the bonds are fully met and discharged.