Wyo. Stat. § 37-7-211
Rates for services furnished by any such system shall be fixed precedent to the issuance of the bonds. Such rates shall be sufficient to provide for the payment of the interest upon and the principal of all such bonds as and when the same become due and payable, to create a bond and interest redemption fund therefor, to provide for the payment of the expenses of administration and operation and such expenses for maintenance of the system necessary to preserve the same in good repair and working order, to build up a reserve for depreciation of the existing system, and to build up a reserve for improvements, betterments and extensions to the existing system other than those necessary to maintain the same in good repair and working order as hereinbefore in this section provided. Such rates shall be fixed and revised from time to time so as to produce these amounts, and the court in its order authorizing the issuance of said revenue bonds shall empower and direct the commissioners of such power district to agree in and by the terms of said revenue bonds, and on the face of each bond at all times to maintain such rates for services furnished by such system as shall be sufficient to provide for the foregoing.
W.S. 37-7-211