Every public utility district in the state is hereby authorized, by resolution, to create a fund for the purpose of guaranteeing, to the extent of such fund, and in the manner hereinafter provided, the payment of such of its local improvement bonds and/or warrants as the commission may determine issued to pay for any local improvement within any local utility district established within the boundaries of the public utility district. Such fund shall be designated "local improvement guaranty fund, public utility district No. . . . .". For the purpose of maintaining such fund the public utility district shall set aside and pay into it such proportion as the commissioners may direct by resolution of the monthly gross revenues of its public utilities for which local improvement bonds and/or warrants have been issued and guaranteed by said fund: PROVIDED, HOWEVER, That any obligation to make payments into said fund as herein provided shall be junior to any pledge of said gross revenues for the payment of any outstanding or future general obligation bonds or revenue bonds of the district. The proportion may be varied from time to time as the commissioners deem expedient: PROVIDED, FURTHER, That under the existence of the conditions set forth in subdivisions (1) and (2), hereunder, and when consistent with the covenants of a public utility district securing its bonds, the proportion shall be as therein specified, to wit:
(1) When bonds and/or warrants of a local utility district have been guaranteed and are outstanding and the guaranty fund does not have a cash balance equal to twenty percent of all bonds and/or warrants originally guaranteed hereunder, excluding bonds and/or warrants which have been retired in full, then twenty percent of the gross monthly revenues from each public utility for which such bonds and/or warrants have been issued and are outstanding but not necessarily from users in other parts of the public utility district as a whole, shall be set aside and paid into the guaranty fund: PROVIDED, That when, under the requirements of this subdivision, the cash balance accumulates so that it is equal to twenty percent of the total original guaranteed bonds and/or warrants, exclusive of any issue of bonds and/or warrants of a local utility district which issue has been paid and/or redeemed in full, or equal to the full amount of all bonds and/or warrants guaranteed, outstanding and unpaid, which amount might be less than twenty percent of the original total guaranteed, then no further revenue need be set aside and paid into the guaranty fund so long as such condition continues;
(2) When warrants issued against the guaranty fund remain outstanding and uncalled, for lack of funds, for six months from date of issuance, or when bonds, warrants, or any coupons or interest payments guaranteed hereunder have been matured for six months and have not been redeemed, then twenty percent of the gross monthly revenue, or such portion thereof as the commissioners determine will be sufficient to retire the warrants or redeem the coupons, interest payments, bonds and/or warrants in the ensuing six months, derived from all the users of the public utilities for which such bonds and/or warrants have been issued and are outstanding in whole or in part, shall be set aside and paid into the guaranty fund: PROVIDED, That when under the requirements of this subdivision all warrants, coupons, bonds and/or warrants specified in this subdivision have been redeemed and interest payments made, no further income need be set aside and paid into the guaranty fund under the requirements of this subdivision unless other warrants remain outstanding and unpaid for six months or other coupons, bonds and/or warrants default or interest payments are not made: PROVIDED, FURTHER, HOWEVER, That no more than a total of twenty percent of the gross monthly revenue shall be required to be set aside and paid into the guaranty fund by these subdivisions (1) and (2).