Idaho Code § 43-1911
The directors of the district issuing bonds pursuant to this act shall prescribe and collect reasonable rates, fees, tolls or charges for the services, facilities and commodities furnished by the works, and shall revise such rates, fees, tolls or charges from time to time, to provide that all works shall be and always remain self-supporting. The rates, fees, tolls or charges prescribed shall be such as will produce revenue at least sufficient (a) to pay when due, all bonds and interest thereon for the payment of which the revenue is or shall have been pledged, charged or otherwise encumbered including reserves therefor, and (b) to provide for all expenses of operation and maintenance of the works, including reserves therefor.
Idaho Code § 43-1911