LOAN FUND.

(a) The board may pay or contract to pay on any bonds which it has sold or pledged, in addition to taxes, other funds derived from:

(1) water charges for use of water in the district;

(2) sale or supply of water to any city, town, municipal corporation, district, or land or user of water outside the boundaries of the district;

(3) sale of water to any commercial or industrial enterprise;

(4) sale of hydroelectric power; or

(5) any or all of these sources of revenue.

(b) The board shall fix the amount to be derived from these sources for this purpose and shall enforce and collect it in the same manner provided to collect charges or assessments for maintenance and operation. All liens and remedies provided by law to secure and enforce the collection of charges and assessments for maintenance and operation of the district are applicable to securing and enforcing the collection of these funds.

(c) Money collected under this section shall be kept in a separate fund called the "loan fund" and shall be used only for the purpose of paying the principal and interest on the bonds for as long as the bonds remain unpaid.

(d) The charge created by this section is an additional and distinct charge and a source of income of the district over and above its income for maintenance and operation and other purposes.

(e) After the loan fund is created and pledged, the action of the board in fixing the amount of the charge and in fixing the total annual charges for maintenance and operation may not be reviewed by the commission regardless of any law to the contrary.