The commission shall establish the payments for water service to be paid by water user entities for purchase of water from the southwest pipeline project. The payments for water service include each water user entity's proportionate share of the operation, maintenance, and replacement costs, and also include a component for payment for capital costs. The commission shall include in its determination of each water user entity's share of operation, maintenance, and replacement costs an amount to be deposited in the southwest pipeline project reserve fund for replacement, as established by section 61-24.3-16, for replacement and extraordinary maintenance of southwest pipeline project works. The amount of such reserve fund for replacement shall be determined by the commission.