Idaho Code § 42-4215
The secretary of the board of directors shall be the assessor of the district, and on or before August 1 of each year shall prepare an assessment book containing a full and accurate list of all water users within the district.
At a regular meeting of the board between August 1 and November 1 of each year, the board of directors shall determine the amount necessary to be raised for the maintenance and operation of the works and facilities of the district and the payment of such fees as may be charged to the district for the use of canals or other diversion works owned or operated by a canal company or companies or other entity or entities, and shall levy assessments against the water users in the district sufficient to raise such amount. Moneys received in payment of such assessments shall be deposited in a separate fund to be known as the maintenance and operation fund. The board also may levy assessments against the water users in the district for the repayment of indebtedness incurred by the board on behalf of the district, as provided in section 42-4216, Idaho Code. Money received in payment of such assessments shall be deposited in a separate fund to be known as the debt retirement fund. The board of directors may, in addition, determine the amount necessary to pay the expenses of making the assessment book, giving notice of assessments and making collections thereof and may levy assessments against the water users in the district sufficient to raise such amount. Moneys received in payment of such assessments shall be deposited in a separate fund to be known as the assessment expense fund.
Each water user shall pay a proportionate share of the total of all amounts to be raised for the purposes aforementioned, which share shall be based on the ratio which the quantity of water such water user is authorized to appropriate under his water right or rights bears to the total quantity of water authorized for appropriation under the water rights of all water users in the district; provided, however, that the combined annual assessment against each water user shall not exceed ten dollars ($10.00) per second foot of water the water user is entitled to appropriate under his water right or rights.
Idaho Code § 42-4215