If the contract mentioned in section 46-1,143 provides for payment of the entire purchase price of such water supply within one year after the making of such contract, the board of directors of such irrigation district shall at the time of entering into such contract pass a resolution that a levy shall be made sufficient to raise such sum as is necessary to pay such purchase price, and the board of directors shall thereafter, and at the same time the levy of other taxes for the district is made, levy a tax against the taxable property of the district sufficient to raise and pay such sum.