Section 1. CONTRACTS FOR POLLUTION CONTROL; TERMS. Any water power control district heretofore organized or hereafter organized is authorized to enter into contracts with any person, firm or corporation or one or more of either, for the sale or disposal of salt water. Provided, no such contract shall be entered into unless it is determined by the Board of Directors of such District that such contract is needed for the purpose of pollution control and unless any such contract in the opinion of such Board of Directors is reasonably calculated to achieve such purpose. If it is determined by the Board of Directors of any such District that in order to effect the sale or disposal of salt water that it is necessary to guarantee a constant flow of water under any such contract, then fresh water may be included, but only to the extent it is necessary in order to achieve pollution control through disposing of salt water. Such contracts may be for a period of time and on such terms as may be deemed necessary by any such Board of Directors.