Whenever any State or political subdivision thereof shall offer to advance funds for a flood-control project duly adopted and authorized by law the Secretary of the Army may in his discretion, receive such funds and expend the same in the immediate prosecution of such work. The Secretary of the Army is authorized and directed to repay without interest, from appropriations which may be provided by Congress for flood-control work, the moneys so contributed and expended: Provided, however, That no repayment of funds which may be contributed for the purpose of meeting any conditions of local cooperation imposed by Congress, or under the authority of section 701h of this title, shall be made.