Such agency on the part of the district shall not in any way impair the lien reserved to the United States on any tract of land for the cost of such construction, or the rights of the United States to any action so reserved by the United States for the enforcement of such lien, and as such agent of the United States the district shall have the right to refuse the delivery of water to any person who has not made the payments and complied with the conditions required by said acts of congress and the public notices and rules and regulations duly issued thereunder.