The board may accept on behalf of the district, appointment of the district as fiscal agent of the United States, or authorization of the district by the United States to make collection of moneys for or on behalf of the United States in connection with any federal reclamation project, whereupon the district shall be authorized to so act and to assume the duties and liabilities incident to such action. But the amounts due the United States for construction shall be carried in separate accounts from the other assessments levied by the said district.