States; modification of assessments.] That any irrigation district cooperating with the United States under the federal reclamation laws and other federal laws shall have the power, through its board of directors, to extend the time for payment of any indebtedness due from said district to the United States, and to otherwise change and modify the time and manner of payment and amount to be paid to the extent permitted under the acts of congress and under any rule, regulation or contract of the department of the interior appertaining thereto, and to that end the board of directors of such district may amend or modify any existing contract with the United States, or enter into a new contract, and may change, adjust, readjust or modify the liens, charges and assessments theretofore made against the lands of said district, and may cancel the taxes theretofore levied by said district, including delinquent tax certificates still held by said district and may do any and all things necessary to carry out such amended or new contract, in accordance with such acts of congress.